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Speaker Selector Switch Simulators

Geoff
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15
Speaker Selector Switch Simulators

The speaker selector switch simulators presented here demonstrate how speaker selectors deal with speaker impedance and power distribution. Speaker selector switches are used to allow you to connect multiple speakers to your HiFi amplifier. They help to keep the total impedance safe for your amplifier. How do they do this? How do the different types work? How do they divide the power among the speakers? Read on…

These speaker selector switch simulators are ideal if you:

  • are thinking of buying a speaker selector switch and want to know the best type.
  • want to know how to use them better
  • would like to know the effect on impedance and speaker power with different settings.
  • like to know how speaker selector switches work

Please note, speaker selector switches are designed for multi-room installs in a home or small low power installs (like an office or cafe). They are generally suited for low power (under 100 watts) amplifiers. They should be not be considered in a commercial install or for use with high output power amplifiers.

To help understand speaker impedance and why it matters, have a look at the article and video in Understanding Speaker Impedance.

How to use the Speaker Selector Switch Simulators

Speaker selector switch simulators schematicThe speaker selector switch simulators below are based one a setup similar to this diagram. Only one channel of the amplifier is shown as speaker selector switches (and the simulators) treat both the left and right channels the same.

Basically you need to fill in the white boxes.

Start by typing in (or select from the drop down list) the rated impedance of each speaker pair connected to the speaker selector switch. If you are using less than 6 speakers, simply select “no speaker” in the drop down list for the unused speakers. You can also make each speaker selector switch simulator act like a 2 way or 4 way speaker selector by using “no speaker” for the unused channels.

The on/off switches under each speaker simulate the on/off switch for each speaker zone on the speaker selector. As you turn each switch on or off the total load impedance and the power through each speaker is re-calculated. Depending on which type of simulator you are using, you may also need to type in the series resistor value or the volume control settings.

Then in the amplifier section, select the minimum impedance your amplifier is designed for. Then type in the maximum RMS power your amplifier will produce at this impedance. This information is normally found in the “specification” of your amplifier’s user’s manual or online.

Speaker Selector Switch Simulators

There are three main types of Speaker Selector Switches. There is a simulator for each type. You can use the buttons as a shortcut to each type. 

Series-Parallel Type Simulator Series Resistor Type Simulator Transformer Type Simulator

Series-Parallel type Speaker Selector Switch

How they work: Series-Parallel type of speaker selector switches use switches to connect the speakers in a combination of series and parallel. Speakers 1 and 2 are connected in series, as are speakers 3 and 4.  Then each series pair are connected in parallel.

Pros and Cons: There is no power lost due to the switch.  They are not expensive. Can be used for 2-4 speakers. Do not work for all speaker/amplifier combinations. Normally recommended for 8 ohm speakers. If using three speakers, don’t turn the spare (4th) zone on, or it will disconnect the 3rd speaker (because there is nothing to be in series with).

4-way-ser-par-switch

  
Series-Parallel Type Simulator Series Resistor Type Simulator Transformer Type Simulator

Series Resistor type Speaker Selector Switch

How they work: When the “protection” switch is on, a resistor is placed in series with the speakers. The minimum load impedance will not go below the value of this resistor. Turning the “protection” switch off removes the resistor from the circuit.

Common resistor values used by different manufactures:
2.5 ohms: Niles
3 ohms: Sima
5 ohms: AVX, Monoprice, Parts Express

Pros and Cons: While the resistor takes care of the total impedance, it can also take a lot of the power. Therefore the resistors can get quite hot. Normally not recommend for higher powered amplifiers. The lower the resistor value, the less power loss through the resistor, but the less impedance protection offered.

6-channel-speaker-switch

 
Series-Parallel Type Simulator Series Resistor Type Simulator Transformer Type Simulator

Impedance Matching Transformer type Speaker Selector Switch

How they work:  Each channel has a transformer which effectively multiplies the impedance seen by the amplifier. For example if the multiplier is set to x2, a 4 ohm speaker will appear to be 8 ohms. The trade off for this is that the power available to the speaker is divided by the same factor.  Most transformer type of speaker selector switchers have a switch at the rear to set the multiplier to x1, x2, x4 or x8. In practice transformers are around 90% efficient – this simulator is based on 90% efficiency.  Most impedance matching transformer based switches also incorporate a separate 12 step volume control for each channel. This simulator also allows for different volume control settings.

Pros and Cons: Can be used for most speaker/amplifier combinations. Are more efficient than series resistor type, and do not normally get hot. Can be designed for higher powered amplifiers. Provide individual volume control for each zone. Are generally more expensive.
4-ch-with-vol

 

If you need to buy a Speaker Selector Switch, you may want to check out my Speaker Switch Summary. Alternatively, you can use the following links to check out Amazon’s range in USA or UK or Australia. Disclosure: If you buy through these Amazon links Geoff receives a small commission from each sale.

How much power do I need?

The above speaker selector switch simulators may surprise you regarding how little power can reach the speaker when you have multiple speakers connected to your Hifi amplifier. Don’t get too stressed. People have been using these switches for many years with no problems. What these simulators show is that you don’t need a lot of power to fill a room with sound, especially for background music.

The loudness of your speakers will also be determined by the speaker’s sensitivity. If you would like to explore more about how much power you need for each room in your house, you can use my Amplifier, Speaker and SPL Calculator

Other articles you may find useful:

Understanding Speaker Impedance

Connecting multiple speakers to your Hifi

Wiring 4 speakers to your amp

Connecting 2 speakers to an amp

Summary of speaker selector switches

Speakers in parallel calculator 

If you have question on installing a speaker selector switch, please read the FAQs before submitting your question. You may also find an answer is the comments below.

How Multiple Speakers Share Power

Geoff
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40
How Multiple Speakers Share Power

Often people are wanting to add speakers to their amplifier to increase power. However, in most cases, adding speakers will reduce the power in any one speaker. This article looks at how multiple speakers share power from the amplifier, whether they are wired in series, parallel or series and parallel.

As in most articles, we are going to talk about speakers connected to one amplifier. That is, either the left or right channel amplifier of your hifi.  So if you want to connect 4 speakers in total, you are only going to connect 2 speakers to each amplifier.

Speaker Power

The rated power of speakers is a concept often misunderstood. Many people think that if they have a speaker rated at 50 watts, then adding another 50 watt speaker will give them 100 watts of power. It is true that 2 speakers rated at 50 watts gives you a speaker system with the capacity to handle 100 watts of amplifier power. It gives you the capacity, that is all. It does not produce 100 watts. If the amplifier can only deliver a maximum of 50 watts of power, then the amplifier can still only deliver a maximum of 50 watts of power irrespective of the power rating (capacity) of the speakers.

The power rating of a speaker is normally indicating the maximum power you can safely drive the speaker with. The speaker will also work when driven at lower power.

Amplifier Power

The maximum power output of an amplifier is dependent on the amplifier design and total load impedance of the speakers connected to it. A more detailed discussion on speaker impedance and power output can be read in the article Speaker Impedance Changes Amplifier Power.

In summary, halving the total impedance (by doubling the number of speakers in parallel) can increase the power output of an amplifier. In theory halving the load impedance will double the power output of an amplifier. In practice this is rarely achievable, but a considerable increase in power is normally achievable. Please note, that even if the power output of an amplifier is doubled, that would only increase the perceived volume by around 25% (see Double Amplifier Power doesn’t Double the Volume).

For an understanding of how amplifier power is calculated and what terms like continuous power and peak power mean, see the article on Understanding Amplifier Power.

Speakers Share the Power

For a given power output from an amplifier, that power will be shared between the speakers connected to it. We don’t need to get technical to understand this. Logically, the power connected to two speakers will be shared by those two speakers. If there are four speakers, then the power will be shared by the four speakers.

So if adding speakers doesn’t double the power (nor the volume), why add speakers to an amplifier? I suggest the main reason to add speakers to an amp is to spread the speaker coverage.

the main reason to add speakers to an amp is to spread the speaker coverage

In a house, you might do this to have sound in another room, or outside. In a church or hall, you would use multiple speakers to spread the sound across a wide area.

 

How Speakers Share Power

Impedance (like resistance) is measured in ohms, and uses the Omega symbol (Ω) for shorthand

How the speakers share power from the amplifier is dependent on whether the impedance of each speaker is the same or not, and if the speakers are wired in series, parallel or a combination of series and parallel. For further understanding of speaker impedance, see the article Understanding Speaker Impedance 

How speakers share power if the speakers are the same impedance

If all the speakers connected to the amplifier are of the same impedance, then the power is shared equally. This is true for speakers wired in series, parallel or series/parallel.

Speakers with the Same Impedance
4 Ohms in Series8 Ohms in Series
power share - 4 ohms in series
Total Impedance = 8 ohms		power share - 8 ohms in parallel
Total Impedance = 16 ohms
4 Ohms in Parallel8 Ohms in Parallel
power share - 4 ohms in parallel
Total impedance = 2 ohms*		power share -8 ohms in parallel - power
Total Impedance = 4 ohms
4 Ohms in Series/Parallel8 Ohms in Series/Parallel
power share - 4 x 4 ohm series parallel
Total Impedance = 4 ohms		power share - 4 x 8 ohm series parallel
Total Impedance = 8 ohms
*Note: Most Hifi amplifiers are not designed for less than 4 ohms

How speakers share power if speakers of different impedance are in parallel

If the speakers wired in parallel each have a different impedance, the lower impedance speakers will draw more than the higher impedance speakers.

Different Impedance Speakers in Parallel
2 speakers in Parallel3 speakers in Parallel
power share - 4_8 ohms in parallel - power
Total Impedance = 2.7 ohms*		power share - 4_6_8 ohms in parallel - power
Total Impedance = 1.85 ohms*
*Note: Most Hifi amplifiers are not designed for less than 4 ohms

How speakers share power if speakers of different impedance are in series

If the speakers wired in series each have a different impedance, the higher impedance speakers will draw more than the lower impedance speakers.

Different Impedance Speakers in Series
2 speakers in Series3 speakers in Series
power share - 4 _8 ohms in series - power
Total Impedance = 12 ohms		power share - 4_6_8 ohms in series - power
Total Impedance = 18 ohms

How speakers share power if speakers of different impedance are in series/parallel

If the speakers wired in series/parallel have a different impedance, the power sharing will depend on the combination. Below are a couple of examples.

Different Impedance Speakers in Series/Parallel
2 x 4 ohm speakers in series, in parallel with a 8 ohm speaker
Mulitple speakers share power - 2 x 4 in series + 8 in parallel
Total impedance = 4 ohms
3 speakers in series in parallel with 3 other speakers in series
Mulitple speakers share power - 2 x 4 8 4 and 8 4 8 in series parallel
Total impedance = 8.9 ohms

If your speaker configuration is similar to any of the above diagrams you can work out how your speakers share power for your amplifier.

Summary

Adding extra speakers doesn’t increase the power to each speaker. Speakers share power from an amplifier. How they share power is dependent on how the speakers are wired, and the impedance of each speaker.

Keep in mind, that as the total load impedance falls, the amplifier will output more power, up to its limits (see this article).

Also consider the sensitivity of each speaker, as this will contribute to the loudness of each speaker. See the article on Understanding Speaker Sensitivity for more details.

To see how power is shared when using speaker selector switches, see my Speaker Selector Switch Simulators.

If you have a question, please read the FAQs before submitting your question.

Speaker Impedance Changes Amplifier Power

Geoff
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35
Speaker Impedance Changes Amplifier Power

Speaker impedance changes amplifier power output. In fact, your amplifier power could be nearly half or double its capacity – depending on the impedance of your speakers. But how much should this concern you?

Impedance is measured in ohms. The Omega symbol (Ω) is used for shorthand.

Amplifier Output Power

Let’s say we have an amplifier. The specifications might say the output power is 100 watts RMS at 8 ohms.

Notice the power output (100 watts) is at a specified load (8 ohms). This is telling us that with an 8 ohm speaker, the maximum output power will be 100 watts.

An Ideal Amplifier

If our sample amplifier were an ideal amplifier, then we can also calculate¹ that:

  • With a 4 ohm speaker, the maximum output power will be 200 watts.
  • With a 16 ohm speaker, the maximum output power will be 50 watts.

The above shows that for an ideal amp, halving the impedance doubles the power output. Doubling the impedance halves the power output.

Halving speaker impedance doubles amplifier power.

Doubling speaker impedance halves output power.

An ideal amplifier is an amplifier which is theoretically perfect. Of course, such an amplifier does not exist, but they are useful when explaining how speaker impedance changes amplifier power.

You can use the following calculator to determine the possible power output with different impedance speakers. Simply type in the power rating of your amplifier and the specified impedance (ohms) – Eg, 80 watts @ 6 Ω.

¹All these calculations use standard electrical formulas which you can read more about in the articles What is Electrical Power, and The Dreaded Ohms Law.
 

In summary, in an ideal amplifier, the current from the amplifier will depend on the speaker impedance (ohms). The lower the speaker impedance (in ohms) the greater the current that can be drawn from the amp, which means the greater the power.

Real World Amplifiers

The above calculations work well for an ideal amplifier, and help show how speaker impedance changes amplifier power output.

In reality, amplifiers cannot maintain the theoretical output levels as calculated above. This is because the power supply on most amplifiers cannot maintain the maximum power when driving the lower impedance speakers.

In a real amplifier, the above principles still hold but the theoretical values will not be achieved. The power output will be increased with lower impedance speakers, but the maximum power output will not be doubled when the impedance is halved.

As an example of a real world amplifier, let’s look at the specifications of a popular PA Amplifier purchased at Amazon through this site, the Crown XLS1000.

XLS1000 specs - speaker impedance changes amplifier power

This shows that for this amplifier, with both (dual) channels used at the same time, the maximum power output of the amplifier changes as the speaker impedance changes:

  • With an 8 ohm speaker, the maximum output power will be 215 watts.
  • With a 4 ohm speaker, the maximum output power will be 350 watts.
  • With a 2 ohm speaker, the maximum output power will be 550 watts.

This example shows that in a real world amplifier, the principle of “speaker impedance changes amplifier power output” is true, just not as much as in an ideal amplifier.

Please note: this amplifier is designed to work with a speaker impedance as low as 2 ohms. Most HiFi amps are only designed to work with a speaker impedance of (or above) 4 ohms.

So What?

So what should you do with this marvelous knowledge? If 4 ohm speakers gives you nearly double the power of 8 ohm speakers, should you only use 4 ohm speakers?

Answer: Yes, and No.

4 ohm speakers are used widely in the car audio industry, as they want to squeeze every bit of power capable from a fixed voltage (~12-14 volts from a car battery). They also mostly design and build their amplifiers to cope with 4 ohms and often 2 ohm loads.

However, it may not be wise to run your Hifi amp flat out at 4 ohms. The reason being, it may mean you are running your amp at or beyond its design limits. The cheaper the amp, the closer you are likely to be at the limits of the power the power supply can cope with. Better to use 6 ohm or 8 ohm speakers, and let your amp comfortably drive them without reaching full capacity. This is similar to a car: better not to constantly drive with the motor at full revs. Interestingly, most Hifi speakers are 6Ω or 8Ω.

A common method of changing speaker impedance is by adding another speaker, either in series or in parallel with the existing speaker. While this will change the output power of the amp, the speakers will share that power. For more details see How Multiple Speakers Share Power.

Most modern amplifiers will, if they are overloaded,  either turn themselves off or reduce the output to protect themselves. However, it is wise not to rely on this self-preservation circuitry, best to design your system conservatively.

Keep in mind that all this is describing the maximum power output of an amplifier. If you don’t run your amp anywhere near full volume, then all this is fairly much irrelevant.

Also keep in mind that doubling the amplifier power only increases the volume by around 23%.  To double the volume you need around ten times the power. For an explanation of this, see the article on Double Amplifier Power does not Double the Volume. 

If you need maximum level from your speakers, pay attention to the sensitivity in the specifications. Using a speaker with a sensitivity of 90dB (1W/1m) compared to another speaker rated at 87dB (1W/1m) is the same as doubling the amplifier power driving the speaker. For more details on this see the article Understanding Speaker Sensitivity.

While speaker impedance changes amplifier power output, it is not a major consideration for most users. It only becomes relevant when running your amplifier at full power, and then it is best not to run it too close to its design limits.

Never use a speaker (or speakers) below the minimum impedance the amplifier is designed for. If you hear any distortion, it is an indication that major trouble is just around the corner – turn the volume down, eliminate the distortion and consider a redesign of the system.

If you have a question, please read the FAQs before submitting your question.

Understanding Speaker Impedance

Geoff
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7
Understanding Speaker Impedance

Speaker impedance is often presented as a complex subject and therefore is either ignored or misunderstood. A basic understanding of speaker impedance is not difficult, and is useful when connecting multiple speakers to an amplifier. This article will give you a practical understanding of speaker impedance and how to connect multiple speakers to your HiFi amp.

What is speaker impedance?

Speaker impedance refers to the load a speaker places on an amplifier. Well, that is the effect of speaker impedance. Technically, speaker impedance is the “resistance” a speaker offers to the current supplied by an amplifier. Because the output current of an amp is AC (not DC, like from a battery), the resistance is called impedance. To be real technical, impedance is the combination of DC resistance, plus any reactance in a AC circuit. But without getting too technical, just remember speaker impedance affects how much current is drawn from the amplifier.

Impedance (like resistance) is measured in ohms, and uses the Omega symbol (Ω) for shorthand. However, unlike resistance, impedance changes with frequency. And since the signal from an amp is voice or music with lots of different frequencies, the speaker impedance is constantly changing. Rather than state the impedance for every frequency, speaker manufactures state the “nominal” impedance, which is sort of the average of the lowest values of the speaker impedance. It is this figure which we use for calculation purposes.Speaker impedance 8 ohms

Most speakers are rated by the manufacture as nominally 4Ω, 6Ω, 8Ω or 16Ω.

Why does speaker impedance matter?

As stated above, speaker impedance determines the current drawn from the amplifier. Remember impedance impedes (or restricts) the current, so the lower the impedance, the more current can flow. A greater current requires the amp to produce more power.  Another way of looking at it is to say the lower the impedance, the higher the load on the amp (and the harder it has to work).

These general relationships can be summarized by:

Lower the impedance → more current → greater load → increased power

Raise the impedance → less current → smaller load → decreased power

The relationship between impedance (resistance), current, voltage and power is determined by Ohms law. See this article for a fuller explanation.

Looking at the above summary, it appears that the lower the speaker impedance, the greater the power the amp delivers through that speaker. This is true – up to a point. It is true up to the point when the amp can not produce anymore current and power. At this point, either the amp fuse will blow, the amp will die or the protection circuit in the amp will kick in and turn the amp off. Therefore, do not run an amp with a load impedance of less than the stated minimum (normally 4 ohms).

The secret is to make sure the speaker impedance is within the range that the amp is designed for.

Why do I need to know about speaker impedance?

You need to make sure the speaker impedance of any speaker (or speakers) connected to an amp is within the capabilities of the amp.

Most HiFi amps are designed for a speaker load impedance of 4-16 ohms. This means the minimum speaker impedance is 4Ω. Therefore if you have a speaker with a rated impedance of 4Ω, 6Ω, 8Ω or 16Ω, the amp will be happy. The lower the impedance, the greater the current flowing through speaker and the greater the power available. But, don’t use a speaker (or speakers) with an impedance below 4 ohms.

This is a real concern when you connect two or more speakers to one amplifier. For example, four 4Ω speakers connected across an amp gives a total load impedance of only 1Ω – way too low for your amp. In this case you should use a speaker selector with impedance protection or impedance matching.

All this is simply illustrated in the following video I put together. It starts with a simple set-up and develops into what happens with multiple speakers, and how speaker switches help with impedance.

Hopefully that has helped you understand what speaker impedance is all about, and how to use your knowledge to safely connect speakers to your amplifier.

Other articles to help you are:

Speakers in parallel calculator 

Connecting multiple speakers to your Hifi

Wiring 4 speakers to your amp

Connecting 2 speakers to an amp

Summary of speaker selector switches

If you have a question on speaker impedance and what it means to your install, please read the FAQs before submitting your question.

How do I connect a VCR to a Flat Screen TV

Geoff
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162
How do I connect a VCR to a Flat Screen TV

You may still have many video tapes that you like to play but find it hard to connect a VCR to your new flat screen TV. Often this is because you can’t find the right connections on the new TV. This article will explain the different options on how to connect a VCR to a flat screen TV, even if you can’t find the yellow socket.

Basically you need to connect from the “line out” of the VCR to “AV in” of the TV. This needs to be done for both the video and for the audio. Some VCRs have one audio out socket (mono) and some have two audio out sockets (stereo) – we will look at stereo first, and look at the differences for mono later in this article.

Connect a VCR with the Yellow, Red and White Leads

Connect a VCR with RCA leads

To connect a VCR to most flat screen TVs, you will need a cable with these yellow, red and white connectors. For non European VCRs, you will need a cable with these plugs at each end. For European VCRs, you may need a SCART plug at the VCR end, and these yellow, red and white plugs at the other end to connect to the TV.

The yellow, red and white plugs are often called RCA or Phono plugs. The yellow cable is used for the video signal, the red cable for the right audio, and the white cable for the left audio signal. Many VCRs come with these leads supplied. If you don’t have any, they should be available at most electronic or electrical stores.

If you need a SCART connection for the VCR, make sure the SCART cable is designed for output. If you use a SCART cable made for input, it won’t work as you need an output cable. Some SCART leads or adaptors have a little switch on the SCART plug to allow it to be switched to “IN” or “OUT”. Select “OUT”.

The rear of the VCR

This photo shows the standard connectors on most (stereo) VCRs. If you look closely, on the right hand side are the “line out” sockets (the left hand side is for “line in”, which we don’t use for connecting to a TV). The top right red socket is for the right audio out. The white middle right connector is the left audio out socket. The yellow socket at the bottom right is the video out socket.

The markings or labels on most VCRs are as hard to read as in this photo, so you may need to use a torch to see the markings clearly. Once you have found the line out sockets, it is a simple matter of connecting the yellow, red and white plugs of the connecting cable to the corresponding yellow, red and white line out sockets of the VCR.

The Rear of an Older Flat Screen TV

Connect a VCR LCD connectors

Older flat screen TVs are easy to connect a VCR to as they have at least one yellow “video in” socket. In this photo you can see it just below the centre of the photo, it is labelled “Video”. Below this yellow socket for video in is the corresponding white and red sockets for the left and right audio in.

Having found the yellow, red and white sockets, it is a simple matter of connecting the corresponding yellow, white and red plugs of the cable connected to the VCR to these sockets.

You may have noticed that in this photo, these sockets are in a section labelled “VIDEO 1 IN”. This normally would indicate that this is the input you need to select on the TV to watch the VCR. Most TVs require you to press “Source” or “Input” on the remote control to select the “Video 1” input signal.

Other TVs might label these inputs “AV” (short for Audio/Video).

Some older TVs might have several AV inputs, normally labelled AV 1, AV 2 etc. Some flat screen TVs have the AV input on the side of the TV.

My TV doesn’t have a Yellow Socket!

I get many questions from people saying they can’t find the yellow socket to connect a VCR into. Don’t worry, I have a solution. But first check the sides of your TV to make sure the designers aren’t trying to trick you by hiding the yellow, red and white sockets up one side.

Other TVs have a little yellow socket (like a headphone socket) often labelled “AV In”. These are designed to allow the yellow, red and white leads from the VCR to connect to the TV via a little adaptor lead.

Some manufacturers provide these adaptors with the TV, other manufacturers assume you will buy one if you need to. If you need to buy one, search for “3.5mm AV lead”. Either way, simply plug the leads from the VCR into the adaptor lead and then plug this lead into the TV.

Don’t worry if you can’t find a yellow socket on your TV to connect a VCR, as many new TVs don’t have one. Manufacturers think there is no need to supply TVs with the ability to connect a VCR through the standard (and old) yellow, red and white sockets. Instead some TV’s let you connect to the green socket, and others require you to use a HDMI input. I discuss each method below.

If there is a Green Socket

connect a VCR to new TV

At the rear or side of many flat screen TVs there is no yellow socket for “Video In”. But as you can see in this picture, they indicate you can use the green socket instead. Notice on this TV, (and most others) there is only one of the green sockets nominated as “Video in” for you to connect a VCR to.

So for this TV, you would connect the yellow lead from the VCR to the nominated green “Video in” socket. The red and white audio leads from the VCR would connect to the corresponding red and white audio sockets below the blue and red.

Be careful not to fall into the trap of connecting the red audio cable, to the other red socket labelled “Pr” – the right audio will not work if you do this. Also ensure you don’t connect anything to the blue or red video inputs or your VCR picture will be in black and white only.

Note that not all TVs label the “video in” as clearly as in the photo above. Some simply put a yellow circle around the appropriate green socket. Some use a combination of yellow and green. Others label this socket as “Composite Video”.

conenct a VCR with Composite Video

Composite Vs Component Video

You don’t need to understand this section – it is for those people who like to understand why it is possible to connect a VCR via the green socket.

The green, blue and red sockets labelled Y, Pb and Pr in the photos above are for connecting a DVD player. These three video signals are called “Component Video”. It is the best way of connecting a DVD player if the DVD player doesn’t have HDMI. The green input from a DVD player is basically the black and white picture. The blue and red inputs are for the colour information of the picture. Then the other red and white sockets are for the right and left audio.

The video signal from a VCR has the black and white picture and the colour information all joined together – called composite video.

Modern TVs are clever enough to know when you only have one lead connected with all the information (composite video) or separate leads (component Video).  Hence they don’t need to provide a separate input for Composite only. For a more detailed explanation of component video see this article, or this article to learn more about composite video.

Connect a VCR with HDMI only on the TV

Many new TVs do not have any analogue inputs. Therefore you need to use one of the HDMI inputs on the TV.  However you can’t connect your VCR directly to the TV. You need a converter box between the VCR and the TV.

The yellow, red and white lead from the VCR plugs into the input of the converter box. The output of the converter box connects to a HDMI lead. The other end of this lead will plug into one of the HDMI inputs of the TV. Note: Some converter boxes also require a USB lead to be plugged into the TV – this is used to power the unit. Other converter boxes receive power from the HDMI connection to the TV.

If you are going to buy a composite(RCA) to HDMI converter consider these tips:

  • Beware, many on-line searches return two types of converters: a RCA to HDMI converter and the reverse, a HDMI to RCA converter. To connect a VCR to a TV using HDMI, you need a RCA to HDMI converter.
  • You may also need to buy a short HDMI lead, if you don’t already have a spare one.
Click here to browse RCA to HDMI converters available from Amazon
Disclosure: If you buy through this link Geoff receives a small commission from Amazon

My VCR only has a white audio out

Connect a VCR mono audio

Many VCRs are not stereo, they are only mono. That is, they do not output a left and right audio channel. Instead they only output one single audio channel (mono audio). Therefore, they do not have a red and white audio output (for right and left audio). They only have a white output, for the mono audio. You may remember most old TVs only had one speaker, so the VCR only needed one audio channel (mono).

To connect a VCR with only mono audio to a flat screen TV, simply go from the “audio out” socket of the VCR.

That is the easy bit. How you connect to the TV will depend on the TV.

Connect a VCR - mono

Some TVs will have sockets on the back like this picture. On the left hand side you should see the Audio right (red) and left (white) input sockets. The left socket is also labelled “MONO”. If your TV is like this, then simply connect the “mono out” from the VCR to the “mono in” of the TV. The TV should direct the sound to both (left and right) speakers of the TV.

If your TV does not have a Mono input, then you have two or three options:

    1. You can simply connect the “mono out” from the VCR to the “Left in” on the TV. This will send the sound to the left speaker only. While you might think this is not ideal, you may be surprised that it sounds fine when sitting some distance from the TV. The red cable is not used if connecting to the TV this way – it can just hang on its own behind the VCR and TV.
    2. You Connect a VCR Mono adapter leadcan use a cheap mono to stereo adapter cable. The single (black) plug is connected to the white audio out of the VCR. Then a normal red and white audio lead is connected from the adapter cable to the right (red) and left (white) audio in sockets of the TV. This will send the same mono audio to both the right and speakers of the TV.
    3. You can also use a mono to stereo adapter plug. This plugs straight into the ‘Audio Out”Connect a VCR RCA splitter on the back of the VCR. Then a normal red and white audio lead is connected from the two sockets of the adapter to the right (red) and left (white) “audio in” sockets of the TV. This works exactly the same as the lead above – use whichever one is available to you.

Whichever way you connect the mono audio, you will hear the sound through the TV. Keep in mind that many video recordings were probably recorded in mono, so you are not missing much.

Don’t forget to also connect the yellow video lead from the VCR to the TV (as described above).

All Connected but no Picture

I get many questions from people who have connected their VCR to the TV by one of the above methods, but still get no picture. This could be due to a faulty lead or incorrect connections, but it could also be dirty heads on the VCR.

There is some simple tests to know if you have it all connected correctly. Insert a pre-recorded tape in the VCR and press play. Select “AV in” or similar on your TV

    1. First off, do you have sound? If so, you are probably connected correctly. At least the sound is working so you know you have selected the correct input on the TV.
    2. If you have sound but no picture, try stopping the tape and starting it again while looking at the screen. Do you see the little Play and stop icons? (some VCRs don’t display these). If you see the control icons on the TV, then you have the connections correct.
    3. Press stop on the VCR and press the “menu” button on the VCR remote (some older VCRs don’t have a menu). When you press menu, you should see it appear on the TV. If you do, then the connections are correct.

If you have sound, and see either the control icons and/or the menu on the TV, then the connections are correct. It probably means the VCR has dirty heads. This is very common with older tapes. If you do an internet search for “clean VCR heads”, you get to choose from over 3 million results. If any of those sound too technical for you, you can try playing the tape for a few hours. Quite often the gentle rubbing effect of the tape passing over the heads will eventually clean the heads. Be aware that no matter how you clean the heads, the next tape you insert might clog them up again – if the new tape has dirt or mildew on it.

If any of the above tests are negative, then you should cover the basics like try a different set of cables.

If possible, try using the same cables to the TV but connect them to another VCR or DVD player. This will confirm the cables are OK and the TV input is working and correctly selected.

There can be other issues with your VCR that prevent it showing a picture. There can be mechanical or electronic failures. A common fault is the rubber belts and capstans perish. These types of faults will require a proper service of the unit.

If you still have a problem to connect a VCR to your TV, list the details of the equipment and how you tried to connect them in the comments box below, and I’ll try to help you work through the issues.

How to Connect 2 Speakers to 1 Amplifier

Geoff
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195
How to Connect 2 Speakers to 1 Amplifier

In this article we look at how and when to connect 2 speakers in parallel or series. Both the theory and practical points on how to connect 2 speakers are discussed. Connecting 2 speakers in parallel or series to your amplifier is useful when:

  • you don’t need to turn each speaker on or off individually, or
  • you don’t need to have separate volume controls for each speaker.

If you need to turn each speaker on or off individually or have separate volume controls, you may need a speaker selector switch. In this case you should read the articles on connecting multiple speakers, wiring 4 speakers, and/or my summary of speaker selector switches.

conenct 2 speakers to stereo

Many people get confused when we talk about a stereo amplifier. A stereo amp simply has two amplifiers built into the one box. We are not talking about connecting two speakers to a stereo amp, as that simply involves connecting one speaker to each amplifier (left and right). There are many cases when you want to connect four speakers to a stereo amp, that is, to connect 2 speakers to each amplifier – or four speakers in total. For the rest of this article, when we talk about an amplifier, we are talking about either the left or right amplifier only.

You may want to connect 2 speakers to one amplifier without individual switching or volume controls if you:

  • have a large living area with four ceiling speakers, or
  • want to cover a large backyard with four speakers, or
  • have any situation where two speakers are not enough.

The are two basic ways of connecting two speakers together – either in series or parallel.

Should 2 speakers be connected in Series or Parallel?

Whether 2 speakers connected to one amplifier should be in series or parallel mostly depends on the impedance of the speakers.

Connect 2 speakers 8 ohms

The impedance of the speakers should be written on the back of the speaker or speaker box. The impedance of a speaker is normally 4 ohms, 6 ohms or 8 ohms. If it isn’t written on the back of the speaker, check any paper work that might have come with the speaker, or look up the specifications on the web. The Ω symbol is often used instead of writing “ohms”.

If both speakers are 8 ohms or more, then the speakers can normally be wired in parallel.

If the speakers are less than 8 ohms, then to be safe, you should wire them in series.

Connect 2 Speakers in Parallel

To calculate the total load impedance of speakers in parallel, see my Speakers in Parallel Calculator.

If both speakers are 8 ohms or more, then it is normally safe to connect them in parallel. This is because two 8 ohm speakers in parallel makes the total load impedance 4 ohms. Most HiFi amps are designed to have a total load impedance of 4 ohms or higher, but not lower than 4 ohms. If your amp is not specified for 4 ohms (some are 6 ohms or 8 ohms minimum), then you should consider wiring your two speakers in series.

This diagram helps show why speakers connected this way are called “in parallel”

Connect 2 speakers in parallel

They are known as being in parallel because, well, they are wired in parallel. Admittedly, I’ve drawn them so they look like being in parallel. However, in practice, we wouldn’t use so many cables and connections. For practical ways of connecting 2 speakers in parallel, see the table below.

If your amplifier has an A and B speaker selector, you can use this for a simple way of connecting two sets of speakers in parallel.

Connect 2 Speakers in Series

To calculate the total load impedance of speakers in series, simply add the impedances together

If both speakers are less than 8 ohms, or the amplifier requires a total load impedance greater than 4 ohms, then it is best to connect the speakers in series. This is because two 4 ohm speakers in series makes the total load impedance 8 ohms. Two 6 ohm speakers in series makes the total load impedance 12 ohms. Most amps work fine with a load impedance of 6-16 ohms.

This diagram helps show why speakers connected this way are call “in series”

Connect 2 speakers in series

As you can see, the two speakers are in “series” with the each other.

How to Connect 2 speakers in Parallel and Series

Below is a table showing how to wire up two speakers in parallel and series for common scenarios. Keep in mind these diagrams are for one amp only (let’s say the left amp), you will need to duplicate this for the right amp also.

If you double click on a diagram you should see a slightly larger version for easier viewing.

Practical Ways to Connect 2 Speakers in Parallel and Series
When all cables are run back to the amplifier location
Connect 2 speakers in parallel
Parallel: Both speaker cables are connected directly to the amplifier
Connect 2 speakers in series
Series:Join two of the wires as shown separate to the connections on the amp.
When the second speaker needs to be connected off the first speaker
Connect 2 speakers in parallel
Parallel: Join the cables of the second speaker to the cables on the first speaker
Connect 2 speakers in series
Series: Cut one wire near the 2nd speaker, and connect the 2nd speaker "in series" with the cut wire.
When there is a (long) cable run to be split to go to both speakers
Connect 2 speakers in parallel
Parallel: Join the cables from both speakers to the cable from the amplifier
Connect 2 speakers in series
Series: Join the two speakers in series, then join this to the feed cable
When the cables from each speaker come back to a wall plate
Parallel: Simply join the terminal as shown
Parallel: Simply join the terminal as shown
Connect 2 speakers in series
Series: The series connection is made with one join

You may have noticed that no matter which scenario is used, all the parallel diagrams are technically wired the same as each other – if you doubt me, trace the connections with your fingers on any two of the parallel connection methods. You can do the same for the series connections below as they are also the same as each other.

Keep in mind that changing the total load impedance of an amplifier will increase or decrease the power output of the amplifier. Connecting in parallel normally increases the output power, while a series connection normally decreases the power output of an amplifier. See Multiple Speakers Change Amplifier Power for more details.

Each speaker may have a different sensitivity which may mean there will be a level difference between them. For more on this see Understanding Speaker Sensitivity.

Also if the speakers each have a different impedance, then there will be different power levels available to each speaker. For more detail see How Multiple Speakers Share Power. My calculators for Speakers in Parallel and Speakers in Series also calculate the way speakers with different impedances share power.

Summary of Connecting 2 speakers

There are only really two ways to connect 2 speakers to one amplifier – either in parallel or series.

download article

If each speaker has an impedance of 8 ohms or more, then you can generally connect them in parallel.

If each speaker has an impedance below 8 ohms, you should wire them in series.

If you need to switch each set of speakers on or off, or you want separate volume controls, see my articles on connecting multiple speakers, wiring 4 speakers and/or my speaker selector switch summary

Click here to browse 2 way speaker selector switches available from Amazon
Disclosure: If you buy through this link Geoff receives a small commission from Amazon

Speaker Selector Switch Summary

Geoff
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60
Speaker Selector Switch Summary

Speaker selector switches are the most common item bought from Amazon through this website (with over 1000 units sold). Therefore I thought it is high time to look a little deeper at the different speaker selectors and the features available. I also present a table (or 3)  outlining the models, features, price and popularity of what readers have bought.

The main reason speaker selectors are used is to distribute sound to multiple speakers while protecting the amplifier from too much load (due to too many speakers).

Please note, speaker selector switches are designed for multi-room installs in a home or small low power installs (like an office or cafe). They are generally suited for low power (under 100 watts) amplifiers. They should be not be considered in a commercial install or for use with high output power amplifiers.

For a more detailed explanation of the issues regarding speaker load and impedance, see my article on connecting multiple speakers to your HiFi. For an explanation on using the various type of speaker selectors and how to wire them, see my article on wiring 4 speakers.

For a good overview on speaker impedance and how speaker selector switches help overcome the issues, watch the video (particularly the 2nd half) in Understanding Speaker Impedance.

Protecting the Amplifier with a Speaker Selector

There are two main technologies employed by a speaker selector to protect the amplifier from overloading due to a low load impedance:

  1. Series Resistor: this is used on lower cost speaker selector switches. It normally means there is a resistor (4-6 ohms) wired in series with the speakers. This gives the total circuit a minimum resistance which will protect the amplifier. However, this resistor gets hot at higher volume levels. That is why most speaker selectors using a series resistor for impedance “matching” have air vents in the chassis. Obviously there is some energy lost in these resistors as they produce the heat. Most speaker selector switches employing a series resistor have a “protection” or “impedance protection” switch. This switches the series resistor in and out of the circuit.speaker switch protection switch When you are using more than one set of speakers at the same time, the “protection” switch should be activated. When only one set of speakers are being used, or you are using impedance matching volume controls, the series resistor can be switched out to allow “direct connection” with no losses.
  2. Impedance Matching Transformer: this is used on higher power and higher cost speaker selector switches. An impedance matching transformer inside the speaker selector multiples the impedance of each speaker which effectively keeps the total impedance around the same as any of the individual speakers (providing the speakers are the same impedance as each other).  For example: a 4 zone speaker selector with an impedance matching transformer would multiple each of the 8 ohm speakers by four (making them appear as 32 ohms), and 4 lots of 32 ohm speakers in parallel makes a total impedance of 8 ohms. As one of the speaker selector promo says, they “maintain a safe operating load at the amplifier while distributing maximum power throughout your system“. There normally is not by-pass switch on a speaker selector with impedance matching transformers.

A few speaker selector switches connect the speakers in various series and parallel combinations to limit the overall impedance. These should only be used with 8 ohm speakers.

Some very budget speaker selector switches have no impedance protection what-so-ever. They are just a switch turning each speaker on or off. These are not recommended.

For a better understanding of how the different types of speaker selector switches work, see my Speaker Selector Switch Simulators. These show how each type helps with impedance, as well as how they distribute power to each speaker.

The Ins and Outs of a Speaker Selector

6-channel-speaker-switch

A speaker selector is normally known by how many pairs (left and right) of speakers can be connected to it. Each pair of speakers is normally in a different room, or zone.  Hence, a speaker selector might be a 4 zone, or a 6 zone speaker switch. Sometimes they are also referred to as 4 way or 6 way. This means they are capable of connecting 4 pairs or 6 pairs of speakers respectively. Be aware some manufacturers also confusingly use the word “channels” for the number of output pairs their speaker switch can connect to.

Some speaker selector switches connect to one stereo amplifier, allowing the speaker selector to connect the one amplifier to each speaker connected to it. This allows the same program (music etc) to be heard in every zone or room.

Other speaker selectors allow two different amplifiers to be connected to them. Then for each zone, you can select amplifier A or amplifier B. These speaker switches are marketed as having A/B inputs. Using two amplifiers with different programs allows each zone to select between the two programs available.

Other Features

Other features often promoted for a speaker selector are:

Volume Controls: These allow the volume of each zone to be separately controlled at the unit.

Power Handling: This states the maximum power (RMS) per channel of the amplifier that should be used with the selector.

Labels: Some manufactures supply pre-printed labels that make your installation look professional.

Speaker Selector Types

There are 4 basic types of speaker selector switches sold by Amazon through this website:

  • Simple Speaker Selector Switches: these simply switch between 2 or more sets of speakers (60% of units sold)
  • Speaker Selector Switch with volume control: As well as switching between 2 or more zones, they have separate volume control for each zone (20% of units sold)
  • Speaker Selector Switch with A/B amplifier input selection (0.5% of units sold).
  • Speaker Selector Switch with volume controls and A/B selection (20% of units sold).

How Many Zones?

Speaker selector switches are also categorized by how many zones (or channels of speakers) they can switch. Readers of this website who have purchased speaker selectors from Amazon have mostly bought 4 zone selectors, but other configurations are also useful:

  • 2 way selectors are useful when the speakers are only 4 ohms, as two sets of 4 ohm speakers is too much load for most amplifiers (13% of units sold).
  • 4 way selectors are the most popular. These can be used for 2, 3 or 4 zones (66% of units sold).
  • 5 way, 6 way, 8 way or 10 way speaker selector switches can be used to wire many speakers. With this many speakers, impedance protection is very important (21% of units sold).

The following tables list the speaker selector switches bought from Amazon through this website. I’ve added as much helpful information as possible including:

  • the supplier/seller
  • the model number and/or description of the product
  • the maximum RMS power (watts) the unit can handle from each channel of the amplifier(s) connected to the selector switch.
  • the average price of each product bought from Amazon
  • the percentage of sales of each item in its class (2, 4 or 5+ zones) through this website
  • a description of the impedance protection method used, warnings and features
  • a link to download the manual, if I’ve been able to locate one
  • a link to each item on Amazon – click on each picture to go to that item on Amazon for further information. If your locality Amazon store doesn’t stock the exact item, the link will take you to a list of similar items which they do stock. Disclosure: If you buy through the Amazon links Geoff receives a small commission from each sale.

If you don’t see the link pictures, please turn off any add blocker you may have installed on your browser

Summary of 2 way Speaker Selector Purchases

ItemWatts
per Ch.		Avg.
Price		% SoldCommentsImage
(click to view
at Amazon)
Monoprice 108231
2 channel A/B speaker
selector with volume		50$62.6631%Uses Impedance matching
volume controls
Monoprice Speaker Selector Manual (with volume)
Download Manual3326 Downloads
Niles SSVC-2
speaker selector with
volume		100$117.0023%Uses Impedance matching
transformer
Niles SSVC Manual
Download Manual4622 Downloads
OSD SSVC2
2 zone A/B with
volume		50$88.604%Uses Impedance matching
volume controls
OSD SSVC Manual
Download Manual3233 Downloads
YIS
2 pair speaker
selector switch		50$28.9531%No information on
impedance protection
Keen-Eye
A/b a B A+b
Stereo speaker
switcher combiner		10$17.508%No information on
impedance protection
Disclosure: If you buy through the Amazon links Geoff receives a small commission from each sale.

Summary of 4 way Speaker Selector Purchases

ItemWatts
per Ch.		Avg.
Price		% SoldCommentsImage
(click to view
at Amazon)
Simple Speaker
Selector Switches
Monoprice 109995
4 channel Speaker
selector		70$26.8827%Uses 5 ohm Series Resistor
Monoprice 9995 Manual
Download Manual2825 Downloads
Pyle PSS4
4 Channel Switch		100$30.5315%Uses Series Resistor
Pyle PSS Manual
Download Manual3324 Downloads
Part Express SS4
4 zone Switch		70$36.6510%Uses 5 ohm Series Resistor
Parts Express SS4, SS6, SS8 Manual
Download Manual2042 Downloads
Radio Shack
Four Way Switch		50$14.365%Uses series – parallel switching
Not recommended to use with
4 ohm speakers
Radio Shack Speaker Selector Manual
Download Manual7033 Downloads
Niles SS-4
Speaker selector		100$69.963%Uses 2.5 ohm Series Resistor
72 Labels supplied
Niles SS speaker selector Manual
Download Manual2348 Downloads
OSD ISS4
4 Zone Speaker
selector		70$48.772%Uses Series Resistor
OSD ISS Speaker Selector Manual
Download Manual2332 Downloads
Wired Home SS4
Speaker Selector		70$29.902%Uses 5 Ohm Series Resistor
Wired Home SS speaker selector Manual
Download Manual1742 Downloads
Niles HPS-4
High Power
Speaker selector		250$140.951%Uses 2.5 ohm resistor
72 Labels supplied
Niles High Power selector Manual
Download Manual2168 Downloads
Sima SSW4
4 Speaker Selector		100$38.941%Uses 3 ohm series resistor
Labels supplied
Sima SSW Speaker Selector Manual
Download Manual2393 Downloads
Monster Cable
SS4
Multi-Speaker
selector		150$99.991%Uses series resistor
Monstor Cable Mulit-Speaker Selector Manual
Download Manual7865 Downloads
Speaker Selector
Switches with
Volume Controls
Pyle PSPVC4
4 Zone with
volume control		100$115.9913%Uses Impedance matching
transformer, for use
with 8 Ohm speakers
Pyle PSPVC Speaker Selector Manual
Download Manual2900 Downloads
Niles SSVC-4
4 Channel with
volume control		100204.357%Uses Impedance Matching
Transformer
Includes 72 labels
Niles SSVC Manual
Download Manual4622 Downloads
Speaker Selector
Switches with A/B
Inputs and
Volume Controls
Monoprice 108232
4 Channel A/B
with Volume		100$83.078%No information on
impedance protection
Includes labels
Specialty AV
600 watt 4 Zone
A/B with Volume		200$169.954%Uses high power rating
impedance matching
transformer
Disclosure: If you buy through the Amazon links Geoff receives a small commission from each sale.

Summary of 5+ way Speaker Selector Purchases

ItemWatts
per Ch.		Avg.
Price		% SoldCommentsImage
(click to view
at Amazon)
Simple Speaker
Selector Switches
Pyle PSS6
6 Channel Switch		100$39.2927%Uses Series Resistor
Pyle PSS Manual
Download Manual3324 Downloads
Pyle PSS8
8 Channel Switch		100$47.7016%Uses Series Resistor
Pyle PSS8 Speaker Selector Manual
Download Manual2013 Downloads
Dayton Audio SS6
Speaker Switch		70$47.722%Uses 5 ohm Series ResistorCurrently not available
Sima SSW-6
6 zone selector		50$41242%Uses Series Resistor.
Includes lables
Sima SSW Speaker Selector Manual
Download Manual2393 Downloads
Speaker Selector
Switches with
Volume Controls
Niles SSVC-6
6 Channel with Volume		100$239.0016%Uses Impedance Matching
Transformer.
Includes 72 labels
Niles SSVC Manual
Download Manual4622 Downloads
Theater Solutions
TS6DV 6 Zone with
volume control		300$120.992%Has 2 inputs but only able to
select one input at a time.
No individual input switch
for each zone.
Speaker Selector
Switches with A/B
inputs and
Volume Controls
Specialty AV
2 x 5 Zone
with A/B & Volume		100$209.959%Uses high power impedance
matching transformer
Monoprice
108230
Speaker Switch		100$37.589%Uses Series Resistor
Specialty AV
2 x 6 Zone
with A/B & Volume		300$159.955%Uses heavy duty impedance
matching transformer
Pyle PSPVC6
6 Channel Speaker
Selector		50$153.995%No Information on
impedance protection
Pyle PSPVC Speaker Selector Manual
Download Manual2900 Downloads
Specialty AV
10 Zone/pair
with A/B & volume		500$259.952%Uses heavy duty impedance
matching transformer
Theater Solutions
TS6DV
Dual Source selector		300$122.722%No Information on
impedance protection
Labels Included
Disclosure: If you buy through the Amazon links Geoff receives a small commission from each sale.

Use the above summary information as a guide only. There are also many other models of speaker selector switches available. Additionally, Geoff has written a review of the Audioflow series of switches which are controllable through your smartphone or Alexa.

If you have an install you need further advice on, please read the FAQs before submitting your question. Alternatively, you may find a similar install in the comments below.

Understanding Distributed Speaker Systems

Geoff
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152
Understanding Distributed Speaker Systems

Distributed speaker systems are also known as “100 volt line” or “70 volt line” speaker systems. They are used extensively where multiple speakers are required. Distributed speaker systems are commonly used in airports, shopping centers, schools, churches, clubs, offices, car-parks, sports grounds and anywhere multiple speakers are required. They can also be used in homes for background music systems.

Advantages of Distributed Speaker Systems

The main advantages of distributed speaker systems are:

  • No need for complicated calculations of total speaker impedance – simply add together each speaker’s wattage (see below for more details)
  • Many speakers can be connected to an amplifier.
  • Extra speakers can normally be added to the system
  • The volume of each speaker can be adjusted independent of the main volume (so the toilet speakers are not as loud as the foyer speakers).
  • Smaller cables can be used. Distributed speaker systems use much less current through the speaker cables
  • Longer speaker cables are possible with minimal line loss. Cables runs can be 100’s of metres or 1000’s of feet.

Disadvantages of Distributed Speaker Systems

The main disadvantages of distributed speaker systems are:

  • Each speaker requires a step-down transformer
  • The transformers affect the quality of the sound – typically the lower frequencies are not transferred as well as a speaker system without transformers.
  • Without using expensive transformers, use is often limited to paging, voice and low level (background) music installations.

Distributed Speaker Systems Overview

The basis of distributed speaker systems is similar to the way electricity is distributed. Power stations use step up transformers to distribute power as high voltage, which means low current, and therefore low line losses and thinner cables. Each town and/or street then converts this high voltage/low current down to low voltage/high current (through step down transformers) for use in your home.

Distributed speaker systems use a similar principle. The amplifier normally has a step-up transformer built into it, producing a high voltage/low current output. Then each speaker has its own step down transformer to convert the signal back to low voltage/high current. This allows the cable to be very long without having any significant line losses.

distributed speaker systems overview

100 Volt Line Speaker System

The most common “high” voltage used in distributed speaker systems is 100 Volts. In many countries distributed speaker systems are known as “100 Volt line” speaker system.  In a 100 Volt line speaker system the output of the amplifier is marked “100 volt”. Indeed at full output, the amplifier puts out 100 volts RMS. Each speaker then has a transformer to reduce the 100 volt line level down to normal speaker level.

70 Volt  Line Speaker System

In North America the most common “high” voltage for distributed speaker systems is 70 Volts. This is because years ago, some states had laws stating that any cable with a maximum voltage greater than 100 Volts peak had to be installed in conduit. This was time consuming and costly to install. So they developed a system where the output voltage of the amplifier was a maximum of 100 Volts peak. This equates to 70.71 Volts RMS. This is commonly known as a “70 Volt line” speaker system. The principle is the same as for 100 volt line systems, but uses a maximum output voltage of 70 Volts. While 70 volt line systems are still the most common in the USA, some 100 volt lines systems are being used.

50 Volt Line and 25 Volt Line Speaker Systems

distributed speaker systems terminals

Less common, but still seen on some amplifiers and speakers are 50 volt line or 25 volt line settings. The principles are the same for all voltages, but the lower the voltage, the more current, therefore the shorter the maximum cable length without significant line losses.

In practice, many commercial amplifiers  and speakers have multiple taps. They may have 100 and 70 Volts, or 70 and 25 Volts, as well as 4 ohm and 8 ohm outputs for normal speakers (without transformers). Normally you should only use one output of a amplifier, that is, either the 100 volt line output, or the 70 volt line output or the 8 ohm output, not all at the same time.

Transformers

Every speaker in distributed speaker systems needs to be connected to a step down transformer. This converts the high voltage level down to normal speaker level.

One side of the transformer normally has a common (or “0 volts”) and a 4 ohm and 8 ohms connection.  An 8 ohm speaker would be connected to the common and 8 ohm taps, while a 4 ohm speaker would be connected to the common and 4 ohm tap.

Most transformers have a selection of input taps. The example in this picture has taps for 20 Watts, 15 Watts, 10 Watts and 5 Watts. The feed cable is connected to the common and any one of the other taps. This allows the relative volume of the speaker to be set during the installation. For example the speaker in a high noise room might be set on 20 Watts, while the speaker in a small, low noise area might be set on 5 watts. Alternatively, the distance between the speaker and the target audience might be different, so the speakers further away can be set at a higher power tapping (or the close speakers at a lower power tapping). To help in determining the correct tap for each speaker in every situation, see my SPL calculator for distributed speaker systems.

All amplifiers designed for use with distributed speakers systems have a step-up transformer built-in. It is also possible to add an external transformer to an amplifier without an integrated transformer. Simply use a speaker transformer in reverse – that is, connect the common and 8 ohm transformer connection to the common and  8 ohm speaker output of the amplifier.  Just make sure the amplifier and transformer are rated with enough power to drive all the speakers to be connected (see Connecting Multiple Speakers below).

Amplifiers

As stated above, most amplifiers designed for distributed speakers systems have the output transformer built-in. They may have various outputs for 100 volts, 70 volt and/or 4 or 8 ohms (for normal speakers).

Most 70 volt amplifiers or 100 volt amplifiers also have an input mixer built-in. This allows convenient connection of microphones and line level inputs. Ensure the model you use has sufficient inputs for your current needs, and perhaps some spare inputs for the future.

For multi-zone systems, you can purchase an amplifier with 2 or 4 amplifiers and transformers built in the one box.

Click here to browse 70V/100V amplifiers available from Amazon
Disclosure: If you buy through this link Geoff receives a small commission from Amazon

Speakers

ceiling spkr for distributed speaker systems

Any speaker can be used in a distributed speaker system, as long as a step-down transformer is used. Many manufacturers produce speakers with integrated transformers for use in distributed speaker systems.

Ceiling Speakers

Ceiling speakers are used in many distributed speaker system installations to cover large areas and/or multiple small rooms or areas. The speaker cable is normally connected directly to the transformer.  To change the power settings you need to connect the speaker cable to a different transformer tap. In the speaker pictured, this is a simple matter of moving the speaker wire to a different terminal connector.

Click here to browse 70V/100V ceiling speakers available from Amazon
Disclosure: If you buy through this link Geoff receives a small commission from Amazon

Wall Mount Speakers

100 volt box speaker for distributed speaker systems

Wall mount 70V100V speakers come in all sorts of shapes and sizes. Many manufactures make a version of their cabinets with an integrated transformer. Connections are often by some form of speaker terminals. To change taps, simply rotate the switch to the desired power setting. Often these switches also have a position for 8 ohms (bypassing the transformer) – this makes them very versatile speakers for the installer. Wall mount speakers (which can also be mounted from a ceiling) are used where ceiling speakers aren’t practical, or where higher sound levels are required.

Click here to browse 70V/100V wall mount speakers available from Amazon
Disclosure: If you buy through this link Geoff receives a small commission from Amazon

Horn Speakers

rear of horn speaker for use with distributed speaker systems

Horn speakers are very efficient, but not very good quality. They are mostly used outdoors when coverage of a large, or high noise, area is required. For example in car parks, sports grounds, school yards and other outdoor areas. In the picture shown, the rear of the horn has a selector switch which needs a flat bladed screw-driver to operate. This is useful to reduce the likelihood of inadvertent changing of the settings after the install.

Connecting Multiple Speakers

This is the fun bit, because there is no need to calculate the total impedance. To connect multiple speakers in distributed speaker systems, just wire them all in parallel and add up the total watts.

Example 1: A PA amplifier is rated at 120 watts @100 volt line. Therefore you could connect:

  • 20 x 5 Watt (100 volt) ceiling speakers (total 100 Watts), or
  • 40 x 2.5 Watt (100 volt) ceiling speakers (total 100 Watts), or
  • 10 x 5 Watt (100 volts) ceiling speakers and 20 x 2.5 Watts (100 volt) ceiling speakers (total 100 Watts), or
  • any combination of speakers that add up to no more than 120 Watts.

Example 2: A small church has a small 25 Watt (70 Volt) PA amplifier with 4 small speakers mounted in the church (2 down each side). They now want to add a speaker in a separate room for an overflow and creche area.

  • 4 existing speakers can be wired at 2.5 Watts (70 Volt), total of 10 Watts
  • A new box speaker can be wired at 10 Watts (70 Volt), this allows it to be louder than any of the small church speakers (since the creche area has much more ambient noise levels).

As shown, it is easy to add the individual speaker watts together. This is much easier than calculating the total impedance.This makes installation much simpler.

Calculating Watts from Speaker Impedances

Sometimes manufacturers of speakers designed for distributed systems only mark their speakers with the impedance of each tap, rather than the Watts. Also, many impedance meters tell you the impedance, and you need to calculator the wattage.

In either case, you can use this simple calculator:

Tips for Using Distributed Speaker Systems

Following are some practical tips for installing distributed speaker systems:

  • Keep all the speakers in phase. This means the the “O volt” or the “Com” of the amplifier speaker terminal should be connected to the “O Volt” or “Com” of each speaker transformer.
  • It is good practice to design distributed speaker systems to use up to only 80% of the amplifier’s total available power. For example, a 120 Watt PA amplifier should only be connected to a maximum of around 100 Watts of speakers. This helps avoid the amplifier’s transformer distorting from saturation (overload), allows for inefficiencies in the system, and allows an extra speaker to be added if required in the future.
  • When designing distributed speaker systems, calculate the total watts of the speakers, and select an amplifier larger than required. For example, If an install requires 10 speakers at 5 Watts each (total load of 50 Watts), a 60 Watt amplifier could be used, but selecting a 100 Watt or 120 Watt amplifier will allow speaker taps to be changed or extra speakers added in the future. It is a relative small increase in price to up-size the amplifier before purchase, rather than have to buy a new one later.
  • When selecting speakers, chose a higher power one than required. For example: If a 5 Watt ceiling speaker is required, chose a 10 Watt or 15 Watt speaker and use the 5 Watt tap on the transformer. This again reduces the likelihood of overloading cheaper transformers, and gives the ability to increase the power level (volume) if required.
  • When connecting many speakers, it is good to have multiple feed cables. For example; if connecting 60 speakers, it is possible to use one speaker cable run and loop in and out of each speaker. However it is better to have several feed cables to smaller groups of speakers. This way if a fault occurs, it is easier to isolate which feed the fault in on. Also the total load (and cable loss) is shared by each cable run. If you have long cable runs, see my Cable Loss Calculator to ensure you use the right size cable.
  • It is possible to get some speakers with a built-in attenuator to control the volume of the speaker. This is useful in situations when you want the listener to control the volume. For example in a creche. It is also possible to get external attenuators to control the volume in a room or for an individual speaker. 
  • If possible, measure the impedance of each speaker feed cable before connecting the amplifier. This is best done with an impedance meter. If installing a number of distributed speaker systems, an impedance meter is very useful.
  • Don’t connect a 4 ohm or 8 ohm speaker directly to a 100 volt line or 70 volt line speaker cable. Apart from severely overloading the speaker (and possibly burning it out) a 4-8 ohm speaker effectively puts a short circuit on the speaker line and overloads the amplifier. See the calculations below for the mathematical explanation of this.
  • If a 100 Volt line amplifier is overloaded, connecting the load to the 70 Volt line effectively halves the load on the amplifier and it will not be overloaded. However the maximum power to each speaker (and therefore the speaker output) is reduced by 3dB.
    • Example 1: The total watts of all the (100 Volt) speakers totals 200 Watts. If connected to the 100 Volt line speaker terminals of a 120 watt (100 Volt) amplifier, the amplifier will be overloaded. Connect the same speakers to the 70 Volt line terminals of the same 120 watt amplifier and the amplifier will only see a load of 100 Watts.
    • Example 2:  The total watts of all the (70 Volt) speakers totals 50 Watts. If connected to the 70 Volt line speaker terminals of a 40 watt (70 Volt) amplifier, the amplifier will be overloaded. Connect the same speakers to the 50 Volt line terminals of the same 40 Watt amplifier and the amplifier will only see a load of 25 Watts.
    • You can use the calculator above to see this by selecting the different system voltages. For those whose like to know, the mathematical explanation of this is below.

Summary

Distributed speaker systems are ideal for multiple speaker installations. They allow long speaker cables and calculation of the total load is easy. Distributed speaker systems are normally mono (not stereo). They are mostly used for paging and background music situations. Although normally used for commercial installations,  they can be used in domestic installations for background music systems

Below are some of the major calculations used with distributed speaker systems (you can stop reading now if you are not into calculations).

Calculations for Distributed Speaker Systems

The following calculations are for those who like to understand the mathematics behind the principles outlined above. You don’t need to understand these calculations to use distributed speaker systems, but it will help you understand and design systems better.

Several principles of distributed speaker systems have been outlined above. A mathematical explanation of each principle is now given under the following sub-headings:

Adding the Power of Each Speaker

As an example, four 5 Watt speakers are connected together (in parallel) to a 100 Volt line amplifier.

The simple way to calculate the total load is to add 5 + 5 + 5 + 5 = 20 Watts.

The harder way (which is why its not normally done) is to calculate the impedance of one speaker, and then calculate the total impedance of 4 such speakers in parallel, and then calculate the total power.

So the impedance of a 5 Watt speaker on a 100 volt line:

Impedance={\Large\frac{Volts ^2}{Power}=\frac{100 ^2}{5} = \frac{10,000}{5} =}\, {\large 2,000}\, ohms

That’s right, the impedance of a 5 Watt speaker with a 100 volt transformer is 2,000 ohms. Now to calculate the total impedance of four of these connected in parallel:

\frac{1}{R_{Total}}= \frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+\frac{1}{R_4}  so  \frac{1}{R_{Total}}= \frac{1}{2000}+\frac{1}{2000}+\frac{1}{2000}+\frac{1}{2000}=\frac{1}{500}

therefore R (total) = 500 ohms.

Now the total power of 100 Volts with a total impedance of 500 ohms can be calculated:

Power={\Large\frac{Volts ^2}{Impedance}=\frac{100 ^2}{500} = \frac{10,000}{500} =}\, {\large 20}\, Watts

Low and behold, that is the same as simply adding the speaker watts together – which is much simpler!

Changing the Amplifier Connection Halves the Load

Example 1: The total impedance of 200 watts of 100 Volt speakers can be calculated:

Impedance={\Large\frac{Volts ^2}{Power}=\frac{100 ^2}{200} = \frac{10,000}{200} =}\, {\large 50}\, ohms

Now look what happens when that same 50 ohm speaker load is connected to the 70 Volt terminal of the amplifier:

Power={\Large\frac{Volts ^2}{Impedance}=\frac{70.71^2}{50} = \frac{5,000}{50} =}\, {\large 100}\, Watts.

Amazing, the same 50 ohm load draws 200 watts of power on a 100 volt line system, but only 100 watts on a 70 volt line system.

Example 2: The total impedance of 50 watts of 70 Volt speakers can be calculated (remember 70 Volt line is actually 70.71 Volts):

Impedance={\Large\frac{Volts ^2}{Power}=\frac{70.71 ^2}{50} = \frac{5,000}{50} =}\, {\large 100}\, ohms

Now look what happens when that same 100 ohm speaker load is connected to the 50 Volt terminal of the amplifier:

Power={\Large\frac{Volts ^2}{Impedance}=\frac{50^2}{100} = \frac{2,500}{100} =}\, {\large 25}\, Watts

This principle is very handy to the installer if the power required by the speaker load is greater than what the amplifier can deliver. Simply move to the lower line voltage speaker connection (on the amplifier) and the power drawn is halved. The maximum power to each speaker is also halved, so the speaker output is halved, or reduced by 3dB, but the amplifier will not be overloaded.

A 8 Ohm Speaker will Overload a Distributed Speaker System

In the examples above we saw the speaker impedance of distributed speaker systems is reasonably high. For example a 5 watt speaker on a 100 Volt line has an impedance of 2,000 ohms. Even a 125 Watt load of 100 Volt speakers is 80 ohms. So imagine the load if the total impedance is only 8 ohms. It should be 10 times the load right? This scenario can be calculated:

Power={\Large\frac{Volts ^2}{Impedance}=\frac{100^2}{8} = \frac{10,000}{8} =}\, {\large 1250}\, Watts

That’s right, connecting a low impedance speaker (4 or 8 ohms) to distributed speaker systems will drastically increase the load on the amplifier.

Speakers in Parallel Calculator

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Speakers in Parallel Calculator
Jump Straight to Calculator

The calculator below is useful in determining the total impedance of speakers in parallel. It also calculates how the power is shared between the speakers.

If all the speakers have the same impedance, the calculation is relatively easy. 

Simple Impedance Calculation for Speakers in Parallel

If all the speakers in parallel have the same impedance, then simply divide the impedance by the number of speakers in parallel.

Example 1: Four 8 ohm speakers in parallel: 8 divided by 4 = 2 ohms.

Example 2: Two 4 ohms speakers in parallel: 4 divided by 2 = 2 ohms.

Not so Simple Calculations for Speakers in Parallel

For calculations involving speakers in parallel with different impedance, the following formula is required (it can be used with speakers of similar impedances too).

If you have a calculator with 1/x button then this calculation is not too difficult. If you don’t have that function on your calculator, or if you don’t like formulas, check out the calculator below.

Using the Calculator

The calculator can be used for 2, 3 or 4 speakers wired in parallel. 

Simply type the impedance of each speaker into the white boxes (or use the drop-down values). Use N/A for unused speakers in this calculator. The total impedance will be calculated for the entered speakers.

Also calculated for each speaker is its percentage share of the amplifier’s output power. This is useful as power sharing is a consideration when using speakers with different impedance.

“Power Differential” is the final calculation. This calculates in dB (decibels) the power level difference between the highest and lowest power as it is shared across the speakers. This shows the power level difference when using speakers with different impedance.

Amplifier Power Calculator

The bottom section of the calculator helps in matching the speaker combination with your amplifier. This is not necessary if you only want to know the total impedance and/or the power ratios.

However if you are connecting these speakers to your amplifier, it may be helpful to input the amplifier power and the associated speaker impedance. In the specifications for your amplifier, it should say something like:

Amplifier power: 80 watts continuous average power @ 4 ohms (2 channels driven, THD 0.08%, 20Hz-20kHz)

This tells you the maximum continuous power the amplifier will deliver into a 6 ohm load is 80 watts. In the calculator below, for this example, you type in 80 for the power and 6 for the impedance. Be advised, some specifications state RMS power rather than continuous power. These are effectively the same.

The calculator will display the effective power of the amplifier for the calculated total impedance of the speakers in parallel. Also displayed (under each speaker’s power %) is the actual maximum power the amplifier will supply each connected speaker. A comment on the suitability of the calculated total impedance for your amplifier is also provided.

Note: the calculator is best viewed in landscape mode on phones and small screens

Download Calculator
as Excel File
Prices in US$

Note: the calculated output power for the amplifier is based on a theoretical “ideal” amplifier. In practise, your amplifier may produce slightly more or less power.

Need to know more?

This calculator will help you understand the total speaker load on your HiFi amplifier. For a better understanding of this and what to do about it, read the articles How do I Connect Multiple Speakers to my HiFi Amplifier and How to wire four HiFi speakers or How to connect 2 speakers to one amplifier or watch the video in the article Understanding Speaker Impedance.Also see How Multiple Speakers Share Power for further details about the percentage power calculations. For more details about the effective amplifier power at higher impedance loads, see How Impedance Changes Amplifier Power.

If you need to calculate the impedance and power sharing of speakers in a different configuration, you can use my Speakers in Series Calculator, or the Speakers in Series/Parallel Calculator.

Please Note: all these calculations are for connecting manufactured speakers (boxes). They are not used when building your own speaker boxes and connecting multiple speakers in a cabinet using a crossover circuit. A crossover splits the signal into different frequencies for each of the speakers and makes the total impedance calculation complex (as impedance is frequency dependent). That is why speaker designers get the big money, and as installers we benefit from their expertise.

If you need further advice on connecting speakers (boxes) in parallel, please read the FAQs before submitting your question. You may also find an answer in the comments below.

Decibel Calculator for Audio (voltage)

Geoff
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3
Decibel Calculator for Audio (voltage)

small calculatorIf you don’t like formulas then you definitely won’t like the formula for calculating voltage ratios expressed in decibels.

So, use the following calculators to get a handle on the decibels with different input and outlet levels.

These calculators also show you the theoretical values for resistors to make your own inline audio attenuator, and a calculator to show you the actual dB attenuation with any two real world resistors.

Note: the calculator is best viewed in landscape mode on phones and small screens

Decibel calculator
Circuit for simple audio attenuator – the value of the resistors are calculated above

For a better understanding of what all this means, read the articles on Understanding Decibels  Part 1 and Part 2.

For those who need to know, the basic formulas used for these calculators are :

\Large{dB = 20 Log_{10}\left(\frac{output\, level}{input\, level}\right)}

and

\large{Attenuation\ Ratio=\frac{\left(Resistor\,1+Resistor\,2\right)}{Resistor\,1}}

 

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