Connecting Speakers FAQs

After answering nearly 1000 questions on connecting speakers on this website, some common themes have emerged.

Please read the answers to these Frequently Asked Questions (FAQs) on connecting speakers before asking your own.

If you have 2 speakers wired in series, then simply add their individual impedance together. For example: A 4 ohm speaker in series with a 8 ohms speaker: 4 + 8 = 12 ohms.

If you have 2 or more speakers in parallel and all the speakers are the same impedance, then divide that impedance by the number of speakers. For example: if you have three 8 ohm speakers, then 8 ÷ 3 = 2.67 ohms.

If you have 2 or more speakers in parallel and all the speakers are not the same impedance, then it is easier to use my Speakers in Parallel Calculator.

Note: all these calculations are for connecting manufactured speakers (boxes). They are not used when building your own speaker box 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.

 

Most Hi-Fi amps require a minimum load impedance of 4 ohms or 6 ohms.

Two 6 ohm speakers in parallel gives a total load impedance of 3 ohms. This is below the minimum of 4 or 6 ohms, therefore it is not advisable to connect two 6 ohm speakers in parallel directly to a Hi-Fi amp.

You can use a 2 zone speaker selector switch which uses a series resistor. This will add a series resistor of 3-5 ohms (depending on the manufacturer.) Therefore the 3 ohms (of the two speakers in parallel) and the series resistor (of the selector switch) will bring the total load impedance above 6 ohms, so all should be good for the amp.  However the resistor will reduce the power available to each speaker (by up to 60%).  See my speaker selector simulator for more details.

You can also simply connect both speakers in series. This will bring the total load impedance to 12 ohms, which will be fine for the amp as it above its minimum load impedance. However, the maximum power of the amplifier will be slightly reduced. For more practical details see my article on How to connect 2 speakers in series.

For more examples of connecting multiple speakers to a HiFi amp see my article on Understanding Speaker Impedance. The video in this article also describes how the different types of speaker selector switches help with impedance.

 

Generally no, but with some speakers you can.

Many Hi-Fi stereo amplifiers have connections for Speaker A and Speaker B. These connections are normally in parallel, so it is the same as connecting two speakers in parallel – but the amp provides switches to turn each set on or off.

These are designed to allow easy connections of 2 sets of speakers. Normally these amp have a warning notice. This notice is saying that when connecting to either A or B, then the speaker should have an impedance of 4-16 ohms. But when connecting to both A+B, then each individual speaker should be 8-16 ohms.

So if you have 2 sets of your speakers which are 8 ohms or more, then you can safely use these connections.  This is because two 8 ohm speakers in parallel gives a total impedance of 4 ohms – the minimum impedance the amp is designed for.

However if your are connecting speakers with an impedance less than 8 ohms, or you have more than 2 sets of speakers, then you should not use these connections as the total impedance will be below the minimum 4 ohms.

For these speakers you could connect them in series to Speaker A only. Or you can use a speaker selector switch connected to Speaker A only.

 

When more one than one speaker is connected to an individual amplifier, they can be wired in series, parallel or (rarely) in series/parallel.

Speakers in Series

Two or more speakers can be wired in series. That is, one wire is used to to go from each speaker to the next. 4 speakers in seriesThis is not normally used for more than 2 speakers. For a practical discussion on wiring 2 speakers in series, see the article on Connecting 2 speakers to an amplifier. 

To calculate the total impedance of speakers in series simply add the impedance of all the speakers together. For example, in the diagram above, if each speaker was 4 ohms, then the total load impedance seen by the amp would be 4 + 4 + 4 + 4 = 16 ohms.

Adding speakers in series is a safe way of adding speakers to an amplifier, but not always practical. The higher total impedance also doesn’t allow the amplifier to produce its maximum power. For more in how impedance changes amplifier power, see the article on How impedance changes amplifier power.

Speakers in Parallel

Two or more speakers can be wired in parallel. That is, two wires are used to connected from one speaker to the next.

4 speakers in parallel schema

This is the easiest and most common way of connecting 2 or more speakers. Wiring each speaker back to the amplifier with separate wires is also wiring them in parallel.

4 speakers in parallel at ampBoth of the above diagrams show 4 speakers wired in parallel. If you follow each wire with your finger on the lower diagram you will see it is effectively wired the same as the first diagram.

Due to the total impedance, it is rare you can wire more than 2 speakers in parallel.

If each speaker is the same impedance, it is easy to calculate the total load impedance of speakers in parallel. Simply divide the individual speaker impedance by the number of speakers. For example, in the above diagrams, if each speaker is 8 ohms, then the total load impedance would be 8 divided by 4, which equals 2 ohms.

If each speaker has a different impedance, then it is is easier to use my Speaker in Parallel calculator.

Wiring 2 speakers in parallel is very common in domestic and commercial installs. You just need to ensure the total load impedance of the speakers in parallel is above the minimum impedance required by the amplifier.

If you need to wire more than 2 speakers in a domestic install, you can use a speaker selector switch if the total load impedance is below the amplifier’s requirements.  For more details on wiring 4 or more speakers to an amplifier see the articles Connecting 4 speakers to an Amplifier, Speaker Selector Switch summary, and my unique Speaker Selector Switch Simulator.

If you need to wire more than 2 speakers in a commercial install, there are three alternatives. Firstly you can get commercial amplifiers designed to work with a load impedance as low as 2 ohms. Secondly, you can use multiple amps, That is, one dual channel amp for every pair or for every 2 pairs of speakers. Thirdly, you can use a distributed speaker system.

Impedance is a characteristic of a speaker you need to take note of, especially if connecting more than one speaker to an individual amp. See the article on Understanding Speaker Impedance for details.

The first important point to note is you should not connect a speaker combination with a total impedance lower than the minimum the amp is designed for.

For example, if your amp says the speakers should be 4-16 ohms, then connecting a 4 ohm, or 6 ohm or a 8 ohm speaker is fine. But connecting two 4 ohm speakers in parallel (which results in 2 ohms total load impedance) is too low. To  calculate the total impedance of speakers in parallel see the popular Speaker in Parallel Calculator.

If you do connect a total load impedance which is lower than the amp’s minimum, you run the risk of overloading the amp; causing it to turn off, blow a fuse or blow the electronics. You can get away with a lower impedance at low volume levels, but as the amp gets close to its full output, it will get hot and stop working.

The second important point to note is you normally can have a total load impedance above the recommended maximum (Eg above 16 ohms). However the higher the load impedance, the less power the amp will be able to produce. See the article on Speaker Impedance Changes Amplifier Power.

Some amplifiers will detect that the impedance is too high and turn off thinking there is no speaker connected, but most amps will have no problem.

The exception is a tube (valve) amp. Most tube amps require some load and don’t like having no load.

 

In a perfect world, every cable should be labelled, identifying which speaker they are connected to. However, that is often not the case. Perhaps you are helping a friend, or you have moved into a new house which has speakers in many rooms, or perhaps the kids have pulled the wires out for fun. Whatever the reason, you’ll be pleased to know there is a cheap and easy way to find what speaker each cable is connected to.

You will need two things: someone to help you, and a 1.5 volt battery.

Each cable going to a speaker has 2 wires. Make sure the wires are stripped (that is, the outer plastic is stripped off, allowing around 12mm (1/2″) of bare copper wire to be seen at the ends.

Hold one of the wires (doesn’t matter which one) on the bottom of the battery. With the other wire, tap it on and off the top of the battery (the +ve terminal). The connected speaker will make a scratching noise. Note: the speaker only makes a noise when the wire is tapped on or off the battery. So keep tapping the wire on and off the battery until your assistant finds the speaker which is making the noise.

Once identified, label the speaker cable.

Other Methods

Use an impedance meter: an impedance meter sends a tone (normally 1kHz) down the cable to measure the speaker impedance. Most meters also allow the tone to be held on continuously so you can test and/or identify what speakers are connected. This is a great way as the meter will also tell you the total load impedance.

Connect to amplifier: You can connect the cable under test to an amplifier playing some music at a low volume level. Just be careful not to short the wires when connecting the amplifier. Probably best to turn amp off when making each connection.

You can certainly design your speaker boxes, but I wouldn’t.

I’m an installer, not a speaker designer. I’ve installed many speakers, but I wouldn’t like to try to design them. The internals of a speaker box (cabinet) is complex.

The simple calculation of speakers in parallel is only useful if your don’t use a cross-over circuit (a circuit which splits the signal into different frequencies to best match each speaker in the box).

The complexity of the total impedance of a speaker (box) is not the only issue. Other things I’m aware of (among other issues) that need consideration are:

  • The internal volume of the cabinet (less the volume of the other speakers) needs to match the characteristics of the biggest speaker
  • The effect of the air movement caused by one speaker might have on the other speakers
  • The matching of the crossover circuit to each of the speakers
  • The phasing of each speaker relative to the other speakers
  • The overall flatness of the resultant frequency response.
  • The power handling of each speaker

So, I leave all that to the people who get paid the big bucks to design speakers. We need to simply install and enjoy the product of their effort.

It is not possible to make two 8 ohm speakers into a 8 ohm load.

There are only two ways to connect two speakers together, either in series or parallel.

In parallel, two 8 ohms speakers give a total load impedance of 4 ohms – too low for any amp designed for a minimum load of 8 ohms.

In series, two 8 ohm speakers gives a total load impedance of 16 ohms. This will work with amps designed for a minimum load of 8 ohms. However the amp will not operate at full power. In a domestic install, a simple series/parallel speaker selector switch can be used to do this, as well as enable any one pair of speakers to be connected on their own. However, with a 16 ohm load, the amplifier’s output power will be reduced by 3dB compared to using just one 8 ohm speaker.  For more info on this see the article on how Speaker impedance changes amplifier power. 

For the best power output, you would be better off to use just one 8 ohm speaker, provided it will cope with the full amplifier power.

So, it comes down to what you are trying to do. If you want maximum power, then use just one speaker. If you want a wider area covered than what one speaker will cover, then use the two speakers in series.

Also if maximum power is not an issue, then you could also use a speaker selector switch with a series resistor. This will add a 3-5 ohm* resistor in series with the speaker. This will allow both speakers to be wired in parallel (4 ohms total load impedance) in series with the resistor (3-5 ohms) to give a total load impedance close to 8 ohms. However the resistor will take close to half the power of the amplifier.  This is not normally a problem when using multiple speakers in a house, but not so good in a commercial installation requiring maximum power.

*the value of the resistor depends on the manufacturers design.

To see how much power a speaker selector switch resistor takes, see my simulator here.

For a more a detailed understating of speaker impedance, see the article on Understanding speaker impedance.

For more on how to wire speakers in series or parallel, see the article on Connecting 2 speakers to 1 amplifier.

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If, after reading these FAQs, you still have a question, please ask it in the “comment” box below.

In your question, please include as many details as you can. Include the make and model of the amplifier and speakers as I often try to find the specifications and/or manual for your equipment to better answer your question.

I also ask for your location. This is helpful as some countries have different policies and practices. It also helps me suggest any products and suppliers available to you if you need some extra equipment.

It takes a lot of my spare time answering readers’ questions, so I filter some questions. I may not answer questions, or only give a brief answer if your question is

  • Already answered in these FAQs
  • Already answered in my other articles (I expect you to have tried to find a solution yourself)
  • Off topic.

I trust you can appreciate I only apply these filters to allow me to concentrate on answering those question not already covered.

Other articles which might help you include:

14 COMMENTS

  1. Geoff,
    first off i would like to say i love your website it has been incredibly helpful so far. im working on a new home theater system 5.1 channel and im wanting to purchase new speakers and build my own speaker boxes for each channel (except subwoofer) now after looking online at the reciever/amp i have i found out it pushes 75 watts to each channel. i know how to combine/wire speakers to get the correct 8 ohms it requires (thanks to your page on how to do that) but i still dont quite understand how the wattage gets spread out over the speakers. if im only getting 75w per channel and i put two 40w speakers on that channel does that mean im going to over power both speakers and blow them or do they each take 50% of the power running them each at a little over 35w? im sure this is a fairly simple question that just hasnt clicked in my head yet but any help would be great.
    thank you so much
    Trevin

    • Hi Trevin,

      In regard to power-sharing, your second alternative is correct. As long as the speakers are of the same impedance they will equally share the power supplied by the amplifier.

      However, if you are building a speaker box you will probably need a crossover circuit. This will split the signal between the low frequencies and the high frequencies to each of the speakers as is best suited. This throws all the impedance calculations out the window. This is because impedance is frequency based and as the frequencies only go to one of the speakers only that speaker counts, except for the fact that is not an instant cut-off, there is power sharing as the frequencies gradually crossover. All this makes such calculations is very complex and is one of the main reasons I do not make my own speakers.

      Matching speakers, enclosure volume, power, phase and impedance with ascetics is why speaker designers get paid the big bucks. It is very difficult to brew your own to sound any better than I bought one. That’s not to say it’s not good to build your own, but is not for the faint hearted. I’ve built speaker kits where all that hard design work is being done for me and that can be a cost saving.

      Sorry can’t help much more as I’m an installer not a speaker designer.

      Geoff

  2. Hi Geoff, great site that has helped me expand my meagre understanding.
    I did read speaker connection and impedance sharing articles.
    My question (another hookup query if you can stand it) is specific to a used amp I just got, Harmon Kardon HK6150 integrated stereo amp (documentation on hifiengine)
    It has 4 hookups (advertised as 2 speaker system stereo sets) but what is not clear to me is how the two stereo sets relate to each other in their connection to respective amps: parallel or series?
    You can select a setting that sums them together.
    The instructions caution not to go lower than 4 ohms net.
    What I have to work with currently is 4 identical Sony bookshelf speakers @ 4 ohms each.
    I don’t need to use them all, but I have them if need be.
    Would optimal impedance matching fall under one of the following scenarios?
    1) 2 speakers wired in series in each channel of output 1 (4 total, but 8 ohms each channel?)
    2) 1 speaker wired normally in each channel of output 1 (4 each channel, but net ohms =?)
    3) 1 speaker wired in each output of 1 and 2, then summed (I tried this last one briefly today at moderate volume, my amp did not fry after 5 minutes….)
    Finally would you care to speculate as to why the dual speaker set summation feature is there in the first place?
    Kind Regards,
    Ian

    • Hi Ian,

      I think the crux of your question is what does the speaker selector switch do? Basically the speaker selector switch is a convenient way of selecting either one or both sets of speakers.

      When you select speaker 1, that set pair of speakers are connected. Similarly, if you select speakers 2, the second pair of speakers are connected. If you select 1+2 then both pairs of speakers are connected in parallel.

      Being in parallel does cause an issue if the speakers are 4 ohms each. As 2 lots 4 ohm speakers in parallel will give a net load of 2 ohms, which is less than the 4 ohms which the amplifier would like.

      So to look at each of your scenarios:

      1) Scenario 1 would work fine. However you would only use speakers 1 on the switch, and you would not be able to switch between both sets.

      2) I’m not clear what you mean by this scenario as you say one speaker wired normally to each channel of output 1. There are only two outputs for output 1 (left and right), therefore not sure how you would get 4 on each channel.

      3) Scenario 3 is as described above where the total impedance would be 2 ohms when both speakers are selected. This is below the 4 ohms which the amplifier will cope with at full power. However at lower levels you could get away with it, but I wouldn’t recommend it.

      Does this help?

      Geoff will

      • Geoff, yes, thanks muchly for your timely response.
        You’re correct, the key fact I was unsure of was that the summation of both sets (1+2) is done in parallel. Then your explanation (as fully fleshed out elsewhere on the site) makes complete sense.
        I apologize for ambiguous wording in scenario 2. I meant one L speaker and one R speaker (2 total), meaning 4 OHMS each channel, not 4 speakers.
        In summary I am realizing it would be unwise and basically redundant to attempt to use more than 2 of my 4 ohm speakers with this amp (or most any amp).

  3. Hi Geoff,
    Great blog! Wonder if you can help with a query, as I have had a look about and not been able to find anything on this.
    I read that you should look to have an amp 1.6x the speaker rating (I am mostly playing pop and voice so nothing too hard) . I have a d&b d6 amp. It rates around 800w @ 8 ohms. I am looking at some bose panarays which rate around 550w @ 8 ohms, so this about works out amp to speaker wise. I don’t want to blow the speakers though. Are amps ratings based on their setting at 0db? Should you therefore always look to keep an amp – 3db or so to avoid speaker damage? I haven’t found any literature to tie amps output dB settings to output Watts (I know it varies anyway depending on frequency).
    Thanks,
    David

    • Hi David,

      Your assumption is correct in that amplifiers are rated at full power, that is when the volume control is turned right up.

      The reason a lot of people suggest to have a slightly more powerful amplifier than the speaker rating will cope with is to give the amplifier some headroom on some of the peaks in music. The assumption is because these peaks are only momentary, they will not cause much grief to the speaker. However this also depends on whether the power ratings of the speaker are maximum, peak, RMS, music or some other PR phrase.

      Provided provided the power ratings of the amplifier and speaker are RMS it should not necessary to turn the amplifier down unless you want less volume.

      However, you always need to listen for distortion. No matter what amplifier/speaker combination use, if you try hard enough, you can always cause distortion. Distortion is your red light to say that something is about to go. So always turn it down if you hear distortion. Otherwise you should be fine.

      Hope this helps,

      Geoff

  4. Hi Jeff,

    As you say, connecting a 16 ohm speaker to this amplifier will reduce the output power. Using the calculator above, 6 W will still give you 102dB – which is not insignificant.

    Which begs the question, if you want to reduce the volume why not just turn input level down?

    Geoff

  5. Hi, Geoff. I’m interested to see if I can use my existing speakers for a proposed surround-sound system. I have a pair of Gale 401s driven by a Cyrus amp. & a pair of JR149s driven by a Lecson pre&power amp. combo. Would it be possible to use the same speakers (along with a centre speaker) with a dedicated AV amp. & SACD player? My other half will object to more ‘hi-fi furniture’ in the room but I could slip a couple more boxes in the hi-fi equipment rack without much trouble. Thanks in anticipation, Mark

    • Hi Mark,

      Wow, some great speakers from the 70s. There’s no reason you can’t use these with a modern amp as long as it is capable of driving loads down to 4 ohms.

      As you say, you will also need a centre speaker. You may not need a separate sub woofer with the Gales. Certainly not as a starting point. If later on you decide you need a sub you could probably replace the Gales with a sub and use much smaller speakers for the front or indeed use the JR’s at the front with a sub and get some small speakers for rears – just a thought to get it past the ascetics committee and she will be removing one of the Gales.

      Hope this helps,

      Geoff

  6. sir i have a question. i have only 1 crown pr800 power amp for my mid. i wanted to load 4 speakers by each channel, 2 targa 12″ 400w by 8 ohms and 2 crown 8″ 700w by 8 ohms, how can i connect it. parallel and series connecton. and what is the total ohms and wattage of it. it is ok to load it into my crown pr800 amp sir?

    • Hi Rima,

      Connecting four 8 ohm speakers to each channel is possible, but may not be the best.

      You could connect the two 12″ speakers in series, and the two 8″ speakers in series, and then these two sets of speakers in parallel. That would give a total load impedance of 8 ohms to the Amp. However you will only get 50 W across each speaker.

      A better way would be to connect any two 8 ohm speakers in parallel. This will give a total load impedance of 4 ohms, and 150 W to each speaker.

      Does this help?

      Geoff

  7. Hello sir i have Technics SU-X502 Rack System Combination but my speakers got damaged so i have to build a new speaker box my own design.
    My amplifier DIN Power
    output =1khz THD 1% = 2×60w , 8 to 16 ohm
    Power consumption 330 w
    Now i wish to add speakers per box shown below
    SIZE. TYPE (Approx) WATTS MAX:

    8″ subwoofer – 300 @ 8Ω or 600 @ dual 4Ω
    6″ super woofer. 100 w 8Ω
    6″ woofer. 100w 8Ω
    3″ tweeter 200w 8Ω
    4″ midrange. 40w 8Ω
    If i build a floorstand speaker box with this all speakers ,
    My amplifier safe or not? If not which speakers need to avoid. Please advice me sir

    • Hi Gireesh,

      As stated in the FAQ above, I’m not a speaker designer, because it is complicated. You will need a crossover circuit to direct the different frequencies to each speaker, and then that changes all the impedance calculation. But it will all depend on what sound you want, what cross-over you use and how all the speakers interact together.

      If you don’t use a crossover, you could keep it simple and just use the 8″ woofer and 3″ tweeter and see how that sounds. But even that will give you a total impedance of 4 ohms which is lower than what your amp wants, so you can’t run it at full power.

      Sorry I can’t help much more

      Geoff

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