How do I Connect Multiple Speakers to my HiFi Amplifier

I am often asked “How do I connect multiple speakers to my amplifier?” Before I answer, let’s define what we mean by the word “amplifier”. In a stereo “amp” there are two amplifiers – one for the left, and one for the right channel. That is, in the one amplifier box, there are two different amplifiers. In a home theatre amplifier with surround sound, there may be 5, 6, 9 or 11 amplifiers in the one “amplifier” box. For the purposes of this article, we are talking about connecting multiple speakers to a single amplifier only, that is, either the left or the right, or any single amplifier. Of course you can connect multiple speakers to both the left and right amp of a stereo – you just need to follow the principles twice, once for each amp.

Multiple Speakers on One Amplifier

Multiple speakers - Connecting two speakersBy adding an extra speaker to the output of an amplifier, you are adding to the load of the amplifier. That is, two speakers is double the load of one speaker. Most amplifiers can cope with a load of two speakers. Similar to a passenger on a small motor bike: add another passenger and the load the bike needs to carry is doubled, but most bikes will cope with two passengers.

However adding more than two speakers will normally overload the amplifier. Similar to the motor bike example: it can cope with two passengers, but starts to struggle with 3 or more passengers. Most modern amplifiers have some sort of limiting circuit to stop the amplifier working if it is overloaded. In some amplifiers, this involves blowing a fuse inside the amplifier. In other (more technical) amplifiers they will automatically turn off until you turn it back on with a load that is under its maximum safe load.

Amplifiers may cope with multiple speakers at low volumes,multiple speakers - bike example (400 x 267) but will have issues when running at high volume levels. Similar to the motor bike illustration: it may cope with 3 or 4 passengers while going slowly on a flat road, but it will struggle when asked to work harder (like go up a hill or go faster). To be safe, never overload your amplifier.

To understand the technical reason for this, I strongly encourage you to read through the technical explanation below. A good overview on this can be found in the video in the article on Understanding Speaker Impedance

If you just want to know how to wire two speakers to one amp, (4 speakers to a stereo) without switching or individual volume control, see the article on How to connect 2 speakers to 1 amplifier.

If you want speaker on/off or individual volume control, or you want more than two pair of speakers, (like three, four or more pairs) connected to your HiFi amplifier, see the article How to wire four speakers to one amplifier.

If you need to wire more than four pairs of speakers, particularly in a commercial installation, see the article on Distributed Speaker Systems.

Technical Explanation

In the specifications for a hifi amplifier might say Output: 100 watts @ 4 ohms

This is normally specifying the maximum power output of the amplifier and the minimum resistance in the speaker circuit. So in this case, the amplifier will produce 100 watts of power when run at full volume connected to a speaker load of  4 ohms. The ohms bit is our main concern. Ohms is a measurement of resistance. In the case of speakers, it is the measurement of how much resistance the speaker has in the circuit connected to the amplifier. Technically speaking, the resistance of speakers is called “impedance”, as the output of an amplifier is AC, and resistance in an AC circuit is called impedance.

To understand what all this means, we need to get technical and use some formulas. An explanation of these formulas can be found in the article The Dreaded Ohms Law. multiple speakers - ohms law We will use the summary table from that article. You don’t need to understand these formulas but we need to use them.

In our example, we know:

Power is 100 watts: P = 100

Impedance is 4 ohms: R = 4

So we can use the various formulas to calculate the output voltage(V) and current(I) of the amplifier.

Calculation of output voltage(V):

V=\sqrt{P\times R}=\sqrt{100\times 4}=\sqrt{400}= 20\ volts

Calculation of output current (I):

I=\sqrt{\frac{P}{R}} =\sqrt{\frac{100}{4}} =\sqrt{25} =5\ amps

So, from the specifications and a couple of calculations, we now know the following:

Power=100 watts Impedance (resistance) = 4 ohms Voltage = 20 volts Current = 5 amps

An equivalent circuit will help us visualise what is happening.

multiple speakers - connecting 1 4 ohm speaker

This illustrates the maximum capacities of the amplifier. With a load impedance (speaker) of 4 ohms, the amplifier needs to deliver 5 amps to produce the 100 watts of power. This amplifier will normally have some sort of limiting circuitry to limit the current output to no more than 5 amps. The reason being, all the electronics will be designed to deliver 5 amps. Therefore to avoid “blowing up” the output stage (and possibly the power supply), some form of current limiting is employed. The most simplest form of a current limiting circuit is a fuse. If a 5 amp fuse is placed in series with the output, then it would supply the current until the total current exceeds the 5 amps at which point it would “blow”.

Remember, these are the maximum ratings of the amplifier. In practice, many speakers are made to have an impedance of 8 ohms. Therefore the equivalent circuit would be similar, but with a different impedance, therefore a different current as shown here:

I=\frac{V}{R} =\frac{20}{8} =2.5\ ampsmultiple speakers - connecting one 8 ohms speaker

The power output of the amplifier is also reduced:

P=\frac{V^2}{R}=\frac{20^2}{8}=\frac{400}{8}=50\ watts

In practice, because the speaker impedance is increased, the load is decreased and the amplifier is capable of outputting around 23 volts which gives a maximum power output of 70 watt @ 8 ohms.

The important principal is: the higher the speaker impedance, the less current required from the amplifier. Also, the lower the speaker impedance, the more current required from the amplifier.

OK, this is all very good, but what about connecting two or more speakers to the amplifier? Glad you ask, this is the fun bit. Let’s connect two 8 ohm speakers to the one amplifier.

multiple speakers - connecting 2 8 ohms speaker in parallel

You will notice that each speaker still draws 2.5 amps from the amplifier. So the combined load on the amplifier is now drawing a total of 5 amps (2 x 2.5=5). You may have noticed that this is the same current (and therefore the same total load) as one 4 ohm speaker. That’s right, two 8 ohm speakers in parallel is the same as one 4 ohm speaker. If you like, you can prove this using the formula for calculating resistances in parallel. If you’ve had enough formulas, just skip this and go to the next paragraph.

\frac{1}{R_{Total}}= \frac{1}{R_1}+\frac{1}{R_2}\ \ so\ \(\frac{1}{R_{Total}}= \frac{1}{8}+\frac{1}{8}=\frac{1}{4}\ \ therefore\ {R_{total}=4\ ohms

The good news is, this is within the specifications of the amplifier as we saw earlier. So, as long as the speakers both have an impedance of 8 ohms (or more), and the amplifier is rated for 4 ohms, then you can safely run the amplifier with two speakers.

Now what do think is going to happen if we are having a party in several rooms and need multiple speakers (like four speakers) connected to one amplifier on the stereo? The circuit would look like this:

multiple speakers - connecting four 8 ohm speakers

If the poor old amplifier can still hold the 20 volts, each speaker is still trying to draw 2.5 amps, meaning the total current draw from the amplifier is 10 amps – way above its specified capabilities. At this point, we hope it has a limit/protection circuit and has turned itself off, or at the very least the 5 amp protection fuse inside has blown. If there is no current limiting circuitry, then quickly turn the power off when you see the smoke rising from the amplifier.

For those who like the mathematical evidence rather than just the pictorial reasoning, the calculation of the total resistance looks like this:

\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}{8}+\frac{1}{8}+\frac{1}{8}+\frac{1}{8}=\frac{1}{2}

therefore\ {R_{total}=2\ ohms

and then calculate the current:

I=\frac{V}{R} =\frac{20}{2} =10\ amps = smoke.

For an easy way to calculate the total impedance of speakers in parallel, try my simple Speakers in Parallel Calculator.

Keep in mind that changing the total load impedance of an amplifier will also increase or decrease the power output of the amplifier. See Multiple Speakers Change Amplifier Power for more details.

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. 

Multiple Speaker Selector Switches

multiple speakers - 4 way speaker selectorThere are ways of connecting multiple speakers to one HiFi amplifier without causing damage, but not by simply connecting one speaker onto the other. For a detailed and practical outline of how to connect four or more pairs of speakers to a HiFi amplifier, see this article. The simple method (with the limitations listed in the other article) is to use a speaker selector switch. A 4 zone switch will allow up to 4 pairs of speakers to be connected to the one amplifier.

Speaker selector switches can use various techniques to allow multiple speakers to be connected to the one amplifier, namely:

  • a series resistor (around 2½-5 ohms) to restrict the minimum impedance of the speakers circuit to this value. This simple series resistor is often marketed as “manual impedance protection” or simply “Protection”. They are normally good for lower powered amplifiers, and the resistor can get hot at high volume levels.
  • combining the different speakers in series and/or parallel to keep the overall impedance above 4 ohms.
  • matching impedance transformers – this is normally the best, but it is also the most expensive.

All these methods allow multiple speakers, but at a lower volume than using just one speaker. This is logical as the signal is being shared by more than just the one speaker. To see how the power is distributed by the different types of speaker selector switches, see my Speaker Selector Switch Simulator.

For a more detailed explanation and summary of the features of speaker selectors, see my Speaker Selector Switch Summary.

If you are interested in purchasing a multiple speaker selector, here is a link to Amazon’s range of speaker selectors in USACanada, UK, Germany, Spain and France.

Instead of using a speaker selector switch to connect multiple speakers to your hifi amplifier you can use impedance matching volume controls, as outlined in the article on connecting four speakers.


Conclusion

Depending on the impedance of your speakers and the rating of your amplifier, you should be able to use two pairs of speakers connected to a HiFi amplifier. However, it is wise to use the example given above as a guide and use the figures in the specifications of your amplifier and speakers to calculate and know for sure what the outcome will be. Otherwise use a multiple speaker selector switch and/or impedance matching volume controls. The video in Understanding Speaker Impedance explains how speaker selectors help with impedance protection

For a practical discussion on how to simply wire just 2 pair of speakers to a stereo amplifier (4 speakers to a stereo amp), see my article on How to connect 2 speakers to 1 amplifier.

For more practical information of how to wire two, three, four or more speakers to one amplifier using speaker selector switches and volume controls, see this article.

Manymultiple speakers -download PDF practical examples of connecting multiple speakers to your HiFi have been discussed in the comments below. If, after reading these discussions, your still have a question please use the comments section below, and we can all learn more together.

Thanks to James from Sydney, Australia who suggested this topic.

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282 COMMENTS

  1. Hello,

    I’ve four 250 w 8 ohm speakers. I need a 2-channel amplifier with 2 ohm impedance. Am I right? And the channels have to be 500 watts each?

    Ignas

    • Hi Ignas,

      With four speakers connected to a 2-channel amplifier, you will only have two speakers connected to each channel. Two 8 ohm speakers in parallel gives a total load impedance of 4 ohms. So you need an amp that will give you the required power into 4 ohms.

      Now the real question is how much power do you need? That depends on how loud you need it to be. The speakers will work fine with 10 watts or more. Perhaps 100 watts will be all you need.

      If you need to get the maximum power from the speakers, then most manufactures recommend an amp around 1.5 times the power rating of the speakers. All these power measurement should be RMS – not peak.

      Remember, no matter how powerful an amp or speakers are, if you try hard enough you can always blow something. If you hear distortion, turn it down. Distortion is the warning sign that something is overloaded.

      Geoff

  2. Ok, Geoff,

    In response to a previous query of mine you said that if I am using in-wall volume controls (with impedance matching) in each room I do not need to use a speaker selector (with impedance matching). You also suggested that I could use the speaker selector, with the impedance matching feature turned off, if I wanted to be able to turn audio off to certain rooms. Well, I do.

    That begs a follow up question. The in-wall volume controls have a selector to specify how many pairs of speakers are installed so that they can properly match the impedances. If I’m using the speaker selector to turn off certain rooms, does that mean I will need to adjust the speaker count setting at the volume controllers every time deselect a room?

    Thank you. Your expertise and your patience with all our convoluted questions is really appreciated

    • Hi again Daniel,

      This is good question.

      As you have discovered, it is important to set the selector on the volume controls correctly. If you have 6 pairs, you can normally set the selector to x4, on the basis that you don’t normally run all 6 sets flat out.

      Therefore if you run only one pair of 4 ohms speakers, then the total load seen by the will be 4 ohms x4 = 16 ohms, which is fine for the amp. Even if the total impedance is higher, most amps will work fine as long as they are not run flat out.
      You can play with this using my speaker selector simulator.

      So, you don’t have to change the VC selector each time. Just make sure you set the amp volume according the steps in this article.

      Hope this helps some more

      Geoff

  3. Hi Geoff,

    First of all i would like to thank you for your precious information.
    I have a 2 channel amplifier, input Voltage:DC 12V/5A, speaker impedance: 4-8Ω, RMS power:40W*2.
    Regarding speakers I would like to connect 3 speakers for each channel. Speakers are 6Ω, 4Ω and 4Ω. I would like to know which is the best way to connect the speakers.

    Thanks
    Ray

    • Hi Ray,
      It is difficult to connect 3 speakers with different impedance to an amp and get even power to each speaker.

      Even if we ignore wanting even power, there is no series/parallel combination that will give you a total impedance above 4 ohms.

      You could wire them all in series. This will give a total impedance of 14 ohms to the amp. This will work fine, but will restrict the maximum power to each speaker a little bit.

      You could use a 4 zone speaker selector switch which uses a series resistor – this would work fine as far as impedance is concerned. However there will still be a power difference to each speaker. The only way to easily overcome this would be to use a speaker selector switch with individual volume controls for each speaker – but these cost more.

      hope this helps,

      Geoff

  4. Geoff,

    I have six in-wall speakers in one room. They are all Emotiva 6 ohm speakers. Will buy a wifi-enabled 2 channel receiver/integrated amp for music only. Better to wire in series/parallel or get a speaker selector?

    Thanks – Jim

    • Hi JB,

      You could use 3 channels of a 4 zone speaker selector. The only problem is you loose a lot of power in the series resistor.

      Assuming you don’t need to switch any of the speakers on/off, then I would suggesting wiring 3 in series for each channel of the amp. This will give more power to each speaker.

      Wiring them in series/parallel will work fine for impedance, but there wont be even power distribution across the three speakers on each channel.

      hope this helps some,

      Geoff

      • Geoff,

        Thank you. Follow up question. I have an early 1990’s Adcom 555 amplifier that I may pair with a Yamaha Musicast pre amp for wifi connectivity. Would running a (6+6+6) 18 ohm load through each channel of that amplifier work?

        Jim

        • Hi Jim,

          The Adcom 555 seems a very solid amplifier. In fact in the users manual it says “All loudspeaker systems having a nominal impedance down to 2 ohms can be connected to,
          and driven by, the GFA-555ms. The GFA-555ms can drive these low impedances at more than adequate power levels with no difficulty.”

          Given that 3 lots of 6 ohms in parallel gives you a total load impedance of 2 ohms, it seems that the amp will cope with this load. However the next paragraph of the manual goes on to say that when running with a load around 2 ohms and “when making excessive power demands from the amplifier, you may trigger the THERMAL PROTECTION on the amplifier or blow one of the DC RAIL FUSES.”

          So, I suggest that if you are not going to be running the amp any where near full power, then it would be OK to run each side with the 3 speakers wired in parallel. However if the amp gets too hot, then you could always wire them in series.

          Geoff

          Geoff

  5. So, if I have a 600W amp with 6 speakers at 8 ohms each, that gives me a 70V system. Instead of wiring the speakers to the 8 ohm post, should I wire to the 70V post?

    • Hi Adam,

      Probably. It depends on your install, and how much high quality HiFi you want, compared to good quality sound. Going through the transformers makes wiring them very easy, but will take some of the bass out of the bottom end.

      For general background music I would use the 70 volt setting and use the transformers on the speakers.

      Geoff

  6. Hi Geoff,
    I can’t seem to find the answer to a situation that isn’t covered ANYWHERE.
    I have an acoustic ACX450 two channel 45 watt amp.
    Each channel has its own inputs, gains EQ, effects, gains and effect gainsOne channel has an xlr jack
    for a mic. My question is, “Why are these two channels wired into only one speaker”?
    Doesn’t this kind of defeat the purpose of a two channel amp?
    I want to know if I can wire these channels separately to two speakers?
    Tnx LBM

    • Hi Lawrence,

      Like most guitar amplifiers, this unit is only a mono amp. That is, there is only one amplifier and one speaker in the box. It has two inputs, often to allow a microphone and a guitar to be used at the same time during practice. Others might use one channel for their guitar and the other channel to play a CD or MP3 track to play along with. Unfortunately it looks like the marketing department took over and saw “2 channels” so called it “Sweet Stereo Operation”. Don’t believe the marketing without looking at the specs. This is not a stereo amp, and is not designed to add a 2nd speaker to.

      Geoff

      • I don’t think its stereo, but It’s advertised as and states right on the front of it
        “45 watt 2-channel acoustic instrament amplifier.”
        Each channel has separate inputs with their own separate volumes, separate eq’s, and separate effects. It even has a foot switch for the effects with two buttons on it, one for each channel. My question is, why does it have to go into one speaker? Couldn’t each channel have its own speaker to make each channel cound clearer?

      • You are correct, it is not stereo. It is two input channels, each of which has its own controls, hence the two buttons on the foot switch. This is similar to any mixer. A 8, 16 , 32 channel (or more) mixer does the same thing. Each channel has it’s own controls, but they are all mixed into one or two channels.

        To have two speakers, you would need two amplifiers as well. With both speakers in the same small cabinet, they would sound like they are coming from the same box (which they are), so you would be paying double for very little (if any) gain.

        Geoff

  7. Dear Geoff

    Thank you very much for an informative website. I understand the principles of resistance etc. and would not want you to repeat your explanation BUT…

    Have you any favorite amp and splitter switches to provide the following:
    Six ceiling speakers (300 MM diameter cut out) preferably powered by some receiver that allows things like spotify and FM radio. As I’m getting on deafness and a middle aged desire to rock my house calls for some good quality but LOUD sounds.

    Thanking you in anticipation.

    Best regards

    Ben

    (I know I ought to know what I want and would if it were a motorcycle, but there seems so many offerings).

    • Hi Ben,

      I’m glad you have learnt from the site.

      It is difficult to recommend specific products as what you think is good sound may be different to me. Also I don’t know what type of music you like, how loud you like it, what the acoustics are in the room, what your budget is and what is available in your area.

      Having said that, there are some guidelines I could offer. But before that, I need to know if the 6 ceiling speakers are all in the one room, or in different rooms. Also are they the only speakers you have or are they in addition to an existing sound system?

      I ask these questions because it seems you like some “rock” type music which means you need good bass, which you may not get with ceiling speakers on their own. I feel you need a sub woofer in the system somewhere.

      Geoff

  8. Your website is extremely useful, but still have a question. I have an old Onkyo 4500 with capability of running 2 sets of speakers (A, B, or A+B). I will be installing two (2) new Niles CM8si’s (each speaker is 2 channels) in my basement rec room. Channel A will be one set of speakers remote from these ceiling mounted units, which will become channel B, and controlled via a Niles in-wall volume control. Do I wire them in the hybrid series / parallel arrangement that you illustrate to keep the ohm load @ 8?. In other words, not a true daisy chain.

    • Hi Tom,

      The Onkyo 4500 amplifier will work into a load of 4 ohms or higher, according the manual I found.

      I’m not sure what your other speakers are, but I assume they are are 8 ohms each.

      Your ceiling speakers are 8 ohms each, but you effectively have two on each channel, giving a total of 4 ohms. however if you set the multiplier on the Niles volume control to x2, then they will look like 8 ohms total. That 8 ohms in parallel with the 8 ohm speakers on channel A, will give total load impedance of 4 ohms, which the amp is designed for.

      hope this helps

      Geoff

  9. hello, i was wondering what amp i should use if i have two bookshelf speakers and then a main speaker in the middle. or could i just use a normal amp

    • Hi Alfie,

      The type of amp will depend on what you are listening to.

      If you are listening to music from the radio, mp3, CD etc, then all these sources are just 2 channel stereo. So a standard stereo amplifier would be fine, and you wouldn’t use the centre speaker.

      If though you are watching movies form a DVD etc, then the centre speaker would be useful, but you would need an amplifier with a processor to deliver the sound to the centre speaker. Probably the best would be a 5.1 surround amplifier, and forget about the rear speakers.

      hope this helps

      Geoff

  10. Hello,
    I have a Amplifier Yamaha RN602 which is rated at 8ohm to start with then 4ohm once connected to another pair of speakers.
    I currently have Q acoustics 2050 which are 6ohm speakers, I’m looking to get a pair of bookshelf Q acoustics 3020 for the rears but these are also 6ohm. would I be right in saying that the over all ohms would be 3ohm so my amp wouldn’t be safe powering it?

    • Hi Dan,

      You are correct in your calculations, in that two 6 ohm speakers connected in parallel will give the amp a total load impedance of 3 ohms. This is too low if the amp is being driven at full power.

      Many people would say this is OK if running the amp at half power or less, as that would not be pulling more current than the amp will supply. Then there is the built in protection in the amp which will turn the amp off if the load draws too much power.

      If you don’t need to switch the rear speakers off/on, then a safe way would be to wire them in series with the front speakers. This will have a slightly less maximum power available from the amp, but probably not too noticeable. If you need to switch them on/off, then a series/parallel speaker selector switch would be ideal.

      hope this helps,

      Geoff

  11. Hello sir …I am new to this speaker electronics …I have a question…can I connect high wattage speaker to a low wattage amplifier(like 50w speaker to a 3w amplifier?

    • Hi Anant,

      Yes you can. Obviously the speaker will not be as loud as it could be, but it will work fine. Just don’t run the amplifier so loud that you hear any distortion, as this will damage the amp and or the speaker.

      For low levels it will be fine

      Geoff

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