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. A simple (but clever) calculator is included to help you work out your speaker configuration.

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).

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.

Alternatively, you can use the calculator below to work out the total impedance and the power sharing of different speaker configurations.

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.

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

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19 COMMENTS

  1. Im getting ready to put together a massive build and have a question for the Ohm gods…..in each dooor of my truck there will be (4) 8 ohm speakers…a total of (16) 8 ohm speakers than i need to get down to a 1ohm stable load…i will appreciate all the help i can get

    • Hi Jonathon,

      I cant’t think of a way to connect all sixteen 8 ohm speakers together to give a total of 1 ohm and have the same power go to each speaker. However if you wire each pair in series, (that is, 8 x 2 pair in series) then each pair will have a total impedance of 16 ohms. The these pairs can all be wired in parallel to give a total load impedance of 2 ohms.

      While this is not the one ohm you are after for maximum output of your amp, the difference in level will probably be around 2dB, which is only just distinguishable by our ears.

      Alternatively, you could use just eight speakers and get you 1 ohm.

      Either way will technically solve the impedance issue, but your may still some interesting acoustic issues with polarity when you have speakers facing each other in close proximity – but that is not my area of expertise.

      Sorry I can’t much more,

      Geoff

  2. Wonder how a 16 ohm n a 8 ohm(both fifty watt guitar speakers) in parallel would work? It’s a Fender 35 watt tube amp! Mthanks, joe

  3. Thanks for the quick comeback…Geoff…
    I could not make it come out to 2 ohm total impedance either…
    Well no big deal, I start looking for a pair of subs with single 4 ohm voice coil or two 2 ohm voice coils per per individual sub. Then I can get to a 2 ohm impedance on my mono block amp… Thanks again for the help Geoff.
    And will catch you later M8…

  4. I’m thinking about buying a pair of sub-woofers.
    Here is what I’m fighting
    I have a 2000 watt mono block amp stable at 2 and 4 ohms…
    (I want to wire this sub-woofers for 2 ohm final impedance)
    Sub-woofer One… 12″ Woofer with Dual 4 ohm Voice Coils…
    Sub-woofer Two… 12″ Woofer with Dual 4 ohm Voice Coils…
    Is there a way to wire this pair of sub-woofers to get a final impedance of 2 ohms…
    I Know I can get them down to 1 ohm but that will not work in my case need to be at 2 ohms…
    If I can’t get them to 2 ohms I will hunt for something with 2 ohms duel voice coils, according to the
    info I found that will bring the pair of sub-woofers to 2 ohms final impedance… Thanks

    • Hi,

      When you say the subs are dual 4 ohms, I assume they are two voice coils of 4 ohms each. Therefore, when both voice coils are wired in parallel, then each sub is 2 ohms. Then if you wire both subs in parallel, then the total load impedance seen by the amp is 1 ohm, which is too low for the amp.

      You could either wire both voice coils in series, or wire both 2 ohm speakers in series,. Either way will give you a total load impedance of 4 ohms, which the amp will like very much.

      I can’t think of any way to wire a 2 ohm speaker with other 2 ohms speakers and keep everything at 2 ohms. It will be much better to run the amp with a 4 ohm load.

      Does this help?

      Geoff

  5. Hi, I need your help please, I have a crossover which is rated 8ohms, and I need to connect two midi speakers of 8ohm and 1 tweeter of 8ohm, my amplifier is also rated at 8ohm, how should I connect these speakers and tweeter so that I may have full power, this is a single speaker box, like a 3way but not practically, only by the look. and i will have another one with the same components. thank you in advance

    • Hujambo Jellodz,

      Unfortunately I’m a not a speaker designer, so I may not be a lot of help.

      However I can say that connecting two 8 ohm mids in parallel will give the amp a load impedance of only 4 ohms, which it wont like. If you connect them in series, the amp will be happier.

      However there is then the cross over to consider. This is where I’m out of my area of knowledge. I would think that as impedance is frequency dependent, then the frequencies going to the mids are only going to see the impedance of the mids, and the frequencies going to the tweeter are are only going to see the impedance of the tweeter. But what happens in the crossover area will be the tricky bit, as the crossover is not a on/off type of cross over, but rather a gradual crossover, meaning some frequencies will see both speakers, or part therefore. This is where speaker designers earn their money, and they have the test gear to verify it all.

      Sorry I can’t help any more.

      Geoff

      • Sijambo kabisa, and thank for your help, I think I should connect them in a way that the amp will be happier, thanks for that tip.

  6. I have a pioneer valve amps-500 27watts per channel with a speaker switch from 8ohm to16ohm
    i would like to connect 2 speakers
    Some splendour s3/5r2 and some epi 100v both rated at 8 ohm
    As an alternative I would like to try some ge 883 speakers and these would be put with the splendour speakers the 883 are rated at 4 ohms and the splendour at 8 ohm
    What should I do

    • Hi John,

      All the articles in this website are based on Hifi amps which don’t use valves (or Tubes as our American friends call them). Most of the content here can be thrown out for valve amps. Valve amps are not as sensitive to lower impedance and solid state amps. However they do not like being run with no load. So you should always have at least one speaker connected to each side.

      Apart from that, I’m not a expert on valve amps. My very general understanding is that they normally have an output transformer with terminals marked 4, 8, and 16 ohm. Using the correct terminal for your load will give you the best transfer of power. So using two 8 ohm speakers connected to the 4 ohm terminal should be fine. My limited understanding is that the amp will probably cope with running a 4 ohm in parallel with a 8 ohms speaker. Or you could run them in series and connect them to the 16 ohm terminal. But, as I said, it is not my area of expertise, sorry.

      Geoff

  7. Hello,

    I need to connect 10 8ohm speakers together, what would be the best way to do this?

    I was thinking 5 in parallel = 1.6 ohm
    And another 5 = 1.6 ohm

    Then collect them in series to make 3.2 to put on a 2,4 and 8 ohm stable pa amplifier.

    Would this work or am i talking rubbish 😀

    Thanks,

    Ben.

    • Hi Ben,
      Technically your method would work, if the amp is capable of driving a load around 2 ohms or more.

      Are you trying to connect all 10 to one amp, or 5 to each side of a stereo amp?

      Have you considered using a distributed speaker system? Depending on what you are trying to do, this is a good way of connecting more than a few speakers.

      Geoff

  8. I am a real novice. I am trying to understand but here is where I am confused.

    I entered speakers 1 and 2 as 4 ohms and speakers 4 and 5 as 8 ohms
    The Yamaha CRX 330 is rated at 20 W + 20 W (6 ohms, 10% THD)

    The total load impedance calculated is 5.3 ohms which is below the 6 ohms the said Yamaha is rated at. I entered 40 watts for the Amplifier Power.

    I am not sure if I should proceed and how. I have read your other article on parallel and series wiring but I am not sure which to choose even though I read the article. Even if I knew which to choose, I actually think it is series, I am not sure how to wire it as the illustrations are tad small, maybe there is a video?

    The speakers are 2 JBL control 5s and the 2 original speakers that shipped with the Yamaha.

    Could you help me a little please, otherwise thank you for some really great articles.

    • Hi Jazzunk,

      It is a matter of working out the total load impedance. Then using that figure to work out the amplifier output voltage for 100 watt power. Then use these figures to work out the power for each speaker based on its impedance and current. Just use the appropriate formula as found in the table at the end of this article.

      Geoff

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