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).

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.

Notify of
Thushantha (Sri Lanka)

Thanks for details and knowledge.

Jeresamuel (Philippines)

hi geoff,
I have 4 wharfedale speakers (300W @8 ohms each). I connected 2 speakers in parallel on the left and 2 parallels on the right so they are now 4 ohms each channel.
Im confused if the computation is 600Wx1.5=900watts per channel amp or is it still 300Wx1.5=450watts per channel amp @4 ohms.

Is a 1000W power amplifier enough?
What amplifier should i use then for maximum sound?
hope you can enlighten me..:)

Jestin (Bahrain)

Hi Geoff,
I have Yamaha RXV383 av receiver, per channel 70w 6-8ohm. I have 30watt 8ohm woofer, 30watt 8ohm midrange and 20watt 4ohm tweeter. How I connect to the amp. How I understand it’s parallel or series connection. And 30watt8ohm woofer is ok for this amp?

Andrew (Vancouver)

So if we wanted to run 3 identical sets of speakers at 8 ohms each from 1 amp, with lots of power reserve available, would a series parallel circuit make sense? Parallel would give 2.7 ohms, series 24. Series/parallel about 5.3 I think. Would this result in all speakers running at the same volume or would the single one draw more power and hence be louder?

Joe (Yogyakarta)

Hi Geoff, thanks for the explanation but I’m still confuse because friend of mine tell me bit different (or I don’t understand yet).
Let’s say I have 2x 800 watt AES at 8ohm and I want to parallel them.
If I refer to this article https://www.crownaudio.com/how-much-amplifier-power (let’s say 1.6x continuous)
Do I need the poweramp with 1600×1.6=2560watt or 800×1.6=1280 watt continuous at 4 ohm?
Thank you.

Aaron Carson (Portland, OR)

Hi Geoff!! This is a great site. I jumped the gun on one of my purchases and an left with some trouble. I have 2 speakers that are treated at 150 rms. And 2 that are rated at 75 rms. The amp is a 2/3/4 channel. The rms output is 70×4 @ 4ohms. So for the front, 75 rms speakers in going to wire them directly to a separate channel and get great wattage. That part I have figured out. The option to bridge this amp is what I was planning on doing. It will put out 200 Watts but… Read more »

Mr Scott Ravenhill (Tamworth)

Hi Geoff,
My amplifiers rating is 2x150w 4OHM.

If I run 2x 8ohm speakers on this, I understand both speakers will receive 75w each.

However if I run 4 x 8ohm speakers in parallel, will each speaker still only receive 150w?

Thanks, Scott

David McIntyre (Nishinomiya, Japan)

Hi Geoff, Your site came up when doing some research and my wife saw your pic and realised we (sort of) knew you from Summer School. We’re now missionaries in Japan. I’ve set up a very basic sound system with a Marantz 1501 AV amp and a pair of Yamaha NS-100 speakers. The speakers have two terminals (or bi-wired). They have a nominal input level or 100 watts and maximum of 300 watts. The amp is 50 watts per channel. I have simply connected the two speakers to the front stereo speaker terminals of the amp. My question was, would… Read more »

Ken Graves (Logansport, IN)

Hi Geoff, I looked at all you’ve written and shown us and a huge thank you is in order – very well presented. I have a situation that’s a little different from what the simulator or other diagrams show. I have 3 speakers, all 8 ohms. two of them are 25 watt rated, the other 75 watts. So I want to run them with a 70 watt amp. Am I correct in thinking that I could put the two 25 watt speakers in parallel and then put that pair in series with the 75 watt guy and everyone would be… Read more »