A typical specification for home theater speakers is the speaker power rating. But, what does it mean? And, how do you match the speaker power to your amp?
The speaker power rating should be an essential consideration for anyone who is looking to buy new speakers.
It will usually be listed alongside all the other speaker specifications – most of which we don’t understand, right?
However, the power specification is an area that is often misunderstood by many people – but which can be important when trying to put together a sound system.
While you will be unlikely to have issues if you are careful, I’m sure you really don’t want to be that person who disintegrates the speaker cones of your brand new set of speakers.
So what do you need to know about speaker power ratings?
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Speaker or Amplifier Power?
Firstly, don’t get confused between amplifier power ratings and speaker power specifications.
Just be clear that the speaker doesn’t generate power – the amplifier does.
Therefore, the power specification that you will see for speakers – measured in watts – refers to how much power the speaker is designed to safely receive from an amplifier before it starts to distort.
If a speaker is driven too hard, it distorts and gets very hot. If so, you may permanently damage the speaker, and it could become unusable.
So we really don’t want to be doing this!
Amplifiers are not all made equal, so you need to check the watts per channel that the amplifier can output.
If the amount of power it can output is well within the speaker’s capabilities, then you can be confident that you won’t ever damage the speaker by driving it too hard.
Follow this link if you want more information about understanding amplifier power specs.
Minimum Power Ratings
When you are looking at the speaker specifications, you may see a minimum value for the power.
This is the minimum power level required to drive the speaker to make any useful noise at all – so your amplifier will need to deliver this amount of power at the very least.
This shouldn’t ever be a problem, and so you don’t need to worry about this figure unless you’re trying to do something extreme – like driving speakers rated for 500-watts with a 10-watt amplifier.
Maximum Power Ratings
More common is the maximum figure, which is the power level the speaker can take before it starts to distort or clip.
Ideally, we don’t want to be going over this number.
However, bear in mind that many figures you see in the specifications are often quite conservative, and in reality, you could exceed them for short periods without having a problem.
So, if the speaker specification says maximum power of 130 watts (as in the example pictured here), you don’t really want to hook them up to an amplifier rated at 1000 watts output.
This is because it probably won’t take much to get that amplifier to send more than 130-watts and potentially damage the speaker.
Having said that, as long as you are careful with the volume control, then you can pretty much drive any set of speakers with any amplifier – regardless of its power.
It’s just safer to match them a bit better.
RMS vs Peak Values
Other significant numbers to look for are RMS (average power) and peak (maximum power) values.
Ideally, the specification should make this clear, although it often won’t.
In our example above, if the 130-watts maximum power is average (or RMS), the speaker would comfortably handle a peak power signal from the amplifier of around 300 watts.
However, if the 130-watts value is a peak value (sometimes called peak music power), the average power it can handle would be more like 70-watts.
So RMS and peak values are entirely different things, and it is important to compare like with like if you are matching the power of an amplifier to a set of speakers.
Always try to make sure you compare two RMS values or two peak values. Don’t be fooled into matching the RMS output for the amplifier – to the peak output for the speaker.
If it doesn’t say if it is an RMS or peak value, then I would usually assume that it is a peak value – as some manufacturers like to give the highest figure as it generally sounds better!
Power Specifications and Impedance
This is another potential area of confusion.
Any power rating you see should be given into a particular load – or impedance.
Therefore, if an amplifier rating provides 100 watts of RMS power into 8-ohm speakers, then the RMS power it provides will be different if you attach 6-ohm speakers.
Always compare like with like.
If the amplifier power specs are rated at 8-ohms, then the speaker power specs should be measured at 8-ohms if you compare them.
Go to this article for more information on speaker impedance matching.
Suggested Amplifier Power Range
A specification for speakers that is becoming more common is a suggested amplifier power range.
Many speaker manufacturers give a suggested range for amplifier power that can comfortably be used with their speakers.
This range is often around 50 to 200-watts per channel – so you’ll have to buy a pretty powerful amplifier before you start worrying about this.
This is often a better way of describing the capabilities of a speaker as it makes it clearer which amplifiers will comfortably drive these speakers – and it keeps it simple to understand.
It also makes the point that you have much more flexibility in matching the power of an amplifier and speakers than you may have thought.
You really don’t need to precisely match a 100-watt amplifier with 100-watt speakers.
The reality is that any reasonably close match will be fine – and only if you go to extremes, then you may start to have problems.
The Bottom Line
The main point is that you want your amplifier and speaker power ratings to be reasonably close so that you can get the best performance from both.
You want to drive the output of the amplifier reasonably hard to get a comfortable listening volume in your room – but also have enough headroom to comfortably handle the odd musical peak.
Or, for the times when you really want to crank up the volume!
Similarly, you want the speakers to be driven relatively hard to get the best sound out of them – but to have enough headroom available to cope with the really loud bits.
Modern speakers will handle all the power from most amplifiers and receivers designed for home use.
So, while it is helpful to check a speakers’ power rating, don’t worry about getting an exact numerical match as you have plenty of room for error.
To understand the different types of speakers you can get for a surround sound system, you might want to take a look at the Best Home Theater Speakers in 2021: Buying Guide & Reviews.
It can be argued that it is better to have an amplifier that is more powerful than the speaker ratings, rather than less.
This is because you can easily limit the volume you send to the speakers – don’t forget that you are in charge of the volume control!
Plus, you will hear if you are starting to reach the limits of your speakers before you do any serious damage.
However, you will need to turn up the volume control very high with an underpowered amplifier to get an acceptable sound level.
And if you do this for long periods, your amplifier may start to send clipped waveforms to the speaker – which probably will do some damage.
So what have we learned about the speaker power rating?
Well, don’t worry about it too much!
Most speakers will be fine for most amplifiers designed for use in a home environment.
Unless you connect an amplifier and to entirely incompatible speakers, they will work just fine together.
You’ll have to try pretty hard to start blowing speakers with most standard amplifiers and speakers available today.
Remember, you have two things on the side of your head that are perfectly designed to detect any problems between your amplifier and speakers.
Yes, your ears should tell you if you’ve got the volume too loud for your speakers. If you hear any distortion, then maybe it’s time to turn it down a bit!
As long as you are sensible and don’t connect completely mismatched equipment, you are unlikely to have too many problems.
However, if you know you love to really crank up the volume for long periods, you may want to be more careful in matching the right speakers for your amplifier.
If all this sounds a bit too complicated for you, don’t forget you have the option of buying an all-in-one system. These will come with an amplifier and speakers that are designed to work well together.
You can take a look at my buying guide to the best home theater systems in 2021 – this takes a look at the options you have if you want an all-in-one system.
About Home Cinema Guide
Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has worked as a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment.
Love the website. Everything is in plain, easy-to-understand language. It's a great resource!