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Speaker and Amplifier Power Ratings

The speaker power rating should be an important consideration to 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. So, what do you need to know about speaker power ratings?

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) is referring to how much power the speaker is designed to safely receive from an amplifier before it will start 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.

Amplifiers are not all made equal, and 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 capabilities of the speaker, then you can be confident that you won’t ever damage the speaker by driving it too hard.

Speaker Minimum Power Ratings

When you are looking at the speaker specifications, you may see a minimum value for the power.

If there is a minimum figure, then this is the minimum power level required to drive the speaker to make any useful noise at all. 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 1000-watt speakers with a 10-watt amplifier.

Maximum Power Ratings of Speakers

More common is the maximum figure, and this 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 you could exceed them for short periods without having a problem.

So, if the speaker specification says maximum power of 130 watts, then you don’t really want to hook them up to an amplifier which is 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, if 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 or Peak Values

Other important numbers to look for are RMS (average power) and peak (maximum power) values.

Ideally, the specification should make this clear (but often won’t).

In our example above, if the 130-watts maximum power is average (or RMS), then the speaker would probably 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 completely 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 you should 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

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.

So if the amplifier power specs are rated at 8-ohms, then the speaker power specs should be measured at 8-ohms if you are to compare them.

Suggested Amplifier Power Range

A specification for speakers that is becoming more common is a suggested amplifier power range.

If you look carefully at the specifications, many speaker manufacturers just give a suggested range of amplifier power ratings that can comfortably be used with their speakers.

This range is often from 50-watts to 200-watts per channel, so you’ll have to buy a 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 exactly match a 100-watt amplifier with 100-watt speakers.

The reality is that any reasonably close match will be fine, and it is only if you go to extremes that you may start to have problems.

The Bottom Line

The main point is that you want your amplifier and speaker power ratings to be close to each other so that you can get the best performance out of both.

You want to drive the output of the amplifier reasonably hard to get a comfortable listening volume in your room. But, 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 hard to get the best sound out of them, but to have enough headroom available to cope with the loud bits.

Modern speakers will be able to handle a large range of power from most amplifiers and receivers designed for home use. So, while it is useful to check the power rating of a set of speakers to get a rough idea if they are compatible.

Don’t be too concerned about getting an exact numerical match as you have plenty of room for error.

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 amount of volume you send to the speakers, don’t forget that you are in charge of the volume control! , and you will hear if you are starting to reach the limits of your speakers before you do any serious damage.

However, with an underpowered amplifier, you will more likely need to turn the volume control up very high to get a good sound level.

When 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 are going to connect an amplifier and speakers that are completely incompatible, like connecting 10-watt speakers to a 500-watt amplifier, then they will work just fine together.

You’ll have to try hard to start blowing speakers with most standard amplifiers and speakers available today.

Remember, you have two things on the side of your head which 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!

If you are sensible and don’t try to connect equipment, which is completely mismatched, then you are unlikely to have too many problems.

However, if you know you are someone who loves to really crank up the volume for long periods, then you may want to be more careful in matching the right speakers for your amplifier.


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