Finding compatible speakers and amplifiers is a common issue for many people when they are looking to buy new equipment. This guide to matching your amplifier and speakers should help to answer some of your questions.
If you don't want to buy a home theater system package, but would rather a separate amplifier and speakers; then it can be difficult to know what to look for.
Most of us have seen all the listed specifications - but we aren't too sure how we go about matching the two together. And, are there other important issues to think about?
The worry is we will buy the wrong amplifier for our speakers (or vice versa) and we have visions of blowing the speakers the first time we switch it all on.
So how much do we need to worry about this - and what are the important issues?
The main thing that becomes clear when we consider this issue, is that it is not something that we should be losing any sleep over.
That's not to say we should ignore it completely. That we shouldn't give it any thought at all. It's more an understanding that you could ignore it and everything will usually be fine. The chances are you would still buy a speaker and amplifier combination that would work well together.
You are unlikely to find speakers and an amplifier, designed for home use, that are completely mismatched. That is, to the extent that you will damage them by connecting them together and turning up the volume to a reasonable level.
Most components that are available for home systems are all going to be roughly compatible with each other. The question is, do you want to study the specifications closely and get a better match? So you get the very best out of your equipment.
There isn't an exact science to matching your amplifier and speakers. And you have plenty of room for error. You won't have too many problems unless you try connecting equipment which is completely incompatible.
One of the most important things to consider is the impedance of the speakers.
All speakers have an impedance (or resistance) and this will be in the specifications of the speakers - usually in the range of 4 to 8 ohms.
Now that you know the impedance of the speakers you are going to use, check if your AV receiver or amplifier supports this. The manual of your amplifier should tell you the speaker impedance it can support. It should be listed as in the picture above.
The example here, pictured above, says the amplifier will be fine with any speaker from 4 to 16 ohms. This is pretty good and should cover most speakers that you can buy for home theater or Hi-Fi use.
In my guide to the best AV receivers in 2018, I display a specification table for each AV receiver which includes the supported speaker impedance.
Generally, most amplifiers will support the majority of speakers available on the market today, but it is useful to make sure this is the case.
The main danger is with speakers that have a low impedance - say 4-ohms. This can put a strain on the power supply of an amplifier if the amplifier isn't designed to handle a low impedance.
The most common scenario will be an AV receiver that only supports speakers from 6 to 8 ohms. In this case, you shouldn't be connecting 4-ohm speakers to it.
For a more detailed explanation, go the article on matching speaker impedance.
You will often find speaker specifications that suggest a suitable power rating. This refers to the power output of the amplifier the speaker is connected to. Again, this is just a guideline. You don't have to find an exact match.
Obviously, the ideal match here is to get the rated watts per channel of the amplifier to match the rated power handling of the speakers.
If the amplifier outputs 100 watts per channel into 8-ohm speakers - then you can look for 8-ohm speakers that are rated to support 100 watts.
The main point is to make sure that the ratings you are looking at are both comparable. That is, they are either both RMS (or average) values, or they are both peak (or music power) figures.
If you compare an average value with a peak value then they are not the same and cannot be compared.
For more information on this, go to the article on speaker power ratings.
However, you are not going to do much damage to your speakers if your amplifier is slightly underpowered or overpowered for your speakers. There is plenty of room for error.
A 50 watt per channel amplifier will work fine with speakers rated at 100 watts. The biggest problem would be if the 50-watt amplifier didn't give you enough volume in your room. If you were always running the volume control of the amplifier at maximum, you would be in danger of sending clipped waveforms to the speakers. This could damage them.
A 150 watt per channel amplifier will work fine with 75-watt speakers. You'll only have a problem with this if you turn the volume up very loud - for a long period. You'll hear if the speakers are starting to struggle with the power you are sending to them.
If the speakers are a good size for your room, then you will probably never need to send too much volume to them.
As a general guideline, it is better to get an amplifier that is slightly more powerful than your speakers are rated for.
In this instance, you will have plenty of power to drive your speakers to the full. The amplifier will have plenty of headroom for loud peaks - and you can rely on your ears to tell you when your speakers are starting to get too much power!
An amplifier that is underpowered can be more harmful than a more powerful one.
If your amplifier hasn't got enough power for the volume you require, you will end up turning the volume knob right up. This can lead to the amplifier sending clipped waveform to the speaker. This can really do some damage.
Go here for more information on AV receiver and amplifier power specs.
One of the most important considerations is room size - and the amount of volume you need to fill it. However, how loud that actually is will vary among different people. Only you can decide how loud you want the audio in your room.
There are standard THX reference levels that you can work to, although these are pretty loud and will be too high for many people in a home environment. It will also require you to measure your room with a sound pressure level meter.
The most important issue is that you have enough power from your amplifier to fill the room that you will be using. It is only large rooms (or if you know you need very loud volumes) that need big amplifiers with a large output - say over 200 watts per channel.
Then, if you are sensible about the size of speakers you need for that room you will have a good match between amplifier, speakers and the size of your room.
For example, if you have a very large room with high ceilings, then you'll probably be wanting a powerful system to give you enough volume to fill the space. If you do, then the chances are you won't be buying small satellite speakers to connect to your powerful 200 watts per channel amplifier.
It's logical that small satellite speakers won't be big enough to give you the volume you need in a large room.
However, if you did this, then it surely wouldn't be a great surprise if you damaged the satellite speakers. You would turn up the volume too much to try and fill your room. You would be sending them much more power than they are designed to handle.
So, in this example, you would be more likely to choose bookshelf, floor standing or in-wall speakers. Those with a power rating close to that of your amplifier. Then you wouldn't have any problems.
The following video gives a good summary of some of the things you want to consider when deciding on the power you need for your room:
The video talks about the concept of speaker efficiency. As if you weren't confused enough already, right? I've tried to help by writing this article on understanding speaker sensitivity and efficiency. It explains how you can get more volume without buying a more powerful amplifier.
Another good way to look at matching your speakers and amplifier is to look at the price of the equipment you are going to buy.
If you really don't want to be bothered with looking at amplifier and speaker specifications (and understanding them!) - then this can be a good way to avoid those boring specifications completely.
If you look to spend approximately equal amounts on your amplifier and speakers, then you won't go far wrong.
For example, if you spend $3000 on an amplifier/receiver, then you might be asking for trouble if you connect them to $50 speakers.
But who would do that anyway? At $3000, you will have a great sounding amplifier. But, you won’t hear this if you connect it to cheap speakers.
However, if you spend $1000 on your amplifier and $600 on your speakers, then you can be confident they will be fine together. That you will be able to get the most from your purchases.
If you look to spend similar amounts on your amplifier and speaker system, then you are almost certain to be buying equipment that will be a close match. It doesn't have to be exact!
Of course, by the time you've read all this boring technical stuff, you might think it's easier just to buy an all-in-one package. A system that comes with the AV receiver and the speakers. Like the Onkyo HT-S9800THX Home Theater System, pictured here.
The obvious advantage of a system is the amplifier and speakers will be designed to work well together. The main downside is you don’t get the flexibility of choosing exactly which hardware you use. And, it will be more difficult to upgrade either the amplifier or speakers later.
If you want to research home theater systems, you could take a look at my article 'The Best Home Theater Systems in 2018: Top 10 Reviews & Buying Guide'.
So, as you can see, if you are buying a separate amplifier and speakers, it can be a technical minefield. It is easy to get confused about matching amps and speakers.
However, when we break it down to the important things, we can see that there isn't too much to worry about when matching speakers and amplifiers.
The main thing is that you buy an amplifier with enough power to give you the volume you want for your room size. Then get some speakers which are a reasonable match for that amplifier (impedance, power rating and size).
You don't want to be constantly running an amplifier at maximum volume to get the required sound level in your room. This can put a strain on the power supply and doesn't give you any headroom for peaks in the soundtrack (the loud bits!).
In my experience, if you blow your speakers, then it is usually your fault. If you use common sense then you should never have a problem. However, if you try hard enough, then you can damage any speaker with just about any amplifier.
Here is a summary of the points discussed above, with a couple of extra tips to safeguard your speakers:
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.