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How to Match Amps and Speakers

Matching Your Amplifier & Speakers: A Simple Guide - amplifier speaker connections

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Are you scared of blowing your speakers? What amplifier should you buy so you don't have problems? Learn what to consider when matching amps and speakers.

Finding compatible speakers for your amplifier – or the right amp to match your speakers – is a common problem for many people looking to buy new equipment.

This guide to matching amps and speakers should help answer some of your questions.

If you don’t want to buy a home theater system package but instead have a separate amplifier and speakers, it can be challenging to know what to look for.

You have seen all the listed specifications – but you aren’t sure how to match the two together. And, are there other important issues to think about?

The worry is you will buy the wrong amplifier for your speakers – or vice versa – and you have visions of blowing the speakers the first time you switch it all on.

So how much do you need to worry about this – and what are the critical issues?

Do You Need to Match Amplifiers and Speakers?

When you consider this issue, the main thing that becomes clear is that it is not something you should be losing any sleep about.

That’s not to say you should ignore it entirely and that you 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 entirely unsuitable – at least to the extent that you will damage them simply by connecting them and turning up the volume to a reasonable level.

Most components available for home systems will 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.

So, you won’t have too many problems unless you try connecting entirely incompatible equipment.

Let’s take a look at some of the issues you should consider.

Matching Impedance

One of the most important things to consider is the impedance of the speakers.

All speakers have an impedance – or resistance – which is often 4 to 8 ohms for home theater and hi-fi speakers.

So, the first thing to do is find out the impedance of your speakers, and you can find this information in the speaker’s manual or on the manufacturer’s website.

Impedance rating for a Kef Q-Series Speaker
Impedance rating for a Kef Q-Series Speaker

You will notice that in the example above, the impedance is listed as a nominal impedance. This just means the average amount, and this is what you need to look for.

You may also be given the minimum impedance, as above, because the impedance varies according to the frequency.

If you’re really keen, you will want to make sure your amplifier supports that too – although, in most cases, you won’t need to worry about that.

Then, you need to find out the impedance range that your amplifier supports. Again, the manual or product page on the manufacturer’s website should give you this information.

Impedance rating for a Denon AV receiver
Impedance rating for a Denon AV receiver

The example shows 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.

There is a specification table for each AV receiver in the guide to the best AV receivers, including the supported speaker impedance.

The majority of amplifiers will support most of the speakers available on the market today, but it is helpful to make sure this is the case.

The main danger is that speakers with a low impedance – say 4-ohms – can stress an amplifier’s power supply 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, ideally, you shouldn’t be connecting 4-ohm speakers to it.

However, it will still work, and you will be fine if you are careful with your listening levels.

If you want to be sure, though, stick within the guidelines supplied by the manufacturer.

For a more detailed explanation, go to the article on matching speaker impedance.

Matching Power Ratings

You will often find speaker specifications that suggest a suitable power rating, which refers to the supported power output of the connected amplifier.

Again, this is just a guideline, and you don’t have to find an exact match – but the speaker manufacturer may give a power range that the speaker can handle.

So, you should check if your amplifier will deliver power within that range.

Speaker power requirement for a Kef Q-Series speaker
Speaker power requirement for a Kef Q-Series speaker

In the above example, you can see the amplifier should output a minimum of 15 watts and a maximum of 130 watts.

That covers most amplifiers designed for home use.

However, not so fast! There are different ways of describing the power ratings of amplifiers, and you need to make sure you are comparing like with like.

There are two main ways of describing an amplifiers power output:

  • Continuous power: aka RMS power
  • Peak power: aka dynamic or music power

The best power specification to look for in an amplifier is continuous power (RMS).

In simple terms, this measures the real-world power that the amplifier produces at a given frequency into a specific load (or impedance).

This is the best way to understand how the amplifier will perform in normal, day-to-day use.

Continuous power rating for an Arcam AV receiver
Continuous power rating for an Arcam AV receiver

Even if you can’t see the term ‘continuous,’ as long as you can see the power given for a particular impedance and frequency, then that will be the continuous power.

Power rating for a Denon AV receiver
Power rating for a Denon AV receiver

Ideally, you will see the numbers given for the same impedance as your speakers – and for at least 2-channels. In the example above, the power is measured against an impedance of 8 ohms.

The alternative is peak power – which is the maximum power that the amplifier can deliver at a particular point in time.

However, the peak power rating will likely only last for a fraction of a second – when there is a particularly loud piece of music or sound effect.

So, most of the time, this isn’t relevant to the general power output.

Some manufacturers like to quote this figure as it gives a higher number than continuous power and appears more impressive.

The main point is to make sure that the ratings you are looking at are comparable – and where you can, use the continuous power rating.

If you compare an average value with a peak value, they are not the same and cannot be compared.

For more information on this, go to the article on speaker power ratings.

However, you should understand that you will not damage your speakers if your amplifier is only 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 for your room.

If you were always running the amplifier’s volume control at maximum, you would be in danger of sending clipped waveforms to the speakers, which could damage them.

Similarly, a 150-watt per channel amplifier will work fine with 75-watt speakers, and you’ll only have a problem with this if you turn the volume up very loud – for an extended period.

Most of the time, amplifiers generate much less power than they are specified for – and you’ll hear if the speakers are starting to struggle because the audio will begin to break up.

In which case, turn it down!

If the speakers are a good size for your room, then you may never need to send too much volume to them.

As a general guideline, it is probably better to get a slightly more powerful amplifier than your speakers are rated for.

In this instance, you will have plenty of power to drive your speakers to the full, and the amplifier will have plenty of headroom for loud peaks.

Then, you can just rely on your ears to tell you when your speakers are starting to get too much power.

Go here for more information on AV receiver and amplifier power specs.

Speakers, Amplifiers and Room Size

One of the most critical considerations is room size – and the amount of volume you need to fill it.

However, how loud you actually want it will vary between different people, and only you can decide how loud you want the audio in your room.

There are standard THX reference levels that you can work with, 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 crucial issue is that you have enough power from your amplifier to fill the room that you will be using.

Only large rooms need amplifiers with a large output – say over 200 watts per channel – or if you know you want the volume really loud in a smaller space.

So, if you are sensible about the size of speakers you need for that room, you will have a good match between the amplifier, speakers, and your room’s size.

Large room with home cinema equipment

For example, if you have a massive room with high ceilings, then you might want 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.

Logically, small satellite speakers won’t be big enough to give you the volume you need in a large room.

However, if you did this, it surely wouldn’t be a great surprise if you damaged the satellite speakers when you turned up the volume too much to fill the room.

You would be sending the speakers 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 – 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:

YouTube video

The video talks about the concept of speaker efficiency.

As if you weren’t confused enough already, right?

If you want to learn more about this, check out understanding speaker sensitivity and efficiency, which explains how to get more volume without buying a more powerful amplifier.

A final point on this issue is that you will often place the speakers in a smaller area around your viewing area, even in a large room.

If you sit ten or twelve feet away from your screen, you don’t have to place the speakers on the back walls of your room – in fact, if the walls are too far away, it is best not to.

You can use speaker stands to create a smaller listening space within your large room and place the speakers closer to your listening position.

In which case, you won’t need a large amplifier and speakers to fill the whole room – just the area where you will be watching the screen.

Matching Speaker and Amplifier Brands

A common area for audiophiles is to recommend particular speaker and amplifier combinations.

For example, these speakers sound pretty bright, so they will work well with this brand’s amplifier.

Or, this amplifier produces a great low end, so these speakers are a perfect match.

However, don’t assume that everybody thinks this way – they don’t.

There isn’t a ‘perfect’ sound that certain amplifiers and speakers produce – there is just personal preference – and a different amplifier with a set of speakers will just sound… different.

Some may like it, and some may not, but there isn’t a right and wrong.

Then there are all the other variables – the room you are listening in, the speaker placement, the listening position and the other equipment in the chain.

All these will change the sound that gets to your ears.

If you want to disappear down this particular rabbit hole, then you should start reading forums for audiophiles and home theater enthusiasts.

You could try this Reddit here, or AV Forums here.

And, if this is really important to you, the best solution is to go to a retailer with a demo room and listen for yourself. Only you know what you like.

Try Matching Price

Another good way to look at matching your speakers and amplifier is to look at the price of the equipment you will buy.

If you really don’t want to be bothered with looking at amplifier and speaker specifications – and understanding them – then this can be an excellent way to avoid those boring specifications altogether.

A common rule of thumb is to spend approximately equal amounts on your amplifier and speakers – but if you have extra money, then spend more on your speakers.

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 $1000+ on your speakers, then you can be pretty confident they will be fine together.

Or match a $500 AV receiver with a $1000 speaker package.

Then you will get the most from all your equipment. But, it doesn’t have to be exact.

Buy a Home Theater System or Soundbar?

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.

An all-in-one comes with the AV receiver and the speakers in one complete system.

The obvious advantage of a complete system is the amplifier and speakers will be designed to work well together.

The main downside is that you don’t get the flexibility to choose which hardware you use – and it will be more challenging to upgrade either the amplifier or speakers later.

So, it’s your choice.

If you want to research home theater systems, you could look at ‘The Best Home Theater Systems in 2022: Top 10 Reviews & Buying Guide‘.

Or, you could also consider a simple soundbar system for your home theater.

Conclusion

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 you break it down to the essential things, you 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 good match for that amplifier in terms of impedance, power rating and size.

You don’t want to constantly run an amplifier at maximum volume to get the required sound level in your room. This can strain the power supply and doesn’t give you any headroom for peaks in the soundtrack – the loud bits!.

To be honest, if you blow your speakers, then it is usually your fault.

When operating your sound system, you should never have a problem if using common sense.

However, if you try hard enough, 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:

  1. Impedance matching: make sure the amplifier supports the impedance of your speakers.
  2. Power ratings: be careful when comparing power ratings between amplifiers and speakers – the numbers may be average or peak figures.
  3. If in doubt: choose an amplifier with a power rating slightly higher than the speaker’s rating – this is better than an underpowered amplifier.
  4. Think about: the room size and speaker size. Larger rooms will need more powerful amplifiers – and speakers to match.
  5. Amount of power: 50-100 watts per channel (RMS) should allow plenty of volume for a reasonable room size for most home theater systems.
  6. Match price: try to match the price of your amplifier and speakers – they will probably work fine together.
  7. Use common sense: it’s not an exact science. Most amplifiers will work fine with most speakers designed for home use as long as you don’t go to extremes.
  8. Equalization: try to avoid excessive equalization. It is better to cut a frequency rather than boost. Boosting can result in large unwanted peaks at specific frequencies.
  9. Switching on: when you switch on your amplifier, try to get in the habit of keeping the volume knob down. Or even at zero. Many higher-end amplifiers will do this automatically. It can protect your speakers from unwanted power surges and noises.
  10. Don’t go to 11: don’t turn the volume control on your amplifier to the maximum, and try to keep it at 70 – 75% maximum. If it’s still too quiet for you, buy a more powerful amplifier or get more efficient speakers.

Frequently Asked Questions

How to Choose an Amplifier for Your Speakers?

When choosing an amplifier for your speakers, you can make several choices – from technical issues to subjective matters like timbre and sound quality. On the technical side, you should ensure the amplifier supports your speakers’ impedance and that the power output is within your speaker’s recommended range. If you want to play things very loud, you will need a more powerful amp – or more efficient speakers.

What Is the Recommended Amplifier Power for Your Speakers?

To find out the recommended amplifier power range for your speakers, you should check out the speakers manual or the manufacturer’s website. All good quality speakers should list this information.

What Amplifier Should You Use for Your Speakers?

The most important thing is that the amplifier supports the specifications of your speakers. Find out the impedance of your speakers and the recommended amplifier power requirements. Then, ensure that your amplifier meets these specifications. After that, you can choose between several reputable amplifier brands, and the choice comes down to cost and perceived sound quality.

What Speakers Should You Get?

When choosing speakers, the most important thing is to make sure they work with your current amplifier. To do this, you should find out the speaker’s impedance and suggested power requirements. Then, the choice comes down to style (bookshelf/floor-standing/satellite), brand (sound quality), and cost.

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Matching Your Amplifier & Speakers: A Simple Guide

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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. You can find out more here.

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