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How to Match Amps and Speakers

multichannel speaker wire terminals on the back of an av receiver

Welcome to your comprehensive guide on successfully pairing amplifiers and speakers.

Navigating the world of audio equipment can be complex, with many factors to consider.

This article will help you avoid common pitfalls, from matching the power ratings and impedance of your amp and speakers to considering room size, brands and price.

You will learn how to protect your equipment from potential damage and achieve the best sound quality possible.

So how much do you need to worry about matching your amplifier and speakers – and what are the critical issues?

Key Points

Here is a summary of the key points discussed in this article, with a couple of extra tips about protecting 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 if 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, buy a more powerful amplifier or get more efficient speakers.

Read on for all the details.

Do You Need to Match Amplifiers and Speakers?

The most crucial point is that matching your amp and speakers isn’t absolutely critical.

That’s not to say you should ignore it entirely and shouldn’t give it any thought.

It’s more of an understanding that you could ignore it, and everything will usually be fine. 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 compatible with each other.

But you can study the specifications closely and get a better match to get the best out of your equipment. It’s up to you.

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

The example above displays the impedance as a nominal impedance. The term nominal means the average amount, which 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.

Next, you need to determine the impedance range 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, which is good and should cover most speakers 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.

Most 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 using speakers with a low impedance, such as 4 ohms. The amplifier’s power supply may overheat if the impedance is too low.

The most common scenario will be an AV receiver that only supports 6 to 8 ohms speakers. Ideally, you shouldn’t connect 4-ohm speakers in this case.

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

But if you want to be sure, 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, 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, the amplifier should output a minimum of 15 watts and a maximum of 130 watts.

That covers most amplifiers designed for home use.

RMS and Peak Power

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).

RMS measures the real-world power that the amplifier produces at a given frequency into a specific load (or impedance).

So RMS power 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

Not see the term ‘continuous?’ As long as you can see the power given for a particular impedance and frequency, 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 for the same impedance as your speakers, measured against at least 2-channels. 

In the example above, the power output uses an 8-ohm impedance.

The alternative measurement is peak power – the maximum power 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 extremely loud music or sound effects.

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

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

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

You cannot compare an average value with a peak value as they are different.

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

Plenty of Room for Error

However, you should also 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. 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 their maximum specification. You’ll hear when the speakers start 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, you will only need to send a reasonable volume to them, and they will never overload.

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

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 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 volume you need to fill it.

However, how loud you want it will vary between people, and only you can decide the ideal sound level for your room.

You could use the standard THX reference level. The reference level is ‘0’ on most receivers’ volume control scale, the same volume used when mixing the soundtrack.

The problem with using reference-level audio is it is very loud and will be too high for many people in a home environment.

The most crucial issue is that your amplifier has enough power to fill the room.

Only large rooms need amplifiers with powerful outputs. Say over 150 watts per channel.

Consider Speaker Size

If you are sensible about the size of speakers you need for a room, you will automatically get 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, you will want a powerful system to give you enough volume to fill the space.

If so, you won’t buy small satellite speakers to connect to your powerful 150 watts per channel amplifier.

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

However, if you did this, it 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 send the speakers much more power than they can 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 won’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.

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.

Don’t Forget Speaker Placement

The final point is that you will usually 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 this 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.

They will say, “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, the sound of particular amps and speakers isn’t a perfect match.

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

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

The speakers you choose will make the most difference to the sound you hear.

All reputable amplifier brands will provide a good overall sound. The more expensive amplifiers will mainly offer more power and better imaging and positioning in the sound field.

But don’t overlook all the other variables – the room you are listening in, speaker placement, your listening position and the other equipment in the chain.

All these will change the sound that gets to your ears. In many cases, more than the amp and speakers your choose.

If you want to disappear down this particular rabbit hole, try reading forums for audiophiles and home theater enthusiasts. Try this Reddit here or AV Forums here.

But, if this is 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 match your speakers and amplifier is to look at the price of the equipment you will buy.

Do you want to avoid confusing amplifier and speaker specifications altogether? In that case, this can be an excellent way to avoid those boring details.

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

For example, say you spend $3000 on an amplifier. In that case, you’ll be asking for trouble by connecting it to $50 speakers.

Why would you do that? At $3000, you will have a great-sounding amplifier – but you won’t hear the quality if you connect it to cheap speakers.

However, spend $1000 on your amplifier and $1000+ on your speakers, and you can be 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.

It doesn’t have to be exact, but a ballpark match will work fine.

Maybe Buy a Home Theater System or Soundbar?

When you’ve read all this boring technical stuff, you might think buying an all-in-one package is easier.

An all-in-one comes with an amplifier and speakers in one complete system.

The obvious advantage of a complete system is the amplifier and speakers will work well together without you thinking about all the details.

The main downside of this approach is that you don’t get the flexibility to choose which hardware you use. And it will be harder to upgrade the amplifier or speakers later.

But it’s an option.

Wrapping Things Up

If you are buying a separate amplifier and speakers, it can be a technical minefield.

It is easy to get confused about what to buy.

However, when you break it down to the essentials, you can see there is less to worry about than you thought.

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 want to avoid constantly running an amplifier at maximum volume to get the required sound level in your room. Excessive volume 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.

You won’t have an issue if you always use common sense when operating your sound system.

However, if you try hard enough, you can damage any speaker with just about any amplifier.

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. Technically, ensure the amplifier supports your speakers’ impedance and 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 your speakers’ recommended amplifier power range, 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, ensuring they work with your current amplifier is most important. You should find out the speaker’s impedance and suggested power requirements to do this. Then, the choice comes down to style (bookshelf or floor-standing), brand (sound quality), and cost.

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About The Author

Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has been 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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