HOW TO MATCH SPEAKERS AND AMPS
Not as confusing as you might think
How To Match Speakers And Amps
Speakers and amps: two components that should go together like peanut butter and jelly. You’ve been scouring the Internet in search of the perfect speaker to take your listening experience to the next level, and now all you need is the perfect amp to pump out those peanut butter vibes. Speaker matching, or better yet, system matching, is all about synergy. It’s not just a matter of matching spec numbers and going about your day. Whether you want a two-channel stereo system that truly sings, or a multi-channel home theater setup that really slams, the only way you’re going to get it is with amp and speaker combos that have the right synergy. From source to speaker, the synergy throughout your system—or lack thereof—is what makes or breaks sound quality and performance. Since every hifi and home theater enthusiast is looking for the best of both worlds, let’s get synergy right from the start.
You don’t need to be Einstein to get this right, but before buying a thing, you do need a vocabulary lesson. These are the key terms used in speaker and amp specs that are critical to your search for good synergy and great sound. First up, Impedance.
Impedance starts with I, just like important. Used in both amp and speaker spec sheets, impedance is a measure of the electrical resistance of your components. It’s measured in ohms and is often represented with the symbol “Ω”—as in 8Ω. This is part of the equation in determining the synergy between your speakers and amp.
Speakers typically carry ratings between 4 and 8 ohms. Amplifiers generally operate effectively in a specified range: say, 4 to 16 ohms. Check your specs, but when that’s the case, connecting a speaker rated between 4 and 16 ohms will be OK.
But—and this is where it gets more interesting—you need to be aware that many amps output different wattages into different ohms. (We’ll go into wattage in more detail below—for now, all you need to know is that it’s a measure of power.)
For example, NAD C326BEE stereo integrated amplifier outputs a continuous 50 watts per channel into 4 ohms and 8 ohms, but its Dynamic Power (sometimes called Peak Power, which refers to when it’s being pushed to its max) hits 100 watts into 8 ohms and 150 watts into 4 ohms. Our word of warning here is to take note of your amplifier’s different output ratings and your speaker’s power handling capabilities to ensure you’re on the path to synergy instead of sacrilege.
Generally speaking, it’s fine to connect higher impedance speakers to an amp; what you don’t want to do is plug low impedance speakers, let’s say 4 ohms, into an amp that specifies a minimum 8-ohm limit. To take some math work and guessing out of the equation, a lot of speaker and amp manufacturers are switching over to using “compatible with” ohm ratings, which makes things a lot easier.
Measured in watts, power comes in a confusing variety of ratings. A common belief is that more watts equal more volume. Watts is more about how much power a speaker can handle and how much power an amp is putting out. It used to be standard practice to mate a 50-watt amp to 100-watt speakers and call it a day. Not so today.
Amp spec sheets often reference Continuous Power (sometimes known as Continuous Power Output or Continuous RMS Power) and Dynamic Power (sometimes called Peak Power). For simplicity’s sake, we’re going to talk about Continuous Power and Dynamic Power in this guide. Continuous Power is where the magic’s at. This is the spec that tells us how powerful an amplifier is.
A typical spec sheet might read something like “50 watts Continuous Power into 8 ohms,” meaning the amp will output 50 watts into an 8-ohm speaker. Dynamic Power is essentially a measure of an amp’s maximum power output when pushed beyond its Continuous Power rating—we’re talking peaks of power for milliseconds during a dynamic song or soundtrack here.
As for speakers, every manufacturer seems to rate power a little bit differently. Many high-end speaker manufacturers are swaying away from offering Continuous Power and Peak Power ratings, favoring “recommended amplification” ratings instead. Take KEF, who simply lists “Amplifier requirements: 25-100W” for the LS50. Then there’s Ascend Acoustics, which still provides Minimum Recommended Power, Maximum Continuous Power, and Maximum Short Term Peak Power ratings for its speakers.
A speaker-specific stat, sensitivity is essentially a measure of how loud a speaker will be in decibels from 1 meter away when driven by 1 watt of power (yes, just 1 watt).
Let’s take the LS50’s 85dB sensitivity rating, for example. With 1 watt of power, the LS50 will produce a sound pressure level (SPL) of 85dB at a 1 meter distance—just about perfect for not going deaf during long listening sessions.
Why does sensitivity matter? It directly relates to how loud a speaker gets. When distance and power are the same, a lower sensitivity speaker (say, 85dB) would sound quieter than a higher sensitivity speaker (say, 90dB) in the same room and setup. Sensitivity doesn’t make or break a good speaker, but a higher-sensitivity speaker could save you from having to buy a larger amplifier to reach your favorite listening levels (but we’ll get to that later).
Here’s another fun fact about sensitivity: Amplifier power must double to increase a speaker’s SPL by 3dB. So, our LS50 would need 1 watt to produce 85dB of sound, 2 watts to produce 88dB, 4 watts to produce 91dB, 8 watts to produce 94dB, 16 watts to produce 97dB, 32 watts to produce 100dB, 64 watts to produce 103dB, and so on if you want to go deaf. Conversely, sound falls off fast. You need to expect about a 6dB falloff every time you double your distance from your speakers.
And this is why we can’t just pick an amp and speakers with a couple of matching specs and hope for the best.
Putting It All Together:
We know this is a lot to take in—and you probably weren’t looking for a math lesson! Unfortunately, system synergy isn’t as simple as numbers matching. You need a plan. How loud? How far? How big? How many? There’s a lot to consider when planning your perfect setup.
Having a good idea of your end goal, whether it be a simple stereo setup with something like theKEF LS50 and NAD C326BEE mentioned above, or a multi-channel home theater, the process for seeking synergy is the same, and it actually all starts with thinking about your listening room.
A large room could require larger speakers or more powerful amps than you anticipated getting. Where the speakers will be located, as well as where you’ll be seated, are big considerations.
Keep in mind that you’ll sacrifice sound quality if your speakers and listening position aren’t planned correctly. We generally recommend spacing speakers 1.5x as far away from you as from each other, angled slightly inward, at the same height, and with the tweeters as even with your ears as possible. And always avoid obstructing your speakers with furniture and placing them in corners or too close to walls (unless the speaker manufacturer advises otherwise).
But back to the point; we know you came here looking for a simple cheat sheet on how to match your speakers and amp. Sadly, there’s nothing simple about getting system synergy right. Too often people don’t account for the impact their room will have on their setup, and we don’t want you to do that. So, let’s put these factors into practice.
First, figure out how far you plan to sit from your speakers. Second, get an idea for how loud you want them to sound. These two figures are essential in determining the speaker sensitivity and amp power ranges you need to work within. If you happen to already have a speaker in mind, Crown Audio has a really handy calculater that you can plug distance, desired SPL, and speaker sensitivity figures into to calculate just how much Continuous Power you need out of an amp. Then all you need to check on is if that power rating is within your speaker’s safe operating range.
Obviously, speaker sensitivity plays a bigger role than a lot of people think it might, and you can use this calculator to see how big of an impact it makes. Point being, if you need 200 watts of power to get your 85dB speakers singing at the volume you want from your listening chair that’s 3 meters away from your speakers, but your speakers are only rated to handle 100 watts of Continuous Power, well, you’re outta luck and you’ve got no synergy. Start looking for a different speaker—or sit a whole lot closer to it.
Also, don’t forget impedance matching. A speaker with a nominal impedance of 8 ohms can easily dip or jump into other ranges during dynamic frequency changes, so just make sure your speaker impedance and power handling is compatible with the impedance range of your amp and the output power it can safely deliver.
We’ve probably made this all sound infinitely more difficult than it is, but with some careful calculations and research into the components you’re eyeing, you can quickly figure out if your system will have good synergy or not.
A Practical Example:
Take the NAD C326BEE amp and KEF LS50 speaker combo again.
We can easily surmise that the NAD C326BEE will drive the KEF LS50 just fine in a small listening room. Why? Because the NAD C326BEE outputs 50 watts of Continuous Power into 8 ohms, and tops out at 100 watts of Dynamic Power. This amount of power is safely within the 25 to 100-watt recommended amplification range of the 8-ohm LS50. And since the LS50 carries a sensitivity rating of 85dB, we know it will play plenty loud in a small room.
So: our amp and speakers match impedance at 8 ohms; the amp’s Continuous Power and Dynamic Power are both safely within the speaker’s power handling range; and the speaker’s sensitivity will allow it to reach good volume levels in a small room. Sounds like we have some synergy here.
Here’s our disclaimer: If you blow up your speakers, or your amp, it’s your fault. Got it? Good.
“You can blow up speakers with virtually any size amp, or you can use them safely with virtually any size amp, depending on how you drive them,” says GoldenEar Technology’s Sandy Goss in an interview with Dennis Burger for Home Theater Review. Offering an example, Goss says he has successfully driven a pair of GoldenEar Triton Two towers (which carry a recommended amplification rating of 20 to 500 watts) with a 22-watt-per-channel tube amp, and even a 6-watts-per-channel amp.
Ask a dozen audio experts about how much amplification a speaker needs given its power handling rating and you’ll get a dozen different opinions. We’ve seen recommendations for 10-percent more Continuous Power over a speaker’s comparable power handling capabilities. We’ve also seen recommendations for doubling a speaker’s Continuous Power rating. These recommendations likely spawn out of the belief that too little power is what damages speakers rather than too much. It actually goes both ways.
There are two very common and unfortunate causes of blown speakers and amps that we want you to avoid at all costs. First is connecting speakers to an amp with a Continuous Power rating that’s way too much for your speakers to handle. What often happens here is that the speaker can’t efficiently dissipate the heat energy from the amp, which then burns up the speaker’s voice coil and suspension, meaning you may as well have lit your hard-earned money on fire instead.
Second is running an amp that is far too weak for the speakers connected to it. It’s not that the lower power is bad, but it gets bad when you keep cranking up the volume knob in search of a suitable listening level that likely doesn’t exist; instead your amp will start burning itself up because you’re demanding more power than it can create. This causes the amp to overheat and start clipping the signal being sent to the speakers, creating excessive distortion and high frequency energy that can, and likely will, waste your speakers away. Then you’ll have a burnt-up amp and speakers.
So, let’s not do that.
Our recommendation for the ultimate safeguard against smoking your system is to carefully look at the maximum power handling capabilities of your speakers and amp, and, based on the listening room specs we talked about, choose an amp that outputs the correct Continuous Power for the volume level you seek, and a speaker that can gobble up twice that amount of power. So, if you need 100 watts out of your amp at 8 ohms, pump it into an 8-ohm speaker that can handle 200 watts of Continuous Power. This should give you plenty of headroom for when the impedance drops, causing those Dynamic Power peaks, and a little more room to spread those gooey peanut butter vibes.