What's with a speaker's amp power recommendation?

[b-rock]

Thanks to this place and Amir's breath-of-fresh-air YouTube channel, my BS detector is bristling. I searched around for an answer, but I didn't find anything to the point...

What's the deal with amplifier power recommendations for various speakers? Why did a reviewer recommend a 50W amp to "properly" drive a set of Neat Iota speakers, for instance? I listen to my setup often at 0.1 to 1 Watt peak output... Isn't my NAD 3020's 1 Watt the same as a "50 Watt" amp's 1 Watt? Common sense tells me that my suspicion is correct and that I shouldn't even bother posting this question -- but there's rather a lot I don't know.

 

[digitalfrost]

I listen to my setup often at 0.1 to 1 Watt peak output... Isn't my NAD 3020's 1 Watt the same as a "50 Watt" amp's 1 Watt?

Yes it is. The thing to understand is the exponential nature of the power requirements to go louder.



See also https://geoffthegreygeek.com/amplifier-power/

So a 100W amplifier does not offer twice the volume of a 50W amplifier. Yes it's a 3dB gain, but to the human ear you only gain ~ 23%. Most consumer amplifiers are around 100W. If you can't reach the desired volume with that power, adding much more will not help very much, you'd need 1000W to get twice the loudness. I have the feeling @restorer-john might correct me here, and I love big amps as well, but really if 50-100W doesn't work for you I'd rather change speakers than spend a lot of money on amplifiers.

Speakers have an efficiency rating of xdB/W/m which will tell you how loud they go at 1W at 1m distance (you can add 3dB for stereo speakers). These typically range from 82-94dB. You can easily see that offsetting these kinds of differences with amplifier power is rather futile.

 

[b-rock]

Quality reply. Thanks.

So the reviewer -- who was considering the Neat Iotas for near-field listening in a small room is out to lunch. Or deaf.

 

[Chrispy]

Or just an all too typical reviewer? Speaker wattage ratings just aren't that useful generally....

 

[DVDdoug]

What's with a speaker's amp power recommendation?

I suspect it's nonsense and I don't think there is a standard. I've seen a case where two speakers from the same manufacturer had the same sensitivity but the speaker capable of handling higher power had a higher "minimum power recommendation".

I listen to my setup often at 0.1 to 1 Watt peak output.

Probably not loud enough to dance to.

According to my handy-dandy spreadsheet going from 1W to 50W is about +17dB.

 

[Chrispy]

LOL love the "minimum" power recommendations....

 

[MrPeabody]

Yes it is. The thing to understand is the exponential nature of the power requirements to go louder.

View attachment 136991

See also https://geoffthegreygeek.com/amplifier-power/

So a 100W amplifier does not offer twice the volume of a 50W amplifier. Yes it's a 3dB gain, but to the human ear you only gain ~ 23%. Most consumer amplifiers are around 100W. If you can't reach the desired volume with that power, adding much more will not help very much, you'd need 1000W to get twice the loudness. I have the feeling @restorer-john might correct me here, and I love big amps as well, but really if 50-100W doesn't work for you I'd rather change speakers than spend a lot of money on amplifiers.

Speakers have an efficiency rating of xdB/W/m which will tell you how loud they go at 1W at 1m distance (you can add 3dB for stereo speakers). These typically range from 82-94dB. You can easily see that offsetting these kinds of differences with amplifier power is rather futile.

Interesting table however I don't believe that the notion of perceptual 2x louder, half as loud, 5x louder, etc., is anything but fantasy. I know when one sound is louder to me than another sound but, but if I'm asked to turn up the volume until I think it is twice as loud, I likely to turn it up to where you can just barely tell that it is any louder, and then insist that it is twice as loud, just to make the point.

 

[MrPeabody]

One of my pet peeves is when, thanks to one of the OTHER audiophile forums on the 'net, the fans of some particular speaker will create a meme to the effect that the particular speaker that they very much like needs an extra helping of amplifier power in order that the speaker will "open up", or some such thing. No mention of any issue with the amp clipping or the amp getting hot or the sound not being loud enough with the volume control all the way up. None of that. Then you try to point out that unless the speaker is actually using the additional watts, the watts it is using are the same as the watts with a lesser amp. Then they start bringing up the "dynamics" and the dynamic range etc. Then you point out that they hadn't mentioned these things at the beginning, only the need for the speaker to "open up", and that if the reason is because of clipping distortion that is expected to occur with a weaker amp, why didn't they say this in the first place? And why wouldn't it depend on how loud the owner wanted to play it, and on what kind of music they listen to, etc? You point out that if that weaker amp was in fact clipping, it would also clip with any other speaker that has roughly the same sensitivity, playing the same stuff at the same volume level, and that as such it would be mainly an amplifier issue and not a speaker-specific issue and that this isn't what they were talking about because they weren't talking about the output voltage capability of the amplifier but were talking about how that one speaker with mystical properties needs an amplifier with a beefier transformer and bigger electrocaps because this is needed in order for that mystical speaker to "open up". The honest truth is that very many audio people really do believe that irrespective of the question of whether the output voltage is banging against the rails, the sound quality of a speaker, particularly its ability to produce bass with "punch", "slam" and "roundhouse kick", will generally not measure up to its true potential unless driven by the one particular amplifier that has been deemed, by the collective mind of those in the knose, to be the perfect, ideal amplifier for that particular speaker, such that if you attempt to drive the speaker with some other amplifier, even one with greater output voltage capability and greater current tolerating capability and lower distortion and noise than the approved amp, the speaker will not measure up to its true potential. If you want that speaker to open up and sound the way it's supposed to, you absolutely have to buy the amp approved for use with that speaker, otherwise you wasted your money on the speaker because there's no way for the speaker to open up with the amp you've been using with it. And if you knew anything about audio, you should already know this, because everyone else who bought that speaker knows it, except for you, 'cause you're a dummy and you can't hear anything anyway because your eardrums are almost certainly covered over with decades of accumulated ear wax.

 

[trl]

It's about dB in the end, here's a thread that might help here a bit: https://www.audiosciencereview.com/...output-level-in-our-home-theater-rooms.11105/. So you need to aim towards to 105 dB for both speakers and 115 dB to subwoofers to achieve the THX standard. Of course, getting 115 dB @ 20 Hz is crazy and pretty much impossible with domestic low-sized subs, but possible for frequencies above 30 Hz (especially if using 2 subs).

Most people listens music with peaks getting between 90...100 dB, so it's all about yourself in getting your system as loud as you may like. However, based on http://www.sengpielaudio.com/calculator-efficiency.htm, with two speakers having an efficiency of 88dB/W@1m the amplifier should have a 2 x 220 W of power (THD < 1% across 20...20000Hz) to reach the THX required 105 dB of acoustic power, while with only 2 x 1 W it will only hit 82.5 dB summed from both speakers.

 

[AnalogSteph]

However, based on http://www.sengpielaudio.com/calculator-efficiency.htm, with two speakers having an efficiency of 88dB/W@1m the amplifier should have a 2 x 220 W of power (THD < 1% across 20...20000Hz) to reach the THX required 105 dB of acoustic power, while with only 2 x 1 W it will only hit 82.5 dB summed from both speakers.

That said, we don't typically listen in anechoic chambers, so the formula used there is likely to be overly pessimistic (when diffuse sound comes in, the 6 dB / doubling decay increasingly flattens out - you can see this in the SPL vs. distance graphs in Genelec's Choosing Monitors, and these are given for fairly well-treated rooms). There's a rule of thumb that says SPL @1 m anechoic ~= SPL at 2.5-3 m real-life room for two speakers. So you may, in fact, only need 25 W in your example.

In real life there is substantial variability in power requirements, all depending on speaker sensitivity, listening distance, room acoustics (absorption) and last but not least preferred listening level (I have found that my own preferred levels tend to be about 10 dB lower than average, for example, and that alone is a factor of 10 in power).

Recommendations for minimum amplifier power tend to be based on about 103 dB @ 1 m anechoic.

 

[trl]

Thanks for the update!

"The industry standard reference sound pressure level (SPL) for cinema and TV sound production work is between 82 and 85 dB at the listening position" - seems that production standard is different than THX, which is common sense after all.

 

[tomtoo]

Interesting table however I don't believe that the notion of perceptual 2x louder, half as loud, 5x louder, etc., is anything but fantasy. I know when one sound is louder to me than another sound but, but if I'm asked to turn up the volume until I think it is twice as loud, I likely to turn it up to where you can just barely tell that it is any louder, and then insist that it is twice as loud, just to make the point.

Yep, realy wonder too. When do i perceive something as double as loud? I mean its a damn good question, but for my self i cant answer it. Whats the double from freaking loud or even better, whats the double from cant hear anything? 0*2=0?

 

[escksu]

Thanks to this place and Amir's breath-of-fresh-air YouTube channel, my BS detector is bristling. I searched around for an answer, but I didn't find anything to the point...

What's the deal with amplifier power recommendations for various speakers? Why did a reviewer recommend a 50W amp to "properly" drive a set of Neat Iota speakers, for instance? I listen to my setup often at 0.1 to 1 Watt peak output... Isn't my NAD 3020's 1 Watt the same as a "50 Watt" amp's 1 Watt? Common sense tells me that my suspicion is correct and that I shouldn't even bother posting this question -- but there's rather a lot I don't know.

It has alot to do with speaker design and characteristics. Some speakers have very low sensitivity and needs alot more power to drive. Some speakers also needs to be played loud to come to life, others may sound distorted instead.

Speaker/Amp pairing is very very important. Eg. you cannot buy 2/4 ohms speakers if your amp only support 6/8 ohm ones. Your amp will not be able to drive the speaker properly. Eg. your NAD3020 is rated 20W. If you use a pair of low sensitivity (Say 80db) speakers, its definitely not going to drive it properly as well.

 

[Head_Unit]

What's the deal with amplifier power recommendations

I suspect it's nonsense and I don't think there is a standard.

Having worked as both a loudspeaker engineer and marketing whore, you don't have to suspect, I can tell you for sure it is useless nonsense. Always provided why? Because it is expected. Sometimes made small so as to seem more accessible. Sometimes big to seem compatible with mega-amps. Meaningless. Even pro sound or CEA or whatever ratings don't mean too much.
For any newbies reading, it works like this:
- It doesn't take much power to play fairly loud, though it can take a LOT of power to play REALLY loud unless your speakers are unusually efficient (i.e. horns).
- As long as the music sounds clean, a big amp won't blow up your speakers, so long as you TURN IT THE HELL DOWN when things start to distort. Cranking to 11 will break everything eventually.