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How much amplifier power is required?

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Awesome thread!

My comment for years has been that most folk overestimate their average power needs and underestimate their peak power needs. Often by an order of magnitude or more either way.
This is an interesting comment, but as an average user, is there any way I can apply this concept into figuring out whether I need higher wattage amplifiers?

In my context, I use a Marantz CR-610 into Dali Menuet speakers (both specs shown below) plus a subwoofer, in a 10 x 13 feet room, desktop setup, computer as source:




Amplifier volume is typically ~16, hardly more than 20 (When analog-in maxes out at 60, can hear lots of hissing. Optical-in at max volume is hiss free).

My initial understanding was that the higher power is only needed when we're either talking about the projection of the audio in a larger room area, or if the speakers are particularly harder to drive.
But when holding the small room size and SPL (and speakers) constant, can a higher wattage amplifier somehow provide better sound quality?
How do I know whether my current amplifier is satisfying my speakers' peak power needs?

Maybe I can then tell my wife that I need to buy a more powerful amplifier, because of, you know, science...
 
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b1daly

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No, not true. A loudspeaker with a flat frequency response and a flat impedance has the same efficiency for all frequencies.
Ok, no loudspeaker has a flat frequency response and/or a flat impedance. But, that does not explain your "when you go higher up the frequencies the required power lowers (with the same SPL)".

I think that I know where your thought comes from:
With a lot of music, the power is spread (roughly) equally accros all frequencies like pink noise. Meaning that there is the same amount of power in the range between 20 Hz - 200 Hz and 200 Hz - 2 kHz and 2 kHz - 20 kHz. If a 2-way loudspeaker has the crossover frequency around 3 kHz, then more than 2/3 of the power goes to the woofer and less than 1/3 of the power goes to the tweeter.
Was this it?
Most music has much higher energy levels in the low frequenches. It will look like a right oriented downward slope on a spectrum analyzer. So less power is needed for the tweeters in a biamped system.
 

b1daly

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I’m still skeptical of mania for high power. I must listening at lower levels than most folks. On a dB meter, at loudest I ever listen to it might peak at 90. Usually averages about 80 with what I think is comfortable.

On one system I use I have a Kenwood KR-5500 (driving ADS L710 which are not especially sensitive) which has roughly 50watts per channel. This is in a small room, with aprox 2 meter listening distance.

It has VU style power meters (with two scales) and the needle is barely moving on the high scale. On the low scale it’s peaking between 1 to 2 watts, but mostly stays below 1 watt I realize these are just measuring voltage in some way, and are averaging, but still, it’s hard for me to believe an amp with power meters barely moving is clipping.

It is obviously highly dependent on how loud you listen and the size and characteristic of your room. A ”live” (undamped) room needs less power to reach the same subjective SPL.

If you are trying to amplify sound outside at any significant distance you need huge amounts of power, as the sound energy quickly dissipates.

This is one of those subjects that cries out for rigorous ABX testing. At listening level A can low power amp B be discerned from high power amp C?
 
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JRG

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I’m still skeptical of mania for high power. I must listening at lower levels than most folks. On a dB meter, at loudest I ever listen to it might peak at 90. Usually averages about 80 with what I think is comfortable.
I think it is related to the size of the listening room.
Apparently, many people who participate in this forum have large rooms that need a lot of power to listen at high volumes.
However, in countries like Spain (where I live), it is normal for people to have their stereo in the living room. A room between 20 and 40 m2 as much.
And in addition people live in apartments with neighbors on the other side of the wall, which prevents listening at high volumes unless the room is soundproofed.

I have a pair of Tannoy XT8f speakers in my living room of about 35 m2 powered with a Yamaha AS501. Rarely the volume pot pass the first 1/3... and when it does, it is because i'm listening a low level recording. It is also true that I mainly listen to modern music and rarely classical music which has greater dynamic.
 

cjfrbw

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No, not true. A loudspeaker with a flat frequency response and a flat impedance has the same efficiency for all frequencies.
Ok, no loudspeaker has a flat frequency response and/or a flat impedance. But, that does not explain your "when you go higher up the frequencies the required power lowers (with the same SPL)".

I think that I know where your thought comes from:
With a lot of music, the power is spread (roughly) equally accros all frequencies like pink noise. Meaning that there is the same amount of power in the range between 20 Hz - 200 Hz and 200 Hz - 2 kHz and 2 kHz - 20 kHz. If a 2-way loudspeaker has the crossover frequency around 3 kHz, then more than 2/3 of the power goes to the woofer and less than 1/3 of the power goes to the tweeter.
Was this it?
I don't think this is strictly correct. Pros who set up active crossovers for speakers generally will state that if all speaker elements have the same efficiency, than average power required tend to drop as the frequency rises i.e. [email protected], [email protected] watts [email protected] [email protected] to 20 watts for a four way system. That is about a 3db drop in amp power per frequency segment from bass to treble, and some place the requirement lower at as much 5-6db per frequency segment. Again, that is presuming the same efficiency per driver.

However, observations have also been made that averaged power requirements vary less for bass and lower midrange i.e. less peak to average, but that peak to average can be very high for midrange and tweeters (even if the average power level is lower), so that also has to be taken into account. I would suspect the 3db drop in amp requirement from bass to higher frequency segments would be more accurate than 5-6db for that reason. That is a halving of required amp power per frequency segment going up from the bass.
 
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This is an interesting topic. I know very little about this stuff but thought I would chip in with my own experience.

As I mentioned on another thread, I am currently running speakers (Revel M106) direct from a Chord TT2.

I have taken up to the top volume level advised (by the TT2 designer) and there is no clipping or distortion that can be heard, and the volume is much greater than I would ever want to listen to. I don’t listen at very low levels and have relatively young ears. I will try and dig my SPL metre out and see what levels I am reaching. The room is 7M x 5M.

I imagine some would expect the sound to be compromised in this setup but it sounds excellent with deep, well controlled bass.

I mention this as the TT2 being used single ended as I am using it, is only 7-8W but has a current output of 10a.

So in my very limited experience, it would seem that current output is just as important as wattage.
 

RichB

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I have in the past looked at the D-Sonic amps which I believe use Pascal modules.
It's a bit irksome when full bandwidth specifications are not available. All power levels quoted are at 1khz.

D-Sonic Amp Specifications.png


The peak output current is shown to be 30 amps on a single channel and 21 amps with Ch2/Ch3 with power varying from 2100 down to 400 watts at 1khz.

This seems odd where the Benchmark AHB2 has 29 amps peak with power from 100 to 180 watts into 4 ohms. Bridged, it is 380 watts into 4 Ohms. All Benchmark specifications are 20 Hz to 20 kHz.

I suspect power requirements are over inflated as are some power specifications. ;)

- Rich
 
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I have in the past looked at the D-Sonic amps which I believe use Pascal modules.
It's a bit irksome when full bandwidth specifications are not available. All power levels quoted are at 1khz.

View attachment 59589

The peak output current is shown to be 30 amps on a single channel and 21 amps with Ch2/Ch3 with power varying from 2100 down to 400 watts at 1khz.

This seems odd where the Benchmark AHB2 has 29 amps peak with power from 100 to 180 watts into 4 ohms. Bridged, it is 380 watts into 4 Ohms. All Benchmark specifications are 20 Hz to 20 kHz.

I suspect power requirements are over inflated as are some power specifications. ;)

- Rich

Yeah those numbers are a load of crap in my opinion. I don’t believe those crazy “typ” figures. Benchmark ah2b and the company that created and manufactures them seems to be one of the few, and very rare, honorable hifi manufacturers left who stays genuine with dignity.
Wish there were more truthful and genuine engineers and salesmen in this audio stuff we have all come to be enthused by. Welp not going to get my hopes up lol I don’t think the oils of snakes will be changing it’s demeanor anytime soon....
 
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I am digging up this old thread, because I didn't want to open a new one and my question seems to be somewhat in line with the topic at hand:

When I try to determine how much amplifier power is required, I was curious whether REWs SPL measurements can be used.
During normal playback I measured an Lzpeak of around 88dB when I crank the volume of a bass heavy track.
Measured at the listening position, roughly 1m from the speakers, since it's a nearfield setup, 2 speakers playing.

Can that number be trusted? If I understand it correctly, SPL(z) weighted does not factor in human hearing and is a flat curve.
Seems awfully low, considering how loud it felt, suggesting that I am in the realm of 1W including transients.
Assuming REW is able to catch these... it sure is able to catch a slammed door, darn Neighbors messing up measurements. :<
 

RichB

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I am digging up this old thread, because I didn't want to open a new one and my question seems to be somewhat in line with the topic at hand:

When I try to determine how much amplifier power is required, I was curious whether REWs SPL measurements can be used.
During normal playback I measured an Lzpeak of around 88dB when I crank the volume of a bass heavy track.
Measured at the listening position, roughly 1m from the speakers, since it's a nearfield setup, 2 speakers playing.

Can that number be trusted? If I understand it correctly, SPL(z) weighted does not factor in human hearing and is a flat curve.
Seems awfully low, considering how loud it felt, suggesting that I am in the realm of 1W including transients.
Assuming REW is able to catch these... it sure is able to catch a slammed door, darn Neighbors messing up measurements. :<
So, you asked is it possible that what you considered to be loud was 88 dB. Yes, because 88 dB is loud.

One rule-of-thumb is that the speaker sensitivity rating 1 watt at 1m anechoic can be a good starting point for 2 channel music and room reinforcement. I found this to be the case for the Salon2s in my room. 2.83 volts produced 86 dB at my listening position.

Here is the measurement based method that I used assess the power required for two speakers in my room.

The following is required:
  • A Multi-meter to measure AC voltage
  • A 440 Hz full scale (0 DBFS) WAV, FLAC, MP3 file.
To measure:
  1. Set your AVR/Processor to low level
  2. Attach the multimeter to the + and - of your speaker terminals (I used clip to banana but you'll have to find a good method for your speakers)
  3. Play the full scale tone.
  4. Adjust the level until the reading is as close to 2.83 volts as possible.
  5. Write down this volume level.
  6. Make sure your are playing the tone from 1 or 2 speakers (but not in surround mode).
  7. Measure the SPL at your listening position with a sound pressure meter. I don't think I would trust a phone.
  8. Write down this DB level.
  9. Consult your speaker documentation. If you think it is closer to 8 Ohms this is approximately 1 watt. The Salon2s were mostly 4 Ohms so that doubles the power, or 2 watts.
  10. Make a spreadsheet with your typical listening levels for music and movies.
I played both speakers with the tone for my tests since this is typical. If you played 1 speaker and agree then double the SPL measured.
For me, 2.83 volts = 2 watt and stereo playback of 86 dB.

Here are the results using this methodology. The Typical listening levels represent my preferences.
Measured SPL at Listening Position.jpg


This is a good amplifier power estimator calculator:
http://myhometheater.homestead.com/splcalculator.html

Using this method and lowering efficiency of the Salon2s to 83 dB (because they are 4 Ohms and use more power), then AHB2 180 watts is estimated to produce 104 dB.

SPL CalculatorSalon2.jpg


According to my measurements, 104 dB requires 128 watts.
According to SPL calculator, 104 dB requires 180 watts.
My speakers are about 2 feet from the corner, so in corner was the correct selection.

The ABH2 clip indicators illuminate as expected with music at -10 or louder, so this is indicates the spreadsheet is correct.

- Rich
 
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Thank you for the explanation. One of these days I need to get me a new Multimeter *chuckles*
So, you asked is it possible that what you considered to be loud was 88 dB. Yes, because 88 dB is loud.
Actually, what I am wondering is whether the transient SPL(Z) values are correct at 88dB. (Measured with a calibrated UMIK-1)
The running SPL(C) value REW displays when I am listening to music fluctuates between 55dB and 65dB and goes into the low 70s when I push it.

At 440Hz, according to Senpai's measurements the Aria 906 have roughly 7Ω Impedance with a phase angle of +40°.
I don't think he measured the sensitivity but sound stage network did and came up with 87dB/W (Focal's datasheet gives an optimistic 89dB/W).
 

RichB

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Thank you for the explanation. One of these days I need to get me a new Multimeter *chuckles*

Actually, what I am wondering is whether the transient SPL(Z) values are correct at 88dB. (Measured with a calibrated UMIK-1)
The running SPL(C) value REW displays when I am listening to music fluctuates between 55dB and 65dB and goes into the low 70s when I push it.

At 440Hz, according to Senpai's measurements the Aria 906 have roughly 7Ω Impedance with a phase angle of +40°.
I don't think he measured the sensitivity but sound stage network did and came up with 87dB/W (Focal's datasheet gives an optimistic 89dB/W).
Here is the SoundStageHiFi.com Review:

https://www.soundstagehifi.com/index.php/reference-components/790#:~:text=The Aria 906’s MDF-based cabinet construction is fairly,however, decidedly differ from those of other brands.

he Aria 906’s sensitivity measured 86.8dB/2.83V/m, which is typical for a speaker of this size and configuration. The impedance remains above 8 ohms from 700Hz to 20kHz, and dips to a low of 4 ohms at 200Hz, but never lower.
There is nothing special about 440 Hz other than it will not excite room modes.
However, if you measure playing a 0 DBFS sine-wave, it represents the maximum volume.
It can be measured steady-state. From there, you can compute the power required for volume as I described above.

Bookshelf speakers so I don't think they are going to remain linear or have reasonably low distortion above 100 dB.

- Rich
 
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However, if you measure playing a 0 DBFS sine-wave, it represents the maximum volume.
It can not be measured steady-state.
I am sorry but I do not understand the statement above. Both sentences seem to contradict each other.

Still no multimeter but I measured a 440Hz 0dB FS sine with my usual "this is loud settings" and got a Z-weighted SPL of 84dB with 2 speakers playing.
Seems to be in line with the formerly measured 88dB peak, considering the Dirac house curve, which has a roughly 4dB boost in the bass region.

Taking the measured sensitivity into account, It looks like that I only use about 1W on transients. Multiplying that by 10 as a safety net, it would seem that there is no point in worrying that my 70Wpc AVR amplifier is ever going to clip.

Bookshelf speakers so I don't think they are going to remain linear [...] above 100 dB.
I'm pretty sure that the correlation between SPL and pitchfork waving of my neighbor is also non linear.
Looks more like exponential function to me. *chuckles*

Judging by Senpai's measurements, one should stay below 90dB for best results.
 
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