There have been questions about the high frequency response of the Sonos Amp. User hodgeal posted a very interesting plot showing the frequency response of the Sonos Amp using the software REW. It didn't show excessive high frequencies in that single test.
I had the opportunity to compare the Sonos amp to my Peachtree amp using the same software (which is very useful and easy to use - thanks hodgeal), and this provides a comparative test of the Sonos Amp frequency response.
The Peachtree Nova 125 SE amp is well-respected in the audio community. It is a class D digital amp, same as the Sonos Amp, but as far as I can tell uses different chips. The test uses Duntech Marquis speakers and a Studio Projects C1 microphone. The mic is setup on-axis at a distance of 120cm, which is pretty standard. But none of the details should matter because this is a comparison under identical conditions - I simply swapped amps and repeated the test.
And the results?
As you can see, the amps are almost identical. Ignore low frequencies - they vary from test to test even with the same amp below about 30Hz. At high frequencies, above about 4kHz, the Peachtree gets gradually brighter, ending up being about 1.5dB louder at 20kHz. This would be imperceptible to pretty much everyone.
Note that there is a slight increase in high frequencies above about 7kHz for both amps, so this could be the speakers. However, I think this is due to the frequency response of the microphone - the specifications show a similar slight increase.
Cheers, Peter.
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Very nice, thank you!
I see that there are two lines for 75%, but are seen as one because they overlap completely?
This bears out what I hear in other Sonos units - a palpable elevation of bass and even some vocals, and I expect that I don't hear the smaller boost to the treble given my already age affected hearing of those frequencies. And because a lot of my music is low/midrange dominated jazz, with vocals not being the opera/soprano kind.
I am little surprised to see that at 50%, which is moderately loud where my play units are concerned, there is still a significant effect of the loudness toggle and that it takes levels to be as high as 75% for it to vanish.
I see that there are two lines for 75%, but are seen as one because they overlap completely?
This bears out what I hear in other Sonos units - a palpable elevation of bass and even some vocals, and I expect that I don't hear the smaller boost to the treble given my already age affected hearing of those frequencies. And because a lot of my music is low/midrange dominated jazz, with vocals not being the opera/soprano kind.
I am little surprised to see that at 50%, which is moderately loud where my play units are concerned, there is still a significant effect of the loudness toggle and that it takes levels to be as high as 75% for it to vanish.
I see that the other LS50 thread has a graph that shows what the loudness toggle on Sonos Amp does and it shows a noticeably higher boost at the low end compared to that at the treble end.
That's at 50% volume levels; I wonder how it would look at the 20% mark.
That's at 50% volume levels; I wonder how it would look at the 20% mark.
Does your graph allow you to see what Sonos actually does via loudness?
See this for my understanding:
"The most famous, well-used measurement for plotting our perception of loudness against the frequency of tones is the Fletcher-Munson curve(s) of equal loudness, published in 1933. The graphs were updated in 1956 by D.W. Robinson and R.S. Dadson. They were refined again in 2003 and adopted by the International Standards Organization as ISO 226. The purpose of the graph is to show that for humans to consider two pitches equally loud, the amount of energy necessary to produce the tone at one frequency may be completely different than at another. The multiple lines, spaced in 10 dB increments, also show that the energy/frequency differences are steeper at lower intensity levels and flatten out at extremely high intensities, though not quite as much as Fletcher and Munson first determined.
The "loudness button" on a stereo amplifier is intended to boost bass frequencies at lower volume levels where the curve is the steepest."
Perhaps it is the 2003 revision that drives the boost to just the bass frequencies. In my listening as well, the impression conveyed by the loudness switch is a higher presence of the lower end at low volumes. But it would be interesting to see what a measurement shows, for Sonos.
It is quite possible that my ears don't hear much treble in the first place, for the increase to be noticed!
See this for my understanding:
"The most famous, well-used measurement for plotting our perception of loudness against the frequency of tones is the Fletcher-Munson curve(s) of equal loudness, published in 1933. The graphs were updated in 1956 by D.W. Robinson and R.S. Dadson. They were refined again in 2003 and adopted by the International Standards Organization as ISO 226. The purpose of the graph is to show that for humans to consider two pitches equally loud, the amount of energy necessary to produce the tone at one frequency may be completely different than at another. The multiple lines, spaced in 10 dB increments, also show that the energy/frequency differences are steeper at lower intensity levels and flatten out at extremely high intensities, though not quite as much as Fletcher and Munson first determined.
The "loudness button" on a stereo amplifier is intended to boost bass frequencies at lower volume levels where the curve is the steepest."
Perhaps it is the 2003 revision that drives the boost to just the bass frequencies. In my listening as well, the impression conveyed by the loudness switch is a higher presence of the lower end at low volumes. But it would be interesting to see what a measurement shows, for Sonos.
It is quite possible that my ears don't hear much treble in the first place, for the increase to be noticed!
As to the loudness thing - the usual design for that is to boost the lower mid to low side of things at low sound levels to bring back some depth/richness to the sound that is otherwise missing at those levels. This boost tapers off as sound levels approach 50%. Treble is usually not boosted by the loudness switch.
I disagree. The usual design of a loudness switch is to boost both bass and treble. The reason is that human hearing is less sensitive in both the bass and treble frequencies at low volumes. This has been traditionally demonstrated by the "Fletcher-Munson curves", although I believe they have been superseded by the similar "Equal-loudness contours".
Cheers, Peter.
That's a really interesting thought. Presumably all amplifiers have to be able to handle the frequency-dependent impedance of a whole range of speakers. I seem to remember my Duntech Marquis have impedance ranging from 3-6 ohms (nominally 4 ohms) at different frequencies. If DDFA-based amps are more susceptible to this variable load, I can imagine there could be some issues. However, presumably all DDFA-based amps would be affected in a similar way. I'm not sure if this has come through in reviews of different brands. Of course there could always be design choices unique to Sonos that exacerbate the problem.
Cheers, Peter.
Peter,
One that talks about the effect of the loudness thing:
https://www.whathifi.com/reviews/sonos-amp
One that says it is bright and claims that this is also how other reviews have found it:
https://www.theverge.com/2019/3/7/18254803/sonos-amp-review-speaker-specs-features-price
Another one that says the same about brightness:
https://www.soundandvision.com/content/sonos-amp-streaming-amplifier-review-page-2
No surprise, none have any measurements attached.
I suspect that posters here that say the same thing have read these and other such reviews and been influenced by these. There is nothing to be said about one poster that found it bright, but found that burning in takes care of that:-).
As to the loudness thing - the usual design for that is to boost the lower mid to low side of things at low sound levels to bring back some depth/richness to the sound that is otherwise missing at those levels. This boost tapers off as sound levels approach 50%. Treble is usually not boosted by the loudness switch. I have no idea how Sonos has built this function for the Sonos Amp.
One that talks about the effect of the loudness thing:
https://www.whathifi.com/reviews/sonos-amp
One that says it is bright and claims that this is also how other reviews have found it:
https://www.theverge.com/2019/3/7/18254803/sonos-amp-review-speaker-specs-features-price
Another one that says the same about brightness:
https://www.soundandvision.com/content/sonos-amp-streaming-amplifier-review-page-2
No surprise, none have any measurements attached.
I suspect that posters here that say the same thing have read these and other such reviews and been influenced by these. There is nothing to be said about one poster that found it bright, but found that burning in takes care of that:-).
As to the loudness thing - the usual design for that is to boost the lower mid to low side of things at low sound levels to bring back some depth/richness to the sound that is otherwise missing at those levels. This boost tapers off as sound levels approach 50%. Treble is usually not boosted by the loudness switch. I have no idea how Sonos has built this function for the Sonos Amp.
In any event, it's a bit silly to have loudness and sub turned on by default.
Can other AMP owners confirm that the default settings after initial setup is indeed Loudness=ON?
IIRC with the Connect and Connect:AMP the loudness is disabled by default.
When I first set up my amp, it took a while to realise that loudness was turned on by default. Perhaps this has caused reviewers to note brightness, since loudness boosts the high frequencies as well. I also noted elsewhere that the sub was turned on by default, although no sub was attached. The latter doesn't affect the sound, but loudness does, particularly at lower volumes (I'm assuming it works this way. hodgeal only tested at 50% volume. Perhaps there is a software bug here? I might try and test this when I get time.)
In any event, it's a bit silly to have loudness and sub turned on by default. Loudness may be reasonable for Play 1's, but not the amp with your own speakers. Perhaps the fact that loudness is enabled should be shown somewhere prominently in the app, like next to the volume control.
Kumar, do you have links to the reviews you mention that complain about brightness?
Cheers, Peter.
Of course the thing about the Sonos Amp is that with a built in DAC as well as DSP, it is more than just an amp. Those that have claimed brightness have also noted that they were able to tame it by using the EQ which should mean that brightness was found with initially flat EQ. And then there is the case of one that found that the sound righted itself after a power down/power on cycle. All of which muddies the waters somewhat.
Nice work! Pretty strong evidence that the brightness reputation is groundless. Maybe some reviewers did not have the amp running with all the settings configured for flat output.
P.S. would you mind plotting just 200-20000Hz and blowing up the vertical scale?
P.S. would you mind plotting just 200-20000Hz and blowing up the vertical scale?
It would be interesting to know of any name brand amp that delivers different results beyond measurement error differences if dropped into this set up; that would disprove the claim that amps do not have sonic signatures as long as they don't clip.
Not that I expect you, Peter, to do this, just saying that anyone that wants to so disprove that statement can do so beyond merely saying so.
Ditto for DACs.
Not that I expect you, Peter, to do this, just saying that anyone that wants to so disprove that statement can do so beyond merely saying so.
Ditto for DACs.
Thanks, Peter. Interesting information, so much better than simplistic qualitative assessments (including my own).
So what you have found is that both amps react with the speakers in the same way and if one is bright, so is the other to the same extent. Certainly that is a lot more than those claiming brightness for the Sonos amp with nothing to back up a subjective and probably defective assessment.
Isn't this just the Amp being able to deliver more power to the frequencies above the crossover, now that it doesn't also have to serve the frequencies below it?
To be clear, I don't think it's an issue, nor does it indicate a brighter sound profile.
Right; over to Peter if he disagrees.
Exactly. Manually, since in the case of a third-party sub, the Amp has no idea of its power output.
But then once that is done, the 3dB boost the Peter refers to becomes a non issue. And no reason for a brighter sound.
To be clear, I don't think it's an issue, nor does it indicate a brighter sound profile. I was just explaining why the Amp's volume at frequencies above crossover would be increased in the presence of a sub.
Isn't this just the Amp being able to deliver more power to the frequencies above the crossover, now that it doesn't also have to serve the frequencies below it?
Ideally, an amplifier's output is simply the input signal multiplied by a gain factor. The output should not sag by having to provide the low end. That would mean it is a poor piece of equipment.
Exactly. Manually, since in the case of a third-party sub, the Amp has no idea of its power output.
But then once that is done, the 3dB boost the Peter refers to becomes a non issue. And no reason for a brighter sound.
It can't though, because there is no equivalent extra available power to elevate the high end (tweeter) to match. The total P:1 volume has to stay calibrated to within what the tweeter amp can deliver.
Exactly. Manually, since in the case of a third-party sub, the Amp has no idea of its power output.
The first reply to a question I posed, on hydrogen audio:
"No boost is applied highpassed signal for the speakers.
The sub has its own amp (active sub) and the sub has a volume control, so if configured correctly, the volume of the sub matches that of the speakers."
In the play 1, I am guessing this happens by default. One can then change the relative levels via the Sub output settings. How would one match volume levels in the case of Sonos Amp, except manually?
"No boost is applied highpassed signal for the speakers.
The sub has its own amp (active sub) and the sub has a volume control, so if configured correctly, the volume of the sub matches that of the speakers."
In the play 1, I am guessing this happens by default. One can then change the relative levels via the Sub output settings. How would one match volume levels in the case of Sonos Amp, except manually?
Even so, a lot of the mid range on the play 1 is via the woofer; relieving it of low frequencies does not elevate the mid range dB.
Isn't this just the Amp being able to deliver more power to the frequencies above the crossover, now that it doesn't also have to serve the frequencies below it?
Do amps work like that? I don't know enough to say. But this would then apply to the amp in a play 1 unit as well. And what it would take to compensate is dialling down volume levels, not anything in the EQ. I don't notice any change in volumes - or treble levels for that matter - when I toggle the Sub on/off in my play 1 set up for which the same priniciple should apply. The midrange clears up subtly for the better with the Sub on, that's it.
The P:1 has two separate amplifiers, and there's no relief for the tweeter amp when you introduce the Sub, so I wouldn't expect the overall volume to increase.
In the case of the Amp, with a single amplifier configuration, it no longer has to supply energy for the frequencies below the crossover (which is current-heavy due to the large amount of air that has to be moved), so that energy can be redeployed to higher frequencies.
Isn't this just the Amp being able to deliver more power to the frequencies above the crossover, now that it doesn't also have to serve the frequencies below it?
Do amps work like that? I don't know enough to say. But this would then apply to the amp in a play 1 unit as well. And what it would take to compensate is dialling down volume levels, not anything in the EQ. I don't notice any change in volumes - or treble levels for that matter - when I toggle the Sub on/off in my play 1 set up for which the same priniciple should apply. The midrange clears up subtly for the better with the Sub on, that's it.
Isn't this just the Amp being able to deliver more power to the frequencies above the crossover, now that it doesn't also have to serve the frequencies below it?
Ideally, an amplifier's output is simply the input signal multiplied by a gain factor. The output should not sag by having to provide the low end. That would mean it is a poor piece of equipment.
No-one said that the Amp 'sags'. It has to operate within a total power envelope with a gain that it can deliver across the required frequency range while meeting its target distortion values. Remove the requirement to amplify signals below the crossover and that total power envelope can be applied to a smaller frequency range, hence the remaining frequencies can benefit from higher gain.
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