Amp freq response: Sonos vs Peachtree

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84 replies

Peter Mc
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.

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.
"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
Peter Mc
P.S. would you mind plotting just 200-20000Hz and blowing up the vertical scale?



Done!
"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
K
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.
L
Userlevel 2
Badge +1
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?
K
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.
pwt
Userlevel 7
Badge +20
Thanks, Peter. Interesting information, so much better than simplistic qualitative assessments (including my own).
4 x P:5 | Sub | 4 x P:1 | 3 x Connect | 2 x Boost | Connect:Amp | 2 x One | Amp | Move | Port
K
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.
Peter Mc
Ideally one would use an oscilloscope to measure just the amp. I don't have one. Even then, one would need to pay attention to the impedance, so the oscilloscope or voltmeter looked like a speaker load. Voltmeters typically have a very high resistance - I don't know how that would change the measurement.

The measurements that hodgeal and I have posted include the speaker and microphone responses. On their own they reveal little about the amp, unless it is noticeably bright as I understand some people have claimed. However, the comparative plots are useful, since they change one variable only. In my case, I change just the amp, leaving everything else the same. The difference between the two plots is then attributable to the difference between the amps regardless of the influence of the speakers or microphone.

Cheers, Peter.
"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
K
I don't understand how frequency responses of mics and speakers come into play, and if they do, how is this a frequency response measurement of an amp? Isn't a signal generator at the input end and a voltmeter/oscilloscope across the speaker terminals of the amp the way to do this?
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