Amp freq response: Sonos vs Peachtree

Forum|Forum|7 years ago
April 11, 2019
84 replies
6698 views

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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Peter McAuthor

Does this then bring to light an undisclosed feature of the Amp? That it will deliver sound levels that are higher across the board by 20-30% if bonded with the Sonos Sub or with a third party Sub of similar power? That is no trivial feature to have. And I don't think that too many legacy HiFi amps can boast of this capability; all they can claim is what comes from the Sub - frequency extension at the lower end.

So, does anyone want to take a shot at answering this?

Sure. I think you're right. It's making optimum use of its 125W power. Of course, it's only relevant if running the Amp at maximum volume is not loud enough. And I have to say, it's already pretty loud at max! I suspect that all other amp manufacturers could choose do the same thing with the power they save by hiving off the low frequencies to a sub.

"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett

K

Kumar

Extra power is always useful - to not just run at max, but for better handling music with high dynamic range. At max, even a Connect Amp is pretty loud, but I wonder if it could not better use this feature. If Sonos ever gets around to giving it that.
And when you say other amp manufactures could do the same, I don't suppose you are referring to the many that use electro mechanical volume controls.

Peter McAuthor

Extra power is always useful - to not just run at max, but for better handling music with high dynamic range.

What's the science behind that idea when it comes to Class D amps? It might be true for more traditional amps where the distortion goes up as the volume increases. But I believe Class D amps go the other way (based on limited reading).

And when you say other amp manufactures could do the same, I don't suppose you are referring to the many that use electro mechanical volume controls.

I hadn't thought about whether the volume control method would make a difference or not. Perhaps non-Class D amps would be trickier, but I don't know enough about amps to really be able to offer an opinion.

"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett

L

lahey

Trending Lyricist II

I think you have discovered the Gibbs Phenomenon. Some people refer to this as "overshoot", and it is related to "ringing". Usually it is observed when low-pass filtering, but it can also happen with a high-pass filter. If the filter has too high a Q factor .

There is also this to consider (filter causing constructive effect).
https://www.soundonsound.com/sound-advice/q-why-do-my-mixes-clip-when-i-apply-high-pass-filter
FWIW I was using a 6db filter in Audaicity for a gentle rolloff on the HP filter like I would think a crossover would use.

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