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Sonos Amp with Acoustic Landscape AS41SYS


I have been disappointed in the Sonos Amp and how it performs with an Acoustic Landscape AS41SYS. The AS4.1 consists of 4 satellite speakers and 1 sub that presents it's self as an 8 ohm load to the receiver. I previously had this system powered by a Yamaha RX-V667 receiver rated at 90w per channel @ 8 ohms. I had tried a Sonos Connect:Amp and it simply didn't produce enough volume. I recently purchased the Sonos Amp rated at 125w per channel @ 8 ohms and really I can't tell a difference between the Sonos Amp and Sonos Connect:Amp. The Yamaha RX-V667 produces more volume (albeit without all the Sonos features). It confuses me that the Yamaha RX-V667 rated at 90w per channel out performs the Sonos Amp rated at 125w per channel both at 8ohms. The speaker setup is the same when testing both receivers. Some of the runs are long (~200 FT) but I used all 12AWG oxygen-free stranded copper.

Sonos support is chewing on this, but I was wondering if others out there have tried this paring. I sent it the diagnostic report when asked and she said there were no obvious issues.
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Best answer by marky4556 9 May 2019, 04:04

I thought i would follow up before closing this topic. After working with Sonos tech support, we determined that the Sonos Amp was not faulty, but instead not the best pairing for the Acoustic Landscape AS4.1. This was in part because the Sonos Amp lacks the dynamic range amplification 8/6/4/2 ohms for 125/160/190/230W for Front L/R.

I ended up returning the Sonos Amp and buying a Sonos Connect and paired it with an Audio Control Rialto 400 amplifier at the recommendation of Origin Acoustics (maker of the AS4.1 system). I am much happer. While i wish i could have gotten down to one unit, the Rialto 400 does a much better job of driving the AS4.1 system and even allows me some room for growth in speakers.

I appreciate Sonos technical support team's help.
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It confuses me that the Yamaha RX-V667 rated at 90w per channel out performs the Sonos Amp rated at 125w per channel both at 8ohms. The speaker setup is the same when testing both receivers.

So you're connect all 4 speakers and the sub to the same speaker connection (probably A speakers) on the Yamaha?
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It's possible you're driving the Yamaha up to levels where it may start to distort, something that shouldn't happen with the Sonos Amp even at 100% volume. With the speakers you're using and the environment they're in, and possibly with the content you're listening to, it may not be possible to detect the distortion.
The Yamaha RX-V667 produces more volume (albeit without all the Sonos features).
How exactly? To conclude this with both having volume controls at the same intermediate settings isn't correct because the Yamaha almost certainly delivers higher sound levels early in its control range, or even at 50%. Does the Sonos Amp deliver lower sound levels when both amps are at 100% on the volume controls?
Thanks for the replies. Here are my answers back.

@melvimbe
2 satellite speakers and 1 channel of the sub are connected to A Channel Left. The other two satellite speakers and the 2nd channel of the sub are connected to A Channel Right. Refer to the 2nd figure on page 7 of the AS4.1 manual (https://pdf.crutchfieldonline.com/ImageBank/v20170125090000/Manuals/981/981AS4SAT.PDF).

@pwt
If I go full volume on the Yamaha I do start to hear some distortion. But that is considerably louder than the Sonos goes. Distortion aside, wouldn't the amount of loudness be directly proportional to the watts per channel if the load is constant?

@Kumar
Yes, the Sonos Amp delivers lower sound levels when both amps are at 100% on volume controls.

@pwt
If I go full volume on the Yamaha I do start to hear some distortion. But that is considerably louder than the Sonos goes. Distortion aside, wouldn't the amount of loudness be directly proportional to the watts per channel if the load is constant?

@Kumar
Yes, the Sonos Amp delivers lower sound levels when both amps are at 100% on volume controls.

All else remaining the same as it seems to be in your case, if both specs are honest, I see no reason for this other than a defect in the Sonos Amp. Perhaps it is on one channel, in which case, playing with the balance control on both amps will tell you which.
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If I go full volume on the Yamaha I do start to hear some distortion. But that is considerably louder than the Sonos goes. Distortion aside, wouldn't the amount of loudness be directly proportional to the watts per channel if the load is constant?
I think it works like this: the Amp has to be able to operate at 100% volume without distortion/clipping regardless of the signal it's fed. So, it has to be able to handle continuously loud music sources (thrash metal?), while set to 100% volume, without distortion. The gain of the Amp is calibrated accordingly. In the case of the Yamaha, the gain can be set at levels that would distort, and it's up to the user to reduce the volume control to a point where it doesn't.

What I'd expect is that if both the Amp and the Yamaha are fed with a continuously loud input source, the Amp at 100% would be louder than the Yamaha adjusted so as not to distort. At this point, both amps would be operating at their power limits. (Note that in terms of perceived loudness, there's not much difference between 90W and 125W.)

One could quite justifiably argue that the Yamaha's manual approach is more flexible, because its gain can be adjusted so that the amp is using the majority of its available power even for quieter input sources.
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I think it works like this: the Amp has to be able to operate at 100% volume without distortion/clipping regardless of the signal it's fed.

I don't understand this. The sonos amp will clip a signal iff volume is too high, just like any amplifier, won't it? Look at the THD+N vs power curve in this review that shows clipping at about 200W into 4 ohms (although this is when fed an analog signal from an audio analyzer): https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-sonos-amp.6957/
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I think it works like this: the Amp has to be able to operate at 100% volume without distortion/clipping regardless of the signal it's fed.

I don't understand this. The sonos amp will clip a signal iff volume is too high, just like any amplifier, won't it? Look at the THD+N vs power curve in this review that shows clipping at about 200W into 4 ohms (although this is when fed an analog signal from an audio analyzer): https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-sonos-amp.6957/

Beyond my electronics competence, unfortunately. My only observation is that in the Amp, the gain is completely under software control, unlike in amplifiers with manual volume control. It can therefore perform gain calibration that manually controlled amps cannot. I'll also note that the testing in the link is performed using the Line-In input, which does have manual gain applied via the Line-In Source Level setting. I don't know if that makes a difference.

What's your theory as to what the OP is observing?
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What's your theory as to what the OP is observing?

I don't know. You could be right. Since this is DDFA, it could make engineering sense to match the maximum volume to full scale 16-bit input. Then the output would only go right up to the power rails and never clip when fed digital signals. Even if they provide a little more gain than this there is probably not so much overkill with gain as with a typical analog amplifier. So the amp might give the impression of being underpowered if it replaces a fairly powerful analog amplifier. To me, the OP's description makes it sound like the reported problem goes beyond this, but maybe that's all it is. My own impression is that the amp has plenty of power. In fact I have the volume limiting set to 90% so that my kids don't do damage to the speakers, and it sounds plenty loud for me.
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I think it works like this: the Amp has to be able to operate at 100% volume without distortion/clipping regardless of the signal it's fed..

I think there is a good chance that you are pretty much correct about this. From Sterophile's review of the NAD M32 (another DDFA amplifier):
A 1kHz digital signal at –12dBFS resulted in an output level of 10.34V into 8 ohms with the volume control set to "0.0dB," which suggests that the M32's gain architecture is well organized.
Read more at https://www.stereophile.com/content/nad-masters-series-m32-directdigital-da-integrated-amplifier-measurements#YUyi03o4AR3H55Lb.99


So this would work out to 211W into 8 ohms if the digital input is increased by 12dB to 0dBFS (output is then 41.1V RMS, power is 41.1^2/8 = 211) , and the M32 is rated at 190W dynamic power into 8 ohms. So there is not much clipping of digital signals at full volume with the M32. Likely the Sonos Amp has a similar gain structure.
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I made a file of 1KHz tone at -40dBFS. When I played this through the Sonos Amp at maximum volume, I measured about 0.45V to 0.5V (RMS) from the amp. This would correspond to 45-50V RMS for a 0dBFS input, which would result in fairly severe clipping. Assuming my measurement with "True RMS" meter is any good, the Sonos Amp provides some gain overkill. So I don't know why the OP's system is not as loud as it should be.
Note also that according to the OP:
No audible difference in sound levels between the 55wpc Connect Amp and the 125 wpc Sonos Amp.
The 90wpc Yamaha outperforms the Sonos Amp on sound levels.

Both above read together point to a defective Sonos Amp, IMO. If the OP observations are accurate and free of expectation bias.

Would any defect in the output stage/s be visible in a diagnostic?
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Both above read together point to a defective Sonos Amp, IMO. If the OP observations are accurate and free of expectation bias.
Quite possibly. It's not the only report of the Amp not being as loud as people expected.

Quite possibly. It's not the only report of the Amp not being as loud as people expected.

But as far as I recall, those are from people not used to the linearity of the Sonos volume control, coming from amps that go loud very early in the control knob movement, and max out a little above 50%. The Connect Amp had a lot of complaints from such people, for sure, for that reason.
The linearity becomes a non issue at 100% of course; and to be honest, I have never run any of my Sonos kit at 100% ever, it would be too loud to bear. I understand that out of doors it may well not be so, so I don't question that the OP ran his at 100%. But if bias can be ruled out, I can't see any reason other than a defective unit.
You should know about the comparison with Connect Amp - by what levels on the volume controls does the Sonos Amp start going noticeably louder than the Connect Amp? - Note that OP found no difference at all.
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You should know about the comparison with Connect Amp - by what levels on the volume controls does the Sonos Amp start going noticeably louder than the Connect Amp? - Note that OP found no difference at all.
I didn't do any objective comparative testing. My subjective impression is that I use about 10% lower volume on the Amp compared to the Connect:Amp, at least at 'active listening' volumes above 50%. Like you, I've never had the need or the inclination to run either amp at 100%, but I got closer to doing so with the Connect:Amp.
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But as far as I recall, those are from people not used to the linearity of the Sonos volume control, coming from amps that go loud very early in the control knob movement, and max out a little above 50%.

Is the volume control really linear? It seems to be fairly ordinary to me (that is to say I would have thought it is logarithmic). I am not sure I would notice though since I'm using a slider on my phone.

edit: also, wouldn't it work the opposite way - a linear control would get very loud right from the beginning? But I don't doubt that the the Sonos control could have a more gradual increase in perceived loudness than other amplifiers.
I thought i would follow up before closing this topic. After working with Sonos tech support, we determined that the Sonos Amp was not faulty, but instead not the best pairing for the Acoustic Landscape AS4.1. This was in part because the Sonos Amp lacks the dynamic range amplification 8/6/4/2 ohms for 125/160/190/230W for Front L/R.

I ended up returning the Sonos Amp and buying a Sonos Connect and paired it with an Audio Control Rialto 400 amplifier at the recommendation of Origin Acoustics (maker of the AS4.1 system). I am much happer. While i wish i could have gotten down to one unit, the Rialto 400 does a much better job of driving the AS4.1 system and even allows me some room for growth in speakers.

I appreciate Sonos technical support team's help.
Good to know that your problem is solved.

It is curious though that this has been done via an amp specified by the manufacturer to be:
Power Output (8Ω): 100W per channel
Power Output (4Ω): 200W per channel

Which is marginally less powerful than the Sonos Amp.

I can't see a reason for this, other than a defective Sonos Amp or a dishonest power spec for the Sonos Amp by Sonos.
I wouldn't go as far as dishonest. My guess is that across certain frequencies the AS4.1 system presents itself as something less than an 8 ohm load and at that lower value, the Sonos Amp cannot adequately drive the system. I didn't have a network or spectrum analyzer to actually sweep the AS4.1 system. The manual for the AS4.1 says 8 ohms nominal, but i suspect it operates lower than that. The Rialto pushes up to 200 watts at 4 ohms. There are no stated specs for the Connect Amp at anything lower than 8 ohms.

Just a guess. The system is substantially louder. In fact i have to dial down the gain on the Rialto to avoid over driving the speakers.
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Likewise the Sonos Amp provides 200W into 4 ohms (see measurements in link below). Strange that Sonos support would say that this amp was not up to the task. I wonder if he/she just gave up on trying to figure this out.

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-sonos-amp.6957/
There are no stated specs for the Connect Amp at anything lower than 8 ohms.

For both the Sonos units, the 4 ohms power delivery is stated to be about double of that at 8 ohms.
And every speaker specified as nominal 8 ohms drops impedance in response to power needs for different frequencies, the only difference between speakers being how much the drop. Bad designs can even drop to 2 ohms. And even if that was the case here, the Sonos Amp would cut out if that happened for long enough periods; it would not sound less loud across the board. It would also not sound just as loud as Connect Amp, as you have said.
I too suspect that Sonos support was lazy, seeing that the alternative outcome involved another expensive Sonos product. I doubt that the Amp spec is dishonest, seeing reports here that speak of audibly louder sound from the Sonos amp compared to the Connect Amp.

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