Connect no longer bit-perfect?

Is Volume normalisation a good thing?

Yes, based on my understanding of it, which is that normalisation should be a change effected in output levels across the entire dynamic range of a track by moving it in its entirety to the left or right as happens when I move the volume control slider to change volume. Relative differences between low and high should not be altered for this feature to be more than just compression done such that the lows can be heard without the highs going too loud. It ought to just have different songs in a playlist be delivered at the same median sound levels relative to each other, not by just having the loud part of every song pegged at one level across. If one of the songs in the playlist has exceptionally loud highs compared to the rest, it should sound to be so; or, if it sounds the same as all other songs, the lows on that song should go a lot lower than those on other songs.

Since my units are zp90s, I have nothing to say on what route Sonos has taken and on whether their claim that it results in a very subtle change in the sound is valid or not. And of course, it is very unlikely that we will see a ABX test between a zp90 and late model Connect to know more about this.

On the subject of Connect sound quality in general, there is a parallel discussion I was engaged in on another thread with a member that finds a day and night difference between music from Connect via its DAC and when used with a Chord DAC downstream. It is of course possible that his Connect is one of the rare ones that is still bit perfect, but that is probably not the case. It is also very likely that his views will change once he comes across this thread.;)

PS: If what Sonos has done is to reduce dynamic range, how is this different from what the recording industry is accused of doing in the context of "Loudness wars"? Somehow, I doubt that this will found to have been the case when audible results are objectively evaluated.

If what Sonos has done is to reduce dynamic range, how is this different from what the recording industry is accused of doing in the context of "Loudness wars"?

Sonos has reduced dynamic range by 1dB; there is no doubt about this as far as the Connect is concerned. And it almost certainly applies to every Sonos speaker as well. They reduce the dynamic range by using a brickwall limiter with no look-ahead, and with zero attack and decay times. If a volume difference of 0.2dB can influence an ABX test (as you often quote), then it is highly possible that a 1dB truncation of the loudest music would also influence such a test.

The weapon of choice in the loudness wars is generally a compressor with attack and decay times chosen to make the sound as transparent as possible. A badly-used compressor is quite audible - you can hear it pumping. Sometimes a limiter is also used at the very end of the processing chain to ensure no clipping, including inter-sample clipping. Again, a suitable attack and decay time is generally chosen to make the limiter sound as transparent as possible. The Sonos gain reduction is achieved using just a brickwall limiter with instant attack and decay (meaning it operates on each sample independently of those around it).

When Sonos applies a limiter, it is in addition to what the recording industry does. It changes the song from the original intention of the artist/mastering engineer.

Note that a compressor reduces the volume of the loudest samples, which then allows the mastering engineer to increase the overall volume without the loudest parts of the music clipping. A limiter just reduces the volume. Of course, then you can turn the volume up yourself :)

I hope this answers your question.

Cheers, Peter.

Note that a compressor reduces the volume of the loudest samples, which then allows the mastering engineer to increase the overall volume without the loudest parts of the music clipping. A limiter just reduces the volume. Of course, then you can turn the volume up yourself :)

I hope this answers your question.

Cheers, Peter.
Yes and no! You say just before quoted that Sonos has used a limiter, not a compressor. But in your quote you say that all the limiter does is reduce volume. But if that is the case, it should do so across the board of the dynamic range of the song, if, as you also say, all it takes to counter that is turning up the volume. To then level match against a zp90 for example, I would have to turn up the volume on your Connect, or reduce it on my zp90. Then there will be no reason for an audible difference to exist. Right? Or where is my logic incorrect?

And it almost certainly applies to every Sonos speaker as well. They reduce the dynamic range by using a brickwall limiter with no look-ahead, and with zero attack and decay times. If a volume difference of 0.2dB can influence an ABX test (as you often quote), then it is highly possible that a 1dB truncation of the loudest music would also influence such a test.

And on the quoted above, with respect to what you think has been done to every other speaker:
This should result in every speaker, from the 1 to the 5, sounding strangled at the louder end of music with high dynamic range, regardless of the volume control setting on the speaker, compared to every other speaker out there where the source has not been so dealt with.
Why is it that no one anywhere has pointed out this as a specific criticism/drawback of the Sonos play speaker line up? Not even ratty as an example of one who is much more knowledgeable than I, who uses a 5 + Sub set up now, replacing a zp80 + third party active pair/Sub.
To say nothing of those that still swear by the Connect, but only if it has an expensive DAC hanging on its digital output.

it is highly possible that a 1dB truncation of the loudest music would also influence such a test.


Or is it the case that this reduction has been applied at the loud end of the dynamic range when the volume control is at the highest end of the scale, as in fully to the right, as well?

If so, is there a volume control level below which this has not been applied? If so, what is that level?

Just to clarify a number in my original post - the original and recorded signals can differ by up to about 1dB. It is the difference signal that can have an amplitude of -21dB (compared to full scale).

The same question to this quote: At what volume levels on the Connect - 100%? And is this at the high end of the dynamic range? If so, this means that there is a 1dB reduction in volume that is applied to music with high dynamic range, to the loudest parts of it, when played at 100% volume. Since I never play my play units in that mode, this isn't the extent of reduction dealt out to me, and this would also be the case for almost every Connect user. And definitely to everyone using a headphone!
Or is it the case that it would be present when the Connect is in fixed output mode, with the volume levels controlled by the downstream unit, but not be applicable when the Connect is used to control volume levels via variable level mode? If this be the case, again, it would also not carry over to Sonos speakers except when running at 100% volume on the loudest parts of music with high dynamic range.
So my question boils down to whether this issue is just a notional and theoretical one for every one other than those using Connect in fixed output mode?
If yes, then the fix is also easy for the remaining set of Connect users: switch to variable level mode.

And on using Connect in variable level mode even with its digital outputs, my understanding is:
Volume control/variable audio IS possible with a digital output but it usually results in digital information being discarded as the level is lowered. What Sonos does is use a 16 bit signal coming out of a 24 bit output. There is enough digital "headroom" that the point at which information would have been discarded is never reached.
Peter, it then seems to me that using the Connect in variable mode, even with an external "high end" DAC as some do, will mean obtaining all the fidelity that is sought and that this 1dB issue will only surface with loud parts of high dynamic range music when the Connect variable volume is set to 100%. It would be nice for that to not happen I suppose, but is it end of days if it does?

Hey Kumar - let me see how many of your questions I can answer:

1. A limiter reduces the loud bits (of music) but not the soft bits. It is effectively a volume-dependent volume control. A compressor is very similar but more flexible, and is often used in multi-band format so it affects different frequency ranges in different ways. The Sonos limiter reduces the loud bits (within 1dB of full scale) and leaves the rest untouched. It will reduce the overall RMS volume ("loudness") of the music by a small amount (less than 1dB). Hence my statement that you can increase your volume control to make up the overall RMS to equal the original. However, the music will be slightly different because the loud bits are now softer relative to the quiet bits, i.e. the dynamic range has been reduced. For more info, check out the wiki on dynamic range compression. Perhaps the first diagram (downward compression) will make this clearer.

2, 3 & 4. I think "strangled" is a bit strong 🙂 It's only a 1dB reduction of the very loudest parts of the music. Many people would not notice this. It may be more a feeling that something isn't quite right, or loud enough, or crisp enough, or punchy enough or whatever. I do wonder whether Sonos applies the limiter before or after the volume control. If it applies it afterwards, then perhaps it only kicks in near maximum speaker volume. However, I suspect it is required as part of the volume normalization DSP just in case the ITUNNORM tags are wrong, for example. Hence the limiter would be applied at any volume. Only Sonos can really answer this (although maybe I could run some tests with a Connect in variable volume mode).

5. Yes, Sonos is clever with their use of a volume control in 24 bit mode. No information is lost until really low volumes are reached. Both the internal DAC and the coax digital output operate in 24 bit mode to facilitate this.

It would seem there is a good question to be answered here: does the Sonos limiter operate at every volume setting?

Cheers, Peter.

1. A limiter reduces the loud bits (of music) but not the soft bits. It is effectively a volume-dependent volume control. A compressor is very similar but more flexible, and is often used in multi-band format so it affects different frequency ranges in different ways. The Sonos limiter reduces the loud bits (within 1dB of full scale) and leaves the rest untouched. It will reduce the overall RMS volume ("loudness") of the music by a small amount (less than 1dB). Hence my statement that you can increase your volume control to make up the overall RMS to equal the original. However, the music will be slightly different because the loud bits are now softer relative to the quiet bits, i.e. the dynamic range has been reduced.
2, 3 & 4. I think "strangled" is a bit strong 🙂 It's only a 1dB reduction of the very loudest parts of the music. Many people would not notice this.

It would seem there is a good question to be answered here: does the Sonos limiter operate at every volume setting?

Cheers, Peter.
1. I thought that your concluding comment in your item 1 - that dynamic range is reduced - is precisely the core issue of the loudness wars thing, where, for much of the music to be heard clearly and loudly, the peaks are reduced because otherwise the earphones will blow out eardrums. And that in turn is a result of compression of the dynamic range in mastering. But this isn't as relevant to the subject as:
2. Is it a 1dB reduction of the very loudest part of the music at 100% volume levels? If so, while easily seen on a scope, isn't it irrelevant in real life listening? Who plays music at 100% volume levels on the Connect except those using fixed mode, and why can't these folk sidestep the issue then by moving to variable mode? And isn't all this a non issue for play units, because who plays these at 100% volume levels? And those who do, should actually be grateful for something that probably prevents speaker damage when music that suddenly goes very loud is played at 100% volume levels.
3. Doesn't your scope tell you what the Sonos limiter does at every volume setting?:D

Yes, limiting and compression both reduce dynamic range. The point is that Sonos is adding its own limiting to material that is already compressed. Hence it is further reducing the dynamic range. It is also doing it with the simplest possible limiter that has no attack/decay/look-ahead. I doubt a mastering engineer would use such a blunt tool.

We don't know if the limiting occurs before or after the volume control - this is a very good question to answer, and I will run some tests when I get the time. So far, I've only ever tested in fixed volume mode to remove that variable.

Cheers, Peter.

p.s. My "scope" is actually an external sound card for a computer (Scarlett 8i6) with analog and digital inputs. It contains a similar Cirrus DAC to the Connect, but is the better-specced CS4272). I record the data in audio software called Sonar (similar to a free program called Audacity). I do my analysis in Matlab (like Excel but much more flexible and easier to use).