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Peter Mc
August 23, 2016
Question

Connect no longer bit-perfect?

  • August 23, 2016
  • 450 replies
  • 29769 views
It looks like the Connect is no longer bit-perfect. Here's my evidence: let's discuss this.

First, I constructed a wav file of pink noise with amplitude ramping up from zero to digital max and back to zero.
I play this through my Connect and record the SPDIF output from the coax output into my PC.
The recording uses a Scarlett 8i6 audio interface set to use the Connect as master clock.
I record into a DAW (Sonar) multiple times - all instances are identical.
However, this recorded signal is not quite the same as the original wav file - it can be up to -21dB different.
See https://www.dropbox.com/s/t8od479xo9hi5el/connect_diff.PNG?dl=1
Note the expanded scale on the difference (third) track.

It looks like the difference gets larger when the signal is larger. To confirm this, I import the
original and difference files into Matlab and plot the raw data (difference vs original). There is clearly audio compression
happening here. See https://www.dropbox.com/s/p1yq6wcqafvnhaj/diff_vs_orig.png?dl=1
The scale is such that digital maximum is 1.

There also appears to be a slight bias when the waveform is negative and the signal is below the
compression threshold. See an expanded version of the previous plot
https://www.dropbox.com/s/9001tl9mkle4wly/diff_vs_orig_zoom.png?dl=1

Happy to answer questions about the method and conclusions.

Cheers, Peter.

p.s. Volume is set to fixed - I haven't tried variable.
In a loopback test (8i6 out from DAW to 8i6 in, no Sonos gear involved), I get bit-perfect cancellation.
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    450 replies

    Majik
    February 19, 2017
    To throw in my 2c...

    I'm personally fairly disappointed with Sonos making this change without considering the impact on users, many of whom purchased the Connect precisely because it was bit-perfect. I understand, to an extent, why they did it (implementing such a compression scheme makes sense when volume normalisation is involved). However, doing so without maintaining what many would consider to be baseline functionality of the Connect in same way (such as a user option to disable) seems like a huge misstep.

    I do hope they address this in a future update to avoid reputational damage.

    I should add that, whilst I have a Connect in my collection of Sonos kit, it's currently not in use and is certainly not likely to be used in anything approaching an "audiophile" setup in the imminent future: that sort of tweaking and tinkering is in my past. So I'm not directly impacted by this, but I understand that others are.

    Cheers,

    Keith
    Majik
    February 19, 2017
    As for Bluesound, I think it's important to note that Sonos started out in this way too: a predecessor to these forums was full of people interacting with Sonos staff, making suggestions. providing feedback, and getting direct responses from Sonos Product Engineering. Many of these discussions resulted in changes to the product and new features being added.

    Once a company gets to a certain size, this sort of interaction is unmaintainable. Sonos has gone from a small start-up with a few thousand customers to one of the top-3 speaker vendors in the world, and probably the leader in whole-house streaming systems. Their customer base is now reported to be in the millions across the world. It's simply not possible for them to respond positively to every customer on every issue. For every customer who wants high-end enhancements, there are 100 who want Sonos to make a low-quality Bluetooth speaker, or wireless headphones, or a portable garden speaker, or the SUB in pink...

    That Bluesound are able to engage in this sort of interaction points to them still being a small company with relatively few customers, just as Sonos were back in 2005. It points to them still being in the development phase of the product and the company. It points to them having a brand new platform without yet having to deal with legacy support/compatibility issues.

    If they ever grow their market share to be any sort of real commercial threat to Sonos, then they will have to abandon this sort of consumer interaction.

    The chances are they won't get that big and, in which case they can be a viable alternative to Sonos, catering to a niche of customers who want something over and above what Sonos does. Although that puts them and their customers in a very precarious position.

    One way or another, in a few years time you are going to be unlikely to have the same sort of interaction with Bluesound staff as you are currently seeing.

    Cheers,

    Keith
    February 19, 2017


    The chances are they won't get that big and, in which case they can be a viable alternative to Sonos, catering to a niche of customers who want something over and above what Sonos does.

    Couple of questions:
    1. As to bits not being perfect - I don't really care since I don't hear the difference and I suspect that many that do, started doing so after this thread started. But I take your point about bits and what would have made a useful difference to me is availability of volume normalisation; has that really improved consequent to this change? I haven't found that to be the case either, unfortunately, but that maybe because what I am looking for is normalisation across mixed source playlists and that may be a different problem altogether.

    2. Sonos went mainstream largely at the expense of Squeezebox, I imagine. Because, with Sonosnet, and less tinkering to set up/stabilise, it offered a better alternative to a large part of the user base, is my guess. Other than Hi Res, what does Bluesound do that Sonos does not? On the negatives, it does not offer mesh architecture, and costs a lot more.Expanding the question, is there anyone visible at this time that threatens the Sonos castle in home audio? Echo?
    Peter Mc
    Peter McAuthor
    February 20, 2017
    How do you know you don't hear a difference? You can't A/B between DSP on and off.
    "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
    February 20, 2017
    Lol. How do you know that you do?! 😃 All I know is that there is no change in how my music sounds playing in the Connect driven zone, singly or in a group. Did you find music sounding different and then investigated things or was it the other way around, having done the investigation as a "fun" project?

    But I do know for sure that I have seen no changes in the normalisation situation. Normalisation within an album doesn't seem necessary to me because my jazz is well recorded, but across albums and sources is when I have a problem playing shuffled mixed source playlists. Much more so with mixed source like NAS + Apple Music.

    And another question: Is there anyone in the market doing this kind of normalisation effectively?
    Prodigy II
    February 20, 2017

    That Bluesound are able to engage in this sort of interaction points to them still being a small company with relatively few customers, just as Sonos were back in 2005. It points to them still being in the development phase of the product and the company. It points to them having a brand new platform without yet having to deal with legacy support/compatibility issues.

    Keith


    Not as small as you suggest. It is part of The Lenbrook Group, owner of The NAD Electronics and PSB Speakers brands.
    Peter Mc
    Peter McAuthor
    February 20, 2017
    I haven't said that I hear a difference related to the DSP. I initially heard a difference between the Connect digital and analog outputs through a new Peachtree amp that has both inputs. It was only when making measurements related to this that I discovered the Connect DSP problems. This DSP is applied to ALL Sonos units as far as I know, so you won't hear a difference between them related to this.

    The Sonos compressor only affects volumes within 3.6dB of the maximum (greater than 66% of full scale), cutting out below this. The volume reduction ratio gradually increases above -3.6dB, and eventually becomes a brick wall, not letting any signal exceed 90% (-1dB less) of the original. It also has a zero attack and decay time. A brick wall compressor with no attack/decay ramp is a bit extreme. This may or may not be audible, but at the very least we should be able to disable it in fixed volume mode.

    I'm totally with you on the normalisation issue.

    Cheers, Peter.
    "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
    February 20, 2017
    It was only when making measurements related to this that I discovered the Connect DSP problems. This DSP is applied to ALL Sonos units as far as I know, so you won't hear a difference between them related to this.


    I have the Connect in just one of five zones; the rest are play units/Connect Amp driven, where the bits are an internal matter to the units, irrelevant to the user and not measurable. Rightly so, IMO, because all that matters is - how does the music sound on its own and compared to that from other solutions out there? And here I find Sonos beyond Connect can still be as good as it gets to my ears, where rooms sizes aren't outliers, being so large as to need a lot more power/sound levels than what Sonos can deliver.

    But perceived sound quality noticeably fluctuates with sound level differences which is why I think normalisation is very important in an environment where mixed source playlists are in use; my solution so far has been to not make/use such playlists. Neither Sonos or anyone else seems to think this is an issue, given the lack of any progress on this front. One day perhaps, once they are bored of devoting resources to controller cosmetic changes!
    Peter Mc
    Peter McAuthor
    February 20, 2017

    But perceived sound quality noticeably fluctuates with sound level differences which is why I think normalisation is more important in an environment where mixed source playlists are in use;


    Totally agree - this is a bigger issue than any minor compression.


    One day perhaps, once they are bored of devoting resources to controller cosmetic changes!


    I wouldn't call the recent controller changes cosmetic - they degrade the user experience. I never know what I'm going to get when I click on a song. There are also a couple of ways of getting a nasty surprise. Occasionally I accidentally touch a song while scrolling and change the song inadvertently. Also, adding a song as 2nd in a stopped queue leads to a musical surprise at the end when the next song in the queue (left over from last night's rave party!) starts blasting.:D
    "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
    February 20, 2017

    I wouldn't call the recent controller changes cosmetic - they degrade the user experience.

    Quite possible; I just learn to take things in my stride each time things change.

    Here is the thing: once things are settled, even with some imperfections, cosmetic changes for no reason other than a change always run the risk of upsetting things that have worked well in the past. In trying to win over some preferences, others are lost. Stability would be far more useful to those that aren't easily bored; workarounds can then become habits for the little issues. But that isn't the way of the world in these areas now, constant churn seems to be the thing.