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Peter Mc
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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      JRausch
      Lyricist III
      January 24, 2017
      My position regarding the change Sonos Made to the Connect is crystal clear.

      Kumar, I do not understand why you have even bothered to post in this thread. it's all about the Connect (not the Connect Amp, which you seem to have) no longer passing a bit perfect digital file and has zero to do with how well the analog output sounds to you on your Sonos speakers. It's irrelevant to the topic.

      This is my last post on this thread. Because I still have a PlayBar, I might use the forum if I have questions regarding it.
        Kumar
        January 24, 2017
        Lol, good idea.

        I believe that my post is relevant to this thread because regardless of what may have happened to it since 2011, my Connect which I also have, with its analog outputs in use to drive a third party amp + speakers, has caused no change in the way the music from my non Sonos speakers sounds. I agree that my post may not be relevant to those that are not concerned about how music sounds, but not everyone that is on this forum thinks that way, many of us are here to listen to the music without dissecting or otherwise parsing the equipment that delivers it.

        On the other hand I also understand that those that want transparency for its sake, for that being the way they want the Connect to work, may want to change brands if Sonos does not restore it to them.
        oivavoi
        Lyricist III
        January 24, 2017
        Thank you for this thread. I recently started to notice that music on my active monitors, with my sonos connect as the source, seemed to have less dynamics than when I listened to the same tracks on headphones, with the analog out on my iPhone 6S as the source. But when I use CDs as the source instead, my monitors have a higher dynamic capability than my headphones. I searched around, and found this thread, which might explain why.

        What to say: This is very annoying. It seems like such a simple thing for Sonos to fix. What do they lose by offering the possibility to stream bit perfect when in fixed mode? I would assume that most Connect users don't even use the fixed mode.

        But my question: Is it correct that connect units that were manufactured befor 2011 should still be ok? I'm heavily invested in the sonos ecosystem, and love it very much, so would hate to let Sonos go because of this. But I've started to look into bluesound. So hoping Sonos comes out with a fix. Or I might try to find a connect unit from before 2011.
          amun
          January 24, 2017
          I would assume that most Connect users don't even use the fixed mode..

          I'd have thought that they would, using the av/hi-fi amp to control the volume.

          IIs it correct that connect units that were manufactured befor 2011 should still be ok? I'm heavily invested in the sonos ecosystem, and love it very much, so would hate to let Sonos go because of this. But I've started to look into bluesound. So hoping Sonos comes out with a fix. Or I might try to find a connect unit from before 2011.

          Yes, I'd be interested in the definitive answer to this too, preferably from Sonos themselves.
            RICH40
            Trending Lyricist I
            January 24, 2017
            I would assume that most Connect users don't even use the fixed mode..

            I'd have thought that they would, using the av/hi-fi amp to control the volume.

            IIs it correct that connect units that were manufactured befor 2011 should still be ok? I'm heavily invested in the sonos ecosystem, and love it very much, so would hate to let Sonos go because of this. But I've started to look into bluesound. So hoping Sonos comes out with a fix. Or I might try to find a connect unit from before 2011.

            Yes, I'd be interested in the definitive answer to this too, preferably from Sonos themselves.



            I would second that and appreciate a response directly from Sonos.
              Kumar
              January 25, 2017
              If and when Sonos responds, I am curious to also know whether this matter has affected the working of Connect in all four modes: Fixed/Variable levels via Digital/Analog outputs.
              I have seen no change in sound quality in Variable Analog output mode, and I have no comment on SQ changes if any via the other three modes, but it would be interesting to know the answer all the same.
                Bob_m10
                Trending Lyricist I
                January 25, 2017
                I agree, it would be interesting to get an answer from Sonos on this. Most of the folks here on the forum are enthusiasts, there is something about Connect being bit perfect that is pleasing, even if we can or can't hear a difference.
                  LeighB
                  Lyricist III
                  January 25, 2017
                  I agree, it would be interesting to get an answer from Sonos on this. Most of the folks here on the forum are enthusiasts, there is something about Connect being bit perfect that is pleasing, even if we can or can't hear a difference.

                  As per my post above, I find the difference between the Sonos and AirExpress to be night and day. I continue to use the AirExpress for serious listening and the Sonos for casual listening. My spouse noticed the difference right away without me saying which input was which.
                    oivavoi
                    Lyricist III
                    January 25, 2017
                    I agree, it would be interesting to get an answer from Sonos on this. Most of the folks here on the forum are enthusiasts, there is something about Connect being bit perfect that is pleasing, even if we can or can't hear a difference.

                    Listening is tricky. If you know what you're listening for, you're likely to hear it. You might even hear it because you THINK it's there, even if it's not. But if you don't know what to listen for, you might miss it in a blind-test, even if it's there.

                    My subjective experience is that I hear a lower dynamic range on some recordings when I use the connect, compared to other sources. I don't hear it on typical studio recordings, pop, rock, etc. But I hear it in some classical and jazz recordings, where the dynamic range is typically much higher.

                    But again: Subjective listening is tricky. I won't swear that I would hear the same things in a blind-test. Now my listening has become biased because I "know" what to listen for. But what I think should be the goal, is just to provide good objective quality - especially if it doesn't cost anything. If the OP is correct here, the DSP Sonos applises actually loses 1 DB in dynamic range. That is quite a bit - 3 DB amounts to a doubling of volume. This is clearly within a range which is objectively audible, and for people like me who love their fair share of dynamic classical and jazz recordings, it's a bad thing. It's as simple as that, really. And it would be really, really easy to fix it. Seems like a no-brainer to me.
                      Kumar
                      January 26, 2017
                      Seems like a no-brainer to me.
                      What we don't know is the reason/s why this was done; based on that, it may be that reverting isn't a no brainer. The other thing is that with Sonos focus is now on voice control, streaming services and allowing the use of Sonos speakers for other home automation tasks, the Connect is no longer a priority based on their target market assessment. Particularly if to fix something that, as Bob commented, causes a difference that can't be heard. I could be wrong, and only Sonos/time can tell.
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