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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
    March 17, 2017
    That the Connect has more capable hardware than the zp90 ought to be a given. Why then can the Connect not do the bit perfect thing and the volume normalisation thing is a mystery to me.

    No one said it couldn't. It just doesn't because it's not been programmed this way. There's no technical reason I can think of that it couldn't (other than the normal issues of resourcing and timescales).

    I have always presumed this was likely to be some sort of error/oversight. It may, of course, have been deliberate, but the ramifications weren't considered. Other possibilities exist.

    Also a mystery is why, if both aren't possible, Sonos prefers to offer volume normalisation over bit perfect.

    I don't think that both aren't possible. However, not being possible is not the same as not being possible within the current development window, or roadmap, etc.

    Unless, not having ever specified "bit perfect", there was no need for them to stay with that if they think that normalisation is of more value than bit perfect to their target market.

    Consider that vastly more people will benefit from volume normalisation than from the Connect being bit-perfect. This is especially true on streaming services where the source is far from "bit perfect" in the first place. I would hazard a guess that less than 5% of the music played on Sonos systems across the world is from lossless sources.

    I'm not saying getting rid of the option for bit-perfect output is the right thing. Personally I would have kept it as an option (and, maybe, they will in the future).

    All assumption/speculation on my part, but offered as food for thought.

    Cheers,

    Keith
    March 17, 2017

    Btw, I agree that two play:1s plus sub, equalized with trueplay, is almost laughably good. I have that setup in my kitchen. I do prefer the other setup I have in the salon by some degree, but the sonos setup really is superb.

    Something to think about - could that preference also be caused just by the fact that you don't have an objective measurement set for the 1 pair + Sub?! Extending that question further, a 5 pair + Sub, that is physically closer to your AVI set up, also is something that you will never prefer to the AVI only because objective measurements for this also are not available?

    Sonos never publishes much by way of detailed specs and there is little out there by way of objective measurements for their kit either, a state of affairs that Sonos and its target market seems to be quite comfortable with. I get that you need these, the questions are just something to ponder:).
    March 18, 2017
    That the Connect has more capable hardware than the zp90 ought to be a given. Why then can the Connect not do the bit perfect thing and the volume normalisation thing is a mystery to me.

    No one said it couldn't. It just doesn't because it's not been programmed this way. There's no technical reason I can think of that it couldn't (other than the normal issues of resourcing and timescales).

    I have always presumed this was likely to be some sort of error/oversight. It may, of course, have been deliberate, but the ramifications weren't considered. Other possibilities exist.


    I might have misunderstood, but I thought that the bit perfect change was also applied to Connects already sold, via a software upgrade that everyone gets from time to time. If that was the case, how come it was not applied to zp90 as well, if, as you say, that is just as capable as a Connect in being able to accommodate the changed programming? Are you suggesting that not applying the change to the zp90 was also an error, in addition to the error of not considering the ramifications of the bit perfect thing?

    And based on what some people here have reported that this change has caused night and day changes in sound quality, it should be very easily audibly noticeable in a zp90 v Connect stand off. Somehow, I doubt that to be the case...something that only a good blind test can decide.

    Of course, confirming that there isn't a day/night difference won't need that sophisticated a test - the null hypothesis thing.
    Lyricist III
    March 18, 2017
    It's not a night and day difference. That would be a huge exaggeration. Maybe sunny and partly cloudy. I might have even used the term night and day somewhere way back in this thread.

    I'd did compare Apple lossless connected digitally to my amp by my Connect, an Auralic Aries Mini and the original CD on an Oppo DV981 also connected digitally. My Peachtree amp has two optical inputs and an AUX input. I could not tell a difference between the Aries and the Oppo, but the clarity of the Connect was obviously degraded. I had to adjust the volume up for the Connect and this made instantaneous comparison impossible. Must have something to do with the volume normalization. Was this THE reason for my perception of clarity? I can't be sure, but I don't think so because my perception of something being wrong started before I started investigating why. I should have removed the normalization tag and tried that, but didn't think of it at the time. So, those who might compare a Connect to a Z90 might want to rip an Apple lossless using something other than iTunes or remove the tag using MP3TAG and see if that makes a difference. iTunes will put the tag in the file even if you have it turned off. The iTunes setting only applies to when you are playing. Apple assumes you might change your mind about volume normalization even if you have it off.
    March 19, 2017

    I'd did compare Apple lossless connected digitally to my amp by my Connect, an Auralic Aries Mini and the original CD on an Oppo DV981 also connected digitally. My Peachtree amp has two optical inputs and an AUX input. I could not tell a difference between the Aries and the Oppo, but the clarity of the Connect was obviously degraded.

    Is this a general statement on the Connect, or is it that the degraded clarity from the Connect you refer to arose after Sonos did their thing to it, and it wasn't the case till then, with the sound on par with the other two sources? And that you noticed this before you came upon this thread - I ask this because some have admitted that to be the case.
    Lyricist III
    March 19, 2017

    I'd did compare Apple lossless connected digitally to my amp by my Connect, an Auralic Aries Mini and the original CD on an Oppo DV981 also connected digitally. My Peachtree amp has two optical inputs and an AUX input. I could not tell a difference between the Aries and the Oppo, but the clarity of the Connect was obviously degraded.

    Is this a general statement on the Connect, or is it that the degraded clarity from the Connect you refer to arose after Sonos did their thing to it, and it wasn't the case till then, with the sound on par with the other two sources? And that you noticed this before you came upon this thread - I ask this because some have admitted that to be the case.


    From 12 days ago when I said:

    "The Connect worked fine for me until I moved in September 2015 and did not get my system reconnected until the end of 2015. It was in a smaller room with hard walls instead of the log walls of my house. I tried a lot of things to figure out why it didn't sound "right", quilt on the wall behind the sofa and more. Then I see Peter's post that started this thread. Seeing Sonos staff member Ryan's post saying he had submitted a ticket, I had hope. It never went anywhere. "

    It still hasn't. I have. Connect is gone now, after comparing it to the Aries.

    People use lots of words to describe how one speaker, CD, or any source of sound differs when compared to another. I used clarity, I could use crisp, maybe a lot more, but that's me. To say the Connect was like tossing a blanket over the speakers would be a bit much, but along those lines. My imperfect ears, but even imperfect ears can detect differences.

    I was searching on the site, and everywhere, trying to find out if others had issues and found this thread. The above comparison I made was after giving up that Ryan S would have any influence for an option to bypass the changes that had been made that Peter Mc explained in the post that started this thread.

    The only comparison made before was with a CD and my own Apple Lossless file through a Connect optically connected to a system costing about a half million at the Kettering, Ohio dealer that sold me the Connect. I couldn't tell a difference. I think it qualified as a true audiophile system. The silver ribbon cables cost more than I spend on most cars. Took it home and with a Marantz amp and my Belle Klipches I had owed since 1976 (reluctantly sold for about what I paid for them due to the upcoming condo move and replaced with a pair of Dynaudio 1.8 Mk II speakers sold to me by friend) it sounded great, and with the Dynaudio speakers too, but I couldn't "entertain" the entire neighborhood.
    chicks
    March 19, 2017
    The "tubes (valves) sound better" audiophiles should love this soft knee limiting, as it's the same thing tubes do when approaching maximum power output. I remember when NAD marketed their "soft clipping", which is also the same thing. The audiophile press loved it. I had one, the circuit failed. Simple to fix, as it was just a resistor and 4 diodes, lol.

    http://sound.whsites.net/articles/soft-clip.htm
    jgatie
    March 19, 2017
    The "tubes (valves) sound better" audiophiles should love this soft knee limiting, as it's the same thing tubes do when approaching maximum power output. I remember when NAD marketed their "soft clipping", which is also the same thing. The audiophile press loved it. I had one, the circuit failed. Simple to fix, as it was just a resistor and 4 diodes, lol.

    http://sound.whsites.net/articles/soft-clip.htm


    No one was ever accused of inaccuracy when overestimating the hypocrisy of the audiophile press. Now excuse me while I try to get the "orange peel" sound out of my amplifier. :8
    Majik
    March 19, 2017

    I might have misunderstood, but I thought that the bit perfect change was also applied to Connects already sold, via a software upgrade that everyone gets from time to time.


    Yes, it would have been, subject to the hardware being capable.

    If that was the case, how come it was not applied to zp90 as well,


    Because the ZP90 clearly doesn't have the capability.

    if, as you say, that is just as capable as a Connect in being able to accommodate the changed programming?


    I didn't say that at all.

    I only said I saw no reason why recent Connect units could not support both "bit-perfect" and the non-bit-perfect normalisation mode. We know for a fact that the Connect is capable of supporting both modes as both modes have been seen in the field, just not at the same time.

    Are you suggesting that not applying the change to the zp90 was also an error, in addition to the error of not considering the ramifications of the bit perfect thing?


    No, I simply believe the ZP90 lacks the hardware resources to support this change.

    Cheers,

    Keith
    Enthusiast II
    March 27, 2017

    From 12 days ago when I said:

    "The Connect worked fine for me until I moved in September 2015 and did not get my system reconnected until the end of 2015. It was in a smaller room with hard walls instead of the log walls of my house. I tried a lot of things to figure out why it didn't sound "right", quilt on the wall behind the sofa and more. Then I see Peter's post that started this thread. Seeing Sonos staff member Ryan's post saying he had submitted a ticket, I had hope. It never went anywhere. "

    It still hasn't. I have. Connect is gone now, after comparing it to the Aries.

    People use lots of words to describe how one speaker, CD, or any source of sound differs when compared to another. I used clarity, I could use crisp, maybe a lot more, but that's me. To say the Connect was like tossing a blanket over the speakers would be a bit much, but along those lines. My imperfect ears, but even imperfect ears can detect differences.

    I was searching on the site, and everywhere, trying to find out if others had issues and found this thread. The above comparison I made was after giving up that Ryan S would have any influence for an option to bypass the changes that had been made that Peter Mc explained in the post that started this thread.

    The only comparison made before was with a CD and my own Apple Lossless file through a Connect optically connected to a system costing about a half million at the Kettering, Ohio dealer that sold me the Connect. I couldn't tell a difference. I think it qualified as a true audiophile system. The silver ribbon cables cost more than I spend on most cars. Took it home and with a Marantz amp and my Belle Klipches I had owed since 1976 (reluctantly sold for about what I paid for them due to the upcoming condo move and replaced with a pair of Dynaudio 1.8 Mk II speakers sold to me by friend) it sounded great, and with the Dynaudio speakers too, but I couldn't "entertain" the entire neighborhood.




    This is pretty much what brought me here.
    I had thought for a while I had an issue with my speakers, Meridian DSP5200s, they are now 10 years old, I know them inside out.
    Recently music sounded flat, music I know well. When I say flat I mean lack of dynamic range, now, this is not on every track, I could get into someone like Diana Krall or Leonard Coen for a few weeks and not really notice it, but then on some classical pieces with big dynamic ranges or on a particular dance track I was sent with a massive dynamic range it was sounding 'flat' on my speakers, where as on the iPhone and a pair of £29 Sennheiser in ears it sounded mental.
    I thought my speakers were playing up, but then I borrowed a Meridian MS200 (a bit like a connect) so I could test our Roon, all of a sudden my system came back to life.

    I didn't even consider that anything had changed on the connect side of things, I just thought that the connect was average at best, hence why I came on the forum, to see if anything else was in the pipeline that maybe was better quality. I then found this thread and posted in it.

    Now, if it is a case that the Connect going back to being bit perfect will bring my system back to life I will be a happy bunny.



    Is Volume normalisation a good thing?
    Can a system that does it on the fly not reduce dynamic range, therefore not alter the actual track itself?
    It would be nice if we had an option to turn it on/off, simply allowing the system to disable it when you chose 'fixed output' would be good enough.