More on Bluetooth

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  • Dave2002
    Full Member
    • Dec 2010
    • 18010

    More on Bluetooth

    I notice a rise in the use of Bluetooth for audio in recent years, and it is even being recommended in some quarters as a way of driving equipment - for example - http://mp3.about.com/od/consumerelec...2b439-0-ab_msb

    I thought I'd check to see what standards Bluetooth actually provides. It seems clear to me that basic Bluetooth is unlikely to be able to support high quality sound. The effective bit rate is only about 2 mbps, and while this is greater than CD bit rate, there is not much margin, and the protocols probably absorb quite a lot of the available link bandwidth. Bluetooth, as other communications systems, is an evolving "standard", and it's not quite clear what methods are used.

    The original intention seems to have been for Bluetooth to extend the capability of mobile phones, to allow headsets and other wearable devices. Thus it is a potentially useful tool for mobile users, but not necessarily to provide high quality - either audio or video.

    There is more on Bluetooth here - http://en.wikipedia.org/wiki/Bluetooth

    It looks as though the earlier versions are relatively limited in bandwidth capacity, and may use techniques such as delta modulation, which are perhaps appropriate for speech, but not necessarily good for music. Also, because of the phone applications, audio may be required to have low latency, certainly for real time operation - and the standards may have evolved round that.

    The v1 and v2 versions have only limited capacity. Possibly v3 and v4 have greater capacity, but note that this is achieved by using other LAN resources cooperatively, such as a local WiFi network. The details look rather involved.

    Essentially, it does not seem to me that Bluetooth provides a means to deliver really high quality audio, though it may be useful to some, and there is the possibility that it will gradually evolve to do so. This will be a fundamental limitation, and irrespective of any other qualities of the equipment being used for playback.
  • richardfinegold
    Full Member
    • Sep 2012
    • 7659

    #2
    Originally posted by Dave2002 View Post
    I notice a rise in the use of Bluetooth for audio in recent years, and it is even being recommended in some quarters as a way of driving equipment - for example - http://mp3.about.com/od/consumerelec...2b439-0-ab_msb

    I thought I'd check to see what standards Bluetooth actually provides. It seems clear to me that basic Bluetooth is unlikely to be able to support high quality sound. The effective bit rate is only about 2 mbps, and while this is greater than CD bit rate, there is not much margin, and the protocols probably absorb quite a lot of the available link bandwidth. Bluetooth, as other communications systems, is an evolving "standard", and it's not quite clear what methods are used.

    The original intention seems to have been for Bluetooth to extend the capability of mobile phones, to allow headsets and other wearable devices. Thus it is a potentially useful tool for mobile users, but not necessarily to provide high quality - either audio or video.

    There is more on Bluetooth here - http://en.wikipedia.org/wiki/Bluetooth

    It looks as though the earlier versions are relatively limited in bandwidth capacity, and may use techniques such as delta modulation, which are perhaps appropriate for speech, but not necessarily good for music. Also, because of the phone applications, audio may be required to have low latency, certainly for real time operation - and the standards may have evolved round that.

    The v1 and v2 versions have only limited capacity. Possibly v3 and v4 have greater capacity, but note that this is achieved by using other LAN resources cooperatively, such as a local WiFi network. The details look rather involved.

    Essentially, it does not seem to me that Bluetooth provides a means to deliver really high quality audio, though it may be useful to some, and there is the possibility that it will gradually evolve to do so. This will be a fundamental limitation, and irrespective of any other qualities of the equipment being used for playback.
    I just purchased an Audioengine Blutooth DAC, supposedly capable of 24/192. It uses some sort of advanced BT protocol. I have found that when I try to stream the few high res downloads that I own from my MacBook there are dropouts. It works much better with the files from my Android phone, which are mp3.
    Regular CD rips don't have the dropout problem to the same degree.
    As far as sound quality goes, there is still an audible difference between blutooth and every other audio source that I have tried. I find myself using the phone
    when I have a few minutes here and there between errands in it is just more conveinent to play the files from it.

    Comment

    • Dave2002
      Full Member
      • Dec 2010
      • 18010

      #3
      Richard

      Is this your DAC - http://www.positive-feedback.com/Iss...oengine_b1.htm ? The review is quite interesting, though contains some significant errors, at least of detail, I think.

      I think that model is available from UK Amazon - http://www.amazon.co.uk/Engine-B1-Pr...+dac+bluetooth

      There is another Bluetooth receiver device from Neet - http://www.amazon.co.uk/Neet%C2%AE-B...KBAANK1ECRB7BH

      This applies to the Neet model "Features aptX@ lossless audio support when paired with a source device with aptX®"

      For more on aptX see http://www.aptx.com/?gclid=CNWVyo2TtsMCFW7MtAodVUsAeA and also http://en.wikipedia.org/wiki/AptX

      The details of how Bluetooth audio works for each device, and for pairings of Bluetooth devices seem to be buried in technical documents.
      It looks as though with an ideal pairing of compatible Bluetooth devices, that good quality sound is or might be possible. However this may require compatibiity with aptX (see above) or Bluetooth v4. Audio may still work with earlier versions, but if it does, then the system probably switches to lower quality methods for transmission.

      Wikipedia has this about Bluetooth v3 (and presumably the v4 versions inherit this ...)
      Version 3.0 + HS of the Bluetooth Core Specification[41] was adopted by the Bluetooth SIG on 21 April 2009. Bluetooth 3.0+HS provides theoretical data transfer speeds of up to 24 Mbit/s, though not over the Bluetooth link itself. Instead, the Bluetooth link is used for negotiation and establishment, and the high data rate traffic is carried over a colocated 802.11 link.
      Perhaps the smartphones and similar devices notice if there is a nearby WiFi network, and send the traffic over that. That would explain the increased range (up to 100 metres) claimed for some devices. That might enable higher quality audio, with potentially higher data rate channels. If that is how things work, then the codecs used in that mode might change to optimise performance.

      There is also this D1 model DAC available from Amazon, but no mention of Bluetooth - http://www.amazon.co.uk/D1-Premium-2...udioengine+dac

      PS: Re dropouts, it seems that there can be interference between Bluetooth and USB 3 devices, which gives dropouts on the Bluetooth links.

      Comment

      • richardfinegold
        Full Member
        • Sep 2012
        • 7659

        #4
        Yes Dave, the link that you provided is the same product that I purchased.
        I was interested in the Wikipedia statement and your explanation. I use an older MacBook for every day workand it will not pair with the DAC. It recognizes it but states it can't make a connection. I have a newer MacAir that I use as a music server and that will pair with the DAC. From the information you provided I am surmising that perhaps the older MacBook can't copulate with both the blu tooth dac and my wifi system simultaneously, while the younger and friskier Air can manage the threesome? Sorry if the analogy offends...
        The Air sits upstairs in my house in my two channel system. The blu tooth is downstairs in a home theatre system. There are many drop outs between the the Air and the DAC so I would take their claims about range somewhat skeptically.
        In the review of the blu tooth that you provided the reveiwer's wife took over the dac to stream files from her phone. I have found myself using the blu tooth in a similar fashion, particularly with Spotify. I like to use Spotify to audition new CDs for potential purchase. I also use it when my two year grandson comes over as he likes to dance to disco while my wife moonwalks with him. In 5 seconds I can be streaming KC and The Sunshine Band, The Village People, Michael Jackson...When playing 320 bps files the difference between blu tooth and other dacs becomes less critical.
        The second link that you provided appears to be for a conventional dac that accepts usb and optical attachments. I am wondering if it uses the same chip as the blu tooth dac. I'd be curious to hear how well an inexpensive dac like that performs.

        Comment

        • Dave2002
          Full Member
          • Dec 2010
          • 18010

          #5
          Re the older MacBook, if it's older than (say) 2011, it just may not do it, but if it's from or after 2011, then an OS upgrade - if you can face it - might just bring it to life, though is not guaranteed. There may also be other reasons not to do an OS upgrade.

          It's also not really clear from the pages I've seen what Bluetooth actually does cooperatively with an 802.11 network. It is possible that it uses a form of ad-hoc networking, which would be similar to AirPlay within Apple's system.
          It may not be using an infrastructure network - I just don't know - as yet.

          Comment

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