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  1. #21
    Member JoeMuc2009's Avatar
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    Actually it's pure physics. If you push one speaker in carefully in a unit that has no power connected, the other will pop out nearly the same amount. It's an air-tight enclosure where the bass woofers are the only moving parts connecting the inside of the case to the surrounding air.
    This also means, if one bass moves, e.g. from my sample that plays a frequency just on one side, the other base is passively moving along with that. And thereby causing sound, even though it is not driven by anything but the vacuum and pressure generated by the bass on the other side. That makes it impossible to check both speakers separately unless the case with its air-tight seal is opened.
    A "mono" bass where both channels are exactly in phase might cancel itself out because both speakers try to push simultaneously out which creates a stronger internal vacuum, and pull in simultaneously creates the respective amount of pressure. This makes bass movement considerably hard. That's where they do some DSP trickery, I think. Putting the bass just a little out of phase on one side might resolve this for good, without a noticeable effect on what your ears perceive.
    All this might be completely wrong but if it isn't, it makes the Boom a true engineering marvel.
    Last edited by JoeMuc2009; 2017-11-11 at 05:00.


    PN me if your Boom / Classic / Transporter display has issues!

    LMS 7.9.0 on Windows Server 2012
    1x Squezeebox Classic SB2
    7x Squeezebox Classic SB3 (one waiting for repair)
    7x Squeezebox Boom (two waiting for repair)
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  2. #22
    Senior Member kidstypike's Avatar
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    Quote Originally Posted by JoeMuc2009 View Post
    Actually it's pure physics. If you push one speaker in carefully in a unit that has no power connected, the other will pop out nearly the same amount. It's an air-tight enclosure where the bass woofers are the only moving parts connecting the inside of the case to the surrounding air.
    This also means, if one bass moves, e.g. from my sample that plays a frequency just on one side, the other base is passively moving along with that. And thereby causing sound, even though it is not driven by anything but the vacuum and pressure generated by the bass on the other side. That makes it impossible to check both speakers separately as long as the case with its air-tight seal is opened.
    A "mono" bass where both channels are exactly in phase might cancel itself out because both speakers try to push simultaneously out which creates a stronger internal vacuum, and pull in simultaneously creates the respective amount of pressure. This makes bass movement considerably hard. That's where they do some DSP trickery, I think. Putting the bass just a little out of phase on one side might resolve this for good, without a noticeable effect on what your ears perceive.
    All this might be completely wrong but if it isn't, it makes the Boom a true engineering marvel.
    Have you seen this?

    http://wiki.slimdevices.com/uploads/...dio_Design.pdf

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    Study/Server - LMS 7.9.1 - Raspberry Pi3/Pi screen/HiFiBerry DAC+/piCorePlayer 3.22/jivelite, 25K library on WDMyCloud, cache and playlists on a USB stick (formatted ntfs).
    Lounge - RPi 2/Max2Play > HiFiBerry DIGI+ > AudioEngine DAC1 > AVI DM5
    Dining Room - Boom
    Garage - Radio
    In car - LMS 7.9.1 > RPi3/Max2Play/Access Point plugin > HiFiBerry DAC+ > car's hifi (files on a 2TB portable USB drive)
    Spares - 1xTouch, 1xSB3

  3. #23
    Member JoeMuc2009's Avatar
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    wow, no, never got this as a complete document. Great, thank you!


    PN me if your Boom / Classic / Transporter display has issues!

    LMS 7.9.0 on Windows Server 2012
    1x Squezeebox Classic SB2
    7x Squeezebox Classic SB3 (one waiting for repair)
    7x Squeezebox Boom (two waiting for repair)
    1x Transporter
    2x Controller (one waiting for repair)
    3x Touch (two waiting for repair)
    1x Radio

  4. #24
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    I've seen this before, which is why I wouldn't be surprised if they push the low frequencies into mono and drive both speakers with it. The point of the DSP design is to maximise low frequency output and in a box this small no-one is ever going to get a sense of stereo separation below about 100hz.



    Transcoded from Matt's brain by Tapatalk
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    Hardware: 3x Touch, 1x Radio, 2x Receivers, 1 HP Microserver NAS with Debian+LMS 7.9.0
    Music: ~1300 CDs, as 450 GB of 16/44k FLACs. No less than 3x 24/44k albums..

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