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Thread: B&W DM70; rebuilding an Icon

  1. #31
    Join Date: Feb 2018

    Location: Somerset

    Posts: 27
    I'm Ian.

    Question Electrostatic panels response cut off

    I did a basic test of the high frequency response on my panels and found that the cut off is around 10/ 11 kHz.
    With a normal tweeter I can hear (just) to 16 kHz.
    This may explain why symbols seem so recessed and why, depending on the music, things just don't sound quite right.

    It could be the power supply to the panels or the panels themselves.
    As my mains is just over 230V where I live, I could try setting the selector on the power supplies to 220V to see if the treble improves.

    I suspect that it it is the panels themselves that need a refurb.
    We will see.

    How was the response on your panels?
    I would expect them to extend to at least 15/ 16 kHz if not higher.
    Last edited by iscm; 04-03-2018 at 00:17.

  2. #32
    Join Date: Feb 2018

    Location: Somerset

    Posts: 27
    I'm Ian.

    Smile

    Quote Originally Posted by i2Paq View Post
    So it has been a while since my last update.

    The Power units are still being restored. I had some difficulties finding the schematics but thanks to a Dutch guy over at the http://www.vintage-radio.net/forum I got a copy.
    Next was finding the right (physical) 800 Ohm resistors; this is still a work in progress.
    .
    Looking at the schematics that I have, there are 3 * 800 MEG ohm resistors in series.
    Do you mean these?
    There are some in the Radio Spares site, but they are not quite the correct shape.

    This is where I obtained my service manuals:
    http://bwgroupsupport.com/manuals/service#ID_DMSeries
    via a very nice chap on another forum

    NOTE: My bass crossover is not the same as in the manual
    B&W-DM7--Bass-Crossover.jpg

    Quote Originally Posted by i2Paq View Post
    I'm in the middle of restoring a pair of DM70 (in White) to original specs.
    I'm looking for a pair of female connectors used in the Power Unit. The unit you connect the Electrostatics to.

    I would be happy with a second hand pair, as long as they are without corrosion.
    Are there shops in the UK that specialize in those vintage B&W?
    I know a German address but I could be more lucky asking you guys in the UK
    I presume that you have the connector by now.
    In the UK One Thing Audio repair the electrostatic units plus the electronics
    http://www.onethingaudio.org/index.p...te=common/home
    and
    http://onethingaudio.net/index.html
    46 Siddeley Avenue
    Stoke
    Coventry
    CV3 1GA
    TEL: +44 (0)24 7627 4573

    They may have parts.

    Wembley Loudspeakers can do the speaker surrounds if required.
    http://www.wembleyloudspeaker.com/
    +44 (0)20 8743 4567
    I will be using them shortly.
    Last edited by iscm; 04-03-2018 at 19:28.

  3. #33
    Join Date: Apr 2011

    Location: Halesowen

    Posts: 3
    I'm steve.

    Default

    Quote Originally Posted by iscm View Post
    I did a basic test of the high frequency response on my panels and found that the cut off is around 10/ 11 kHz.
    With a normal tweeter I can hear (just) to 16 kHz.
    This may explain why symbols seem so recessed and why, depending on the music, things just don't sound quite right.

    I would expect them to extend to at least 15/ 16 kHz if not higher.

    P1020270.jpg

    this is the frequency response graph from the original handbook

  4. #34
    Join Date: Feb 2018

    Location: Somerset

    Posts: 27
    I'm Ian.

    Default

    Quote Originally Posted by koyaanisqatsi View Post
    P1020270.jpg

    this is the frequency response graph from the original handbook
    Thanks
    That is what is claimed, but what I wanted to know was peoples experience with repaired or original DM70 panels.

  5. #35
    Join Date: Feb 2018

    Location: Somerset

    Posts: 27
    I'm Ian.

    Lightbulb B&W DM70 Reference documents

    Here are links to all the reference documents that I have so far.
    https://1drv.ms/f/s!AsdR4rYZVpE4sUzCKIvZoEG9f5Ag
    Note that that this is my working area and there could be duplicates.

    This is interesting, as it give an insight into the development of the speakers.
    https://1drv.ms/b/s!AsdR4rYZVpE4sDU7GJjlvhBf1_2N

    I hope the above links help

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