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Thread: B&W DM70 - my journey so far

  1. #1
    Join Date: Feb 2018

    Location: Somerset

    Posts: 35
    I'm Ian.

    Question B&W DM70 - my journey so far

    I thought that I had better start my own thread

    These speakers were bought by myself about 2 years ago.
    They seemed in very good condition and I was told that the veneer had been done together with the bass units being repaired.
    I was also told that the mid treble panels had been serviced by One-Thing.

    At first they played just fine until about a year ago after I moved house.
    First I noticed some distortion in the bass from one of the units.
    On closer examination I could see that an incredible bodge had been performed.
    Each bass unit had two surrounds.
    One was formed out of thick paper and a second (12 inch) foam surround put on top.

    More recently, I noticed that I was missing the treble.
    This coincided with the building of a new housing estate at the bottom of my street.
    About 40 houses were added to the mains transformer until one day it blew up.
    When it was replaced, I noticed that my treble returned some of the time.
    I then started measuring my mains voltage and found that when it was low (at around 18:00) my treble was low, but later at say 23:00 the sound was much better.

    I phoned One-Thing and the suggested that I send in the energiser units for repair, as fluctuations in voltage should not affect them so much if at all.
    When I have time, I will send them in for repair.

    Now regarding the Bass units, I now have Leak Sandwich 13 inch units which are a lot better.
    I had to do some modification in that I needed to remove about half the speaker stuffing to make these units perform correctly.
    In order to prevent the stuffing getting into the bass unit and to keep the stuffing central and suspended, I purchased two packs of 3 laundry bags (the sort to use in the washing machine). This has worked well, as before, with less stuffing it was settling to the bottom.
    Now it is all where it should be, in the middle.

    I was still noticing a but of a mid bass honk which I thought may be a reflection from the rear panel.
    To minimise this, I bought two rubber backed natural door mats.
    I used spray carpet adhesive to stick these.
    This seems to have worked as the sound seems much cleaner than before.
    I may, in the future, do the same to the other internal panels.

    Now I am left with three main resonance nodes at 54 78 & 111 Hz.
    Depending on the kind of music being played these can show.
    Now it may be that when I get my energizer units serviced, the increase in treble output will mask the bass issues, but I would still like to know what to do to minimise.
    It may even be a function of my room, because I do not remember them being so obvious in my old house.

    One may wonder why I go to such a lot of trouble.
    It is just that when working correctly, these speakers can produce magical sounds.

    These days I am using a
    Focus One recodr deck with SME III arm
    Conrad Johnson PV9a pre-amp
    Art Audio Quintet power
    plus Chord Cables

    I will, when I get time, get my Alphason Sonata back as my main source.
    There is also a Unico CD player for digital and for streaming I have a Marantz unit.

  2. #2
    Audio Al is offline Pishanto Specialist & Super-Daftee
    Join Date: May 2012

    Location: Dagenham Essex

    Posts: 11,215
    I'm Allen.

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    Hi , Sounds like you know what you are doing and having fun doing it , Well done and keep up the good work
    [

  3. #3
    Join Date: Feb 2018

    Location: Somerset

    Posts: 35
    I'm Ian.

    Default

    Quote Originally Posted by Audio Al View Post
    Hi , Sounds like you know what you are doing and having fun doing it , Well done and keep up the good work
    It is good to have that illusion.
    The truth is that the deeper a speaker goes, the harder it is to integrate into ones room.
    It is also very hard to work out the difference between a room resonance and that of the speakers just with ones ears.
    This is why B&W were one of the first manufacturers to build their own chamber, so as to be able to differentiate between how a speaker works in a room and problems with the unit itself.

    Now I am thinking logically, I realise that my three main resonance frequencies are probably my room nodes.
    Before my damping modifications, there was also some reinforcement at one of the resonance nodes by the cabinet.
    One of the speakers was a bit close to the corner and moving the speaker by about 10 inches forwards seems to have cured room node issue somewhat to the point where it is not so intrusive.

  4. #4
    Join Date: Feb 2018

    Location: Somerset

    Posts: 35
    I'm Ian.

    Default Bass Surrounds DM70

    I have just ordered surrounds for the bass units in my second pair of DM70's

    https://www.ebay.co.uk/itm/B-W-DM-70...EAAOSwlStauOhM

  5. #5
    Join Date: Apr 2010

    Location: Bristol, since 1978. Current house since 1996!

    Posts: 909
    I'm Chris.

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    At least the surrounds won't decay on the Leak bass units; they use 'doped' fabric.
    Chris.

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