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"re-coning" dynamic microphones?

Discussion in 'Electronic Repair' started by N_Cook, May 13, 2013.

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  1. N_Cook

    N_Cook Guest

    Not this time as I used the core of a Shure dynamic mic as a parts mule for
    a dropped radio mic, but just wondering if it can be done for some worthy of
    repairing expensive mic in the future.
    Both the Shure and the one with the broken hair-fine wire of the voice-coil
    have a thin diaphragm glued to a rigid surround . For speaker re-coning the
    cone is quite substantial and heat tolerant compared to this diaphragm
    material and hot-air heating usually removed the supension surface from the
    basket, but I doubt that process is possible with a mic - anyone been here
    before?
    As part of the fitting I intend using silicon rubber rather than the more
    rigid rubber of the originals, any thoughts as to any effect on sound
    quality? I was thinking a less rigid support may give more allowance as far
    as not transmitting shock-loads to the mic core . Initially I was wondering
    about a material more like a spring would give a reverb-tank spring-lime/joy
    spring reverberant character but then remembered a lot of studio mics are
    surrounded by springs.
     
  2. If you change the diaphragm, you will change the mic's sound.

    Given the tight tolerances and precise work required -- and the fact it's
    highly unlikely you'll produce a useful microphone -- I can't see this as a
    project justifying any expenditure of time, unless you have absolutely nothing
    else whatsoever to do.

    There's nothing wrong with experimenting to see what will happen -- unless the
    experiment has no possible theoretical or practical outcome.

    This is an Edison experiment. And that is not meant as a compliment to Thomas
    Alva.
     
  3. Leif Neland

    Leif Neland Guest

    Følgende er skrevet af William Sommerwerck:
    Are you referring to T.A.E is said to have tried thousands of different
    materials for the filament in light bulbs without thoughts of what
    might have been useful?

    Leif
     
  4. N_Cook

    N_Cook Guest

    While with microphone audio. Can anyone explain why you don't need mics with
    12 or more inch diameter diaghrams to register the audio from 12 or more
    inch diameter loudspeakers?
     
  5. N_Cook

    N_Cook Guest

    Well I seemed to have learnt something by burrowing in. Has anyone come
    across failure of a microphone from having been laid down against the
    heatsink of an amplifier ?

    I desoldered the VC tails and then with a warmed blunted needle lifted the
    diaphragm from the rim, without any obvious deformation. It looks as though
    the VC is held to the diaphragm with a wax of some sort, ie relatively low
    temperature melting.

    So microphone assembly construction, I assume is something like this
    melt a thin line of wax over the end of the former , the thickness of the
    former
    lay the VC in the hole in the magnet
    solder the 2 tails
    lay a thin layer of wax in the preformed hollow of the diaphragm , of
    diameter a bit larger to a bit smaller than the VC former diameter
    with a carefully controlled amount of DC or some sophisticated signal to the
    coil , to make the VC move towards the diaphragm evenly and centrally locate
    itself with even air gap to the magnet gap (perhaps an active system
    monitoring capacitance between VC and magnet body)
    a blast of warm air , perhaps only about 80 deg C to melt the wax , in the
    central area of the diaphragm
    keep the centralising signal present while the wax cools

    I won't bother unwinding 1 turn off the VC and reassembling as it was only a
    basic mic to start with and I've a robbed a mic core to replace it with
    anyway, with just adjustment of the suspension rubber as a different size
    rather than that wax business
     
  6. "Leif Neland" wrote in message Følgende er skrevet af William Sommerwerck:
    That's the story. I'm not sure it's true. It might have been that Edison
    wanted to make himself look industrious and hard-working. Regardless, whatever
    the material, it had to be conductive, and reach a high enough temperature to
    emit light, without falling apart. There aren't that many materials. I don't
    know whether a common metal -- such as iron -- would have worked.

    It's noteworthy that General Electric developed the sintered-tungsten filament
    that replaced Edison's carbon filament. GE was the first company to set up a
    laboratory for basic research, because it understood that a better
    understanding of basic science and applied technology would result in
    profitable products.

    Edison also developed one of the first storage batteries, again after testing
    hundreds of possible electrode materials. I once asked someone (I don't
    remember who) why he didn't just drop a note to Josiah Gibbs and ask for list
    of likely suspects. I was told that he /did/ consult with scientists about
    such things.
     
  7. N_Cook

    N_Cook Guest

    I don't often deal with microphones of any sort, so not come across this
    before. Putting the plastic cased radio mic back together I could not work
    out how to screw in the double threaded fitting that the mesh globe screws
    onto, into the transmitter body .
    4 turns to fit and putting a reverse 4 turns in the wire it still ended up
    pulling out the connector to the mic part. This area of the body is split
    seemingly to take the escutcheon for the switch , but actually that slot in
    the body must be for putting in a wedge, I used an ISO TO220 transitor. Open
    up the gap and simply axially push the aluminium threaded intermediary part
    , remove the wedge, and tighten just half a turn.
     
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