"re-coning" dynamic microphones?

[N_Cook]

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.

 

[William Sommerwerck]

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.

 

[Leif Neland]

Følgende er skrevet af William Sommerwerck:

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.

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

 

[N_Cook]

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?

 

[N_Cook]

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

 

[William Sommerwerck]

"Leif Neland" wrote in message 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?

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.

 

[N_Cook]

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.