Linkwitz Mods On Panasonic WM61A Mic - Page 2 - diyAudio
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Old 15th August 2009, 10:21 PM   #11
teleman is offline teleman  Norway
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Bigwill,
I wrapp a thick rubber band around the handle of a pair of pliers. ply it open,then insert the capsule in the gap to keep it cool while soldering it. I also use one of these cheapo helping-hand(s) with a magnifying glass ...very handy indeed!

It helps if you apply a little conductive silver on the tiny ground trace/capsule casing as well before soldering.(Maplin sells a small vial) Lead free solder is better for this task I gather, 'cause it contains a little silver in the brew!!

I use only 16-18 strand 1.3-1.5mm soft sheath signal wire, similar to ribbon/network cables.These wires are a bit expensive, but don't exert any strain on the capsule either.The wire/sheath should have little or no capacitance as possible, otherwise it'll just add to the mic's capacitance & will contribute to the noise spec as well!!

Most importantly,it's best to use a 15w-18w soldering iron with a 1.3mm or 1.5 tip at the most!
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Old 15th August 2009, 10:26 PM   #12
Theo404 is offline Theo404  United Kingdom
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Quote:
Originally posted by scott wurcer


I bisect the pad with a fresh XACTO blade then you can solder three wires more easily. I use #30 wire wrap so the insulation does not melt away.
I think will was talking about soldering to the case, which the linkwitz pages suggest. I also found this difficult to do without fears of nuking the capsule, so with my latest one I just roughed up the edge of the case and twisted a stiff single core wire around pressing the contact against the case, sounds flakey but it has maintained a good connection for quite a while now.
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Old 15th August 2009, 10:43 PM   #13
teleman is offline teleman  Norway
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Zap,
Could you please explain the theory/topology behind it?
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Old 16th August 2009, 12:19 AM   #14
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Quote:
Originally posted by Theo404


I think will was talking about soldering to the case, which the linkwitz pages suggest.
I meant that you can cut the pad where the case and source are shorted together and leave enough pad so you can solder to the case connection easily (normally),
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Old 16th August 2009, 01:15 AM   #15
Theo404 is offline Theo404  United Kingdom
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Quote:
Originally posted by scott wurcer


I meant that you can cut the pad where the case and source are shorted together and leave enough pad so you can solder to the case connection easily (normally),

Ahhh I see. Looking at a virgin cap now I can see what you mean. Thats a much better idea...
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Old 16th August 2009, 02:12 AM   #16
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I bought 10 I think I've destroyed (and possibly lost) a quite a few (I think I only have two unmodded ones left).... One thing I read (can't remember if it was on the linkwitz site or elsewhere) suggested using conductive glue instead of soldering... not sure where you get it though.

One of the problems is that it is very easy to damage the seal on the mic capsule, this can be because of the cutting, or because of overheating. I think the suggestion of using the big rubber band on the pliers and using them as a heat sink is a great one as is the one of cutting the track with an exacto and soldering to both sides of the track as this should reduce the risk of both of the things that can cause seal failure. I might try again on one of my remaining capsules, I've been suspicious about whether my mics have been working correctly or not. Have had quite mixed results with my measurements and changing mic capsules has made quite big differences. Hopefully will be getting back to doing some testing in the not too distant future, provided I can keep the momentum going, and the new house we are looking at comes off

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Old 16th August 2009, 03:15 AM   #17
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FWIW, I've always found these small capsules a disappointment because the noise floor isn't that low. It's just the nature of the beast. The 1/2" B&K capsule on our SPL meter at work is about 25 dB better, but the mic alone costs about $1K!! The big studio condenser mics you can get for about $70 (imports) have a great noise floor, but the response is invariably tweaked to sound "good", not flat. I haven't yet found the perfect diy measurement mic.
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Old 16th August 2009, 04:15 AM   #18
cuibono is offline cuibono  United States
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The noise floor on them may be better than you think - place the omni mic in a zero noise chamber, then measure. The main reason omnis usually get tagged as noisy is they pick up directional noise that our ear/brain usually masks out.
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Old 16th August 2009, 03:48 PM   #19
teleman is offline teleman  Norway
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Here's another excellent link on wiring a modified WM61A capsule.

http://www.airraidsirens.com/posts/wm61a.html

I do it a little differently in that,I don't shave off the casing,but solder both the the ground pin & the exposed ring together while keeping the capsule clamped in a pair of pliers & under a magnifying glass.

Winding the solder end of the wires a couple of times on a 5-6mm screw,bolt or any suitable thin rod, making a"spring" before soldering will definitely reduce the capsule picking up unnecessary mechanical vibrations & will further reduce the wires coming apart by accidental pulling.

Sealing the back of the capsule with soft silcone or any soft suitable glue will further help to keep the wires intact & most importantly will reseal/close any holes one may have exposed inadvertantly while soldering, since this will have a significant effect in the low freq.response & sensitivity of the mic capsule.
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Old 16th August 2009, 05:18 PM   #20
bigwill is offline bigwill  United Kingdom
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One of the microphones I modified with the two wire method had far less dynamic range than another - it would clip far earlier, confirmed with a scope. I guess this was due to the heat, although I had it in one of those helping hand mounts like teleman mentioned

Something to keep in mind
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