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Old 14th March 2005, 04:07 AM   #1
scone is offline scone  United States
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Join Date: Nov 2004
Location: Austin, TX
Default finished WM-61a measurement mic

So it's finally spring break.

I assembled a measurement mic based on Linkwitz's mod (site here ). Works pretty well from what I can tell... I haven't taken any measurements with it though. I should have it plugged into speaker workshop and measuring my pair of John Krutke's Vifa XG18 MTMs soon (hopefully) . The capsule itself is heatshrinked and stuffed into the end of a bic pen. Total cost of parts was around $15.

Here's a pic (sorry it's a little fuzzy):
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Old 14th March 2005, 04:17 AM   #2
scone is offline scone  United States
diyAudio Member
Join Date: Nov 2004
Location: Austin, TX
and here's a picture of the protoboard.

There's one thing I don't quite like however. The mic is very noisy when I turn up the gain up high enough that I can actually here myself talking into it. I understand that the mod is supposed to lower the sensitivity of the mic so it's better suited to SPL measurements, but I'm quite surprised by how much it lowered it. I'm not sure whether it's an issue with the microphone, or if it's the mixer's fault (Behringer MX-602A ). It seems to me that I'll have to drive the speakers pretty hard in order to take any measurements with it... though I can't say for sure since I haven't tried it yet. Perhaps someone else who has built this mic can comment?

For reference, I am using the (b) modification on this page. I've got 3 24g wires that run from the capsule to the protoboard, and an 8ft long 1/4" patch cable that runs from the board to the pre.
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Old 14th March 2005, 06:01 AM   #3
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Join Date: Jul 2004
Location: BC, Canada
if you're using a 1/4 input on the mixer, that's most likely your problem with the noise. Use the XLR conenctor. It's at mic level.. the 1/4" connector is probably at line level.
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Old 14th March 2005, 08:52 AM   #4
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Join Date: Jun 2004
Location: Italy
some times ago I made a simple comparison between different class microphones. I measured the frequency response of the same loudspaker with these mics:

- BRUEL & KJAER 4190 (very expensive)

- Sennheiser electret capsule KE-4 (around 50$, discontinued)

- Panasonic electret capsule WM-61B (around 2$ or less)

View the results (very good for the WM61) here:
Mic comparison

In my tests I connected the WM61 following the manufacturer suggestions and not the Linkwitz's mod.


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