[fraseyboy]

Picked up a few WM-61a capsules for use in a stealthy binaural recording rig for gigs and such. I've performed the 2-wire Linkwitz mod on a pair of them and attempted to implement the circuit design found here http://www.linkwitzlab.com/images/graphics/microph2.gif.

As expected the output level is greatly reduced, but the recordings also sound a lot less sparkly and airy. Spectrum analysis of the modded pair (top) compared to an unmodded pair (bottom) confirms that treble seems to be rolling off around 15khz:

This is my implementation of the Linkwitz circuit. I'm fairly new to DIY audio so it's a pretty ugly job and I probably did things in a less than optimal way:




Anyone have any ideas what I did wrong?

 

[jgazal]

I do not know about the circuit, so you will have to wait until someone technically inclined to give you a hint, but I once had dull response from an electret capsule just because I soldered them with a high wattage solder iron, probably melting the diaphragm.
 
I see your project further modify the electret capsule, so you may need to use a temperature controlled iron and to touch the pins as fast as possible.
Such mod exposes the electret to more heat and it seems very tough job unless one has seasoned soldering skills.
 
I can’t see if you applied silicone or hot glue to fix the capsule in the cup, but the latter may add more heat…
 
If the capsules are okay, then I can’t help any further than this.

 

[fraseyboy]

My soldering skills are pretty bad so there was a decent amount of heat applied. I also used hot glue. However both capsules seem to have the same treble problems. I guess it's possible I melted the diaphragm in both but isn't it a bit too coincidental that I broke them both in the same way? I guess it's a possibility anyway.