Modding cheap Chinese SDCs

[dgatwood]

You'll notice I've never said anything good about CAD's SDCs. That's because I've used them and they're pretty terrible... or at least I've used the Astatic CTM-1000 that they also build. They seem to be basically identical to the Nady CM-90, but with slightly larger drill holes in the backplate and an added bass roll-off switch.

Anyway, I decided I'd go ahead and remachine the capsule by hand with a Dremel. It took a small eternity, but I ground off the front 1/8th inch of the capsule, resulting in removal of the metal bars that create so much comb filtering. I also rounded off the resulting thin lip at the front and removed one layer of the screen. Wow, what a difference in the sound.

I did have one unfortunate mishap, though. I inadvertently dropped and severely wrinkled one of the three spacers. For now, I'm running it with two, but it seems to occasionally misbehave in a way that makes me believe the diaphragm may be smacking into the backplate. Hopefully the spacer will flatten back out on its own so I can reinstall it.

I'll post samples this weekend if I think about it.

Above: the stock capsule.
Below: the remachined capsule.

 

[Chili]

Nice. What are the spacers you're talking about? Got pics of those? How do you keep the capsule in place if the grill is not there anymore? Can you do a frequency sweep sample compared with both mics??

I don't think you mean comb filtering, probably just poor freq response. That grill is not going to cause any phase distortion in the audible spectrum.

Thanks for posting this.

 

[Brian Oshman]

I decided I'd go ahead and remachine the capsule by hand with a Dremel. It took a small eternity,

Could have done that in a couple of minutes with a belt sander and it would have also been straight.

 

[dgatwood]

Nice. What are the spacers you're talking about? Got pics of those? How do you keep the capsule in place if the grill is not there anymore? Can you do a frequency sweep sample compared with both mics??

The grille doesn't hold the capsule. There's a narrow part of the capsule that the capsule is pressed against. I'm actually putting the metal mesh grille between the capsule and that rim, which is something of a hack, but without the front grille, there was no other way to keep the mesh in place... glue, maybe, but....

I don't think you mean comb filtering, probably just poor freq response. That grill is not going to cause any phase distortion in the audible spectrum.

It sure sounds like comb filtering. The capsule produced a really harsh top end before, with what sounded to my ear like it had all sorts of peaks and troughs. I guess I could run a frequency sweep.

 

[dgatwood]

Could have done that in a couple of minutes with a belt sander and it would have also been straight.

That's not a bad idea. I might do that.