Aqua Marine

Posts: 3,641 Member Since:14/02/2011

#561 [url]

Owlander, nice job, nice tune.
Kyle, wow nice player, so nice to see someone play an organ.
Cool jobs you guys have there!

OK it's cold here

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Gold Finger

Posts: 955 Member Since:22/02/2011

#563 [url]

More mad scientist studiohacking from me: didn't video any of it, so I can only tell the tale.
You can get pretty good sound out of two SDCs by putting them up on an overhanging wall (one of those 45 degree almost-ceilings) as a PZM pair, about 20 inches apart… the wall looms right over my drumkit, but using the PZM concept it disappears, which is handy. Not every day you get a wall that also serves as drum overheads and room mics at the same time…
Extensive experimenting to get the right spacing and positioning. There will be no 'hard panning' positioning, but I'm also not going for super mono: I'm looking to get a faintly 'dummy head over headphones' effect. Looks like the correct spacing is a bit more than what you'd use for, not inter-ear distance, but circumference of head distance. There did turn out to be a placement with a good balance of 'holophonics' and center solidity. To experiment without cutting 4000 holes in blackburn lancashire I mean 'the wall', you bonk the SDC mic against the wall face-on at a slight angle, creating a small gap for sound and pressure to get in. You get lousy treble because it's not impacting the element directly, but the correct PZM effect.
Had to extend the element of the mics (only Studio Projects SDCs, though I had already modified them) because the wall's likely not deep enough to take a mic end-ways including the plug of the cable. Proved a messy procedure: taking apart the actual elements so soldering heat wouldn't just melt the diapragms, discovering that one I'd obviously fooled with before and put back in with the frail spacer ring all screwed up… mic worked, but volume was reduced and obviously it failed to be a matched pair (or really any good—no wonder I was having trouble with it). Cannibalized a cardioid element from the same Studio Projects set, stole an intact diaphragm/spacer, stuck it into the omni. Discovered I wasn't tightening the retaining ring, and the backplate was loose and flopping around. Discovered that's what the spring inside the mic body was for: these things have intentionally loose elements, held against the spacer by the electrical contact mechanism. Bodged an acoustic foam and electrical tape spring to do that job while the element's away from the mic body. Discovered later that this cleans up some issues in the highs by damping the hell out of the inside of the element… there's also a danger of the foam deteriorating and foam dust getting into the element, good thing it's a garbage mic eh? Wired up a tiny shielded cable to extend the head of each mic, wondering if it'll do interesting things to the mic to have this little capacitance in there. Replaced a 470pf ceramic cap that passed the whole signal to the first transistor, with a 470 pf polystyrene. Tested mics, worked but had some hum. Shielded 'em with aluminum foil, held against the body with vinyl electrical tape again. Tested again, found the highs considerably better but without a proper infinite baffle on the omnis they got no bass. That must wait until they're mounted in (and flush with) the wall, then it'll be fine…
All in all, a pretty busy night. I just mention it because working with condenser mic element parts was unusually tricky, and I'm pleased I got out of it with a matched pair of bizarre homebrew PZM mics. That's actually more than I had when I started, because I didn't know one of my mic elements was screwed up when I started work this evening…

Chris Johnson, airwindows.com

Last Edited By: chrisj . Edited 1 time.

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