I read something today in the old products section of the AKG website on the old CK-8 capsule for the 451 preamp. I knew I had one of these inside a zepplin windshield in the store, but hadn't done anything much with it since I had other shotguns. What made me think was that AKG noted it's use on hand held vocals, where it was good at reducing popping. I pulled it out and discovered yes indeed it does seem to work. Then I wondered why, and started to discover things I'd not considered. Shotguns tend to use interference tubes to achieve the cancellation of off-axis sound, and I'm happy with the physics of this, but the CK-8 doesn't actually appear to be an interference tube in the usual sense at all? It's a long tube, capsule at one end, open end at the others and has a slot cut top to bottom. For over 300 degrees of circumference it's a closed tube, so singing into one end limits how close you get, but the side slot confuses it. So it's not pressure operation, it must be pressure gradient, BUT the polar response seems to ignore the fact that one side is closed and the other open?

Anyone care to guess how on earth you get a hyper-cardioid to lobar-ish polar pattern from a microphone that is not symetrical? I put it in a housing when I bought it for video and never gave any thought to the design. I put it in the housing with the slot facing up. Rotating around the long axis seems to make no difference?

It's so old as not to really matter - but maybe it could be good on a noisy stage to pick out voices - like a sort of proximity effect free hyper/super?