Well John, are you sure you are not describing comb filtering due to some kind of single frame time differential? I'm certainly a Trekkie and my favorite one was the reverse reverb which was pretty cool in 1966. You may also be hearing a slap and the resulting comb filtering from the microphones on the set. There was always plenty of that the closer folks got to walls. I mean obviously, in 1966 if you are talking Star Trek TOS, there were no digital effects. So they're either natural ambient occurrences or, Acoustic chambers if not that newfangled thing From 1958 by Dr. Kuhl? You know that metal bed frame with the sheet metal Mattress support & ceiling tile? (I know that's confusing but it was called an EMT plate). I would think you were hearing one of the acoustic chambers in all actuality. Distance from speaker to microphone could cause a wonderful fixed phase effect comb filter mush. Which is what it sounds like you are trying to describe? You're not talking about TNG are you?

If you're going to be doing phase tricks with microphones & speakers, etc., are definitely going to have to flip phase back and forth on everything to find out if something adds or cancels. Otherwise, they had nothing more than filters & chambers. They utilized a lot of that plate for sure for sure in many episodes. In addition to that, you're probably listening to a tube original release version of the plate. The plate also had a switch with a 2:1 compressor on it along with adjustable high pass filtering. We all use those things to their full extent. Great to make stereo from Mono with one of those by taking the EMT plate reverb time down to minimum. It wasn't reverb there. It was a space. A place. I miss both of mine. The EMT was cold rolled steel but the later Studio Technologies utilized a stainless steel plate. I loved the brightness of the EMT but I also loved the greater brightness from the stainless steel competitor. My knowledge of the AKG Spring-based reverbs only goes back to their BX 20. Even at its minimum setting, and always produced a longer reverb than the plate so I don't think they used one of those and I don't think one of those existed at that time? I forgot when they came online? It could've been that? I only knew that from 1973 and they were already off the air by then. Could have been an earlier version as I've seen some that are not familiar to me?

When I'm doing phasing tricks I'm always listening to the low-end. I generally judge things by whether the low-end is accentuated or attenuated. I generally emphasize accentuation which generally ensure something will sound bigger. The other way around is when you lose things from the frequency/Time based dependent attenuation. And this is why I'm always punching the mono button on the monitor system in the control room. I know a lot of folks that mix strictly for stereo and don't give a damn about Mono collapse. I don't understand that at all? And these guys are generally more anal oriented engineers than I.

Also remember Back then they were probably using a NAGRA III with a 60 Hz resolver. It wasn't SMPTE. So you could easily also slip that to achieve a time-based phase effect. Sort of like the original flanging utilizing 3 simultaneous running tape machines. Remember you were recording on one of them. Playing back normally from one of them. Dragging your finger on the third and then dragging your finger on the second and back again. Yup, not a plug-in but good old-fashioned finger manipulation.

John, I know you know how to finger this out.
Mx. Remy Ann David

Remy, I think you are right, it must be comb filtering. Probably was the wall/mic combo.

Thanks! I'll keep experimenting.