Comb stereo ?

Posted: Sun Feb 24, 2002 8:26 pm

Hi there,

In regards to TV-/PostProduction what is meant with "comb stereo" ?

"nothing" may be a valid answer ?!?

Thanks,

Matthias

Posted: Sun Feb 24, 2002 11:22 pm

Quote:

Originally posted by Matthias Postel:
Hi there,In regards to TV-/PostProduction what is meant with "comb stereo" ?
Matthias

Hi Matthias! So far it seems like it would be a valid glossary term for today's modern TV stereo post production technique, but I couldn't find it. LOL. I do know there are some problems with stereo (TV), and the ways that stereo is perceived by the listener. So some comb-filtering stereo processes are used to offset negative effects, a sort of pseudo stereo. Or,it could be that lttle switch on my VCR that say's Audio Norm,HI-FI,SEP,COMB....but I think it is more about effects. Hope someone else can nail this down a little tighter, anybody?
--Rick

Posted: Mon Feb 25, 2002 1:39 am

Thanks Rick,

At least there is some direction,

Quote:

some problems with stereo (TV), and the ways that stereo is perceived by the listener. So some comb-filtering stereo processes are used to offset negative effects, a sort of pseudo stereo.

Usenet searches I made went along similiar lines - but still quite blurry,

Quote:

Or,it could be that lttle switch on my VCR that say's Audio Norm,HI-FI,SEP,COMB

In this context, I'm pretty sure that it's COMBination or COMBined (like SEPerate).

The situation is: Client says (actually not to me but a colleague): "Can you lay it back in comb-stereo ?" - Probably my colleague was nodding and thought "???" Wink

Anyway, it would be appreciated if someone could specify it a bit more.

Thanks anyway,

Matthias

Posted: Mon Feb 25, 2002 6:34 am

Quote:

The situation is: Client says (actually not to me but a colleague): "Can you lay it back in comb-stereo ?" - Probably my colleague was nodding and thought "???" Wink

[/QB]

Loving a good mystery, found some more...

(Quasi Stereo..
Quasi Stereo acts on the common (mono) portion of a stereo signal. It divides the "shared" signal into a stereo path and applies complementary comb filters to each channel. These filters disperse their outputs to the left and right channels in such a way as to alter the impression of the stereo image. This process has no effect on mono files.)---MMMM???
-- Sounds to me like the client wants to be assured that there will be no problems when it comes to the mono signal. I mentioned these precautions to an engineer friend, who's commercial, which I heard, had no announcer(off air to boot), but all the background sound and music came through. He said "When it leaves the studio, it is out of my control" So, to assure all the sound will reach the listener, including a complete phase reversal of left and right to mono(bad wireing job somewhere), which would normaly cancel out center channel information..will still present enough to be useable. Are we getting any closer?.. LOL
--Rick

Posted: Fri Mar 01, 2002 2:25 am

Take any mono signal and mult it out into 2 channels of graphic eq. On the first channel, boost every other frequency band and cut the others. On the second channel, cut the frequencies that you boosted on the first eq, and likewise boost the ones you cut. When the 2 channels are summed into mono, it will be identical (yeah, right!) to the original signal. You can play with the amount of cut/boost for each frequency to make some bands "wider" than others. For instance, you might want the voiceover frequencies (200Hz-350Hz & 800Hz-2kHz) to stay relatively centered, while background sounds and music are spaced further apart. (image placeholder)

You can call it Quasi-stereo, Pseudo-stereo, or whatever you like. Just make sure the polarity doesn't get flipped!

Posted: Fri Mar 01, 2002 5:23 pm

Quote:

The situation is: Client says (actually not to me but a colleague): "Can you lay it back in comb-stereo ?" - Probably my colleague was nodding and thought "???" Wink

I think that "nothing" is the answer to what is meant by "comb stereo" in this context. I've worked in audio-post for over ten years, delivering a wide variety of broadcast and non-broadcast programming, and have never come across it as a layback format.

So, what did your colleague do, not knowing the answer? Did he plead ignorance and ask the client what he meant by "comb stereo"? Or did he just nod and do a straight-up stereo layback, figuring if the client didn't really know what he was talking about it wouldn't matter anyway?

In any case, thanks for the question. We still may not really know the answer, but I learned some cool stuff about quasi stereo. And Ang1970, thanks for the tips on how to set that up and put it to work. I had great time playing around with it today.

Posted: Sat Mar 02, 2002 1:54 pm

Hi Jeffrey,

Thanks - that's another very interesting statement (because that's what I thought, too).

Quote:

So, what did your colleague do, not knowing the answer?

It's not that dangerous because the production is coming up soon - so there was some time. What he did was to ask people. In conversation with the client I guess he ignored it since it didn't need to be done right away. But I wasn't there.

Thanks for all the info !

Matthias

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