Working further after SQ decoding to get discrete channels

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quicksrt

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 5, 2002
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Los Angeles
I was wondering if folks out there who do SQ conversions ever use other software on the rear channels in an effort to get stronger separation as the end result.

Like using the best software out there being used for upmixes, and use it to fine tune already decoded SQ LPs, especially the rear channels? Seems like this might be a way to take SQ files to a higher level of discreet playback, particularly if one had the Q8 to use as a guide as to what one is shooting for.

I would think that upmixing software could help eliminate program material that has leaked into rear chans that should not be there.
 
No one? You mean I've come up with the secret recipe of making SQ as discreet as Q4 and I didn't even get a Like? (Joke)
Wow.
 
The upmixing software I am familiar with (Plogue Bidule utilizing SPEC) could extract discrete instruments and other information (ambience, reverb, etc.) from the rear channels. The easiest way to do this would be to make a stereo file of just the rear channels and process that file through the program. The downside would be that if you did not dial in the program enough, it really would not eliminate enough to make the process worth the time and effort. On the other hand, if you processed the file aggressively it would isolate dominant frequencies but it could also eliminate information that is intended to be in the rear channels (and excluded from the front channels). Meaning those sounds would be eliminated from both front and rear channels - "Hey! Where did that organ solo go?"

There may be other upmixing software available that allows the user to very selectively eliminate an particular instrument or sound, but I am not aware of any that is consumer grade available. There are several programs (Adobe Audition, for example) that has things like "vocal eliminator" that in theory would allow you to make your own karaoke tracks, but if you have ever played with it you know that while it does a fair job of suppressing the vocals on a track (providing they are mostly centered in the stereo image) you also lose anything else that is also centered (kick drum, bass, maybe even lead instrument). I have never tried using that method on just rear channels, but I think the results would not sound pleasing.

Also, in an given SQ recording, how can you know what was intentionally leaked to the rear channels by the artist/producer/engineer and what is simply leaking due to weakness in the processing chain?
 
If the drums are supposed to be in the rear channels, they could be diminished by artifacting from the process. #trialanderror
 
Lots to say on this but short of time at the minute.

In a nutshell there is absolutely a way to all but eliminate vocals in the rears of your SQ decodes to the point you would think you have a discrete presentation, I have experimented with it and done so several times with Columbia SQ 4-corner Quads where I'm familiar with channel placement in each of those corners.

Basically you decode the SQ as normal, take the rear pairs and sum them to mono and output the 2 x sets of identical summed mono rears, one pair conjoined in SR another summed pair in SL.. then reimport that MCh file into Audacity.. then you hard pan 100% each summed mono rear pair (SL panned to extreme/hard Left and SR panned to extreme/hard Right) and hey presto you get Rear Left and Rear Right channels with all of the decoded rear channel information present and correct with no vocals from the front channels.

However, I cannot get Audacity to export the results.. I have tried and tried and its maddening because it is all there and it feels tantalisingly close.. but I would say based on my little experiments it is possible imho.. and someone more technical who knows how to export stems from Audacity with such L&R pans intact could do it.

If any of this is unclear (which I totally understand, not least because it is a fairly batty concept and I'm possibly not explaining it too well as I'm doing this in a rush in between other things sorry but I just found this thread and thought I'd better chip in before I forgot I'd ever seen it :eek: ) anyway I will make a short video clip tonight and a few 30 second clips of the summed rears from various things (maybe also from a couple of SQ only Quads, though you have no exact point of discrete reference so maybe a waste of time at this stage?) so you can hear what I'm on about.
 
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