there are many VST plugins that will shift all frequencies by a specified (arbitrary phase).
^^^
This is what I'm trying to do. Thanks for the links Jason, I'll look into them.
Joe, your are correct that a simple time shifting technique will create a varying phase shift that is frequency dependant instead of a constant shift across all frequencies.
Charlie, thanks for the offer but I think you have me confused with someone else. I'm Lee.
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If anyone is curious, I want to try this for decorrelating a single mono signal to create two signals. If any of you are aware of good alternate techniques for decorrelating a single mono signal to two signals please let me know. Maybe some 'pseudo stereo' techniques could work?
I've been doing a bunch of 4 channel surround recording by adding a second stereo pair consisting of a center and rear pickup to a standard left/right stereo spaced or baffled omni pair. Playing the files back on a typical 5 channel playback system, I currently split the mono rear feed to the two (or more) rear surround speakers. The primary thing I want to do is
decorrelate the single rear surround signal to create discrete left surround and right surround signals in an attempt to defuse the ambient surround information around the back half of the room. I'm not concerned with imaging back there, instead looking for an open ambient 'feel' of the space. Sometimes it's a issue of trying to make the sound of the occasional loud clapper that was right behind my rig, more spread out and less localized right at the rear speaker, so as not to draw attention to the speaker.
One simple way to decorrelate is to duplicate the mono rear signal and flip the polarity of one of them, but that means one side is 'in phase' with the front 3 channels and the other 'out of phase' - less than ideal. Rotating or shifting the rear signal 90 degrees before splitting them and flipping polarity makes them out of polarity with each other, but symmetrically 90 degrees out of phase with the 3 main front speakers. Delay and eq could be used to decorrelate the mono signal but seem like less than ideal solutions that might just make for comb filtering phasy weirdness.
Part of the reason I'm looking to do it this way is that as I understand it, this
constant 90 degree phase shift over the whole spectrum is a technique used by the matrixed Dolby surround versions to decorrelate a mono surround signal to two speakers. Secondarily, even though my primary goal is a discrete 5 channel output, I'd also like to play around with DIY matrix encoding to stereo for playback on a typical surround receiver. I'm imagining folding the mono center and mono phase shifted surround signal into the right/left signal to create a Lt/Rt matrixed stereo output that might decode reasonably well on a DPLIIx, Circle surround, Logic 7, or DTS NEO6 receiver. I'd guess there are VST surround tool plugins for doing matrix encoding but that
phase is further down the road and I haven't yet looked into it.