Left and right, but not center

[eduardo_b]

I'm trying to implement a technique I've heard on CDs in which the right and left channel have an identical simultaneous signal, yet there is nothing in the center. Among the advice I've been offered to do this was to pan one track hard left, another hard right, but inverse the phase of one so they cancelled the center. Another was hard left and right, but delay one by +5 ms and the other by -5 ms. I'm wondering if the effect I've heard was done by making a slight pitch adjustment to one channel that is imperceptible but sufficient to create the simultaneous effect in both channels. Anyone know how this effect is really done?

[mjau]

Don't know if this helps, but what can be really cool is just tracking the part twice and hard-panning those two tracks. Use different guitars, different mics / mic placements / preamps...or not. I do this with acoustic guitar all the time.

[wedge]

Is this what they call Big Mono? If you have the same thing coming out of left and right, then it will appear to be coming out of the center. You might as well pan it center, because that's what it'll sound like, right?

[eduardo_b]

Is this what they call Big Mono? If you have the same thing coming out of left and right, then it will appear to be coming out of the center. You might as well pan it center, because that's what it'll sound like, right?

No, the entire point of the effect is to NOT have anything in the center even though the left and right channels are identical. It is most definitely not mono.

[Mark Alan Miller]

Same thing in either channel with one channel polarity inverted will not sound particuarly good. The phase cancellations and wierdness is exzactly like having one speaker wired backwards.
Adding a little delay to one side or the other will decrease the absolute phase cancellations, but increase comb filtering, at which frequencies will be dependent on the delay time (all other things being equal).

And mono-compatibility is obviously out of the question.

I don't think this will be what you want it to be.

Is this what they call Big Mono? If you have the same thing coming out of left and right, then it will appear to be coming out of the center. You might as well pan it center, because that's what it'll sound like, right?

This is exactly true. Sending identical signals to left and right is the same as panning center (aside from a possible level difference, due to the way panpots are designed, etc, etc...)

I'm trying to implement a technique I've heard on CDs in which the right and left channel have an identical simultaneous signal, yet there is nothing in the center.

Best thing to do here is to point us to some examples of this. I have to hear what you're referring to to be possibly of any help on this one...

[Bill @ Irie Lab]

Is this like the Karioke trick? (or a step in Mashing [UK]).

A tutorial for Tracktion but some info here in removing center channel information.

www.paintingbynumbers.com/bootcamp

P.S. Tracktion is cool beans for anyone wanting to jump on the DAW bandwagon.

[Phiz]

Another was hard left and right, but delay one by +5 ms and the other by -5 ms.

This will just make it sound like the sound is coming from the +5ms side.

[eduardo_b]

Another was hard left and right, but delay one by +5 ms and the other by -5 ms.

This will just make it sound like the sound is coming from the +5ms side.

Okay, that makes sense. The phase reversal doesn't seem right either given it can be used to remove vocals. I simply can't figure out how to run the same identical track hard right and left without getting the center. I'm trying to find an example of the effect to make available somewhere so someone with better ears can perhaps figure out how it was done.

[Professor]

Delaying one side or the other should only help to peg the sound into one speaker. The 'precedence effect' would kick in and your ear would hear the first arrival as the source and the second arrival as an early reflection. I suppose if you delayed one side but increased its volume you might be able to pull something off but it would takesome work to get that to balance quite right and it would likely collapse in a less-than-ideal stereo speaker setup.
If it's a mono signal going in, that may be you're only bet. You could probably try delivering it inverted to one side, but you would have the problem of losing the signal in mono and just plain making the signal sound weird.
For a stereo source you could try a sum & difference matrix to reduce the 'mids' and increase the 'side' signal which emphasizes what is different between the tracks while reducing what is the same. That would leave a hole in the middle but if used to the extreme it will have the same effect as inverting one signal.
Either way you swing it, I would hope you are then mixing something else into the center of the mix, right? If you are trying to achieve the effect as an absolute on just a stereo mix then you will have a hard time getting there. But if you are reducing the middle area enough that there is a hole left for vocals or other stuff to fill in the middle, then you really only need to reduce the middle enough for it to be masked by the other sounds.

-Jeremy

[eduardo_b]

I would hope you are then mixing something else into the center of the mix, right?

Absolutely. What I want to do is use the effect of simultaneous right and left of the same audio as part of the mix, and not necessarily for the entire length of the track. It would have a similar feel to overdubbing a voice or acoustic guitar or whatever, but instead of this being in the center, it would be heard only from hard right and left. I've heard this used on a number of CDs (I'll have to do some searching for them) with headphones -- with speakers it would be more like widening the stereo field. That no one knows immediately what I'm referring to makes me think this is not all that common an effect.

[aeijtzsche]

I would think doing very slight anything to one side would be enough to pull the sound out of the center. Raise the pitch a cent or 5, EQ one side a wee bit. I dunno.

[blunderfonics]

Absolutely. What I want to do is use the effect of simultaneous right and left of the same audio as part of the mix, and not necessarily for the entire length of the track. It would have a similar feel to overdubbing a voice or acoustic guitar or whatever, but instead of this being in the center, it would be heard only from hard right and left. I've heard this used on a number of CDs (I'll have to do some searching for them) with headphones -- with speakers it would be more like widening the stereo field. That no one knows immediately what I'm referring to makes me think this is not all that common an effect.

Not knowing exactly what records you are referring to, I'm going to go out on a limb here: I think that what you are possibly hearing as the same signal in the left and right (but with no center image) when using headphones is not the same signal at all, but a very, very tight double. With good talent, patience and all the tools available these days (such as Auto Tune and Vocalign) it's possible to get double or triple or quadruple-tracked takes extremely tight, but with enough subtle cues for the brain to discern them as stereo. I think headphones will exagerate the hole in the center when listening to these types of doubles.

If you think of a good example of what you are talking about, try listening to it in mono. That will give you a better idea as to what's going on. The subtle delays or pitch shifts might become more obvious as you hear them comb-filter or pulse in mono.

[Professor]

I've heard this used on a number of CDs... with headphones -- with speakers it would be more like widening the stereo field.

All of the potential techniques that have been mentioned were aiming for a 'trans-aural' effect like you would hear over speakers. You are hearing an effect accentuated because of the 'binaural' effect of listening on headphones. With headphones, there is no acoustic interplay of the sound arriving from both speakers. So if the effect you're seeking sounds like a "widening" on speakers, then that's what you should be attempting to do.
The sum & difference matrixing I mentioned for a stereo source would be a really good bet for what you're trying to do.

-Jeremy

[joel hamilton]

I use sum and difference all the time. I also use stereo pairs of things like guitars in an M/S setup during the mix sometimes, especially for AC gtr. Having the center pump to two tight overdubs can sound like a third "center" gtr, or conversely, flipping the "center" 180 out can "disembody" the tracks very much by killing all the phase coherent stuff and leaving only the anti phase information to the outsides. this can be a great track when you have 4 tracks of guitar, maybe two tght stereo tracksof heavy guitars for instance.... Take one pair, bus to a mono comp, send up the middle. Ram it up the middle with a bunch of compression. Take the other pair, bus to a different bus with a comp limiting the HELL out of the sum, ram that up the center of the stereo pair, and then flip the phase on that one track. Huge, wide, controllable weirdness and width, that totally collapses to mono pretty gracefully, even without getting into the M/S stuff... that is a whole 'nother ball of wax...

What you are prbably hearing though, as stated above, is just a tight double track of an element, panned hard L-R. Amazing how little info seems to "live" in the middle when in headphones. Very common. The technique I mentioned above is MUCH more rare.

[bluespkr75]

Pan one hard left, one hard right and then apply chorus to one side. Adjust the wet/dry so that the chorus goes almost out of the audible range (while being soloed). Now play both sides and adjust the volume for each side. I've always had to turn the chorused track up a bit. If you do it right, you won't hear the chorus at all but both sides will be separated with just about nothing down the center. Obviously, using a stereo chorus would not work here. Good Luck!