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head_unit 29th April 2013 02:03 AM

If headphones are out-of-phase, can you hear it?
I'm not talking about the "Wood effect" of detecting absolute polarity.

I'm riffing on a remark I heard that if the channels of a headphone are out-of-phase it will "cancel." Well, out-of-phase speakers will certainly cancel, but how about headphones? I don't have a handy way to check...

opc 29th April 2013 02:13 AM

Absolutely... and it's not a subtle effect.

You go from "in your head" imaging and soudstage, to a strange reverberant and completely unfocused image.

If you don't want to swap wires, you can make a sample file using Audacity and swapping the polarity of one of the channels. No need for hardware changes.


chris661 29th April 2013 08:59 AM

But many people complain about the "in your head" sound of headphones.

Is it worth adding a phase reverse switch to one side?

Steve Eddy 29th April 2013 02:01 PM


Originally Posted by chris661 (
Is it worth adding a phase reverse switch to one side?

No. The bass will turn to crap, especially with open 'phones.

When I test headphone cables before we ship them out, I use Lenny Kravitz's Fly Away. The opening guitar part lets me know that left and right channels are correct, and the bass after that opening part tells me that polarity is correct. If one channel's polarity is reversed, the bass is significantly diminished.


lcsaszar 29th April 2013 02:09 PM

The effect is pleasant for a few minutes (wow, there is no more sound in my head!), then it becomes quite confusing. Usually the conclusion is that the in-head sound was still better.

xnor 29th April 2013 02:17 PM

Think of it this way: the wavelength of low frequencies can be a few meters, yet the distance between our ears is just a couple of centimeters. Even if a low frequency sound source is completely to your left or right the other ear will receive pretty much the same with a tiny phase shift only.
For an inversion (or 180 phase shift) you'd have to have a huge head. In other words: it's completely unnatural. Think of the unnatural stereo separation in headphones only 10 times worse.

DF96 29th April 2013 02:24 PM

Out of phase speakers cause partial cancellation in the air. Out of phase headphones just confuse your brain. The fact that we can hear this is evidence that our ears can detect phase for at least some frequencies.

megaohmz 5th May 2013 05:00 AM

It's funny you are asking this question. I will throw my two cents in, but I think you have your question answered.

If you are listening to a modern mix, the upper freq are usually put out of phase slightly to give the illusion of soundstage. If you have the headphones out of phase, then you will undo and reverse the phase on one side and it wil be in phase for the upper freq, but BUT the bass will be out of phase and seem to cancel each other, but this is actually going on in your brain, not physically cancel each other in the air, as two subs might do. Weird huh?

Radio FM stereo is about 50% out of phase I believe, to add to this Illusion of stereo.

Remember that true (origonal) stereo is just guitar-drums on left with uppers out of phase 50% and vocals-bass with uppers out of phase.

All in all you should be able to easily detect it.

DF96 5th May 2013 08:56 AM

So studios deliberately destroy proper stereo imaging?

FM stereo radio takes this to the ultimate degree?

True stereo is pan-potted to left, right and (out of phase) centre?

To me this sounds like complete nonsense - could someone who actually knows about studios and broadcasting comment on this? Each statement is the exact opposite of what I have always believed.

iaxxaxxai 6th May 2013 04:24 AM


Originally Posted by megaohmz (
Remember that true (origonal) stereo is just guitar-drums on left with uppers out of phase 50% and vocals-bass with uppers out of phase.

No, it's not. You are maybe talking about some screwy rock albums from the 60's where they were trying to cram 30 layers of overdubs onto 4 tracks, but REAL stereo recordings of the 50's and since have never had things like that done to it.

Only time I can think of any manipulation being done with true stereo recordings is when a shuffling box was used. But that's only to be used specifically with certain techniques using spaced omnidirectional mics with the intention of correcting low frequencies.

Regarding modern recordings: phase is sometimes manipulated at different frequencies to create a certain special effect during the mixdown. But, tasteful engineers can use this artistically to create something interesting to listen to. I hear it in experimental electronic stuff alot, in a good way. As far as I know, fake stereo widening is not the normal thing all mastering studios do just to make something pop out more. It does get used, but more often than not to try and repair and salvage a poor mix that's pretty much already mono. Most of the modern pop music you might here that being done to sounds like freakin' garbage anyway, so it really doesn't matter. Its not normal to do it to REAL recordings.

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