Technically, regardless of frequency, L-R and R-L are exactly the same signal. Any differences come from 'Phase Inversion' of one
relative to L+R summed mono.
Once again, L-R (R-L) is how Dolby Prologic extracts a rear channel.
Another use of L-R & R-L signal is how Getto Blasters made the "Stereo wide/Matrix" sound. It used an EQ'd version.
Adding L-R sound to your system effectively reduces the volume of Mono content.
EG. Using ONLY L-R sound is what karaoke machines do to remove 'Centre Vocals'.
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There are a couple problems with the phantom center. Both stem from the fact that two speakers are trying to make a sound seem to come from a direction where there isn't actually any sound. The first problem is that the sound is hitting the outer ear from the wrong angle for something that's supposed to be right in front of you. That's probably the less important issue. The second problem is that both ears end up hearing both speakers with a very slight time delay that results in a big dip in response at around 2 kHz, followed by a series of narrower dips above 2 kHz. This causes a tonal difference between sounds that are panned to the sides compared to sounds panned to the center.
From what I can tell, this comb filtering of the center panned sounds creates an effect that some people actually like, setting the center further back. When a real center channel is introduced, a lot of people find this to sound too up close, like it draws too much attention to itself. I find that it indeed does stand out, especially if the center panned instrumentalist or singer has been close mic'd. and mixed in. I like that effect. I can hear how it was mixed and that's fine by me. I can also understand why some would not prefer that. For them it's easy - just use two speakers.
But, another issue with the change in tone of the center seems to have something to do with the overall presentation of the soundstage being inconsistent. It's like picture that's blurry in the middle but sharper around the edges. That's an odd effect to my ears. I'd rather a picture, or a sound stage be clearest in the center, and if it has to get blurrier or less accurately defined, to do so off to the edges.
My 3 speaker array reverses the problem, creating a hard center and phantom left and right. But then below 900 Hz it switches back to normal 2 speaker stereo, because the center array doesn't work as well as the frequency goes down, and the comb filtering is not a problem below 900 Hz.
One interesting effect I've noticed is that on some tracks you can end up with the bass, which is essentially mono, seeming to come from the tweeters, which are right in front of you, but all the high frequency sounds which are panned wide in stereo seeming to come from the woofers, which are far off to the sides. This happens on some electronic, EDM stuff. I get a phantom center bass, and phantom sides ambient high frequency effects.
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HiFi & linear freq response is just a bad joke , make people think having linear equipment yields perfect results!
They forget the HRTF (incl. power response thereof) and the equal loudness contours! (ELC)
Just to name 2 major faults .. there are more issues ...
And whatever our brain processes out of the complex signals!
Btw - funny how easily people adopts the 60deg listening triangle as if it would be cast in stone!
In all those years I have never seen this discussed anywhere!
Shame on you - DIY bunkerheadz!
welcome to reality
(bites hard hard hard)
They forget the HRTF (incl. power response thereof) and the equal loudness contours! (ELC)
Just to name 2 major faults .. there are more issues ...
And whatever our brain processes out of the complex signals!
Btw - funny how easily people adopts the 60deg listening triangle as if it would be cast in stone!
In all those years I have never seen this discussed anywhere!
Shame on you - DIY bunkerheadz!
welcome to reality
(bites hard hard hard)
It's definitely a problem, but there's still a lot of validity to having linear performing individual speakers. They do sound better, and the frequency response combing caused by the phantom center is fairly well masked by room reflections in most situations, as the reflections will help to fill in the gaps, and create a bunch of new ones. But still, that direct sound between the speakers causes a problem because it's very early, faster and louder than any individual room reflections. It's fast enough to pretty much count as the direct sound from the speakers. So I find it worth it to try to do something about it. As I've mentioned before, listening with a barrier between the speakers was the first revelation to me of how much sonic degradation is caused by crosstalk.
Thanks for that > very interesting reading
There is one thing for sure, and that is the 'Recording Studio Control Room' is always symmetrical and usually "Live end - Dead end".
Also, the now standard 'near-field monitoring' is very different to the average home listening room.
The other thing for sure is that we ARE at the behest of how recording engineers choose to mix things. This means that some material
will sound better given a particular set-up than some other material. This also means the use of some 'spacial presets' can sometimes help.
I am also a believer that some degree of ACTIVE CENTER can really bring stereo music to life. Good quality speaker placement is the challenge.