What is the point of a centre speaker?

Properly set up two channels perfectly recreate center channel.
Yes, but only for seating positions which are equidistant from the two channels. So if you have guests they have to sit exactly above and below you 😀

Oh and even if you're listening alone, you better not move away from the sweet spot!

You don't need a centre channel for headphones because there is no head related transfer function at play, and your ears never move relative to the drivers.

Constant directivity speakers with toe in can handle the loudness issue. There still is the delay though. Just reading about Precedence effect Precedence effect - Wikipedia
which seems to state that few milliseconds path delay won't move the phantom center, and up to maybe 5 milliseconds delay the phantom center moves slightly. So, your message is a bit too generalized 😉 The two millisecond window might cater a three seat sofa or wider in a home theater to perceive solid phantom center. Not the case in a big theater though (very large screen). But still, shouldn't drag the center to the nearest speaker until about 50ms difference, that is more than 15 meters path difference. Of course acoustics matter and all, just wanted to check out this one aspect about stereo phantom center.
Carry on 🙂
That is valid, although it is much easier to build a conventional centre speaker than it is to make stereo speakers with the required constant directivity for the average home lounge layout which could have some people listening as much as 30 degrees off axis. Another consideration is that intelligibility goes down when there is a significant path difference between two speakers playing a mono source, because of comb filtering.
 
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Listening 30 degree off axis shouldn't be a problem for constant directivity speaker, per se. Only problem is how the room, speakers and listening position relate. Here are some illustrations AudioRoundTable.com: Pi Speakers >> Imaging, placement and orientation

Intelligibility should be better with center speaker, that is very true, but only if L and R speakers do not output the same signal (comb filtering). Regards comb filtering, I could imagine speakers having some directivity will sound better, since room reflections are somewhat reduced. Room reflections from furniture, walls and floor / ceiling add a lot comb filtering. If constant directivity the room reflections are more uniform to direct sound as well.

ps. Dave Rat has cool videos in Youtube on comb filtering in Live sound situation. He seems to be using a center channel, plus many others. Basically, a speaker system per band member! Someone should start releasing albums as multitracks so we could do this at home as well 😀
 
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None of pro centre-speaker seem contain any logic. As a person you have two microphones and supreme decoding algorithm. If a sound is emitted at equal volumes from both left and right speakers your brain perceives the origin of the sound to be directly in front of you. Any disparity between levels of sounds received from the left and right ears is how we calculate direction. [Simplified] If you were having a 90dB conversation with Anna, Bob, and Charlie who were standing 1 metre in front of you, the brain calculates their position loosely based on the following: Anna: Left ear, 90dB / Right ear, 89dB. Bob: Left ear, 90dB / Right ear, 90dB. Charlie: Left ear, 89dB / Right ear 90dB. A centre source of sound can not benefit this calculation.

The sitting off-centre argument is also moot. Move 2m to your left and your brain will use the new data to inform you that everybody is to your right. Anna is closest, followed by Bob, then Charlie.

You cannot criticise and sound system that remains true as to your location to the source.

Environmental arguments are also moot. The premise is cancelled out by the facts. If you are sitting off-centre in a room with velvet drapes along one wall - you will perceive the sound as if you are sitting off-centre in a room with velvet drapes along one wall . . . oh, wait, that's exactly what you're doing.

Arguments put forward in this debate remind of arguments of old about the gauge of speaker wire. Back in the day some amplifiers contained in-line output fuses. Whatever the brochure said, whatever the raw data said about the benefits wire thicker than jumper cables - it was all moot. Any system is only as good as its weakest link. At some point in time the output signal was required to pass through a single strand of wire - the fuse.
 
It depends on your setup and what compromises you are willing to make. Ideally you would have matched L + C + R speakers behind an acoustically transparent screen (like in the cinemas) but that is almost impossible to do for home use

I prefer using a phantom center to a small, mismatched one that fits in the entertainment unit, because the TV is too large to allow for a decent center speaker
 
As a person you have two microphones and supreme decoding algorithm.
that supreme algorithm has some flaws in the vertical plane but that's a different kettle of fish


If a sound is emitted at equal volumes from both left and right speakers your brain perceives the origin of the sound to be directly in front of you.
an entire host of conditional criteria has to be met to truly have it be a convincing illusion.


Any disparity between levels of sounds received from the left and right ears is how we calculate direction. [Simplified]
since you've acknowledged that that is a simplified version there's no need to introduce phase into the issue...or is there?


If you were having a 90dB conversation with Anna, Bob, and Charlie who were standing 1 metre in front of you, the brain calculates their position loosely based on the following: Anna: Left ear, 90dB / Right ear, 89dB. Bob: Left ear, 90dB / Right ear, 90dB. Charlie: Left ear, 89dB / Right ear 90dB.
if it worked that way there would be no way to discriminate sources and their relative positions at 90 deg to you, something else is happening don't you think?


A centre source of sound can not benefit this calculation.
well the trio are not a television screen or video display and that's where the center channel comes into it's own it's due to our visual systems overriding our auditory systems, early work in television and motion picture sound found that any perception cues that caused a discontinuity between visual and auditory cues with respect to location was considered objectionable


The sitting off-centre argument is also moot. Move 2m to your left and your brain will use the new data to inform you that everybody is to your right.
in the case of no center when you move off axis of the screen you are now closer to one of your stereo speakers so no chance of the sound seeming to come from the screen which is the visual center





You cannot criticise and sound system that remains true as to your location to the source.

Environmental arguments are also moot. The premise is cancelled out by the facts. If you are sitting off-centre in a room with velvet drapes along one wall - you will perceive the sound as if you are sitting off-centre in a room with velvet drapes along one wall . . . oh, wait, that's exactly what you're doing.
and this is where the whole thing becomes a problem it means there's only one place in the room where the "center" illusion holds true.
 
The sitting off-centre argument is also moot. Move 2m to your left and your brain will use the new data to inform you that everybody is to your right. Anna is closest, followed by Bob, then Charlie.

If I sit in the seat to my left, all the sound will appear to come from the left speaker, not the centre.
Your argument is nonsensical and bears no relation to reality.
 
...Any disparity between levels of sounds received from the left and right ears is how we calculate direction...

This is fundamentally incorrect. At low frequencies (that is for wavelengths larger than the head), the sound levels at the ears are identical for sounds from all directions. Instead direction is perceived in response to the phase difference between the signals at the ears. At higher frequencies, the situation is more complex (although further explanation would appear somewhat needless at this point in time).

The important fact to understand is that the impression of direction is formed from the sum of all loudspeaker outputs at each ear and the subsequent difference between those signals. Using two loudspeakers only is a compromise for many reasons already mentioned in this thread and (when used appropriately) three loudspeaker stereo offers significant improvements - in particular to material that is panned centrally in stereo channels.
 
I'll give you all a real practical example. Lord of the Rings.



There was literally some dialogue which until I had a center AND equalized it in my room I never heard correctly. I don't remember the exact locations, but neither in the theater nor in my home could I hear it. Put in center, equalized it to match my sides and correct for shelving boom, and voila. Clear as crystal.
 
What would you do with three channels when it comes to headphones?
You place it to your forehead?

I refer to my previous post in that a fundamental misunderstanding is apparent where a left stereo channel is thought to be destined for the left ear and vice versa for the right. Stereo is instead a matrix of two information channels that should be presented to both ears.
 
While I’m definitely not a fan of the Hollywood sound, and overblown special effects using multiple channels, there may be a case for center-located L/R speakers when they are individually aimed outwards a bit. Certain (small) rooms can use this.
 
Hi Phase,


The thing I am most grateful for with the advent of DD was not signal quality, but the death of the Dolby Surround steering mechanism.

It aggravated sound editors and me too. It forced you to use the sound system purely for explosive effects, even when the recordings themselves included immersive and wonderful environments. Now it is up to the recording engineers, not Dolby, how immersive and subtle soundtracks are and I think we are catching up.

Couple of great examples of movies that can combine both are Master and Commander and Hateful eight.
 
Dolby Surround was the commercial name for it. It used analog steering mechanisms to dynamically adjust the levels of each of 4 channels (L, C, R and S) in an attempt to get more channel separation from the actual 2 tracks on the film or VHS. It also made it impossible to do "subtle" in the mastering booth.



The first consumer version to incorporate this steering was called Dolby ProLogic. It replicated the theater effect.



Best,


E
 
Thanks Eric. I remember looking at the schematics of a few Dolby decoders in the cinemas I worked in. I vaguely remember the analog steering circuits. That was slightly before the consumer version hit the market.
 
Best setup I ever heard was a prologic one almost 30 years ago.

But prologic rolled off the rears highs, surrounds were bipolar 6' off floor beside you, and surround channel back then was fill (atmosphere). Under water sounded like under water.

But people wanted 20-20khz, and most love a sound moving between the rears.

It was accomplished, at the cost of losing "put you in the scene".


Sorry, back to center.

If my center was a flat load, I'd wanted to try a mono center (can be done passively). The negative speaker wires together, run through center with an l-pad around it (otherwise it will be 6db too loud).

How To - Car Stereo - How To Install A Center Channel

But i never did.

See post 174 for my buddy's comments on it (years ago).

Master Nagaoka Tetsuo explorations on matrixed single stereo speakers

Look at the front wiring in the picture below for an instant understanding.
 

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