I remember reading some time ago that if you put the main L and R speakers too far from the screen (no matter the size) it can lead to a bit of cognitive dissonance that can mar the immersive experience of surround sound. Later I had a chance to listen to a friend's setup where he had a good sized screen but his main L and R speakers were towards the corners of the room. It did sound odd and kind of distracting to hear a sound that was obviously from something on the screen but to hear it from the far corner of the room.

So, I'd say it's more a case of how far the speakers are from the edge of the screen more than how big the mains are. I've heard some pretty large speakers closer to the screen and it wasn't a problem. Of course, between arranging the speakers for audio or TV I'd always default to audio and live with whatever compromise occurs for TV, but your priorities may be different.

Jeff wrote:

I remember reading some time ago that if you put the main L and R speakers too far from the screen (no matter the size) it can lead to a bit of cognitive dissonance that can mar the immersive experience of surround sound. Later I had a chance to listen to a friend's setup where he had a good sized screen but his main L and R speakers were towards the corners of the room. It did sound odd and kind of distracting to hear a sound that was obviously from something on the screen but to hear it from the far corner of the room.

Once in a while Jeff and I agree on a subject - this is the case here!

But people are sometimes strange - I have met not a few people, who had their front speakers located behind (or mostly behind) thier seating position....

.....and I could not convince them to make a change.

Some times because the speakers ‘look better’ there, some times because they liked them better there for music........the wierd effect, when they watched tv., dud not seem to disturb.

MM

I think we agree more often than you think MM. 😕 Not sure if that's a sign of the impending Apocalypse or not though.

L and R mains behind the listening position? Takes all kinds I guess. But as many "bad" setups as I've seen over the decades, I've not seen that!

If anyone is operating a BV (but guess it could be any other tv) with the BL90, 50 or 5, I would recommend muting the centre channels and internal L/R channels; this is because to me the TV sound is terrible compared to the phantom image of this type of loudspeaker. I find even the Eclipse sound bar to be very rough and distracting.

Mr 10Percent wrote:

If anyone is operating a BV (but guess it could be any other tv) with the BL90, 50 or 5, I would recommend muting the centre channels and internal L/R channels; this is because to me the TV sound is terrible compared to the phantom image of this type of loudspeaker. I find even the Eclipse sound bar to be very rough and distracting.

It's important for the center and mains to be voiced similarly, have as similar a tonal balance as possible. The center also needs to be capable of enough volume and dynamics as up to 80 percent of the front sounds come from it. I've noticed a lot of people who used "small" and less expensive for a center with poor results. When I was using my BL8000s and the AV7000 I used an NHT VT1C center which I found matched if not perfectly, well enough. Listening to pink noise and panning it across the fronts is a good way to check if a center matches the mains.

Phantom center can work well as long as you sit fairly close to the center, off axis it gets problematic. I wonder though, with speakers capable of wide dispersion, offering a wider listening area, like the ones you mention, especially the 50s/90s in wide mode, if the a phantom center is acceptable over a wider area as well.

Hi,

Maybe a little (slightly inaccurate, and annotated) historical background will help here.

Properly-configured 2-channel stereo, where you have a symmetrical positioning of the two loudspeakers with respect to the listening position was invented by Blumlein in 1933 for film sound. The idea was that, using only two channels, you could position the perceived location of a sound source anywhere on a line between the two loudspeakers.

It's pretty easy to find out, however, that this effect (the perception of a phantom image somewhere between the loudspeakers) is extremely dependent on the time of arrival of the two signals. If the audio signal from one of the two loudspeakers arrives earlier than the other, then you will hear the phantom image location as being closer to the loudspeaker with the earlier signal. This effect is extremely sensitive. For example, in a "perfect" stereo configuration (with the stereo loudspeakers at ±30º wrt front centre, and equidistant to the listening position) in a room with low-level sidewall reflections, delaying one of the loudspeakers by 220 µsec will shift a phantom centre image by 10º towards the other loudspeaker. (note 1: 220 µsec is equivalent to the delay incurred by placing one of your loudspeakers 7.6 cm further away) (note 2: a 10º shift in that system is 33% of the distance between centre and the loudspeaker. That's a lot...)

So, although a phantom centre works very well, it only works very well if the difference in the times of arrival of the two stereo channels (the Inter-Channel Delay Time) is 0. This either means that you're sitting in the middle of a symmetrical configuration, or that the signals have been correctly time-aligned for your listening position.

In cases where you are not sitting in the correct location, the phantom centre image will appear to be closer to, or completely in, the nearer loudspeaker. This is true for almost everyone in a movie theatre. Consequently, a movie theatre with only 2-channel stereo will only work for the centre "column" of seats, up the middle. Everyone else will hear the dialogue coming from the closer side of the screen.

So, a centre speaker was put in, so that dialogue could be heard coming from the face on the screen... This was original done (in Dolby Stereo - remember that "stereo" means "not mono" - therefore it is not confined to 2 channels) using a "matrix" which is basically like an upmixer. You take what is common between the left and right, and send that to the centre. (In the encoding process, you put whatever you want to be in the centre into both left and right - that makes it common...) Since it was easy to do, you can take another signal and (while you're encoding) send it to the left channel and an opposite polarity (commonly, but incorrectly called "out of phase") copy to the right channel. Then, in the decode process, you subtract the right signal from the left signal and you get back that original signal (the "surround" channel).

Now you have a system that has a centre channel (the dialogue), and everyone in the theatre hears the voices from the centre of the screen - where their faces are. YAY!

The moral of the story (so far) is that you need a centre channel if you're not sitting in the right place (or if your 2-channel stereo is not time-aligned to the listening position).

Fast-forward to the International Telecommunications Union recommendation number ITU-BS.775 and you will find a standardisation of the "correct" way to set up a multichannel audio system. In order to help ensure that a signal can be positioned between any two loudspeakers, it is highly recommended that all loudspeakers in the system be identical. It also recommends that, in order to ensure that you can have differences in the low frequency content in different channels, that all loudspeakers be full-range and that no subwoofers be used. However, since it is impractical for normal people to put 5 large loudspeakers in a perfect configuration, it is common to install a subwoofer. This is fine if the signal (the movie mix) is designed for such a system - the re-recording engineer (the movie equivalent of a "mixing engineer" in a music recording studio) puts the low frequency EFFECTS on its own channel (the ".1" in a 5.1 system) but it might not work if there are differences in the low frequency content of the "main" channels and they are mixed into the subwoofer (which is why multichannel music recordings recommend that you do not use a bass management or a subwoofer).

However, IF the signal (the audio mix in the movie) does not use panning between adjacent loudspeakers (which is typically true in most movies - the dialogue is in the centre channel, and not panned to left or right from there...) then it is less crucial that the centre and the left / right loudspeakers are matched.

So, if you don't sit in the middle - or you watch a movie with friends - you should use a centre channel. If you have one chair and no friends, you probably don't need it.

If you only listen to multichannel music, you shouldn't use a subwoofer and a bass management system. You should buy 5 full-range loudspeakers - which is not a problem because you don't have a TV that would be behind that centre loudspeaker...

Hope this helps!

cheers
-geoff