Is a centre channel really necessary?

[Martyn]

Given that good two channel audio already provides excellent spatial imaging, what does a centre channel add? I would imagine that the compromises associated with the positioning of a centre speaker could outweigh the benefits.

[junior77blue]

A center channel is needed if more then one person is watching the film. i.e. the sweet spot can only be obtained by one individual. If people are sitting off axis, then a dedicated center channel will anchor the sound in the center.

But, give it a try...see for yourself.

[aud19]

Something like 75% of the average movie is mixed for the center channel. Besides the reason above, I'd say that's also a pretty good reason to have one

[kgveteran]

If you begin to think in terms of movie sound, it is a must.The dialog is centered as J77B stated.Nothing against plain vanilla stereo, but a properly setup 5.1 or 7.1 system will allow you to enjoy what the director intended you to hear.These are all discrete channels, unlike the days of dolby surround.So, if you were to watch a movie by yourself directly in front of your TV and your speakers were on either side, you would kinda get a center image.Now move off to the right or left and the image is in the right or left speaker instead of being centered on the TV like a center channel would do.

Don't throw away the stereo setup, but start to look into a surround system, you will really enjoy movies alot more.

KG

[Kal Rubinson]

Given that good two channel audio already provides excellent spatial imaging, what does a centre channel add? I would imagine that the compromises associated with the positioning of a centre speaker could outweigh the benefits.

Better and more accurate imaging and soundstage. Do you know that the original multichannel experiments of Blumlien and others (back in the 1920s, iirc) indicated that a minimum of 3 channels was required for accurate imaging? However, there was no medium to deliver it until recently.

So, for movies AND for multichannel music, a center channel is more than desireable.

Kal

[Martyn]

Thanks, all.

I started this thread because it seems to me that a centre channel will be vying with my 50" plasma TV for the same piece of real estate. To place the centre channel above the TV would be aesthetically unacceptable to me, while placing it either above or below would place the tweeter vertically off-axis unless the speaker were tilted.

My thoughts then drifted towards the possibility of two centre channels, one each side of the TV with the tweeters at ear level, but this seemed to place them so near to the mains as to make them more or less redundant.

Any thoughts on this, or should I wait until someone has invented a TV whose screen is an audio transducer?

[Kal Rubinson]

Any thoughts on this, or should I wait until someone has invented a TV whose screen is an audio transducer?

NXT have done this already with their projection screen design. In addition, there are acoustically-transparent projection screens for video.

More to the point, I, too, have a 50" plasma on the wall and use 3 floor-standing speakers in the front. They are just short enough to fit beneath the screen and I have now problems with any anomalies in imaging. OTOH, the audio is more important to me than the video.

Kal

[aud19]

Kal has the best solution if you can make it work with your room. If not the next best would be the horizontal centre above/below the screen and tilted appropriately towards the listener.

[Russ L]

I just purchased a good quality B&W speaker stand for my center. This can address imaging problems and improve bass.-Russ

[stantheman2]

Why a center channel? As I recall reading, the first demos of non-monophonic sound (RCA in the early 40s, maybe?) used three channels, based on their research that indicated three channels (at a mimimum) were needed to produce a realistic soundfield - two were not enough. Stereo was a compromise of that three-channel "ideal" based on technology limitations (at that time) and cost considerations.

[Karma]

HI Stan,
Actually, it was Bell Labs.

Sparky

[Russ L]

It makes sense that 3 speakers would be necessary for realistic "stereo" soundstaging since the ear is very good at locating where sounds are actually comimg from. Kal Rubinson has written some good articles on three channels.-Russ

[Martyn]

OK, you have me convinced!

My next question might be more suited to the Mission Possible section, but I'll throw it at you guys because you've all given me some calm, rational responses so far.

My present HT system comprises my plasma TV, DVD player, and two channel audio system. This is going to change. I will be moving the TV and DVDp to another room and adding an AVR and 5.1 speakers. I will build the speaker cabinets myself and use a kit design.

Unfortunately, the new room, which is about 15' x 22' x 8', has some deficiencies from an HT perspective. The TV will be off-centre on a long wall with its centre about 6' from one end wall. The viewing/listening position will be against the wall opposite the TV. If we assume that the main drivers are a couple of feet away from the TV wall, the listener will be about 12' max. in front of them, and one of them will be quite near a side wall. The surrounds will probably have to be mounted on the wall behind the listener, with one close to the corner.

Furthermore, because my wife and I favour furniture over racks of technology, I will custom-build a cabinet (a sort of audio sideboard) that will support the TV and house at least the centre speaker. It will probably also house the sub, although the sub's box will be de-coupled from this cabinet. I might build a separate piece to house the DVDp and AVR.

Along with all these compromises, I will inevitably use this sytem as a second two-channel audio system and will be disappointed if its two channel audio performance is significantly inferior to my main audio system. I anticipate buying either a Rotel 1057 AVR or perhaps the forthcoming replacement for the Arcam 300 AVR (although I don't really want to spend that much).

So now I'm getting near to my question. For the speakers I'm favouring Dennis Murphy's MBOW1 3-way design for the mains - the version with the GR Research tweeter. This means that I could also use his 2-way box for the centre speaker with (I think) the GR Research AV1RS upward-firing wall-mounting surround speakers which use exactly the same drivers. I haven't done the sums yet, but I'd guess that $1,500 would cover the parts for all five speakers, excluding cabinets and the sub.

I think this should get me a reasonable HT system that can also do a good two-channel job, although I am concerned about the various compromises I've alluded to above. So my question is a basic: "whadayathink?" Is this a sound approach given the realities I must live with (including my budget)?

[rav934]

I think the center channel is a major source for frustration. I prefer floor standers properly positioned. My JMLabs 1027 Be provide amazing dialog with proper positioning for movies. My wife and I sit in the center (sweet spot) and my kids sit in front of us on their fave bean bag chairs...all happy listeners.

[David G]

I agree with the previous poster. With good speakers, a phantom centre image works just fine. All of a sudden people are saying we can't do without a centre channel, yet we've all been happily listening to 2 channel stereo for ages!
The compromises in terms of vertical offset of a centre channel, I think is just too great. Bring your left & right speakers slightly closer to centre if you need to improve your centre image stability.

[Russ L]

rav934 or David G- Do you use 2 front and 2 rear speakers without the center for movies? If so do you find this satisfactory? I just ordered my center and stand this week8O Russ

[Kal Rubinson]

I agree with the previous poster. With good speakers, a phantom centre image works just fine. All of a sudden people are saying we can't do without a centre channel, yet we've all been happily listening to 2 channel stereo for ages!

Actually, we have been aware of the compromises of 2 channel sound for years. (See Paul Klipsch's papers.) It is only now that we have the technology to implement more channels.

Now, I grant you that 2 channel stereo can be pretty marvelous but that doesn't mean that one cannot do better, both technically and esthetically.

Kal

[David G]

rav934 or David G- Do you use 2 front and 2 rear speakers without the center for movies? If so do you find this satisfactory? I just ordered my center and stand this week8O Russ

Yes, exactly & I've found it entirely satisfactory, but then I'm in a fairly small room and it covers a small seating area. Just listen to a movie in 2 channel and decide for yourself.

[aud19]

IF, you can position your speakers and listening area in your room properly given your room and furniture layout and IF you never plan to have more than 2'ish people watch movies, it's "possible" to not use a center speaker of some sort....

[David G]

Actually, we have been aware of the compromises of 2 channel sound for years. (See Paul Klipsch's papers.) It is only now that we have the technology to implement more channels.

Now, I grant you that 2 channel stereo can be pretty marvelous but that doesn't mean that one cannot do better, both technically and esthetically.

Kal

Actually I don't dispute that Kal, but my concern is the compromises caused by the vertical offset to cater for a large TV screen, and the horizontal off axis irregularities resulting from the common "sideways-MTM" centre-channel designs. I guess I prefer to err on the side of simplicity.

[Kal Rubinson]

Actually I don't dispute that Kal, but my concern is the compromises caused by the vertical offset to cater for a large TV screen, and the horizontal off axis irregularities resulting from the common "sideways-MTM" centre-channel designs. I guess I prefer to err on the side of simplicity.

True. My position is that one should choose the compromise that works best, if one must compromise.

Kal