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Old 14th January 2009, 02:02 AM   #1
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Default O/B Centre Channel

I'm not normally inclined to want a centre channel on my HT set-up. Too difficult to line up the centre on the same axis as the left and right fronts - without having them all either above or below the television screen. And the front pair do a pretty good job by themselves!

Then someone mentioned trying the same speaker on both sides of the TV - that would centre the image somewhat and allow the front speakers to be at the correct height.

Then I thought - new LCD TV, that's almost like a baffle for an OB speaker, why not design an OB speaker using the TV as a part of the baffle?

Am I completely mad after drinking too little over Xmas/New Year? Or is it because the temperature was 39 degrees yesterday (102 degrees, for those in the USA)? Or is it a possibility?

I was thinking, maybe 5 (or 6) 3" F/R's on either side, with some 'wing' baffles. Could it reach the relevant 80Hz required for a small centre channel? What sort of (cheap) drivers could do this? Or maybe I should look at some 8" drivers (maybe 3 per side) to do the same thing? There's some drivers available locally with a Qts of ~2.3, maybe they would work...
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Old 14th January 2009, 03:25 AM   #2
Key is offline Key  United States
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I've done this as a quick fix to listen to 5.1 on my 4.1 system. I just stacked another stereo set right on top of my Lf and Rf speakers.

It works but I find I actually prefer to just redirect the center channel to L and R and use the that phantom center instead.

I'm with you on not liking center channels. The phantom center channel works PERFECT for dialog - the sounds bounce of the front of the screen and look like they are coming out of the peoples mouths. Now why would I want to take a inferior speaker and stick it under or above the screen and point it down or up.

And in the manual for my speakers it recommends using a matched center speaker if you are going to use one. Well these are vertical standing speakers.

So yeah I sort of see 5.1 music (full range center) as being a completely different from movie 5.1 (limited range center) and they are not compatible because of the screen.
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Old 14th January 2009, 04:14 AM   #3
chops is offline chops  United States
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I'm using Av123 X-Statik mains with a matching X-Voce center channel, and the sound from left to right is perfect and seamless. Then again, the dual mids on all of these speakers are OB. But at any rate, the center channel imaging appears to come right from the screen and is crystal clear.

Click the image to open in full size.


However, I have to say, I have tried quite a few different times using only the mains (of all the speakers I've had over the years) with a phantom center and it never sounded correct. The dialog was never locked in the center the way it should be, and got much worse when you move away from the center seating position. It always had a soft, fuzzy sound to it and was never crisp and clean-cut sounding the way it should be.

HT is meant for a family and/or a group of friends to sit and enjoy a movie. It's not very enjoyable when the phantom center channel image is disconnected and confused sounding and coming mostly out of the speaker closest to you.

IMHO, there's no replacement for a "real" dedicated center channel speaker. Just my 2 pennies...
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Old 14th January 2009, 10:22 AM   #4
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Quote:
Originally posted by chops
HT is meant for a family and/or a group of friends to sit and enjoy a movie. It's not very enjoyable when the phantom center channel image is disconnected and confused sounding and coming mostly out of the speaker closest to you.

IMHO, there's no replacement for a "real" dedicated center channel speaker. Just my 2 pennies...
IMHO's are what I'm looking for (not other types of HO's ).

Chops, I get where you're coming from, but with my current set-up (42" HD LCD TV) the phantom centre channel is pretty much perfect. The voices seem to come from the exact right position on the screen. And when you're over to the side, the image is compressed just the right amount for the screen. But, I have to admit that the 4 surround channels aren't very good, so the whole thing is held together by the excellence of the front 'sound image'. Once I've done the surrounds properly I think I will have to look at some sort of centre. So at the moment it's just ideas.

I also thought of doing the "dual line array O/B" on top/bottom rather than left/right. This would centre it more than the l/r approach (although a suitabl toe-in would alleviate that somewhat.
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Old 14th January 2009, 01:49 PM   #5
el`Ol is offline el`Ol  Germany
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I have just played with edge and it seems you have better chances to achieve your goal with something like that. Lobing will be a problem in either case, I donīt know whether you can live with it.
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Old 14th January 2009, 10:58 PM   #6
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Quote:
Originally posted by el`Ol
I have just played with edge and it seems you have better chances to achieve your goal with something like that. Lobing will be a problem in either case, I donīt know whether you can live with it.
el`Ol,

I'm not exactly sure what you are driving at - which do you think is better?[list=A][*]drivers on the left and right of the screen[*]drivers on the top and bottom of the screen[*]drivers on the top, left and right of the screen[*]drivers on the top, bottom, left and right of the screen[/list=A]

I'm doing this as an excercise at the moment until I become uphappy with my set-up. But it's always interesting to see what options are out there.
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Old 15th January 2009, 11:09 AM   #7
el`Ol is offline el`Ol  Germany
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I mean one left, one right and two on top. There can also be two at the bottom or both two at bottom and top, I just thought you donīt have the space for free ratiation at the bottom
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Old 15th January 2009, 03:25 PM   #8
GM is online now GM  United States
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Quote:
Originally posted by Cloth Ears

.........which do you think is better?[list=A][*]drivers on the left and right of the screen[*]drivers on the top and bottom of the screen[*]drivers on the top, left and right of the screen[*]drivers on the top, bottom, left and right of the screen[/list=A]

Taking a 'page' from Bell Labs/W.E.'s original cinema sound design 'play book': B if there's a wide/flat enough power response or D if not. For an ultra wide/flat power response, make the CC a close coupled stereo pair where the left channel points to the far right listening position and vice versa. I've experimented with these and suggested them on several occasions over the years and the few who've tried them were pleased with the improved dialog and action pans, so a top/bottom adjustable volume summed mono center variant can also help folks that have a problem 'picking' the dialog out of basic mono/stereo TV.

Note that ideally the mids/lower HF should be positioned (or focused) at 2/3 screen height to lock the dialog to the general location of the actor's heads, same as for cinema sound, so vertical power response is just as important as horizontal for best performance.

GM
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