BEC

Seems like everytime someone asks about using identical speakers for left/center/right, there's always a group of people who claim a (timbre matched)horizontal center speaker is better because it has wider horizontal dispersion.

Why do people believe this myth? Where did they get it come from?

It seems really the opposite case. Placing the drivers horizontally introduces a narrowing effect in the horizontal plane, so you tend to get LESS dispersion. Both midrange cones interfere w/the tweeter near 2kHz leading to nulls on either side of the tweeter. You can get a very uneven response horizontally for different frequencies.

A designer actually tries his darnedest to work against this effect. He'd RATHER have a horizontal pattern like that from vertically arranged drivers.

Is the only advantage of a horizontal speaker the need to reduce the height of the speaker so it fits on top/below a TV?






[This message has been edited by BEC (edited October 18, 2000).]

Lush

Anyone with grade 12 physics knows that sound disperses widers through a narrower opening. Therefore, like you said, diffraction is greater when a center channel is placed vertically.

The real advantage of horizontal placement is so you can get the tweeter as close as possible to the center of the screen because dialogue should come from the actors' mouths. Those with front proj + acoustically transparent screen don't have to deal with this. I used to place my Paradigm LCR-450 vetically, and it did provide clearer performance when I sat at the ends of the sofa. But, it was kinda ugly, and I always get the best seat in the house

BTW, good topic. I like Q/A's that teaches me more. I am so goddamn sick of seeing "favorite actor in x role, "Top 10 favorite scenes", "best movie to watch when you're high", favorite-this, favorite-that...

David600

excellent topic!
Never happy with my center speaker (JMLab Centris, horizontal), I skip it and listen in 4.1 Phantom. With now JLB pro speakers with horns and horizontal beam of 90° and vertical of 40°, I am in heaven ( as long as I sit on a width of 1.5meter, 7meters from the 3meters screen. Ideal is three vertical speakers ( preferably with horns) behind the accoustically transparent screen of course. Anything else are so-so compromises. The second best solution to me is the phantom mode. No more boxy sound, no more uneven sound, no more sound at different height.
IMHO

Andy Kim

Hmmmm....interesting.
I too was not always happy with how the center channel info sounded.
I tried turning my center channel vertically (its a dedicated center but only has one woofer and tweeter like my fronts).

Now, whether the differences I heard were psychological in nature I don't know. But I did find that sound was clearer and not so muddled and I also heard better channel separation. I could hear sounds coming from the right or left channels more clearly.
Again, it could be attributed to the psychological effect of changing speaker setup.

To BEC and Lush, I know you talked about how vertical speakers get more horizontal dispersion. I'm assuming this means the sound is more widely spread horizontally to the listening position instead of being carried "only" to where the speaker is directly pointed. I was wondering what kinds of audible difference should be exhibited when the speaker is vertical instead of horizontal?
Thanks
Andy

PS. I definitely prefer more tech questions too.

SEH

This is interesting since I am using three identical front bookshelf speakers and my center is tweeter over woofer like a regular bookshelf.

The only problem I have noted is that because the speaker is tall, it doesn't sit on top of the tv well (mostly because of stability). As a result, I have been forced to put the speaker on a shelf below the tv, which places the tweeter about 8" below the bottom of the screen. Sometimes I notice that the voices seem not to come from their mouths. Anyone have thoughts on how to cure this?

BEC

Lush:

quote:<HR>Anyone with grade 12 physics knows that...<HR>

LOL. Ahhhh high school physics, perhaps the last time physics was useful. On top of diffraction, throw in the picket-fence-like multi-slit interefence pattern, and you start to get an idea how ugly horizontal sound profile could be.

Lush:

quote:<HR>I always get the best seat in the house<HR>

David600

quote:<HR>I skip it and listen in 4.1 Phantom. <HR>

Right. If you've got the center seat, there's no real problem (unless the center speaker is a POS even on axis). You could even listen w/o a center for more seemless audio. Quite a few people prefer that, although not the THX/Dolby crowd.

It's really the poor slobs away from center who are effected. In a way, having a horizontal center speaker is at odds w/the one of the main reasons for having a center speaker: so that people who sit off center can have a clear,even dialog anchor. Sometimes, you may even want to sit off center to avoid a bad acoustic room mode.

BEC

Andy:

quote:<HR>I was wondering what kinds of audible difference should be exhibited when the speaker is vertical instead of horizontal?<HR>

Depends on what the designer was after, usually an even frequency response w/o sudden dropoffs/nulls as you move off axis. Less modulated, clearer dialog. Larger dispersion can lead to smoother LCR panning. This is less important if you sit dead center. However, even as a solo viewer, there maybe reasons you want to sit slightly off center: room acoustics. The room location w/the smoothest response is usually off room center, i.e, 2/3, 1/5, 3/5 the room dimensions LxWxH. The last issue of SGHT had a write up about that.

To a lesser extent, if the speaker was INTENTIONALLY designed to limit dispersion, a benefit is limited reflection from side walls (horizontal drivers) or the ceiling/floor (vertical). Most people who worry about reflections can treat side walls (curtains, baffles). It's tough to reduce the reflections from the ceiling.

SEH:

quote:<HR>Sometimes I notice that the voices seem not to come from their mouths. Anyone have thoughts on how to cure this?<HR>

Buy a FPTV or RPTV?

Angle the bookshelf up. Sit at a fixed distance.

Build a special stand/shelf for the speaker that pushes the tweeter closer to the screen.

Compromise w/the devil: place the speaker sideways on top of your TV. The usual horizontal center goes midrange-tweeter-midrange and has two null on either side of the tweeter. A sidweways two way bookshelf will have one null (usually on the tweeter side).

Sell your soul to the devil: buy a horizontal center speaker. Not all horizontal center speakers are evil, but probably most (guess Liz Hurley put me on this Satan kick). It takes alot more effort (and money) than a bookshelf for a good one.






[This message has been edited by BEC (edited October 20, 2000).]

Shazam

This is exactly why some manufacturers place the tweeter either above or below the horizontal midpoint on the center speaker. This is supposed to lessen the amount of cancellation.

BEC

The tweeter offset places the nulls a little higher above (lower below) the plane of the woofers, but the cancellation is still there. It is a very common tweak for center speakers. Sort of like a tipping two vertical tweeter-midrange speakers +60 and -60 degrees from vertical, where they share the same tweeter.

A vertical arrangement places a null usually well over your head, leaving the horizontal plane unaffected.

[This message has been edited by BEC (edited October 23, 2000).]

Andy Kim

I'm convinced now that standing my center vertically sounds better.
I tested it out with Shanghai Noon. I watched it once with a horizontal center and I had to fiddle with the volume throughout.
I watched it again later with a vertical center and I noticed dialogue was clearer and I didn't need to do much thumbing on the remote.

Since I got my center I wasn't 100% satisfied with it. The only way to really get clear dialogue was to jack up the volume. And the center seems to kind of "cancel" the sound from the other channels.
But now that I have it vertically, I can hear the dialogue clearer at lower volumes.
And I can hear dedicated sounds coming from the right and left speakers more clearly.

To all out there, you should try it and see what results you get.


[This message has been edited by Andy Kim (edited October 24, 2000).]

Utopian

So let me get this straight...if your tweeter is above the horizontal plane of the woofer, like the JBL S-Center, then it is sufficient to leave the center in a horizontal orientation. But if your speaker was not designed this way and all drivers are laid out on the same plane when horizontally placed, then it is beneficial to have them vertical, yes?

BEC

A tweeter offset doesn't guarantee good performance. You could try orienting a JBL center vertically as an experiment. There will be trade offs.

In terms of dispersion and inteligibility, a center speaker identical to the fronts will probably work best. You can try running centerless as well.