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#288692 - 01/25/10 11:15 PM Speaker-Screen Positioning
donlboy Offline
buff

Registered: 11/08/09
Posts: 41
I'm looking at using an AT screen with speakers behind and can't make sense of the geometry based on the guidelines I see. The SMPTE guidelines are for a viewing distance of 1.86 times screen width, which gives a viewing angle of about 30 degrees, and the THX guidelines are for a 26-36 degree viewing angle, so they are pretty similar. But recommended speaker listening angles are around 45-60 degrees for home theater (maybe less for 2-channel). In practical terms, for a 120" diagonal screen the viewing distance would be around 16 feet, and the listening distance would be around 8 feet (to keep the speakers within the 105" width of the screen). I understand some compromise from the ideal is OK, but this seems too far off to compromise. For a normal screen the L and R speakers would be outside the screen edges, so the optimum ratios can be met for both video and audio. What am I missing about using an AT screen?
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#288703 - 01/26/10 12:41 AM Re: Speaker-Screen Positioning [Re: donlboy]
PhillipD Offline
veteran

Registered: 01/19/10
Posts: 142
Loc: Grande Prairie, Alberta
I would try moving the L/R just inside the screen as long as there is no border interferance and have the center channel in the direct center. I think the most important thing is to have all the L/C/R channel tweeters at prime seating lear level. For me I have two rows so I went with row one as the prime row, if you have three rows I would slpit the differeance and have them set for the second row height.

if you can try this out for a few movies and then if you like for S&G you can move them out side to the higher angles and see if you are missing anything. I will bet you find you are not missing too much but I have been known to lose the odd bet LOL

You can also try these links:
http://www.avsforum.com/avs-vb/showthread.php?t=974274
http://www.avforums.com/forums/projector...ice-needed.html


later
Phil

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#288709 - 01/26/10 02:42 AM Re: Speaker-Screen Positioning [Re: PhillipD]
grunt Offline
connoisseur

Registered: 12/04/06
Posts: 3569
Loc: Nirvana
I’m curious what reason you have for wanting an AT screen. Not that they don’t have there uses but just because it’s AT doesn’t mean your overall setup will be better as it really depends on the situation IMO.

You really should determine what screen width you want by experimenting and not just following someone else’s guidelines. If you don’t already have a projector you can shine on the wall to gauge screen size from then the best way I know is to go to a theater and find the seat that gives you the best viewing angle. Pace off the width of the screen and the distance to it from that row and calculate your own screen width to seating distance ratio.

That said there’s only a few ways to reconcile the angles.

Use as wide a screen as you are comfortable with and put the L/R mains as far out as you can and live with it. By my calculation your seating would only be 13’ away from a 105’ wide screen at a 36 degree angle. You may also find you actually prefer to sit closer.

Put only the center speaker behind the AT screen allowing the L/R mains to be positioned farther out. This may also allow some more flexibility in placing the mains to give you the best overall soundstage rather than your screen dictating how your soundstage is set up.

The best way I could figure out was to ditch the idea I had to use an AT screen and go with a standard screen with my speakers under it. Doing this I avoided the risk of morie’ and any possible sonic hit to the high frequencies caused by the AT screen. It also gives me complete placement flexibility for my front 3 speakers so I can have the best possible soundstage.
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#288713 - 01/26/10 04:00 AM Re: Speaker-Screen Positioning [Re: donlboy]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10634
Don, yes you're right that the suggested viewing and listening distances are quite a bit different. For your 120" screen example a 12' distance could be used as a compromise that should work acceptably for both visual and audible factors.

As Dean questioned, however, why is the AT screen concept so attractive? Mains positioned outside a regular screen and an identical or at least similar(e.g., M22 with M80s)vertical center below it would work well. Or, if the AT screen is used, consider placing only the center actually behind it, with the mains wider and outside.
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#288724 - 01/26/10 07:56 AM Re: Speaker-Screen Positioning [Re: JohnK]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13579
Loc: Iowa
I agree as well, not sure why people are so interested in AT screens. I want to "see" my investment, why hide what you paid for? Also, getting the speakers setup for best soundstage requires trial and error, you will be limited if you hide them behind a screen.
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#288728 - 01/26/10 08:59 AM Re: Speaker-Screen Positioning [Re: SirQuack]
donlboy Offline
buff

Registered: 11/08/09
Posts: 41
I have been looking at an AT screen mainly to get the speakers in optimal relation to the screen. Also, this will be a mostly HT/music room, but will also double as a family/rec room with grandsons, so have been thinking about speaker vulnerability. I don't have room for a 120" screen (16:9) with L & R speakers flanking it, so may have to drop down to smaller screen with speakers to the side. That would simplify some wall construction issues I would have with the AT setup.
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Don

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#288733 - 01/26/10 11:08 AM Re: Speaker-Screen Positioning [Re: donlboy]
alan Offline

connoisseur

Registered: 01/29/02
Posts: 3267
Loc: Toronto/New York/parry Sound
Hi Donlboy,

I would echo the comments already made here. Most AT screens cause various reflections and audio anomalies as well as visual degradation. If you still want to go with an AT screen, here's a link to some interesting tests done by Mix magazine. Only one of those tested was reasonably transparent in terms of audible degradation of frequency response:

http://mixguides.com/studiodesign/product_features/new-perforated-screens-0405/

The dispersion of good speakers like Axiom really make the notion of optimal speaker placement in relation to the screen a non-issue.

Regards,
Alan
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#288752 - 01/26/10 02:21 PM Re: Speaker-Screen Positioning [Re: alan]
Potatohead Offline
aficionado

Registered: 05/14/09
Posts: 670
Loc: Vancouver
I had the same "problem" about 5 or 6 months ago. Do you use a larger A/T screen and put the speakers behind it, or do you use a normal, smaller screen and place the speakers beside/below it? i was limited to 12' width and had to choose one or the other. I chose the latter personally, I went with a 110" diagonal when I was hoping for more like 120". I sit about 15' back from it. I just have a hard time believing the screen doesn't affect sound quality, and we do know the screen affects picture brightness. I just was not willing to sacrifice both audio and video quality to gain less than 10% in screen size.

Of course your opinion may differ and I know many people are happy with A/T screens. I do recall reading a test someone posted here once though where they tested three screens, and the only one that was decent was about three times the price of the others.

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#288769 - 01/26/10 03:23 PM Re: Speaker-Screen Positioning [Re: Potatohead]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13579
Loc: Iowa
My room is also a HT/Rec Room that is 8,000 cu ft. The kids stay away from the speakers if you teach them. \:\) My boys always have movie nights and it works out fine.
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#288787 - 01/26/10 06:34 PM Re: Speaker-Screen Positioning [Re: alan]
donlboy Offline
buff

Registered: 11/08/09
Posts: 41
Alan-

Thanks for your input. I have been considering the AT screen material from Seymour AV - they're in my neck of the woods in Ames Iowa (I'm in Ankeny). They seem to have designed their latest fabric to minimize most of the issues raised in the Mix article you referenced. I would appreciate your comments on the information in this link: Seymour AV Screen Design and Tests. I haven't yet seen the screens in action, but plan to in the near future before I decide which way to go. I can make a 103.3" diagonal DIY screen for about $350, so it is attractive, but of course it has to perform.
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