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  Topic Review (Newest First)
09-08-07 11:16 AM
harrier
Re: Perforated Screens

I've used a Stewart perforated screen for a project.
All the front speakers were installed behind the screen.
We did not do any comparison with/without the screen in place but it sounded ok, didn't sound muted.
07-18-07 05:07 AM
JonFo
Re: Perforated Screens

Quote:
chriscmore wrote: View Post
Hi guys -

IB subs, or any others with high air displacement need to be at least 12" from most AT screen materials. If you can feel the breeze from the ports or your "outie" IB (great project JonFo - I've been a part of the Cult of the Infinitely Baffled for years), then it can move the material and cause some defocusing effect. Short term it's actually kind of cool, but I find it becomes like a video game and is inconsistent.
...

Chris, thanks. And I agree, keep high air mass moving items away from hanging fabric, or watch it flap in the breeze

One of the cool features of the outie, is that it does not concentrate the air movement in a 24” square manifold mouth, but instead radiates from all four sides, which means at close proximity, you only get the impact of one driver (which is still substantial).

In my case, the screen in is just above the top of the IB cabinet, so even the front-firing driver is not ‘blowing’ through the screen. I’ve not noticed (and I’ve looked for) any screen movement, even when playing deep bass pretty loud.

Cheers,

Jonathan
07-18-07 04:57 AM
JonFo
Re: Perforated Screens

Quote:
Tommy wrote: View Post
JonFo, thanks for answering. It seems you jumped off topic after the first sentence and went back to discussing audio loss though. Primarly I'm more concerned with video loss then audio loss.

Of course I think it would depend on the projector and the screen itself but Ive read references up to an including needing to double the brightness in order to reach the same equivelant picture on some setups.

You mentioned that in your opinion the light loss is around 10% however I would think even 10% is a large loss in light. 10% degradation on my projector would indeed be a large difference

Googling the subject shows a large range of quality loss percentages so I would like to hear an insiders comments on it.
Tommy,

Yes, I do get focused on the sound part, don't I

My subjective assessment on the light loss of a G70 on AT screen vs non-AT (Stewart StudioTek 130 material as well), is that I can't tell a difference. Of course the PJ's are in separate houses, so side by side is hard to do. And as noted above, CRT's aren't exactly light-cannons.

10% is well within the range most digitals can afford to loose and still maintain >12 ft-lamberts off the screen. So unless you are really pushing a digital to its limits on a non-AT material, I'd say it's probably not a big deal.

As Chris notes, if the material is less than unity gain to begin with, then there might be an issue, but I would doubt that.
There is a market for screens that have 8 to 30% gain loss (GrayMatte, GrayHawk etc.), so someone out there wants lossy screens
07-17-07 10:43 AM
chriscmore
Re: Perforated Screens

Quote:
JimP wrote: View Post
Darrel,

Sounds like a good plan.

I had read about not placing IBs anywhere other than the front. Sounds like you've got it covered.
Generally true. A couple caveats, though, is that if you install them exactly center-rear, people do a poor job of hearing front versus rear. That's why 7.1 is generally preferred over 6.1. Having a mono rear channel is (at least in theory - it's not an epidemic, however) frowned upon, because in a lab condition you can mistake the rear for the front center.

So, sure the front is a goal, but if you go for the exact 180 degree that can work too. That's what I do with my IB. Another parameter is the crossover point. The lower your IB is set, the less localizable your IB will be if it's not front/center. Mine is crossed over at 30 Hz in the back, and images perfectly with the rest of the soundstage.

Cheers,
Chris
Seymour AV
07-17-07 10:30 AM
chriscmore
Re: Perforated Screens

Hi guys -

IB subs, or any others with high air displacement need to be at least 12" from most AT screen materials. If you can feel the breeze from the ports or your "outie" IB (great project JonFo - I've been a part of the Cult of the Infinitely Baffled for years), then it can move the material and cause some defocusing effect. Short term it's actually kind of cool, but I find it becomes like a video game and is inconsistent.

A light loss of around 10% is common. They aren't hard to light if they are positive gain, like the StudioTek 130, or some other screen fabrics. But if you are watching 1.3 and punch out 10.2% of it, you end up with a 1.16 gain, which would be comparatively dimmer for you. It can still be a bright image depending on what pj you're using or where you're coming from (e.g. the 0.85 gain fabrics).

Light blow-through can be an effect with any of the AT materials if something is reflective enough behind your screen. Stewart's and some others are more opaque than the below-unity gain woven fabrics. There are many simple solutions if this is an issue. Order a sample and see how well it behaves in your room.

Cheers,
Chris
Seymour AV
07-17-07 07:42 AM
Tommy
Re: Perforated Screens

JonFo, thanks for answering. It seems you jumped off topic after the first sentence and went back to discussing audio loss though. Primarly I'm more concerned with video loss then audio loss.

Of course I think it would depend on the projector and the screen itself but Ive read references up to an including needing to double the brightness in order to reach the same equivelant picture on some setups.

You mentioned that in your opinion the light loss is around 10% however I would think even 10% is a large loss in light. 10% degradation on my projector would indeed be a large difference

Googling the subject shows a large range of quality loss percentages so I would like to hear an insiders comments on it.
07-17-07 07:01 AM
JonFo
Re: Perforated Screens

I'd say it's more like only 10% light loss.

Even with my CRT, it's plenty bright on the AT screen. But then I'm not trying to push my PJ to hard, as it's only a 100" 4:3 screen.

With a digital, I'd hardly worry about it.

Now, you do need to be concerned with light spill *through* the screen. My ESL's are reflective (as you can see in the pic), so I had to use a blackout cloth between the speakers and the screen.

So in my case, the center is having to push sound through two pieces of fabric, yet it still sounds great.
I think people get too hung up on the concept of acoustic loss, and ignore the benefits of correct placement for the center relative to the screen & audience.

A little EQ generally takes care of the problem anyway, so no real issue in my book.
07-17-07 06:31 AM
Tommy
Re: Perforated Screens

JonFo can you provide any info as to light loss with these screens and is it accurate that up to 20% more light is needed by any projector to match a picture on a different type of screen? To me, a 20% loss in video light is much more disturbing then a slight loss in audio.
07-16-07 05:52 AM
JonFo
Re: Perforated Screens

Hi there,

Acoustically transparent screens are getting to the point of where they are quite neutral with respect to sound loss. The ScreenPix materials from Screen Research are quite good, as supposedly is the new Stewart AT material, MicroPerf X2
John Kotches reviewed this in WSR last year and found it to be perfectly ‘transparent’ to sound save for a 1db drop in level.
See article here:
http://www.widescreenreview.com/wsr_attractions.php

Here is an article that compared the old Stewart material and the Screen Research and one other.
http://mixguides.com/studiodesign/pr...-screens-0405/

I use a Steward Microperf StudioTek 130 for my PJ and a custom Center channel, which is screwed to the top of my quad 15” IB.

The sound quality is impressive, and matches tonally the L/R (but I did have to EQ a bit).

06-07-06 10:22 PM
Darrel Hawthorne
Re: Perforated Screens

Hey Jim,

Quote:
I had read about not placing IBs anywhere other than the front

Like many things in this hobby we do what we can with what we have...LOL

Ideally, you would want your low bass information to come from the location of the visual connection to the sound source. ( screen)
The saving grace for folks that this location is not feasible is that fact that this very low bass information is very hard to localize. We can place IB sub systems anywhere within the room with varying degrees of success. The secret to success with this is to cross over to your subs as low as possible. My main speaker run out flat to mid 20's, so I basically use the IB for frequencies from about 25hz down to single digits...Not much of a chance of telling where this data is emanating from... LOL.
It workes out well to place ours in front but I wouldn't hesitate to run an IB even if I had to place them way off to one side for example... They are pretty forgiving....or I am, can't tell which some times...
Darrel
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