How acoustically transparent ...

[fauzigarib]

... are acoustically transparent screens? I'm in the process of designing my HT / Living room, which is always a B!T(H to design because of the WAF...

... So ofcourse, I have to get a motorized screen and pull it down a wall which is, otherwise being fully utilized when the room is in Living Room mode.

Therefore, my idea was to put the speakers / screen in such a way that the screen comes down in front of the speakers... Therefore I was wondering, say the High Contrast Audio Vision surface from Dalite, or equivalent other surfaces from other companies... How transparent are they if you put the speakers BEHIND the screen.

Just wondering if I should even consider this as an option.

Regards,

Fauzi

[ThomasW]

Were there truth in advertising the screens wouldn't be called acoustically transparent. They should be called 'more acoustically transparent than our other screens', or less acoustically opaque compared to our other screens.... :B

There's really no such thing as a 'acoustically transparent' screen. They all block higher frequencies to some degree.

Might be a good idea to get a sample of the screen material you're considering. Look through it, then tape a section of it over one of your tweeters. That should answer your question....

[Dean McManis]

And on the other side of the coin, I've now had two perforated screens, and I could never go back to an ordinary screen. :T
But I will admit that they are not for everyone.

My first perforated screen was a Da-Lite Audio Vision screen, and the sound was very good. My screen size is larger 180" diag. and so placement of ALL of my front speakers are behind the screen.

The big advantage is that the sound is coming right out of the image that you are seeing, just like it is at a real movie theater. 8)

The downsides are that the perforation takes about a 10% toll in light reflection (Gain) from the screen. This black matrix does somewhat enhance percieved contrast, but it does mean that you need to either have a brighter projector or limit the screen size on a lower light output projector. It isn't much of an issue if you have full room light control, but if you like to leave room lights on when watching a movie, the image can get more easily washed out if your projector isn't that bright.

Plus on some projectors (especially LCD) the perforation pattern can line up with the pixel gap pattern and create moire patterns that can be visible in very bright scenes and lighter sky shots in movies. The chance of this happening depends on the pixel gap of your projector, and size of the screen.

I made sure that I had the screen manufacturers send me 8' X 10" samples of their perforated screen material and I projected different movies up on the material with a image size similar to my final planned screen size to determine how the perforations reacted. DLP and LCOS have much smaller pixel gaps, and screen sizes larger than 120" are less apt to have moire patterns, so this wasn't an issue for me, but I did see the effect on some screen materials, projectors, at certain screen sizes with certain movie scenes.

And in those same bright scenes you can see the perforations themselves when viewing from closer than one screen height away.

My current screen is a Stewart Grayhawk, still 180", with their microperforations. The sound transmission was even better than the Audio Vision screen, the holes were smaller and pattern was more dispersed.

With the combination of the gray screen and perforations, the overall gain is 0.85. So I do need a dark room to see movies at their best with my projector. But I almost always have watched movies in a pitch black room anyway.

Stewart included a audio compensator for adjusting the sound attenuation of the center channel speaker behind the screen (the way most people have their perforated screens set up), but I have ribbon-hybrid speakers as my center and front channel speakers and they are naturally a bit bright, so the compensation was not needed at all.

Cost is another issue as perforating screens can add a lot to the price, depending on the screen manufacturer.

But as I mentioned, I love the added screen audio directionality, and cleaner look (with the speakers hidden) that a perforated screen provides, and the sound quality is outstanding, so I don't ever see going back.
But not everyone will want a perforated screen, depending on their HT setup, budget, and personal preferences.

[fauzigarib]

Hmmm..

Dean - That's very interesting stuff. What is an audio compensator and how does it improve the sound? I assume that it makes the sound a bit brighter, so that sound going through the screen should be "normal?" Is that right? I'm glad that you've had a good experience... The sound not coming out of the screen has always been my biggest issue of Home Theaters... So this is definitely something to consider.

Thomas - Unfortunately, I live in Pakistan, and as such, getting dealers (they're usually unauthorized) to do that sort of thing is like convincing a hen to give milk. But I'm gonna work on it.

Any price idea from either of you on, say a 119" tab-tensioned motorized perforated screen?

Regards,

Fauzi

[Dean McManis]

Yeah, my guess is that the manufacturer knows exactly what the high frequency attenuation of the perforations is, and the inline box compensates somehow.

But the sound that I get through the screen is so bright, crisp, and clear that I never used the box.

I couldn't even guess at the pricing in Pakistan, but you might reconsider getting the motorized screen. Getting a tensioned pulldown screen often costs half as much, for a small loss in whiz-bang factor of a motorized screen. 8)

I'm not sure if Carada (this website's sponsor) has perforated screens, but it's worth checking out their website for screen info. :T

[Uncle Eric]

Were there truth in advertising the screens wouldn't be called acoustically transparent. They should be called 'more acoustically transparent than our other screens', or less acoustically opaque compared to our other screens.... :B

There's really no such thing as a 'acoustically transparent' screen. They all block higher frequencies to some degree.

Might be a good idea to get a sample of the screen material you're considering. Look through it, then tape a section of it over one of your tweeters. That should answer your question....

I've used several so called acoustically tranparent screens. The best of which I've found to be Stewarts Microperf and Screen Researches Clearpix 2 material.

The weakness with Stewarts microperf is two fold. As resolutions get better (1080p), folks often sit nearer without the adverse effect of screen door etc, many can see the perforations/holes at viewing distances of 1.5-2x the screen width. Secondly, Stewarts microperf blocks a substantial amount of high frequencies. So much so that Stewart now provides EQ electronics to conteract this problem. Not ideal IMO.

In recent years Screen Researches Clearpix 2 material has gained pole position as makers of the ultimate acoustically transparent screens. I've been involved in several tests with electric SR screens in the up and down positions and can tell you it is virtually impossible to tell when the screen is dropped in front of the speakers. Screen Research state that their material offers less than 1dB difference across the entire frequency band. From my experience with these screens (I now use a 2.35-1 fixed version myself), they are more acoustically transparent than some speaker grills I've come across.

[Chris D]

I too use a large perforated screen, (119" diagonal) have all 3 front speakers behind the screen, and will never go back to non-perforated. (assuming future theater setups allow it)

Everything else important has been said above. One thing, though, Uncle Eric--the ability to perceive resolution and screen door effect does vary with screen size. Seeing perforations does NOT, unless the manufacturer happens to increase the perforation hole size as they increase screen size.

[JBJR]

For those interested in a DIY screen of this type take a look at this screen material.

http://www.smxscreen.com/forum/

There also is a thread over at AVS about it.
I am looking to do a 2.35 with it.

Here's the AVS thread: http://www.avsforum.com/avs-vb/showthread.php?t=640385

[Chris D]

DIY perforated? Oooooh, I'd be really hesitant to do that. I'll give that link a look when I have a minute, though.

[JBJR]

Its not perf, it's a special weave material.