Is a Perforated Screen Worth it

It's probably the optimal way to go for best sound "imaging".

However, I doubt but maybe 25% of people actually do it. (just guessing)

My center is mounted directly below the screen and sounds great.

While perforated screens put the sound exactly where you want it, the drawbacks are that you'll take a 28% hit on brightness, a 14% loss in contrast, plus the audio will be attenuated in the upper octave.

An article detailing the above can be found in digitaldesignline. Do a search in Google for "Defining the difference in perforated screens for video projectors" to get the URL (I can't post URLs yet).

There are several AT screen materials available... not all of them will provide that same level of drawbacks.

Here's a picture of an acoustically-transparent (AT) screen from the article (link) you referred to:


And here are some closeups of some other AT screens (SmX and Stewart) that I was comparing last month:





The weave/perf pattern plus the gain of each material will effect the final light output and the sound attenuation.

Without knowing the specific material that the original poster is considering, it might not be fair to state "you will take a 28% hit on brightness, a 14% loss in contrast".

Maybe "you could take a 28% hit on brightness, a 14% loss in contrast"

or "you will take a hit on brightness and a loss in contrast"

My room is a little narrower than yours, but the same length. I originally had the same concern. I ended up mocking up where a false wall would go and evaluating it from my seating distances to see if I liked it. I ended up with a stage that extends a hair over 4' from the front wall. My screen wall is the thickness of a 2x4 and there is 24" of room behind it. I have pics in my construction thread which should give you an idea of what it would look like. I don't have a pic of the finished screen posted yet, but there is one with the frame in the screen wall. I have been playing with the projector with the screen in place over the last couple weeks and everyone who sees the room is blown away. I would go for it.

If I set up sound both ways, I defy anyone to find the difference using their ears alone. The question is a matter of proper speaker placement and setup; great speakers make all the difference. It comes down to whether you want the brightest picture available or not. [If you go with AT screen] You'd better get a projector to match.

Personally, I like the idea of setting the center speaker behind the screen and the L & R's out front. The nearest seat in my theater will be 16' from the screen, seeing perfs is not a concern.

Regardless of where your speakers are, set the tweeters of the Left, Center & Right front speakers at ear level. Mounting speakers, not less than 12", behind the screen simplifies this task. Not to mention, helps cut floor or ceiling sound anomalies; which can all be fixed using tweaks.

"Is a Perforated Screen Worth it?"

A "perforated screen" probably not.
A "weaved audio transparent screen" definitely Yes.

I want to point out a few things about the current audio transparent screens on the market.

First off, there are 2 types of audio transparent screens on the market.

First type is perforated/micro perforated screen, they start off with a solid screen and send it through a large machine to punch small holes in it to make it audio transparent. Companies that manufacture perforated screens are Harkness Hall, Hurley Screens, Technicote, MDI, Stewart, Draper, Da-Lite, Vutec, etc.

Second type is a weaved screen which is a woven screen that is made with fiberglass or pvc strands that are either basket weaved or have another type of weave. Companies that carry weaved screens are Screen Research, Vutec, Dazian and Draper.

First lets talk about Perforated/Microperf Screens

First off, Perforated/microperf screens have really bad audio transparency issues. They comb filter really bad even at the recommended 8" speaker placement distance from the back of the movie screen (which most people don't have space to do). Combfiltering is caused by the audio bouncing back and forth between the speaker and the back of the movie screen then coming through the movie screen. This creates an unwanted hollow effect to audio know as comb-filtering.

Besides comb-filtering, perforated screens also destroy the audio by creating huge dips and peaks thoughout the natural trend of the speaker. Companies like Stewart include 1 proprietary EQ to help reduce these peaks and dips on your center channel. Even though this EQ helps the audio to some degree, it doesn't help with comb-filtering. Plus if you want to have all 3 of your speakers behind the screen to have a consistent front sound-stage, you would need 2 more EQs to balance it out.

Next problem with perforated screens is the highly unwanted moiré effect on video. This is caused by the fixed pixels (screen door) on digital projectors lining up with the perforated pattern on the movie screen. The two clash and create bright moiré streaks across the screen during bright scenes. It is a horrible effect on video. The only company I know that is working with customers to help eliminate moiré with perforated screens is Stewart. They do this by rotating the screen material on the frame based on the projector, screen size and throw distance you are using.

With perforated and microperf screens, every digital projector type, screen size and throw distance requires a different rotation to avoid moiré. Although this is a great effort by Stewart to help fight moiré with their screens, what happens when it's time to upgrade your projector? Better yet, what happens if you move and your throw distance changes? If the moiré comes back, your stuck with it.

Right now, even commercial cinema's are trying to fight the moiré issues as they are converting over to digital projectors. The existing perforated screens for film are not working with the new digital 720 DLP projectors they are installing across the globe. So they have to defocus the projector to reduce the moiré.

Another factor with perforated/microperf screens is the perforation size. Perfs and microperfs can be very noticeable from seating distances up to 30 feet (depends on your eye sight). This drove me crazy with a past microperf screen I had as it made bright clouds look muddy and HD look grainy.

There is also a certain loss of light with perforated and microperf screens that must be accounted for. Every manufacture is going to vary with that.

Now lets talk about Weaved Screens.

First off, the audio transparency of weaved screens are much, much better than perforated/microperf screens and in most cases, don't require any EQ (many reviews and tests show & prove this). There are no huge dips and peaks thoughout the natural trend of the speaker like with a perforated and microperf screen. This means you can put all 3 of your front speakers behind a weaved screen to maintain a consistent sound-stage without worrying about buying multiple EQs.

With weave screens, comb-filtering is to a minimum and is usually undetectable by the human ear. Everything you put in front of a speaker is going to comb-filter to some degree, even the speaker grill cloth on speaker grills comb-filter, it's just not noticeable by the human ear (unless you have super-ears ).

As far as moiré with weaved screens, some companies guaranty no moiré and others don't. All the major screen companies that offer weaved screens right now all have a negative gain white matte material (.80 - .85 negative gain) which means you either need to use a smaller screen or buy a bright projector to get the recommended FL.

As far as perf size on a weaved screen, it is usually very small and undetectable from 10 feet or closer.

With all this being said, to me, there is nothing in the world like having your speakers behind the screen.

Movies are mixed in hollywood with the speakers behind the screen to replicate how the movie is going to sound in the theaters. All the commercial theaters I've ever been to have the front sound-stage all behind the movie screen. When a person is talking, you want the dialogue to come out of the mouth like it was intended to be, not above or below the screen.

If you're building a dedicated theater, I would imagine anyone would want to replicate a commercial theater environment plus better video and audio.

So my vote is for the speakers behind the screen.

Ruben

My center is behind the screen and sounds great.

I would do it again w/o question.

I second that of the last post. Having gone to an AT screen and hearing the difference I wouldn't consider a solid screen.

I have a weaved screen (SMX) and don't find the gain too low for my AX100U even at 50% room lighting.

Grant

I agree with Rubin (SandmanX). A Weaved AT screen setup is absolutely THE way to go. It is the only proper way to get correct dialog localization and the only practical way for most folks to get the speakers all the same level and at the proper height for the best acoustics. I'll also second a vote on the SMX screen. I have one and it is awesome. No complaints about sound quality with the Klipsch THX Ultra 2 speaker package and no video complaints even on a 160" wide 2.35 screen. Only thing I had to do is bring the speakers up about 2db hotter but no drop off in sound transparency.

IMO, the main reason is to allow more flexibility in speaker placement, and to allow full sized, vertically oriented speakers to be used as center.

In home theaters with non-AT screens, many times designers have to resort to horizontally oriented speakers for the center just to fit above or below the screen.

We shouldn't get into a discussion of speaker dispersion characteristics here, but let's just agree that it's a compromise to use anything other than three identical speakers, in the same orientation, at the same height for the left, center, and right channels.

So, AT screen for best sound and a slight compromise in PQ...

or

Non-AT screen for best image and a slight compromise in SQ...

Your decision.

I've been using Ruben's SMX screen for some time now and I can say it's fantastic.

No dropoff in treble or loss in sound quality.

But the thing I love most about it besides the price is that it has some gain. 1.16 to be precise. No loss of PQ to my eyes. Try doing that with the other AT screens on the market. All seem to have a negative gain (Screen Research) or if they have gain, they are perforated yuck! (Stewart etc)

I think the only reason not to go AT screen is if you need a higher gain screen.

Get an SMX and don't look back.
I got in on the initial shipment and can not conceive of not having it(!?!)
Identical speakers all around, great PQ and audio.
An AT screen is definitely the way to go.

How many of you guys are using SMX with motorized masking systems ?

Art

Is there any (easy) way to retrofit a Carada solid screen with SMX?

Art,

I'm currently setting up my AT screen with motorized curtains that are used for side masking on my 2.35.

Guys,

My Klipsch KLF-30's with maching center have never sounded better with SMX. There is no substitute period.

This screen is absolutely the BEST AT screen I have ever seen OR HEARD period. Being a CRT owner right now, I have to crank up the tubes a bit more for maximum foot lamberts but boy what a reward and well worth it.

I've shot a Sony Pearl as well on this material at 11ft wide and it's, well, DA BOMB.

Screenshots at 11ft wide with 2 Sony G90 CRT's:







Cliff

So big dog, what is your opinion of the SMX material after spending some very nice first hand experience????

Cliff

curious as well to know how much space curtains would take up

Is there a way to retrofit this material into the frames of one of the masking systems ?

Art

This is probably accurate for the Clearpix2 and Vutec Soundscreen as they both have been tested by various reviews to have a 0.80 - 0.85 negative gain with the White Matte materials.

The first weave photo that Clarence posted above appears to be the White Matte Screen Research Clearpix 2. Stewart used that same image in their white paper on perforated screens vs weaved screens. Stewart has the gain listed on the Clearpix2 picture as a 0.76 which is even lower than what various reviews found.

Ruben

Smx is absolutely the way to go. I have my REVEL Performa LCR speakers all behind my 120" wide SMX and I would never use anything else. Picture quality is fabulous and sound is amazing.

Funny you should ask because that's exactly what I did.
I originally ordered some Fabricmate "holders", sorry hard to describe but their original use is for holding fabric for wall panels.
In any event I could not get the SMX fabric inserted into the channel with an even tension so decided to use the FabricMate strips as simple hold downs for the SMX fabric.
The plastic strips are like 6 ft long and approx 1 1/2" wide.
I drilled holes in the Fabricmate strip to match the spacing of the threaded snaps that Carada uses to attach the vinyl screen.
I then cut slots in the SMX fabric with a small hole at the top of the slot that also matched the spacing of the holes in the Carada frame.
The slot\\hole combo was to allow for tensioning the screen without any binding.
I put the frame face down on Kraft paper and laid the SMX fabric over the frame lining up the frame holes with the slot\\holes in the fabric.
I then put the Fabricmate strips on top of the SMX fabric, lining up the holes in the strips with the frame & fabric ones and screwed the threaded snaps into the frame.
I only lightly snugged up the snaps at this time.
I then worked my way from the center out on one long side gently tensioning the fabric and snugging up the screws.
Repeat the process on the opposite long side.
Repeat the above 2 steps on the short(vertical) sides.
I then did a couple minors adjustments and voila, virtually flat material that is secure.
Sorry for the OT post and forgive me if I have not clearly described the process.
I have been meaning to post the pics of my 97% completed room but between work\\school and watching HD movies I haven't made the time yet.

It's as simple as Acrylic Adhesive Velcro. Remove the existing snaps from the frame and replace them with 1" - 2" Velcro. It works like a charm and you can always simply re-tension your screen in the future if ever needed.

Ruben

So Velcro will hold it tightly enough in the frame ?

Art

I love the idea but the 1080p PJ's currently on the market and in my budget (<$7k) don't have the brightness to support my 120" wide screen requirements at the moment. Hopefully in the next few years this will change and I can revisit this again. SMX is a great product from what I've read - and at a great price!

Before I decided to go with another company's AT screen I was researching Ruben's SMX screen and the tests that Alan had a professional do on the screen material showed a very large drop off in high end frequency's as well as a color problem that he said was "unacceptable". They conducted some other tests but refused to disclose the findings (you can go to this link and see the discussion between Mr. Poindexter and Mark P - http://www.avsforum.com/avs-vb/showt...640385&page=67 )

I also believe that SMX can only go 98" wide without creating a seam (also a problem since I wanted a 110" wide screen).

For the price, I think SMX is a great deal. I just don't want people thinking that PQ and AQ is perfect or as good as other alternative, albeit those alternatives may cost 10x as much.