The official SeymourAV center stage screen thread! - Page 5

I sprung for the 24" x 24" sample of the Sheerweave 4500. If you're interested in exploring this material further, I'd be happy to drop by with it. Acoustical testing with a bigger sample might give results with a higher confidence level.

Did you happen to try re-orienting it to "remove" the bias to see if there was any moire with your HS60?

Me too, and I'm not even sure what grokking means.

I ran some tests this week because the original sound data I mentioned wasn't what I was looking for. So far the data doesn't show any bothersome effects with respect to speaker angle, which of course really bothers me. I have one more test to run, hopefully today but I've been told I should be watching football instead.

I'll answer each and every question and expand on my wrongness asap.

Cheers,
Chris

Yes, you should have been watching football! Great games this weekend. We look forward to your impressions Chris. I sure can't pick up any difference in angling my speakers, but then again I used to listen to Boston cranked up on an eight track tape deck with a Spark-O-Matic amp in my '67 Pontiac. What distortion?

If comb-filtering is occurring, it might be easier to hear by moving left-to-right (and back again) several feet than to remain static. Being a rocker, you'll understand when I say that you'll be listening for flanging. Granted, it won't be as dramatic as the effect that Tom Sholz occasionally used, but you'll know what to listen for.

pepar,

Excellent point, flanging is a very good analogy to use in describing what comb filtering sounds like. Here is a link to a Wikipedia definition page, that even has example sound clips to listen to. http://en.wikipedia.org/wiki/Flanging I've definitely not heard anything like that with my screen and system so far, but I might try listening a little closer, and moving around as you suggested.

Well, the data is in and it shows me not only how some of my experiences derive from, but also where I'm wrong. My basis for recommending that folks try to minimize their speaker angles with respect to the screen (e.g. fire them straight through - don't tow them in) came from previous experience with acoustically transparent large and small-format screens and their tendency to affect the sound at different speaker angles. My analogy with the light opacity at different angles seemed to support that the material acts like it has a different openness at different angles and hence its permeability and sonic transparency would be affected. Fire straight through and get the full openness of the fabric, increase the angle and you're thereafter trading off acoustical transparency. After running through the tests with the Center Stage screen fabric, the measurements didn't support this. If you're wearing a tie, your summary is that the Center Stage screen doesn't perform worse at increased speaker angles, and that comb filtering is not significantly affected by speaker angle.

Test setup: A calibrated Behringer ECM8000 microphone was placed an inch from the test screen, which was located about 6 in front of the center speaker. I didn't rotate the speaker or the mic, as this would cause its acoustical performance within the room to change. I'm not here to measure the off-axis performance of my speaker, so I only rotated the fabric. I then subtracted the measured performance from my speaker's frequency response, so you're only looking at the change from adding and angling the screen. Here's a pic of the setup:


The general consensus is that people can only discern 1/3 octave frequency variations; that our hearing naturally smoothes out narrow bandwidth artifacts. I argue that this is a bit crude, so I'll show the 1/24 octave to see what the microphone can hear, and a 1/6 octave resolution to see what effects could be audible.

First up is a perforated vinyl AT screen like I have had prior experiences with in residential and commercial theater sound. I've known since the around 1991 (first stage sound job) that the sound of speakers firing through perforated vinyl screens changed depending on what angle they fired through the screen. The effect is admittedly minor compared to the typically-huge changes in speakers' natural off-axis performance, but is clearly audible. While this should teach me not to learn from prior experiences, it won't because that would be learning from a now-prior experience.

This first chart is a perforated vinyl AT screen, measured with 1/24 octave resolution. This chart shows a change in how the screen combfilters the sound passing through it at different angles. I don't get too much from this chart other than these screens give acoustically transparent a bad name. I'd be just slightly more likely to do this to my speakers than I would be to replace everything with a Wave radio and mp3s (now possible via the Aux jack - yea!)


More importantly, the following is what you hear. At 1/6 octave resolution, the chart below shows that while the vinyl screen will easily sound different versus speaker angle, it doesn't necessarily sound worse. The speaker's frequency response is significantly different versus screen angle, but the variation in the screen's acoustical attenuation isn't significantly changing. As my brother often says, That's where you're wrong. I calculated the standard deviation in order to put a number on how much audible comb filtering the screen is doing versus angle, and it doesn't change much. That chart is at the end of the post.



Here is a 1/24 octave chart with the Center Stage screen material. There is measurable comb filtering (even many speaker grill fabrics will measure comb filtering), but the general takeaway is that the measured performance isn't significantly affected by speaker angle.


In the 1/6 octave chart below, we are better able to discern what would be the audible effects of changing the firing angle of the speaker through the screen fabric. From the +/- 40 degree angle sweep, the acoustical transparency of the screen is within 1dB, which is about what my test uncertainty is. Even at significant angles, the fabric is just not acoustically reflective enough to affect the sound much. With this, I'd say to angle your speakers however you think best for the room surfaces, speaker radiation pattern, seating angles, and overall preferences and not worry about any screen effects.


Judging the squiggly-ness of the lines quantitatively, I calculated the standard deviations of each angled measurement to map out audible changes in frequency variation versus angle. Below is the chart showing that various angles don't affect the audible comb filtering much for either AT screen type. While perforated vinyl screens are arguably acoustically transparent at all, their frequency response varies greatly no matter what angle the speaker is. Being highly variable, their response will audibly change versus angle, but their variability is not increased with angle.

Similarly, the Center Stage screen's degree of frequency variation is consistent versus speaker angle. The material is acoustically inert enough that the speaker angles have a minimal effect. There may well be more good reasons for angling your speakers than there are against. I'll hit more on vision and sound-field philosophies in another post.


Sorry for my confusion. I'll trim down my earlier rants to better reflect what's been learned here.

Next up, some speaker/room angle points and some answers to some specific questions.

Cheers,
Chris

Thanks, that "clears" it up nicely.

Hi pepar -

No, the goal is not always to sync the soundstage to the image, but to rather realistically reproduce what was put together in the mixing soundstage and recreate the full sensory experience as it was intended. Off-screen sound effects are regularly placed in the L/R channels, as well as initial panning to the surrounds. Studies have shown that with dramatic audio, people perceive the video as more dynamic as well (they recalled that the screen size was larger than it actually was).

Your video field should be about 36 degrees per THX. You can cheat this +10 degrees or so if you watch more HD sources, accept the reduction in image punch, increased motion artifacts, and personally enjoy a bigger feel. But it's still a worthy goal post.

Your audio field is 360 degrees, but talking strictly about the front soundstage, that visual goal post of 36 degrees is narrower than the audio standards and most good practices allow. Below are the recommended speaker locations per Dolby:


First you can note what a boorriing front display they have, and that irresponsibly-horizontal, non-identical center channel. But it's a valuable guide on sound field setup, because it is how the standards and practices are followed. Notice that you can get your screen size up to around 44 degrees before it starts to encroach into the L/R zone. That's why I mention that if all three of your speakers are in front of your screen, it's likely that your screen is too large (>45 degrees) or your L/R separation is too narrow (<43 degrees).

If your L/R speakers are too close together, you compromise the channel separation among the front L/C/R. Also, you open up a sonic hole from your L/R to your side surround speakers, which reduces how smooth surround effects can pan front/back.

I've always thought that the audiophile 2-channel history of a 60 degree L/R goal was too wide, but now that a center channel is there to lock the imaging and complete the front soundstage, the standards of 44-60 degree L/R separation are a perfect sonic goal.

Cheers,
Chris

I don't think I've ever seen a mfr do this, at least not without lots of challenges & criticism beforehand.

You are to be commended, sir!

Thanks for the reply, Chris.


A few AVS members who work in the film industry (and mix some of the movies we watch) report that the standard practice is not only to have the monitors all behind the screen, but to locate them within the 1.78:1 area of the 2.35:1 screen. I do not recall reading their seating distance, so I don't know their viewing/listening angle. But if the goal is to realistically reproduce what was put together on the mixing soundstage, and I do wholeheartedly and enthusiastically subscribe to that philosophy, LCR must be behind the screen.

And certainly the speakers at the cinema are all behind the screen.


I think the Dolby diagram is helpful for a lot of people and the representation of the display is intended to look familiar to the general home theater consumer. But I'd bet, though, that very few people hanging around the "Screens" forum have a display like that.


The 60° L/R layout of audiophile 2-channel reproduction puts the listener at the apex of the golden (equilateral) triangle and, usually, in the nearfield. Magical things happen at that point; except for bass nodes, the room pretty much disappears and one hears what the mixing engineer and producer heard. But that's 2-ch reproduction.

Quite a few members, myself included, size their screen to their room width. My present 92" wide 1.78:1 screen *does* leave enough space outside of the frame for my L&R speakers. My next screen, a 2.35:1 at 110" wide, will not. But that was my point; max out the screen width and get LCR all behind it. Good acoustical treatments can get the listening postions close to nearfield monitoring; mine do.

Chris,

Great post. It's nice to see some good numbers on the apparent minimal audible comb filtering of your screen material.

BTW, I agree with BOTH you and pepar about locating speakers behind the screen and striving for 60 degree speaker angles, and have actually come quite close to doing both. My LCR speakers are all behind my screen, and speaker angles are 66 degrees (49 degrees at the listening point angle) Here's how I did it. My screen is 115" wide (plus 4"/side for masking), and the L&R speakers are 9.5' apart. My viewing/listening distance is 10.5' feet, and the "listening" distance to my speakers is 11.5 feet . This puts my viewing angles at 38 degrees for 16:9, and 49 degrees for 2.35 "scope" films. That may seem too big for 2.35 movies, but we don't think so, and neither do our guests. Doing a true CIH setup with a scaler and anamorphic lens no doubt helps maintain image quality for 2.35 movies. The room does seem to "disappear" when we watch movies or listen to music, and with the right movie or CD it is magical!

The open (hole) area is around 5% and is the openness factor. That means the holes areas are approximately 5% of the area in comparison to the threads. The fabric allows more than 5% light through it because light will travel through the fabric as well. Most non-AT projections screens will cast an image on their back surface and allow light to transmit through the material as well. Although this effect isn't often a problem, typically only the heavy, reinforced vinyl screens, often with black back sides are truly opaque. The openness factor surely affects the light transmitted through the screen, but the color of the fabric is another major contributor. A 5% open black fabric would come close to what you're describing.


The black backing is a 10% open material, and thus will allow about that much light through since it otherwise absorbs and is a very poor re-transmitter of light. From the viewing area, light bounce-back has to go through any layer twice, so it's in practice not that big an issue. Or at least not nearly the issue that Stewart markets it as (woven screens [which require a secondary black backing] goes their advertisement).

Probably 80% of the retractable screens we've made have had black backing layer. This is because the purpose of a retracting screen is to get out of the way from something that should be seen behind it, be it a window, plasma screen, entertainment center, etc. Those things are highly reflective and the reason why most retractable woven AT screens will need the black backing layer.

Probably 95% of the fixed screens folks have been building do not require the black backing material. These installations are typically purpose-built and what's behind the screen is intended to be entombed. Those surfaces can be darker and less reflective.

The general rule is that as long as your surfaces are medium shade or darker, and reasonably non-reflective, you won't need the black backing layer. Only light color surfaces and things like plasma screens, windows, or shiny metal require it. Also, ceiling retractable installations with a 3+ feet behind the screen often need the black backing so side viewers don't see a secondary image splashed on the back wall. I always advocate people to use paint or otherwise treat the surface first. No sense putting another layer there if you don't need. But if you do, it's a great solution.


No, unless you have a real problem (e.g. light walls behind the screen) that the black backing needs to fix. It's only a corrector, not an upgrade.


It averages 1dB attenuation in the top octave, so it's more acoustically transparent than the screen. From my other post that the screen proved basically immune to speaker angle, the black backing layer would be even more so.


Only unless you have unusually high port velocities and are squeezing the minimum screen-to-speaker distance of 2. In practice you can put the screen right on top of the speaker, but depending on the speaker type at lower frequencies, the driver and/or port may need more breathing room. Practically speaking it isn't an issue. Subwoofers can go behind the screen, but in those cases we recommend getting around 12 of distance to the screen, and not directing any ports right at the fabric. Unless you could blow out a candle with the airflow, you won't move the screen.

Cheers,
Chris

Greetings all,

I don't know if this has been addressed before, a couple of different searches revealed nothing. I have a new Mits 4900 1080P projector and am investigating buying AT material from Chris for a DIY fixed frame AT ~90" diagonal screen. The Mitsubishi remote seems to have an occasional problem with the projector accepting remote commands bounced off the current BO cloth screen, more so than my Optoma did. My question is- does the AT fabric pass IR remote signals bounced off the screen with about the same efficiency as a solid material?

Thanks! Cheers!

Well I got my AT sample from Seymore and though I'd throw up a quick mini review from what I saw. Behind this cloth is a 10 dollar laminate from HD and next to it are the Wilson Art Laminate samples, my picture is being thrown up with a Mitsu 4900.

First is that from my seating distance, roughly 10ft, this screen looked great and it had a smooth picture with no panning issues that *I* could detect; the ONLY time I could see any of the weave was on pure white scenes which showed itself as a very slight hint of grain. For AT material overall I'd say this throws up a "solid" picture as well as the highly touted Wilson Art laminate.
Also compared to the other surfaces the Seymore cloth had a *slightly* darker color being thrown back and I can almost promise this is due to the holes in it, not anything to do with the cloth itself. The cloth has plenty of punch that I saw and overall I could not tell this was AT material. Unfortunately for me I could not place my speakers behind it, nor have some way of floating the cloth infront of them.

If I didnt have any of the other materials next to it, it would be very hard to even see any of these changes (which I have to say are VERY very minor). Just to be clear, for those that are curious I'll restate that unless you have something right next to it, this AT material performs, to my eyes, as well as any solid projection screen. Even with solid materials around it, it was VERY hard to spot differences. I had to pause, get close and look for where the material made a difference in the picture. (Understand I have a small sample of course)

Now my questions are directed toward my lack of knowledge about electrical screens in general.

Will a tabbed screen develope ANY wrinkles? (ever?)
How long do these electrical motors last?
Can they be replaced easily?

Considering these are the cost of a projector, I'm am interested in how many trouble free years such a purchase would last me as I don't intend to constantly aquire new ones

My remotes seem to all shoot through the SeymourAV screen just fine, with no problems at all, like it's not even there.

Great post BAYN....interested in the answers to the same questions you have.

WS

Chris, I will also commend you on your ongoing investigative work. I have really been waffling between a 110 and 130" screen for the fact that I really like my mains toed in. Now I don't have to worry about it and can pick up the 130.

Hi Bayn -

1) The fabric doesn't stretch much, just over 1%, so is very stable for the long run unlike unreinforced vinyl screens which can stretch over time. The purpose of the tab system, which is rarely used in reinforced fabrics, is to further ensure that once it's calibrated flat it stays that way. Our tension system uses turnbuckles which are adjustable if they ever need a tweaking. Sometimes after shipping they get shifted a bit and a little tweak is all that's needed, but once it's set it won't develop any wrinkles or waves.

2) The standard RF motors are rated for appx. 20,000 cycles. We've been using them now for four years without any that have worn out. I don't yet know what the upgrade Somfy motors will be rated at, but they are widely used.

3) No, it'd need to be replaced here. It's not a field fix.

Cheers,
Chris

I'd guess about the same. Although there are several screens out there with the 4900 pj, we haven't specifically experimented with a projector that's otherwise borderline-strong with it's IR signal. All the Sonys and Pannys we've played with have been fine.

Sorry I don't have a more exact experience to point to. Perhaps someone using the fabric and the 4900 could share their thoughts?

Cheers,
Chris

Thanks for the feedback. I will report back with the results once I get my screen done.

Chris- I want to thank you for all the good info you offer up. I was all set to order some material from you when I stumbled across someone who had SW4500 chunks for sale at a greatly reduced price. I need to pursue that opportunity as the savings will about pay for a Blu-ray player. No small issue when the wife, who happens to be a loan officer at a bank is watching the transactions like a hawk. My apologies for my biz going elsewhere. Now should that deal not materialize- I'll be in touch in a heartbeart.

Thanks!

Fully understood... a deal is a deal, so cheers to you. I hope it works out well for you. If you have any pearls of wisdom to share afterwards, don't be a stranger...

Cheers,
Chris

Well seeing that this is the offical thread I wonder if a rumor can be answered?? Is it true Chris that you will now have a Canadian distributer? I have been looking everywhere in Canada for your product with no luck and while compairing AT screens I gave a company your site, now I here that Seymour AV could be coming to Canada. I am very excited I was kinda worried about shipping via fedex from the US.

I will be ordering my PJ this week and a while down the road hope to be getting one of your screens.

Later
Phil

MMMMM...very interesting, is that true?

Guess it is not rumor any more.............
http://www.complete-it.ca/ProjectorScreen/Seymour.php
Thought I tlaked to the right guy LOL

Later
Phil

Well, my goal of getting my new theater up and running in time for our annual Super Bowl party has been accomplished! I haven't had much time to play with everything, but I certainly am pleased with the Sound Stage screen.

Here are a couple of -- lights on, with flash, no image projected -- pictures of the screen up and down.

Very Nice Bill!

Let us know how the BIG GAME looks!!!

HT Obsessed

Nice setup Bill. I'm sure this will add to your Super Bowl enjoyment immensely. If someone in the halftime show does "a Janet" I'll bet you won't miss it!

I'm considering upgrading to a 1080p projector, from my current Panasonic AE-900, 720p. It looks pretty good, but I'm lusting for better black levels and more detail.

So....those of you have viewed several types of 1080p projectors on this AT screen, what looks best? A Panasonic 2000 "smoothscreen" or Sony Pearl "film like" projector, or a razor sharp Mitsubishi 5000, JVC RS1 type of picture? I'm especially concerned with moire' being an issue. Do the sharper image projectors have a bigger problem with this?

I view a 10' wide screen from about 11 feet. My current screen is not angle cut, but I will be changing to a 15 degree angled screen soon.

TOO big, that's how. At 9.5' away from the 7.5' wide screen, the action was too much for our eyes and brains. After a while I used the zoom to make the picture about 6.0'-6.5' wide. That was easier to handle. But everyone sure did like it on the big screen! Toss in great food, a great game, and it was a top notch evening !