Stewart microperf x2 owners please comment about your systems audio fidelity with this screen - Page 2 - AVS Forum
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post #31 of 36 Old 06-26-2013, 04:14 PM
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Originally Posted by BobL View Post

With any of the woven screens it will not effect bass or midrange.  They don't start to roll off until about 2-4kHz gradually decreasing as you go higher in the frequency range.  With Enlightor 4K it is ~ -4db at 20khz with the black backing.  And there is no problem putting a sub behind the screen if it is a good location for the sub.  I wouldn't place it very close to the fabric as a good sub might flap the fabric.  But acoustically the screen will not affect the bass frequencies.

Mmm. Good point about the sub. I'd also be wary of putting a ported sub behind an AT screen, even if it was 12" away. A serious amount of air is moving at port resonance frequency.

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post #32 of 36 Old 06-27-2013, 01:41 AM
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Originally Posted by Bulldogger View Post

In most case it's not going to boost the bass at all. Typically the only speaker behind the screen is the center channel and it's crossed over typically around 80hz. When you balance the channels, the level of the center for the frequencies it produces will be down. HOWEVER smile.gif, the sub will not be effected because when you balance it's level relative to the rest of the speakers, having never actually been behind the screen, it will not be effected. Whether or not a thin piece of fabric would attenuate the bass is irrelevant for nearly every application I have seen. The subs are typically in different locations. I would not think it wise to put subs behind the screen at any rate, just the center.

I think quite a few people put subs on their front wall, but for the sake of argument assume no subs and just a center behind the screen, crossed at 80Hz like you said.
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Originally Posted by Bulldogger View Post

Note also the entire frequency response as they define it with their chart starts about 500hz. Considering the chart, I don't think they are actually making the claim that the frequency response at 40hz for example is effected http://www.screenexcellence.com/products/projection-surfaces/enlightor-4k.html .

What happens to the center channel's output level between 80hz and 499hz if you just turn up its volume to compensate for the 2.5dB loss above 500Hz ?

 

 

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post #33 of 36 Old 06-29-2013, 11:59 AM
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Originally Posted by rabident View Post

I think quite a few people put subs on their front wall, but for the sake of argument assume no subs and just a center behind the screen, crossed at 80Hz like you said.
What happens to the center channel's output level between 80hz and 499hz if you just turn up its volume to compensate for the 2.5dB loss above 500Hz ?
For me, concentrating of the frequency response of the two types of screens is an outdated argument in 2013. Any room measurements are likely to reveal LARGE peaks certainly from about 300hz down because of "room gain" regardless of screen used.Therefore, you'll need to EQ most of the spectrum below 300hz any way. Parametric EQ or one of the methods of room correction are readily available either included with the current processors or can be injected via a media server running Jriver. When, the screen required the purchase on an external EQ,then the argument that the woven screen had an advantage might have merit in an anechoic chamber smile.gif. I realize that the screen companies are still using what I now consider largely an irrelevant argument, though I note that Screen Excellence includes impulse response, energy time curve, and shroeder response. I'd like to see the results of these types measurements with the vinyl screens. Poorer results are what I would expect.

The primary advantage and disadvantage of the vinyl perforated screens are the increased reflectivity. It's an advantage for video providing a higher gain screen and in my observation a better picture for the most part. It's a huge disadvantage for audio however.

When I was experimenting with different types of screens, one of the things that I wanted to determine was how much an effect on sound quality the lowered screen had on audio even when just listening to stereo. Experimenting with two channel music, it became immediately apparent that vinyl perforated screens when lowered had a type of "boundary effect." The sound was akin to placing the speakers closer to the front wall. First and second room reflection work to smear the sound without some type of absorption at those points. Hanging a large piece of vinyl between two stereo speaker could be described as anti-room treatments because that is the effect I experienced. With un-backed Screen Research fabric, the effect was almost not there. The effect was greater with two of the other woven screens but much much less than with vinyl.

How much of an effect, the type of screen has on audio will also depend on placement and not just the material of the screen. I never tested, but I assumed that woven fiberglass, what Screen Research uses, could have a less detrimental effect on sound than plastic because of the properties of fiberglass. If you mount your speakers on wall and the screen is mounted on top of them, I'm not sure that the reduction of the boundary effect is nearly as great. Logic would seem to suggest it should not be, because of the proximity of the front wall, the reflectivity of sound of the vinyl would be less relevant. I"m not sure it's quite that simple as even when screens are placed on wall, absorption materials are often used. I suspect how freely sound can pass back and forth between the screen materials can impact comb filtering as well.

IMO, both types of screens have advantages and disadvantages. The true audiophile will have an issue with a perforated vinyl screen for audio based upon my experience. Conversely, the true videophile will have issues with the woven screens for picture quality because of screen gain and surface smoothness. Screen Excellence offers the least compromises providing you have a very bright projector. Needing a very bright projector, however is somewhat a compromise.

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post #34 of 36 Old 06-30-2013, 05:36 PM - Thread Starter
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Dennis designed my room with around 12" between the screen and speakers, and Linacoustic on the baffle wall, so hopefully that boundary effect is mitigated, or eliminated. In any case, I think I am going to bite the bullet and buy that Stewart. I will have both screens at the same time so perhaps I can take some measurements. I only have XTZ for measuring right now, so I am not sure if I posess the right equipment to measure anything beyond frequency response. But I would think it will be apparent if the Stewart is seriously harming the audio. So many high end theater designers specify Stewart Microperf that surely it's a great option and not just a profit center.. I would think their reputation would suffer if it were.
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post #35 of 36 Old 07-01-2013, 06:26 AM
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Rather that the difference is an attenuation of the high frequencies that is fairly progressive and linear, and that can be almost completely corrected with a decent EQ. That is what I keep being told, and what I hope!
That is exactly true and Stewart will provide (at no cost) a compensator for each speaker behind the screen to correct. On the other hand, you apply the correction and then turn on THX Re-EQ, you just put back what you fixed. (That's if you use Re-EQ.)

The sound energy which is seen as rolled off from the viewing side of the screen, did not just disappear poof into lala land. Those frequencies are reflected off the back of the screen and absorbed by the 1" black fuzz you have on your baffle wall or back wall behind the screen (SBIR mitigation).

Dan makes a terrific point. The slight; but, correctable audio characteristics of the Stewart Microperf pale in comparison to other "stupids" found in the rooms of "audio is important to me" listeners ... poor speaker placement, inappropriate speakers for the space, bad choices in seating distance, totally out of whack acoustic treatments, etc., etc. In fact, in the vast majority of cases I've seen, the distance between the listener and his/her speakers where such that the high frequency roll off looked very much like the roll off from a Micro Perf screen and no attempt was made to correct it. Another point, made above, was build quality. The screen is every much a component of an audio/video space as the speakers and other kit. I don't for the life of me understand the logic behind saving $3000 to $4000 on the screen when way more than that has been spent on speakers, projectors, sometimes silly expensive speaker cables in order to have "quality" stuff.

None of us listen to speakers at 1 watt, 1 meter. smile.gif
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post #36 of 36 Old 07-05-2013, 03:35 PM
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It's not just frequency response. It's also not just rear reflectivity either. It is also the reflectivity from the FRONT of the screen as well. For speakers mounted on wall this may not make any difference. For floor standing speakers, glass, wood floors, or any reflective surfaces have an effect on audio. Lowering a perforated retractable screen between two speakers will have a negative impact and no amount of EQ can fix those reflections. Screen Excellence also seems to be showing that the audio out of the FRONT of the screen is redirected for a perforated screen to a greater degree than a woven http://www.screenexcellence.com/technical-concepts/acoustics-of-woven-screens.html

What about time domain, impulse response? Screen Excellence gives time domain graphs on their Enlightor 4k. I"m curious as to the results with perforated vinyl? Is it significant? Seems logical that the perforated vinyl would cause more of a delay than the woven? Has anyone seen impulse response comparisons?

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