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Acoustical Treatments Master Thread - Page 302

post #9031 of 10167
Quote:
Originally Posted by CruelInventions View Post

5 years later...
I've seen one-legged turtles move faster than you.
tongue.gif

OUCH!!! But true. I tend to over-think and under execute. I'm a highly motivated procrastinator. tongue.gif

Like all projects, I need the first domino to fall and then I get going, and that's usually cleaning out the gargage so I have room to work....
post #9032 of 10167
I tease, but I'm this side of horrendous on the procrastination scale myself. Reassuring to see someone else with the same malady. redface.gifbiggrin.gif

I only found that because I was doing a search on AVS for wicker and bass traps as I know the subject has come up a few times before. Nothing substantial turned up in the search results in the short time I was seeking the info. A couple members or former members had done something like that, apparently. But without much detail or pictures provided. But again, it was just a quick search so maybe something more substantial would have turned up eventually.
post #9033 of 10167
Did the same search before posting here with little results. My thinking is something along the lines of using a couple or more baskets to build a tower/s with a similar circumference lamp shade & light somewhere in the lower part for ambient lighting. Or using smaller towers as plant holders etc...
I imagine unfinished wicker baskets would be easy to spray paint or stain to match decor and I'm assuming they would be acoustically transparent enough for bass trapping if the weave is not too tight.
post #9034 of 10167
Quote:
Originally Posted by rnrgagne View Post

Did the same search before posting here with little results. My thinking is something along the lines of using a couple or more baskets to build a tower/s with a similar circumference lamp shade & light somewhere in the lower part for ambient lighting. Or using smaller towers as plant holders etc...
I imagine unfinished wicker baskets would be easy to spray paint or stain to match decor and I'm assuming they would be acoustically transparent enough for bass trapping if the weave is not too tight.

I was thinking they might also provide some diffusion for high-frequencies, given the weave?

Mark
post #9035 of 10167
Quote:
Originally Posted by giomania View Post

I was thinking they might also provide some diffusion for high-frequencies, given the weave?
Mark
I am not an acoustician nor did I stay ...

I would think that bass frequencies would pass through wicker while some, minor, diffusion of HF would occur. But I'd further think that the latter would be so slight as to be insignificant. Here's a test. find a wicker waste basket, put it over your head and listen to some music. What do you hear and what don't you hear?

And we want pictures of you doing the test! wink.gif

Jeff
post #9036 of 10167
I hear my wife laughing! Not sure what frequency that is, I want to say.... "often"? tongue.gif

All kidding aside, it seems like a simple but effective idea.
post #9037 of 10167
Quote:
Originally Posted by pepar View Post

I am not an acoustician nor did I stay ...
I would think that bass frequencies would pass through wicker while some, minor, diffusion of HF would occur. But I'd further think that the latter would be so slight as to be insignificant. Here's a test. find a wicker waste basket, put it over your head and listen to some music. What do you hear and what don't you hear?
And we want pictures of you doing the test! wink.gif
Jeff

Quote:
Originally Posted by rnrgagne View Post

I hear my wife laughing! Not sure what frequency that is, I want to say.... "often"? tongue.gif
All kidding aside, it seems like a simple but effective idea.

Jeff,

I think you are on to something, but to take it to the next level, how about this:

Set up a calibrated microphone at the LP
Place subject wicker basket over the top of the microphone
Play whatever appropriate measurement tones
Measure

Does it sound like I am a basket-case? On second thought, don't answer that...tongue.gif

Mark
post #9038 of 10167
Quote:
Originally Posted by giomania View Post

Jeff,
I think you are on to something, but to take it to the next level, how about this:
Set up a calibrated microphone at the LP
Place subject wicker basket over the top of the microphone
Play whatever appropriate measurement tones
Measure

Well, if a test for "acoustically transparent" is to blow through cloth, wouldn't it make sense that hearing through wicker would also be valid?

Back to the humor/humour of some aspects of audionerditis, Youtube video of this test would be precious. I bet it could go viral!

Jeff
post #9039 of 10167
I have a question about ceiling reflections and the use of fiberglass insulation batting. Recently I replaced some of the drop ceiling tiles in my home theater with framed black cloth tiles. The cloth is acoustically transparant and the batting above is being used as absorber. My question is the batting has the thin plastic covering which helps make it less messing. How critical to remove that to get the high freq absorption. I do not have measuring equipment but when I hold a piece of the thin plastic covering over my speaker it only attenuates the very highest freq. Does that probably mean thos freq are being reflected? I dread removing that platic because it is so messy. I hate going up into that ceiling at all but I will if it is going to make a big difference.
post #9040 of 10167
I'm pretty sure you don't want the highs bouncing around up there and then re-entering your room.
post #9041 of 10167
I was afraid you were going to say that. I really appreciate the feedback, now where did I leave my hazmat suit?mad.gif
post #9042 of 10167
Quote:
Originally Posted by lbrown105 View Post

I was afraid you were going to say that. I really appreciate the feedback, now where did I leave my hazmat suit?mad.gif
Tell me, do the hazmat suits there have cheese heads?
post #9043 of 10167
no but they should because cheese heads usually have a beer holder with a straw for hands free enloyment of ones beverage and I could have used that while working on the ceiling tonite. Anyway I was able to take some extra acoustimac absorption material I had and get it place between the ceiling tiles and the plastic covered insulation. problem solved room sounds good thanks for the advice:D
post #9044 of 10167
Quote:
Originally Posted by lbrown105 View Post

no but they should because cheese heads usually have a beer holder with a straw for hands free enloyment of ones beverage and I could have used that while working on the ceiling tonite. Anyway I was able to take some extra acoustimac absorption material I had and get it place between the ceiling tiles and the plastic covered insulation. problem solved room sounds good thanks for the advice:D
Excellent!
post #9045 of 10167
I am planning to make absorption panels 5 to 6 of 4inch Owen corning 703 with 2 inch gap. I will wrap in 4oz polyester batting and put stretch velvet cloth. Appreciate any feedback. I am hoping that it would absorb high frequency reflections and do some bass traps.
post #9046 of 10167
I am at loss of understanding why some speaker manufactures suggest sometimes 10-12 inches of space between the front LCR's and the back of a Stewart Microperf screens, while some well-known speaker mfg say its not necessary except for an inch or two. And How do the cinemasonic processors Stewart provides work or take into account the distance the speakers are from the back side of the screen?
post #9047 of 10167
I think it's because perfed screens can be afflicted with comb-filtering (from some of the sound bouncing off the rear of the screen and interacting with the direct sound. Some then will bounce off the face of the speaker and interact with the sound that just bounced off off the screen. When I had a perfed screen, I made and applied a mask to reduce/eliminate that. It is imperative that the entire cavity behind the screen be properly treated and the "bouncing" sound can be between the wall and the screen rear. Woven screens don't seem to have a problem with comb-filtering.

My understanding of the Stewart processor is that is merely lifts the higher frequencies to compensate for the loss due to the perfed screen. But no EQ, not even the Stewart one can correct comb-filtering.

The newer generation of Stewart screens Microperf2 have smaller holes and more of them to allow more sound to pass. But the effect is still present. Personally, I would never own anything but a woven screen.

Jeff
post #9048 of 10167
There are two recommendations you'll find ... one from StewartFilmscreen and the other you MAY find from a speaker manufacturer. If a speaker manufacturer is suggesting a value different Stewart, ask for their internal test results.

The processor provided by Stewart (at no additional cost) is designed to compensate for the High Frequency roll off which occurs when speakers are placed behind their screen. Please note, placing anything in front of a speaker will result in varying amounts of HF roll off...including air...which is a significant problem with long throw distances in home theaters.

Further, any screen, woven or otherwise, will reflect sound energy off the back of the screen. These back reflections must be "terminated" (usually with absorptive treatments behind the screen). While there is a bunch of unsubstantiated arm waving about comb filtering from Stewart MicroPerf screens (usually from manufacturers of competing products). Tests by accredited organizations poo-poo this suggestion.
post #9049 of 10167
Wouldn't something like Audyssey perform the same, or similar compensation for the HF rolloff?
post #9050 of 10167
Dennis - do you have links to those "accredited organizations" and their reports?

I know that in my theater, going from a Stewart Microperf screen to a woven design noticeably improved my sound. Everyone can take that or not.

As I understand it, while the Microperf2 holes are very small, "non-screen" parts of a woven screen are a lot smaller with a lot more of them. Essentially, there is more open area for sound to pass. More sound passes, less is reflected. And of course, back reflections need to be terminated. I never implied that there were no reflections and the cavity behind a woven screen did not need treating.

Jeff
Edited by pepar - 8/20/12 at 8:41am
post #9051 of 10167
Quote:
Originally Posted by au-734 View Post

Wouldn't something like Audyssey perform the same, or similar compensation for the HF rolloff?
Yes.
post #9052 of 10167
Quote:
I know that in my theater, going from a Stewart Microperf screen to a woven design noticeably improved my sound.
That would be a matter of proper calibration. The sound will change but for better or worse will vary from room to room.
Also...the more air which moves through the screen, the less the light gets reflected back to the seating area (there's your compromise) and the other down side could be the available screen coatings and reflectivity characteristics of the screen coatings available from woven vs Stewart screen materials.

Audyssey may or may not address the HF roll off. Audyssey is going to look at the total HF spectra at the seating location(s) and make some adjustments; however, like all automagic systems, they are very conservative in that area so they don't end up boosting the HF domain to the extent your drivers get overheated and damaged. Just saying.
post #9053 of 10167
So I was told to post this here to get the best responses.

I tried searching for tips on how and why this is done but couldn't find much of anything, not sure if I am not using the right terminology or what to find what I am looking for. I have read some stuff about splayed walls (going the length of the room) and I may consider that but I was in an auditorium today where the side walls were angled / slanted inwards. I assume this was done for acoustically reasons... I am not sure what this 'architectural' technique is called but wondering if there is anyone that has any experience in this area that can give any advice like how helpful it is with acoustics, what angle(s) need to be used to be effective, etc. I guess this could be considered a splayed wall but it goes from the ceiling to the floor. I read that with splayed walls you would want a 6 degree angle on each wall to get the acoustic benefit. It seems that it would be fairly easy to do by having the top plate of your framing moved inwards in the room (not being directly plumb above the bottom plate) and possibly mitering the top and bottom stud to fit the angle.

Made a quick sketch to display visually what I am talking about:



The top pic is just a normal room with 180 degree vertical walls with columns and a soffit. The bottom pic has the angled walls and where you can see the columns not protrude out of the wall as much because the wall is slanted in as you go up to the ceiling.

Rob
post #9054 of 10167
Quote:
Originally Posted by Dennis Erskine View Post

That would be a matter of proper calibration. The sound will change but for better or worse will vary from room to room.
Sure, there was nothing scientific about my experience. And I might have heard an improvement because I expected to.
Quote:
Also...the more air which moves through the screen, the less the light gets reflected back to the seating area (there's your compromise) and the other down side could be the available screen coatings and reflectivity characteristics of the screen coatings available from woven vs Stewart screen materials.
Yup, upsides and downsides to both. Gain is limited with woven, though I *think* the latest generation has improved on that aspect.
post #9055 of 10167
Quote:
Originally Posted by au-734 View Post

Wouldn't something like Audyssey perform the same, or similar compensation for the HF rolloff?

Audyssey typically rolls off the high end anyways, so with a good woven you might lose 0.5-1.0db in the last upper ocatave.  Audyssey's target is even more rolled off than that so you wouldn't see any boost by Audyssey as a result of the screen itself.  Unless you turn off Dynamic EQ that is....

post #9056 of 10167
Quote:
Originally Posted by NicksHitachi View Post

Audyssey typically rolls off the high end anyways, so with a good woven you might lose 0.5-1.0db in the last upper ocatave.  Audyssey's target is even more rolled off than that so you wouldn't see any boost by Audyssey as a result of the screen itself.  Unless you turn off Dynamic EQ that is....

That's probably true. MultEQ begins rolling off at 10k and bends the slope more, I believe, at 16K. DEQ only boosts highs and lows when the MV is below reference, so while the highs may be "relatively" boosted, highly unlikely that the tweets are being stressed.

Jeff
post #9057 of 10167
Quote:
Originally Posted by NicksHitachi View Post

Audyssey typically rolls off the high end anyways, so with a good woven you might lose 0.5-1.0db in the last upper ocatave. 

 

Quote:
Originally Posted by pepar View Post

That's probably true. MultEQ begins rolling off at 10k and bends the slope more, I believe, at 16K. 

It depends on the version of MultEQ that you have.  Some offer a flat response option.

post #9058 of 10167
From reading the white papers on Microperf from Stewart. To obtain the best acoustical transparency of a Microperf screen, the loudspeaker (all loudspeakers regardless of brand, assuming all direct radiating) should be placed a minimum of 12" away from the back of the perforated screen and the active Cinemasonic processors should always be used to restore the 10k -20khz attenuation. This method has been studied and proven by THX labs to ensure the best acoustical transparency. I am totally ok following this method, which solves my acoustical concerns, and allows me to enjoy the far superior visual performance of a Stewart screen over a woven screen. Which having seen both side by side, I do not feel woven looks as good (I understand this is my personal opinion)

However, my concern is when the design of the room does NOT allow for 12" of space behind the screen and say your limited to 1 or 2 inches and your set on staying with Stewart Microperf. What is the expected comb filtering effects and what solutions are there to correct it. It would be nice to see the data that THX did that ultimately convinced them to set the minimum at 12". I would like to see the data that shows audio performance when they set the same speaker at 1" from the screen. (I am sure that exist somewhere). Or I can take the data some of the woven screen manufactures use to show the attenuation of perfed screens in their marketing literature, as they seem to never test the speaker at 12" usually its 4 inches or less, and use it to get some idea. I guess at that point the SIMPLIEST solution is to remove the Cinemasonic processors (which are designed to work at 12") and rely on the Audyssey to correct, as best possible. Or a more advanced approach to break out the Goldline and try to manually adjust those frequencies as best you can. I don't know.

As much as I respect Triad, I have been told by them to disregard the 12" of distance on Stewart Microperf, that is perfectly ok to be 2-3 inches from the screen. How can that be? For now, I will default to Stewarts recommendation's in all case where I can permit 12", but remain curious.
post #9059 of 10167
Quote:
Originally Posted by Kal Rubinson View Post

It depends on the version of MultEQ that you have.  Some offer a flat response option.
Kal, I don't think Audyssey Flat is ... flat. It just doesn't apply the same degree of slope needed to hit their home theater interpretation of the X-Curve (or whatever it's called).

Or am I wrong on that?

Jeff
post #9060 of 10167
Quote:
Originally Posted by Kal Rubinson View Post

Quote:
Originally Posted by NicksHitachi View Post

Audyssey typically rolls off the high end anyways, so with a good woven you might lose 0.5-1.0db in the last upper ocatave. 

 

Quote:
Originally Posted by pepar View Post

That's probably true. MultEQ begins rolling off at 10k and bends the slope more, I believe, at 16K. 

It depends on the version of MultEQ that you have.  Some offer a flat response option.

Good Point.  I don't have a "flat" option per say, but if I disengage Dynamic EQ the response goes back to flat(Onkyo).  I leave it on as I can't hear much beyond 15K and I enjoy the house curve it provides.  Additionaly I currently don't use high efficiency mains and those 1" silk domes just aren't capable of 105db explosions at the LP so its probably good that Audyssey does it from a safety and sound quality stand point.

 

Its rolled off considerably, as mentioned by pepar, above 10K way beyond what the screen induces.  I doubt any positive EQ boost/gain on my setup attributable to the AT screen while Dynamic EQ is on, in the frequency range which the woven screen is guilty of attenuation.

 

I can appreciate the concern for those running a "flat" setting.

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