:)

The OP mentioned them, so it seemed like an option. Space, or the lack thereof, is a big factor in the layout in a lot our our home theaters. And 24x24x34 corner traps are humongous.

Oh yeah...I agree with you 100%.

Frank

http://img15.imageshack.us/img15/4798/screenwallopenedup.jpg







Folks, as usual the HT reno is moving s-l-o-w-l-y. Which gives me time to worry and ruminate on my decisions. As I mentioned earlier in this thread the plan is to make this open screen wall into a sound absorber, stuffing the whole thing with acoustic material, behind and around the screen, then covered with a layer of fabric. (Instead of drywalling).

The main thing I want to do is help control bass frequencies given I have to place the speakers pretty close to this wall - about 14 inches to the back of the speaker and somewhat in the corners. We will be having a large "bass trap" put over-top the screen.

My question is: Is it worth it filling the screen wall this way? Will it really help out much, in terms of controlling sound/bass absorption? The whole thing would be easier to drywall if it's not going to do much for me acoustically. FWIW there will be curtains and 5 hanging velvet fabric panels
in each of the screen wall corners behind the speakers (don't know how much that would help things). Also, if I instead drywalled this wall there's a little room between the side edges of the screen and the side walls. I'd have room to place 9" wide, 7 foot tall, 3" deep absorption material between the side ends of the screen and the side walls, if that might help things.

Advice? Opinions?

Thanks.

Is it worth it filling the screen wall this way?

Yes, but with only a few inches depth you'll want to use rigid fiberglass rather than the typical fluffy type.

--Ethan

I'm experimenting with acoustics in an unusual shaped room. In terms of acoustics issues, does anyone have an idea how the meeting of two walls at 135 degrees compares to 90 degrees, especially at the ceiling (90 degrees there)? Is it likely to be worth trapping the 8' length of the wall interface? Or maybe just the ceiling corner? The room has 2 90 degree corners, 2 135 degree corners (and one missing corner that is open to a hall).

Thanks!
Gerry

Yes, but with only a few inches depth you'll want to use rigid fiberglass rather than the typical fluffy type.

--Ethan

Thanks Ethan. Looks like we have about 3 1/2" depth for filling in that wall. Do you suggest just stacking fibreglass boards solid, or do we need any space in between each board?

Solid, no space.

does anyone have an idea how the meeting of two walls at 135 degrees compares to 90 degrees

A corner is a corner, so that's still a great place for bass traps.

Is it likely to be worth trapping the 8' length of the wall interface?

The more total corner surface you treat, the better. Always.

--Ethan

The room has 2 90 degree corners, 2 135 degree corners (and one missing corner that is open to a hall).

So the room is 5-sided, with one missing corner? If so, do as Ethan says. I am curious. Can you give the dimensions of the walls and also the corner angle which has the open hall? I may do a quick 2-D finite element analysis to identify the room modes, just for the heck of it.

- Terry

Solid, no space.

Much obliged, that helps a lot.

Rich

Oh man, another quick issue has just arisen:

Whether to order some black velvet "backed" or "un-backed" for acoustic reasons.

On either side of my screen I'll have hanging velvet panels, on automated roller panels, which will open and close to reveal the screen (and do various AR widths masking).

So I'll have Five 18" wide by 7 foot tall hanging velvet panels in a stacked-behind-each-other position on either side of the screen. (I figure this may serendipitously help out the acoustics of the speakers in front of them, perhaps a tiny bit).

Anyway, behind those velvet panels is the screen wall which, as discussed above, I'll be filling with 3 1/2" of fibre-board, covered with fabric, for acoustic treatment.

So the question is: I believe the black velvet can be ordered either "backed" (which would help it adhere on to surfaces, as I'll be doing around the screen wall), or "un-backed" which is typically how you want to order fabric that you want sound to pass through.

Do you think it would matter in this case if all the velvet is backed? Would that create a barrier between the back of the side speakers and the acoustic material on the other side of the velvet panels, nullifying some of the effect of the acoustic treatment? Or is the backing a negligible effect in this case?

Thanks.

So the room is 5-sided, with one missing corner? If so, do as Ethan says. I am curious. Can you give the dimensions of the walls and also the corner angle which has the open hall? I may do a quick 2-D finite element analysis to identify the room modes, just for the heck of it.

- Terry

Here is a quick drawing of the room size. I haven't measured the angles, but by the sizes of the walls (and a little geometry) they should be very close to 135 degrees.

I did do some tests with REW and found that the room starts to clean up nicely with trapping (and Audyssey MultEQ also works quite well). The nodes are very position dependent, however.

Thanks!
Gerry

Guys, I just want to make sure that I am on the right track.

1" Linacoustic RC on lower side walls about 42" from ground , the whole back wall and side wall next the front wall.

1 1/2" Acoustaboard Black Acoustic Tiles by Certainteed on the top portion of the wall and some on the front ceiling.

4" bass traps in each corner.

Is this correct?

Thanks Taz

Guys, I just want to make sure that I am on the right track.

1" Linacoustic RC on lower side walls about 42" from ground , the whole back wall and side wall next the front wall.

1 1/2" Acoustaboard Black Acoustic Tiles by Certainteed on the top portion of the wall and some on the front ceiling.

4" bass traps in each corner.

Is this correct?

Thanks Taz


The experts here are going to tell you that all of that is too much absorbtion and may tend to make the room dead sounding, just find primary reflection points and treat those areas

Do you think it would matter in this case if all the velvet is backed?

Having a backing is okay for corner bass traps, but probably not for absorbers at reflection points.

--Ethan

So, I treat the primary reflection areas on ceiling and walls. Do I use 703 3" or 2" boards with GOM?

Do I need to do anything with lower part the walls?

What do I use to treat the area behind the false wall?


Thank you for all the Help.:)

Here is the link to my HT build.

http://www.avsforum.com/avs-vb/showthread.php?t=1148971

Super...thanks Ethan.

Having a backing is okay for corner bass traps, but probably not for absorbers at reflection points.

--Ethan

why is backed velvet ok to use for corner bass traps if air has a hard time going through it?

So, I treat the primary reflection areas on ceiling and walls. Do I use 703 3" or 2" boards with GOM?

Sure.

Do I need to do anything with lower part the walls?

What matters most is ear level, and a few feet above and below.

--Ethan

why is backed velvet ok to use for corner bass traps if air has a hard time going through it?

Because the backing serves as a sort of membrane that increases LF absorption. More here:

Density Report (http://www.ethanwiner.com/density.html)

--Ethan

Because the backing serves as a sort of membrane that increases LF absorption. More here:

Density Report (http://www.ethanwiner.com/density.html)

--Ethan

So the backed velvet would actually make my superchunk corner traps absorb better than using gom?? That is nice to know, velvet looks so much better.

Thank you Ethan. :)

I called a local HVAC supply company and they carry JM 800 duct board and OC 1400. I don't see them on Bobgold site:

http://www.bobgolds.com/AbsorptionCoefficients.htm I do see 814 as comparable to OC 703.

I did find these specs. on 800. Will these work for the first reflections and maybe double them for Bass traps?

http://www.jm.com/insulation/performance_materials/products/ahs334_matfaced_microaire.pdf

http://www.owenscorning.com/quietzone/pdfs/QZDuct_DataSheet.pdf


125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
0.17 0.86 1.14 1.07 1.02 0.98 1.00 -OC 703

0.17 0.63 1.10 1.05 1.04 1.06 0.95 -JM 800 type

0.14 0.72 1.15 1.12 1.06 1.07 1.00 -OC 1400

They seem very close to OC 703.

EI-800 duct board is a heavy duty product with a density in the range 3pcf-6pcf. The EI rating for fiberglass board is a measure of flexural stiffness. You can substitute this for OC 703 or 705.

- Terry

Thank you Terry.

I just found out that I need an account with the company that sells the OC 1400. However, its good to know that I am able to use IE 800 and I don't need an account with that company.:)

http://img15.imageshack.us/img15/4798/screenwallopenedup.jpg



Ugh.

Well I finally got the quote from a company to do the acoustic treatment of this screen wall - that is filling it with acoustic absorption, then covered with fabric and hanging my screen.

A bit over $4,000!

I'm thinkin' my bank account can only handle so much and that's too much to add at this point.

Does anyone think I lose much if I just drywall the screen wall instead? (It would certainly be less of a headache to do so; I'm just not sure how much
benefit I'd lose if I did that over making the wall absorptive...the room will have lots of absorptive surfaces throughout - thick shag rug, massive stuffed sectional sofa, lots of velvet curtain etc).

(I suppose another route perhaps I could get my contractor, the one doing the rest of the work in the room, to fill it with some sort of absorption and essentially "do it ourselves."...??)

Ugh.

Well I finally got the quote from a company to do the acoustic treatment of this screen wall - that is filling it with acoustic absorption, then covered with fabric and hanging my screen.

A bit over $4,000!

I'm thinkin' my bank account can only handle so much and that's too much to add at this point.

Does anyone think I lose much if I just drywall the screen wall instead? (It would certainly be less of a headache to do so; I'm just not sure how much
benefit I'd lose if I did that over making the wall absorptive...the room will have lots of absorptive surfaces throughout - thick shag rug, massive stuffed sectional sofa, lots of velvet curtain etc).

(I suppose another route perhaps I could get my contractor, the one doing the rest of the work in the room, to fill it with some sort of absorption and essentially "do it ourselves."...??)


WOW! $4K. Someone correct me if I am wrong, but if it just have screen wall, couldn't you just stuff it with R-11 put the drywall on. Put Linc. RC or 2" OC 703 or a similer product on the wall and make a 2x4 frame for the screen to go on?

the price for JM 800. $58.70 for 48" X 120" x2".

I think all you can do - at a reasonable price - is to stuff the cavities with fiberglass and look into something to provide some de-coupling between the studs and the drywall you are about to install. Of course, the "reasonable price" thingy only happens - as you might have guessed now - if you do it yourself, at least on the fiberglass stuffing part.

I'm a bit confused here.

You guys are talking about both stuffing the screen wall AND doing drywall.

I thought putting on the drywall defeats the purpose of what we were trying to do.
That is, make the screen wall a big "trap" or acoustic absorber to help tame base frequencies in the room, especially behind the L/C/R speakers. I was led to believe that
putting a layer of drywall over the acoustic material would be self-defeating, since it would tend to put a barrier between the acoustic absorption material and the sound it is supposed to absorb. Which is why when you make acoustic panels you surround them with fabric, not some hard substance like drywall or wood.

So I'm unclear about how you think I'd combine drywalling the screen wall, while simultaneously achieving the goal of making it an acoustic absorber. I thought that to make the screen wall act, in essence, like a giant acoustic panel I'd be covering it in fabric, not drywall.

(I'll have a big bass trap on the ceiling above the screen, and could put one near the back of the room hidden in the ceiling treatment as well. I don't know if that will be good enough that I could just forgo trying to make the screen wall an absorber as well).
??

Yeah I thought drywall wasn't very transmissive for sound?

I'm a bit confused here.
Maybe me, too. :o

You guys are talking about both stuffing the screen wall AND doing drywall.

I thought putting on the drywall defeats the purpose of what we were trying to do.
That is, make the screen wall a big "trap" or acoustic absorber to help tame base frequencies in the room, especially behind the L/C/R speakers. I was led to believe that
putting a layer of drywall over the acoustic material would be self-defeating, since it would tend to put a barrier between the acoustic absorption material and the sound it is supposed to absorb. Which is why when you make acoustic panels you surround them with fabric, not some hard substance like drywall or wood.

So I'm unclear about how you think I'd combine drywalling the screen wall, while simultaneously achieving the goal of making it an acoustic absorber. I thought that to make the screen wall act, in essence, like a giant acoustic panel I'd be covering it in fabric, not drywall.

(I'll have a big bass trap on the ceiling above the screen, and could put one near the back of the room hidden in the ceiling treatment as well. I don't know if that will be good enough that I could just forgo trying to make the screen wall an absorber as well).
??
My apologies if I missed/forgot where you were not going to drywall and only stuff. I thought acoustical isolation was your only goal. In that case, I would not only place 'glass between the studs, but probably extend the 'glass several inches *beyond* the plane of the wall studs. The thicker it is, the lower the absorption will extend. This will also provide acoustical isolation by reducing/preventing the lows from getting to the studs to be transmitted to the floor above.

I have been following this thread for awhile, and am finally getting around to planning the installation of room treatments. I have taken in a lot of information from this thread, so many thanks to all the contributors. I have a few questions before I finalize the plan and obtain the material. My dedicated theater is 27'-3" x 19'-8" x 7'-6.5" and is finished in drywall.

My basic plan was to build a false wall approximately 18"-24" out from the front wall and place SSC bass traps in the front vertical and horizontal corners. I would cover the remainder of the front wall with 2" JM814, and would also use this for the SSC bass traps. JM 814 (2") is what they have in stock at my local SPI store.

I would re-hang my non-perforated screen on the false wall, and cover the remainder of the false wall with GOM FR701. The L/C/R speakers would sit in front of the false wall, as I have plenty of room. I could place the L/R speakers behind the false wall, but it is not a requirement. Due to accessibility requirements on the right side of the front wall, the false wall would not cover the entire 19'-8" length. The false wall would stop short about 3'-4' on each side, and I would hang curtains between the end of the false wall and the side wall.

I would also buy enough 2" JM814 to make side wall and ceiling FRP panels.

So, here are my questions:

1) For the SSC bass traps, I was thinking to make them all the 24" x 24" x 34" triangles, but would I be better off with some of the 17" x 17" x 24" triangles?

2) Should any of the SSC bass traps have FRK / FSK on the face?

3) Are the curtains OK in front of the SSC bass traps?

4) Do I need to ensure there is a gap between the SSC bass traps and the front wall treatment to eliminate the edge effect?

5) I want to use some material to absorb some of the sound of my projector fan, and would appreciate some recommendations. I cannot build a total enclosure, as I cannot cool it.

Thanks for any help.

Mark

I have been following this thread for awhile, and am finally getting around to planning the installation of room treatments. I have taken in a lot of information from this thread, so many thanks to all the contributors. I have a few questions before I finalize the plan and obtain the material. My dedicated theater is 27'-3" x 19'-8" x 7'-6.5" and is finished in drywall.

My basic plan was to build a false wall approximately 18"-24" out from the front wall and place SSC bass traps in the front vertical and horizontal corners. I would cover the remainder of the front wall with 2" JM814, and would also use this for the SSC bass traps. JM 814 (2") is what they have in stock at my local SPI store.

I would re-hang my non-perforated screen on the false wall, and cover the remainder of the false wall with GOM FR701. The L/C/R speakers would sit in front of the false wall, as I have plenty of room. I could place the L/R speakers behind the false wall, but it is not a requirement. Due to accessibility requirements on the right side of the front wall, the false wall would not cover the entire 19'-8" length. The false wall would stop short about 3'-4' on each side, and I would hang curtains between the end of the false wall and the side wall.

I would also buy enough 2" JM814 to make side wall and ceiling FRP panels.

So, here are my questions:

1) For the SSC bass traps, I was thinking to make them all the 24" x 24" x 34" triangles, but would I be better off with some of the 17" x 17" x 24" triangles?
If you have the space in your room (and your budget) for the biguns, I'd recommend that that's what you use. They will reach lower in what they absorb.

2) Should any of the SSC bass traps have FRK / FSK on the face?
The facing is not necessary/will not improve performance with the SSC design. I think it adds expense.

3) Are the curtains OK in front of the SSC bass traps?
I think so, but an acoustician on this thread should advise if there is any particular material that should be avoided.

4) Do I need to ensure there is a gap between the SSC bass traps and the front wall treatment to eliminate the edge effect?
No.

I would strongly recommend that you consider an acoustically transparent screen. At the entry-level, DIY stage, Sheerweave 4500 is dirt cheap. Once you have become accustomed to the sound coming from the picture, you will not be able to enjoy the theaters of your friends w/o AT screens.

1) For the SSC bass traps, I was thinking to make them all the 24" x 24" x 34" triangles, but would I be better off with some of the 17" x 17" x 24" triangles?

The bigger, the better to a point. 24"x24"x34" will do a better job down lower, so if they're just as easy to do, go for it.

3) Are the curtains OK in front of the SSC bass traps?

Sure, but theater velour is pretty absorbent in the high end. You won't affect the bass trapping performance at all though.

5) I want to use some material to absorb some of the sound of my projector fan, and would appreciate some recommendations. I cannot build a total enclosure, as I cannot cool it.

I'm not sure what you mean by this. Do you mean that you want the treatment reduce some of the fan noise? If so, then it absolutely won't. One thing has nothing to do with the other. The only way to reduce fan noise is to use the projector on the reduced energy setting or to build an enclosure, which you said you didn't want to do.

Frank

I'm not sure what you mean by this. Do you mean that you want the treatment reduce some of the fan noise? If so, then it absolutely won't. One thing has nothing to do with the other. The only way to reduce fan noise is to use the projector on the reduced energy setting or to build an enclosure, which you said you didn't want to do.

Frank

Frank,

Thanks for the response. The intent is to prevent the sound from coming forward in the room. I was thinking that rigid fiberglass absorbs noise, so would it not reduce the fan noise as well?

Mark

No.

I would strongly recommend that you consider an acoustically transparent screen. At the entry-level, DIY stage, Sheerweave 4500 is dirt cheap. Once you have become accustomed to the sound coming from the picture, you will not be able to enjoy the theaters of your friends w/o AT screens.

Jeff,

Thanks for the response. Was the edge effect regarding the SSC traps actually discussed here? I only recall seeing a passing remark.

For the AT screen, when I upgrade my projector to a Laser DLP:D, I will look into switching the screen. My projector is perfectly Optimized (by William Phelps) to my Stewart StudioTek 130. The center channel is right below the screen, and I have the screen mounted as high as possible.

Mark

Frank,

Thanks for the response. The intent is to prevent the sound from coming forward in the room. I was thinking that rigid fiberglass absorbs noise, so would it not reduce the fan noise as well?

No, not the way you're thinking. You'd need a solid wall, air tight...hence the issue of the enclosure. Acoustic treatment will do nothing to reduce the fan noise because it'll just find a flanking path elsewhere.

Frank

Jeff,

Thanks for the response. Was the edge effect regarding the SSC traps actually discussed here? I only recall seeing a passing remark.

For the AT screen, when I upgrade my projector to a Laser DLP:D, I will look into switching the screen. My projector is perfectly Optimized (by William Phelps) to my Stewart StudioTek 130. The center channel is right below the screen, and I have the screen mounted as high as possible.

Mark
M,

My understanding of edge effect has to do with the edges of speaker cabinets; is there another context? If not, then I don't think the "edge effect" has an . . effect at low frequencies. The chunk traps go tight into the corners. The straddling-sheet-of-fiberglass corner traps must touch the walls. Panels at mid-wall benefit from a gap, but it's not related to the kind of edge effect I just described.

J

Hey all,

I am installing in wall speakers in a basement. I was thinking of using rigid fiberglass (oc type 475) behind the speakers to minimize any hard reflections from the concrete walls. Also, I was going to use the fiberglass to line enclosures for in-ceiling speakers to minimize bleed through in the floor above. Am I doing the right thing or should I do something else? If this is right which way should the foil side face, or should it be peeled off entirely?

Thanks for any help you can offer. I have been researching acoustics, but it is not an easy subject to understand.

No, not the way you're thinking. You'd need a solid wall, air tight...hence the issue of the enclosure. Acoustic treatment will do nothing to reduce the fan noise because it'll just find a flanking path elsewhere.

Frank

I guess my intent was to flank the path of the sound towards the rear of the room. Do you think that would work to reduce the level?

Thanks.

Mark

pepar:

Studiotips superchunks work best isolated. If you have no other treatment in the room, superchunks are perfect.

Putting them up against a bunch of other absorbtion reduces the edge effect boost, but
a) they're still deep absorbtion (good)
b) they're still in corners (all modes active in tri-corners, good)

Jeff, here is the post I saw which generated my "edge effect" question.

Mark

I have a pretty small room, and was going to use some soffit style moulding to hide my wiring.

http://www.invitinghome.com/crown_molding_lighting/molding-for-spot-lighting-sunnyvale.htm

I was wondering, maybe I should make the soffits, so I can bass trap with them. Every soffit I see is pretty big, I'd like to keep it around 5"x5" or. Would that be too small to effectively trap the cieling corners?

Thanks!

Jeff, here is the post I saw which generated my "edge effect" question.

Mark
I don't recall the context, but it might have been wrt the absorption of adjacent treatment, not the SSC traps. The SSC traps I've seen all have some sort of framing that serves to hold them in place, whereas flat panel - "broadband" - absorbers can be mounted without a frame increasing, according to those that argue it, their effectiveness. I don't recall seeing any data on that though; perhaps it is one of those things that are accepted on faith. :) Perhaps Bob is available for comment.

Here is a post (http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=10297&start=15) that might give you more insight.

pepar,

I'm not Bob, but can comment on the "edge effect" for absorbers. While there may be some contribution from exposed edges, there is a significant increase in absorption at edges even if the sides of the absorber are masked off/baffled. This has been studied a lot (the earliest journal paper I have on it is from 1930!), and is due to diffraction effects.

- Terry

pepar,

I'm not Bob, but can comment on the "edge effect" for absorbers. While there may be some contribution from exposed edges, there is a significant increase in absorption at edges even if the sides of the absorber are masked off/baffled. This has been studied a lot (the earliest journal paper I have on it is from 1930!), and is due to diffraction effects.

- Terry

Thanks Terry.

So, to apply this to my original question, would it be OK to "butt" the front wall absorption panels 2" JM 814 right up to the edge of my 34-inch face SSC corner traps, which will also be made from JM 814?

Mark

Thanks Terry.

So, to apply this to my original question, would it be OK to "butt" the front wall absorption panels 2" JM 814 right up to the edge of my 34-inch face SSC corner traps, which will also be made from JM 814?

Mark
By abutting two pieces of JM 814 against each other, you will not get an edge effect from either at this common edge. If you left a gap between them, it would have to be roughly comparable in size to the wavelengths involved. So the performance of both absorbers will be reduced a bit compared to ones which have a good distance between them.

- Terry

pepar,

I'm not Bob, but can comment on the "edge effect" for absorbers. While there may be some contribution from exposed edges, there is a significant increase in absorption at edges even if the sides of the absorber are masked off/baffled. This has been studied a lot (the earliest journal paper I have on it is from 1930!), and is due to diffraction effects.
Hi, Terry. Does the edge effect have an effect on absorption of LF? And the effect that it does have (on any absorber), is it absorptive or diffusive? I ask this because of your use of the word "diffraction."

Hi, Terry. Does the edge effect have an effect on absorption of LF?
Yes, pepar. The edge effect occurs when the dimensions of an absorbent surface become as small as (or smaller than) a wavelength.
And the effect that it does have (on any absorber), is it absorptive or diffusive? I ask this because of your use of the word "diffraction."
It is absorptive. Diffraction in this case refers to the bending of waves toward the absorber. This bending causes the absorber to "capture" extra waves which would otherwise not be in its geometric path. More sound is absorbed near the edges as compared with any other part of the absorber.

- Terry

OH NO; I had just managed to get mind around absorption and diffusion, when diffraction had to come into play :)

Bragg's Angle anyone...??

OH NO; I had just managed to get mind around absorption and diffusion, when diffraction had to come into play :)

Bragg's Angle anyone...??
:D

Sorry, but I don't make the rules. Nature does. :)

- Terry

Are there some pictures of the "edge effect" you are discribing somewhere?

Are there some pictures of the "edge effect" you are discribing somewhere?
Yes, as a matter of fact. With new and fast computer techniques, we can now get numerical solutions and graphical plots for acoustical equations which were previously impractical to compute. Here is a 2005 paper by Yasuhito Kawai and Hiroshige Meotoiwa, "Estimation of the Area Effect of Sound Absorbent Surfaces by Using a Boundary Integral Equation":

http://www.jstage.jst.go.jp/article/ast/26/2/123/_pdf

I don't advise wading through the math. :( Just have a look at Figure 2. The arrows are sound velocity vectors near an absorber (impedance boundary) and hard surface (rigid boundary). Notice how arrows which would have otherwise hit the rigid boundary angle toward the impedance boundary when they get close.

- Terry

I have measured light velour felt (7.5 oz.) from Jo-Ann, and it has no significant attenuation at low frequencies. Jo-Ann burlap is better only at frequencies much higher than the bass region. The latter is transparent enough to be used as speaker grill cloth.

- Terry

Terry I went to Joan fabrics today and found black Royal velvet. The material seems to pass the blow test ok and would love to use it because it sucks up light great and I want to use it to cover my bass traps and highfrequency wall traps but do you think it is suitable to use for what Im trying to do?
Thanks in advance

Terry I went to Joan fabrics today and found black Royal velvet. The material seems to pass the blow test ok and would love to use it because it sucks up light great and I want to use it to cover my bass traps and highfrequency wall traps but do you think it is suitable to use for what Im trying to do?
Thanks in advance
Just fine for bass traps, probably just fine for wideband wall absorption. The blow-through test is amazingly good. If it offers just a little resistance, the fabric most likely blocks just a few dB of the highest frequencies. There are some real dogs of fabrics out there sold for use in acoustical panels. The blow-through test nabs 'em. You can easily feel a lot of resistance to your breath. You can go blue in the face trying to blow through at least one of them. :(

You probably have the advantage (as do most) of not having specific engineering goals for your room besides "make it sound good." :) That gives you a lot of latitude!

- Terry

Just fine for bass traps, probably just fine for wideband wall absorption. The blow-through test is amazingly good. If it offers just a little resistance, the fabric most likely blocks just a few dB of the highest frequencies. There are some real dogs of fabrics out there sold for use in acoustical panels. The blow-through test nabs 'em. You can easily feel a lot of resistance to your breath. You can go blue in the face trying to blow through at least one of them. :(

You probably have the advantage (as do most) of not having specific engineering goals for your room besides "make it sound good." :) That gives you a lot of latitude!

- Terry

On the subject. Are there any decently acoustically transparent fabrics that don't look like burlap?

Thanks,
CJ

Terry I went to Joan fabrics today and found black Royal velvet. The material seems to pass the blow test ok and would love to use it because it sucks up light great and I want to use it to cover my bass traps and highfrequency wall traps but do you think it is suitable to use for what Im trying to do?
Thanks in advance

funlvr1964 thanks for posting. I may have to look into that material this afternoon.




Hi Terry, Do you think I can use the black Royal velvet to cover my false wall or look into GOM or Dazian?

The black Royal velvet may look nice with my velvet AC panels.

Thanks Tas

Yes, as a matter of fact. With new and fast computer techniques, we can now get numerical solutions and graphical plots for acoustical equations which were previously impractical to compute. Here is a 2005 paper by Yasuhito Kawai and Hiroshige Meotoiwa, "Estimation of the Area Effect of Sound Absorbent Surfaces by Using a Boundary Integral Equation":

http://www.jstage.jst.go.jp/article/ast/26/2/123/_pdf

I don't advise wading through the math. :( Just have a look at Figure 2. The arrows are sound velocity vectors near an absorber (impedance boundary) and hard surface (rigid boundary). Notice how arrows which would have otherwise hit the rigid boundary angle toward the impedance boundary when they get close.

- Terry

Just fine for bass traps, probably just fine for wideband wall absorption. The blow-through test is amazingly good. If it offers just a little resistance, the fabric most likely blocks just a few dB of the highest frequencies. There are some real dogs of fabrics out there sold for use in acoustical panels. The blow-through test nabs 'em. You can easily feel a lot of resistance to your breath. You can go blue in the face trying to blow through at least one of them. :(

You probably have the advantage (as do most) of not having specific engineering goals for your room besides "make it sound good." :) That gives you a lot of latitude!

- Terry
Whew. Going forward, I will try to limit my "advice" on this thread to pointing to Bob Gold's charts and where to purchase fiberglass. I clearly know squat about acoustics. :o

Oh...my gawd...I'm going insane.

Every time I think I know what I'm doing I talk to another contractor and come back with more questions.

As written earlier, we have opened up the screen wall, no drywall, just a bare stud wall. We are going to fill it with absorbtive material then staple fabric over the wall, then place the screen on the wall.

The question is: WHAT ABSORPTIVE MATERIAL TO USE?

My contractor suggested Roxul, as he's worked with it before. I looked it up and noticed some people saying it's a bitch to work with, suggesting harder mineral wool boards (e.g. Rockwood) or Fibreglass boards (e.g. OC 73 or a local made equivolent OFI 48).

We just have to get this stuff in between the studs, then cover the whole thing with fabric. What should we use? Which material would be easiest (and perhaps least messy) to work with?

A company that supplies such materials - GlassCell - suggested using SAFB material.

Also suggested putting a lining of linacoustic over whatever we stuff between the studs.

Opinions?

On the subject. Are there any decently acoustically transparent fabrics that don't look like burlap?

Thanks,
CJ
Have a look at Guilford Wilshire 2735. Its acoustical transparency is excellent, as good IMO to be used as speaker grill cloth. Very close behind is Guilford Lido 2858. In the "next tier," marginal for use as speaker grill cloth but still excellent for covering wide band absorbers (and not extremely burlap-looking), are Guilford's Bailey 2299 and Spinel 3582, Acoustimac DMD fabric, and C.F. Stinson Galaxy.

- Terry

Oh...my gawd...I'm going insane.

Every time I think I know what I'm doing I talk to another contractor and come back with more questions.


The answer is simple. Stop listening to contractors, and tell them what you want! :D The advice provided by the members here on acoustically absorptive materials is by and large excellent.

- Terry

Oh...my gawd...I'm going insane.

Every time I think I know what I'm doing I talk to another contractor and come back with more questions.

As written earlier, we have opened up the screen wall, no drywall, just a bare stud wall. We are going to fill it with absorbtive material then staple fabric over the wall, then place the screen on the wall.

The question is: WHAT ABSORPTIVE MATERIAL TO USE?

My contractor suggested Roxul, as he's worked with it before. I looked it up and noticed some people saying it's a bitch to work with, suggesting harder mineral wool boards (e.g. Rockwood) or Fibreglass boards (e.g. OC 73 or a local made equivolent OFI 48).

We just have to get this stuff in between the studs, then cover the whole thing with fabric. What should we use? Which material would be easiest (and perhaps least messy) to work with?

A company that supplies such materials - GlassCell - suggested using SAFB material.

Also suggested putting a lining of linacoustic over whatever we stuff between the studs.

Opinions?

The answer is simple. Stop listening to contractors, and tell them what you want! :D The advice provided by the members here on acoustically absorptive materials is by and large excellent.

- Terry
;) http://www.bobgolds.com/AbsorptionCoefficients.htm

The "3pcf" density spec is what you should look for when you compare. Within materials with that density, see what you can purchase most economically. Here in the US, many of us buy from this company (http://www.spi-co.com/directory.html). You may not want to make a road trip, so I would suggest looking for a similar company in GTO.

In terms of the terminology, HVAC insulation = good, and acoustical insulation = bad. It is all the same, but the appearance of the word "acoustical" adds $$$.

On the subject. Are there any decently acoustically transparent fabrics that don't look like burlap?

Thanks,
CJ

Guilford FR701 doesn't look like burlap.

Frank

Have a look at Guilford Wilshire 2735. Its acoustical transparency is excellent, as good IMO to be used as speaker grill cloth. Very close behind is Guilford Lido 2858. In the "next tier," marginal for use as speaker grill cloth but still excellent for covering wide band absorbers (and not extremely burlap-looking), are Guilford's Bailey 2299 and Spinel 3582, Acoustimac DMD fabric, and C.F. Stinson Galaxy.

- Terry

Great- this is exactly what I need.

Thanks!
CJ

Guilford FR701 doesn't look like burlap.

Frank

LOL- that's actually what I was thinking of when I asked since I didn't like the coarse weave of the 701 :) Maybe it's just because the sample is so small that it doesn't look good to me.

CJ

LOL- that's actually what I was thinking of when I asked since I didn't like the coarse weave of the 701 :) Maybe it's just because the sample is so small that it doesn't look good to me.

CJ
I've had more than one client reject GOM FR701 for the same reason as you. :)

- Terry

My neighbor has 3 boxes of these from his remodel that he will sell me for $30.00 total. I think there is about 30 (2 x 4) tiles.

If i strip the white covering off they leave about 3/4 inch of fiberglass. I was wondering if I double them up to 1.5 inch if the will serve the same purpose to treat the bottom half of my walls or front wall if I triple stack them?

http://img.hisupplier.com/var/userImages/old/czbyjc/czbyjc$615144713.jpg

Actually ... remove the backing on one tile only.

Your layers would be fiberglass, vinyl, fiberglass.

Dennis I am assuming that he should follow the same advice that was given to me here by known audio engineers which is to NOT treat the bottom half of the wall around the room because it makes the room sound too dead. Where did all of this get started from anyway, I read it all the time where people want to treat the bottom half of the rooms up to ear level and batting above ear level only to be told that thats incorrect. For something to be so accepted on such a widespread level someone of some assumed authority on the matter must have dictated it to be so.

I know exactly where that came from. Among the effects of that is to reduce overall reverberation time of the space while not killing the reflections which create envelopment and width of the sound stage. Now, if you want to get into diffusion, we have a different animal. The real challenging part here is to come up with a "rule" which works in all rooms ... and there ain't no such animal. Treating the bottom portion of the room doesn't, of itself, make the room too dead. It depends on (1) what you treat the bottom of the walls with and (b) what did you do to the rest of the walls?

This is also a geometry lesson ... what's the height of the speakers with respect to the ears and room treatments (these are small rooms ... geometry becomes seriously important.

I have a relatively small room at 12 x 18 and I would think you would want it more "dead" then not. The top half of the wall will be treated at first reflection points that I will have to determine when I get that far. My tweater height after stage is built will be roughly 40-41" on a stage.

Dennis, does leaving the vinyl on (sandwiched) help to not deaden the room as much?

It lowers the frequencies the absorber will be effective on.

Hi I'm new to this thread and I have a small project that I'd like to do right.

I have a pass through above my media center, and it passes thru to a den type room behind it. The base of the pass thru is a 10" sophet shelf that is about 3' deep to the other room. I'd like to seal this space until the time I can afford to build a new media wall. the 3' depth I'd like to split as to make a pot shelf onthe other side for the wifes things. I only need enough space for the center channel to reside. The opening is 11' W x 3' H.

Is there a link to a thread to show me the best way to do this, framing, insulation, sheet rock, glues or adhesives, absorbtion material etc.. The room is an open floor plan opening to a nook, kitchen and entry hall.. I'd like to keep it very simple as the media cenetr that holds the TV and the speakers R/L is solid and broken up fairly well with open storeage of DVD and AV equipment. My plan was to frame it, R13 insulation, sheet rock (maybe two layer on theater side), but didn't decide on finishing..

Any advice? Thanks..

-fab5valentine

I'm still trying to make sure that the idea of leaving our screen wall unfinished (not drywalled) and filling it with acoustic absorption material will be "to Code" in my area.

If it's not: What if I fill the wall with Roxul or OC 73 or whatever, and then drywall over it? Will this entirely negate the effects of the Roxul/OC 73 for absorbing bass frequencies?

While I'm at it: I've also got a drop ceiling of about 6" depth. It will be covered in stretched felt fabric (which has some acoustic transparency; I can blow through it).
Ideally I don't want the whole thing filled with absorption because I don't want a dead sounding room. So I like the idea of putting some diffusion up there. But if the diffusion (e.g. wood slats or some commercial diffusion panels) ends up beneath the felt ceiling material, does that defeat the diffusion effects? Or will the diffusion still occur even with the diffusers placed behind the felt?

Gotta make my decision within one or two days...

Thanks.

Hey Guys; My HT room is "acoustically challenged" the bass is relatively flat and the overall sound is just too punchy... the highs are too high and I can do a simple "clap"test and it echoes. I have done e/thing in terms of processor settings- sub and audusey; in the end it is my room. The pics show (hopefully) my front stage... it is the Aperion 6T's... please notice my screen is mounted on the wall and to either side of the screen are cutouts.. directly below screen is my center and sub are both behind the wall (cutouts). The room itself is 13 wide by 19 deep- so space is at a premium. I was thinking acoustic panels at the reflection points and possibly Tri Traps behind my towers... so; am I missing anything here? I am confused by ALL the choices in terms of acoustics and given the cost of these things I want to do it right. I appreciate any ideas or feedback. Thxs in advance! Apologize for my camera skills- hopefully the pics show ok.

How important is it that I put a bass trap in a corner as a triangle? I can do that. But my projection booth extends out into the theater by 1 foot, creating a 5' by 1' alcove between it and the rear sidewall that I could completely fill with OC 703. Would this be more effective than a triangular trap?

Folks,

As mentioned I'm having my dropped ceiling covered in felt fabric. I have about 6" depth in which to place possible acoustic material. But I don't want to just fill it with absorption (over-damp). So I'm curious if some diffusion products will do any good if placed on the ceiling, behind the felt. I found these, MiniFusor Sound Diffusor from auralex:

http://www.auralex.com/sound_diffusor_minifusor/sound_diffusor_minifusor.asp

If I put a bunch on the ceiling behind the felt, would they still be of any use in doing some diffusion to help the room?

Thanks,

How important is it that I put a bass trap in a corner as a triangle? I can do that. But my projection booth extends out into the theater by 1 foot, creating a 5' by 1' alcove between it and the rear sidewall that I could completely fill with OC 703. Would this be more effective than a triangular trap?

I don't know about "more effective" but yes it would be effective.

Folks,

As mentioned I'm having my dropped ceiling covered in felt fabric. I have about 6" depth in which to place possible acoustic material. But I don't want to just fill it with absorption (over-damp). So I'm curious if some diffusion products will do any good if placed on the ceiling, behind the felt. I found these, MiniFusor Sound Diffusor from auralex:

http://www.auralex.com/sound_diffusor_minifusor/sound_diffusor_minifusor.asp

If I put a bunch on the ceiling behind the felt, would they still be of any use in doing some diffusion to help the room?

Thanks,

Can you blow through (breath through) the felt? If so, chances are good the high frequency sound can get through, and diffusion behind will be helpful, depending on the location and amount and the room.

I'm not sure whether the auralex product is the best one.

It has always impressed me that diffusion products are so much more expensive than absorption products, and that there is so much less scientific data about which are the most effective, and that there are so few DIY approaches.

Be careful when covering a diffuser with fabric. If it is a Schroeder type diffuser (anything which has fixed or variable well depths and flat, non-angled surfaces), you may have a problem. Such diffusers are very sensitive to restrictions in air flow near their front surface. Give them some depth (at least a few inches) behind fabric. Even very acoustically transparent fabric can add enough acoustical resistivity to make them less effective.

With old-fashioned curved diffusers (like the Auralex MiniFusor), there are no issues.

- Terry

Guys,

I bought the JM 800MF (48"X120") duct boards and one side has the matt black finish. It almost feels like fabric and the other side has the aluminum finish. Am I able to keep just the matt black with out loosing the absorptive properities? I will be making the 24" X48" panels and use the rest for the front wall.

In the pic you can see front of one board and the back of the other board.

http://i138.photobucket.com/albums/q244/tasameena/JM800.jpg

Thanks Tas

Nathan and Terry, thank you very much!

Rich

Thanks Terry.

So, to apply this to my original question, would it be OK to "butt" the front wall absorption panels 2" JM 814 right up to the edge of my 34-inch face SSC corner traps, which will also be made from JM 814?

Mark

By abutting two pieces of JM 814 against each other, you will not get an edge effect from either at this common edge. If you left a gap between them, it would have to be roughly comparable in size to the wavelengths involved. So the performance of both absorbers will be reduced a bit compared to ones which have a good distance between them.

- Terry

Hi, Terry. Does the edge effect have an effect on absorption of LF? And the effect that it does have (on any absorber), is it absorptive or diffusive? I ask this because of your use of the word "diffraction."

Yes, pepar. The edge effect occurs when the dimensions of an absorbent surface become as small as (or smaller than) a wavelength.

It is absorptive. Diffraction in this case refers to the bending of waves toward the absorber. This bending causes the absorber to "capture" extra waves which would otherwise not be in its geometric path. More sound is absorbed near the edges as compared with any other part of the absorber.

- Terry

Terry,

Would you please tell me how far the gap between the edge of the 34-inch face SSC corner traps made with JM814 and the 2" JM 814 panels covering the remainder of the front wall should be?

Thanks.

Mark

Terry,

Would you please tell me how far the gap between the edge of the 34-inch face SSC corner traps made with JM814 and the 2" JM 814 panels covering the remainder of the front wall should be?

Thanks.

Mark
For optimal performance, the gap should be on the order of the width of an absorber. But this does not seem to be possible in your situation. So you might as well just abut them. I don't think adding a couple of inches would make a difference.

Note that the absorbers will still work just fine. They just won't be "all that they can be." :)

- Terry

How important is it that I put a bass trap in a corner as a triangle? I can do that. But my projection booth extends out into the theater by 1 foot, creating a 5' by 1' alcove between it and the rear sidewall that I could completely fill with OC 703. Would this be more effective than a triangular trap?

Thanks for answering Nathan. But let me ask this another way. Would a 2' wide triangular corner bass trap be less effective than filling the 5' by 1' alcove? Which should I do?

Thanks for answering Nathan. But let me ask this another way. Would a 2' wide triangular corner bass trap be less effective than filling the 5' by 1' alcove? Which should I do?

Sorry, the math to compare the two is way beyond me.

I know that either of your options would be beneficial.

And I know that doing both TOGETHER would be even better. So if you have that option, I recommend doing both.

Terry, is there any edge effect on a triangular SSC-style bass trap?

Terry, is there any edge effect on a triangular SSC-style bass trap?
Sure. That is what likely makes a big corner absorber so good in the 80-100 Hz range:

http://forum.studiotips.com/download/file.php?id=5191
Link: http://forum.studiotips.com/viewtopic.php?f=8&t=536

It's not any kind of panel or membrane resonance, because these bass traps don't have any such coverings.

I've never seen a mathematical analysis of a corner bass trap. This is on my "to do" list -- for 2020. :D

- Terry

Sure. That is what likely makes a big corner absorber so good in the 80-100 Hz range
I only ask because there does not seem to be an edge, per se. The edges that are there taper effectively to zero.

I only ask because there does not seem to be an edge, per se. The edges that are there taper effectively to zero.
Ah. You see, the edges are at the boundary between absorber and the perpendicular hard wall surfaces. The fact that they have no thickness (no exposed sides) doesn't matter. The "pure" edge effect does not depend at all on having the sides of the absorber exposed. It is a wave diffraction effect created by the sudden impedance change between absorber and wall.

- Terry

Ah. You see, the edges are at the boundary between absorber and the perpendicular hard wall surfaces. The fact that they have no thickness (no exposed sides) doesn't matter. The "pure" edge effect does not depend at all on having the sides of the absorber exposed. It is a wave diffraction effect created by the sudden impedance change between absorber and wall.

- Terry

I've read that the corner absorber is more effective in some way if suspended out about 4" from the wall. I guess that's changing the boundary characteristics somehow.

For optimal performance, the gap should be on the order of the width of an absorber. But this does not seem to be possible in your situation. So you might as well just abut them. I don't think adding a couple of inches would make a difference.

Note that the absorbers will still work just fine. They just won't be "all that they can be." :)

- Terry

Terry,

I have 20 feet across the front wall, so I have the space. However, you guys always say to cover the entire front wall with absorption. I guess the question is, what is the lesser compromise?

Thanks.

Mark

Terry,

I have 20 feet across the front wall, so I have the space. However, you guys always say to cover the entire front wall with absorption. I guess the question is, what is the lesser compromise?

Thanks.

Mark
Sorry Mark, I misunderstood. End your front wall absorption about one corner absorber width (2-3 feet) before the edge of each of the front corner absorbers.

- Terry

I've read that the corner absorber is more effective in some way if suspended out about 4" from the wall. I guess that's changing the boundary characteristics somehow.
I've never heard of this.

Hi all.

I have a quick and very urgent question.
If you click on my signature below, you'll see pictures of my room, which has double brick rendered walls.

It's a funny shaped room. Its front and rear walls aren't perpendicular. But on average, there's 4 metres between them, and a glass door on the right which leads to the balcony.
The main listening area is about 3.7 metres wide, with an adjacent entrance to the front door & kitchen adding another 2.5 metres.

The neighbour's apartment is right on the other side of the projection screen wall.

Behind the pull-down projector screen and curtains, I've stashed a jigsaw puzzle of packing foam and styrofoam against the wall.
This serves 2 purposes...
1. It helps to reduce sound transmission to the next apartment (most importantly).
2. It helps to deaden the room a little more.

(Beneath the screen, I'm using a black carpet-like material called Wonderwall, which is tacked onto the foam. This will remain.)


But now, I'm needing to replace the foam with something else.

As you can see, there's only so much I can do.
* For one thing, it's a rented unit. So I can really only tape some sort of material against the wall.
* Ideally, I just want to gaffer tape the material to the underside of the projector screen headbox and let it hang over the wall.
* On either side of the curtained area, I'm wanting to leave that area uncovered. So sound will always transmit unimpeded.
* I have no more than 5 cms behind the screen

After looking into a few materials, I bought 7 square metres of this stuff..
POLYROLL 32/25 BLACK, a third of the way down the list...
http://www.peaceandquiet.com.au/price_list.htm


Now, holding up some of this Pollyroll material against a speaker, I notice that it's blocking relatively little sound from coming through, compared to styrofoam, cardboard, etc.

I'm wondering if I should swap it for something more like this barrier material...
http://www.peaceandquiet.com.au/NOISEBAR_BASE_PQ.pdf
...although I was advised that absorbtion on my side would be the best way to stop sound transmission.
A barrier material would be mostly useless as the sound will get in on either side anyway?



What's the best possible (and most cost-effective) material that I could use in this case?
As it's concealed, colour and ugliness are non-issues.


Two other points:
* The left/right main speakers have front & rear bass ports, and go down to around 25Hz.
* I have a slight bass boom problem, which I'll be helping to alleviate by making some bass traps for the corners.



Thank you very much, in advance!

...
I'm wondering if I should swap it for something more like this barrier material...
http://www.peaceandquiet.com.au/NOISEBAR_BASE_PQ.pdf
...although I was advised that absorbtion on my side would be the best way to stop sound transmission.

Yes, the heaviest of these materials would help some, but it is a rather expensive option. You need mass. Whoever told you that sound absorptive material would stop sound transmission is basically wrong.

A good cheap type of massive material is interior drywall. Unfortunately, you won't be able to just tape it up. But that's true of the NoiseBarBase stuff as well. :(


A barrier material would be mostly useless as the sound will get in on either side anyway?
Which is why you would need to thoroughly and seamlessly cover adjacent "flanking paths" as well.

- Terry

Thanks Terry. Love your work, by the way.


It sounds like I'd be better off paying a few dollars more and swapping the Pollyroll material with the 4kg Noisebar, right?

Unless I'm able to completely cover and seal the wall with the material, it's always going to be a semi-lost cause. But is it still fair to say that a barrier material like the Noisebar will make more of a difference on the other side, while having a similar effect in deadening my room?

Like I said, simply holding up the material over a loudspeaker made me question the effect of the Pollyroll. It's effectively useless at blocking sound.
The packing foam I used previously seemed to transmit noticeably less, and I imagine its absorbtion properties wouldn't be too bad either(?)

As you can see from my pics, I could use a thumping good bass trap or two - especially in the front right corner!

Is it fair to say that less sound will be transmitted if more of it is being absorbed on my side, whatever the frequency?
When I put in some bass traps, and succeed in reducing booming, summing and standing wave issues on my side, then there'll simply be less of that bloated bass to escape, correct?

Hi Haggis,

It sounds like I'd be better off paying a few dollars more and swapping the Pollyroll material with the 4kg Noisebar, right?

Yes. But as I said, this is a heavy material, so be prepared to use some really strong tape around the edges to hold it -- duct tape or gaffer's tape. And you can use anything else which comes in sheets and is heavy.


Is it fair to say that less sound will be transmitted if more of it is being absorbed on my side, whatever the frequency?
When I put in some bass traps, and succeed in reducing booming, summing and standing wave issues on my side, then there'll simply be less of that bloated bass to escape, correct?
'Fraid not. This is a case of what seems obvious and intuitively correct doesn't really work when you look at the numbers.

Lets consider a typical low frequency, like 125 Hz. This is low enough to be readily treatable by bass traps. It's not even into the subwoofer frequency range, but it can still be annoying as hell when it comes through your neighbor's wall.

Typical single-stud residential walls have a transmission loss of around 10 dB at 125 Hz. That means than if you play a 125 Hz sound at 75 dB (a reasonable volume) in your room, it will be 75-10 dB = 65 dB on the other side of the wall. This will be bothersome to someone trying to carry on a conversation, let alone sleep.

Now you put up a lot of big, aggressive bass traps, and succeed in absorbing 50% of the 125 Hz room energy. This will improve your low frequency sound quite a bit. Room modes at around 125 Hz will be noticeably quieter, and their decay times will be slashed in half.

But in terms of decibels, a 50% reduction in energy is only 3 dB. So now the 75 dB sound at 125 Hz which your neighbor hears is only reduced to 75-10-3 dB = 62 dB. This is still not quiet by any means. Compensating for the fact that we don't hear low frequences as well as mid frequencies, this translates to a Noise Criterion level of NC 50. A typical "quiet room" is about NC 30. The maximum recommended noise level in a sports coliseum is no more than NC 55. This will likely be small comfort to your neighbor. :(

- Terry

Hi Haggis,

Yes. But as I said, this is a heavy material, so be prepared to use some really strong tape around the edges to hold it -- duct tape or gaffer's tape. And you can use anything else which comes in sheets and is heavy.


'Fraid not. This is a case of what seems obvious and intuitively correct doesn't really work when you look at the numbers.

Lets consider a typical low frequency, like 125 Hz. This is low enough to be readily treatable by bass traps. It's not even into the subwoofer frequency range, but it can still be annoying as hell when it comes through your neighbor's wall.

Typical single-stud residential walls have a transmission loss of around 10 dB at 125 Hz. That means than if you play a 125 Hz sound at 75 dB (a reasonable volume) in your room, it will be 75-10 dB = 65 dB on the other side of the wall. This will be bothersome to someone trying to carry on a conversation, let alone sleep.

Now you put up a lot of big, aggressive bass traps, and succeed in absorbing 50% of the 125 Hz room energy. This will improve your low frequency sound quite a bit. Room modes at around 125 Hz will be noticeably quieter, and their decay times will be slashed in half.

But in terms of decibels, a 50% reduction in energy is only 3 dB. So now the 75 dB sound at 125 Hz which your neighbor hears is only reduced to 75-10-3 dB = 62 dB. This is still not quiet by any means. Compensating for the fact that we don't hear low frequences as well as mid frequencies, this translates to a Noise Criterion level of NC 50. A typical "quiet room" is about NC 30. The maximum recommended noise level in a sports coliseum is no more than NC 55. This will likely be small comfort to your neighbor. :(

- Terry

So.... a 100% reduction in energy is only 6 db? Or is there some curve I don't know about. Admittedly I'm very new to this.

Cheers again.

My walls are all rendered brick, with double-brick separating me from the next unit. Not sure how that measures against plaster/gyprock/stud walls ?

I got a call back from another material supplier today.
By all accounts, it sounds like I'm either better off just keeping the 32kg/25mm (NRC- 0.55) Pollyroll material I've got and adding another layer of the same... or better still, a layer of 4kg loaded vinyl between the Pollyroll and the wall?

By the way, is anyone familiar with Audimute? I'm not in the US, but it's woth bearing in mind...
http://www.audimutesoundproofing.com/audimute-sound-absorption-sheets-materials-that-absorb-sound-soundproofing-blankets.aspx


But by far, it seems the biggest transmission yields will come from bass traps.

I'm thinking of making two stacks of Toblerone-shaped traps for the front left and front right corners. (Again, my signature will take you to the pics).
They'd be 850 to 1000mm wide, and go from the floor to the ceiling, which is 2400mm.
I was looking at this material (minus the foil), which is available in thicknesses of...
50mm (NRC - 0.9)
75mm (NRC - 1.05)
100mm (NRC - 1.1)
All are 48kg per cubic metre...
http://www.acoustica.com.au/hdbatts.html

At least for now, I was thinking of just cutting up the 75mm or 100mm batts, putting them diagonally into the corners and leaving out the frames and fabric for the time being.

I might also hang a 50mm slab on the back wall behind the listening position, at least 1000mm wide and 500mm high.

I want to stay away from fibreglass. Are these batts a good material, or can I do better without breaking the bank?

I was looking at this material (minus the foil), which is available in thicknesses of...
50mm (NRC - 0.9)
75mm (NRC - 1.05)
100mm (NRC - 1.1)
All are 48kg per cubic metre...
http://www.acoustica.com.au/hdbatts.html


Check out Ultratel or Supertel by CSR - you'd have to call a CSR place for them to give you a supplier, where'd you live? It's not cheap though, about $350 per bag. You want to look at the absorption across the board i.e. frequency spectrum - not just the overall NRC. I think? I assume your more concerned about lower frequency issues?

See:

http://www.bobgolds.com/AbsorptionCoefficients.htm

I am. I'm actually very happy with the room's mid-high performance, although I see no reason not to improve it as far as is monetarily possible, without destroying the room.
Bass boom is the big issue, in both the absorption and transmission departments.

The CSR suggestion looks great, if pricey.
Another issue is that I'm in... Sydney, Australia! This puts paid to quite a few options, methinks.

Doing what I should perhaps have done in the first place - looking for the most ideal product from the cheapest specialist suppliers - I've come up with these materials...

Dense (no more than 50mm), absorbent material for behind the screen/curtains with reasonable transmission properties...
http://www.thefoambooth.com.au/front.asp?pid=46&ProductID=Acc50/25
... no need to tape it to the wall or headbox, either.

Bass Traps for the front corners. (Convoluted face)
Two of these for each corner will fit snuggly from floor to ceiling, require no fixtures, and be ready to go...
http://www.acousticalsolutions.com/products/traps/alphacorner.asp
... As I'm metering out the budget, I might start with two and add two later.


Acoustic panel for the rear wall...
http://www.acousticalsolutions.com/products/panels/Anchorage.asp
I'll leave this one till last, using some leftover Sonex-like material in the meantime, and may even build my own in the end.


Are these materials good bang for buck, compared to similarly priced alternatives?
(Again, click on my signature to see the room.)

Thanks again...

I should have said I live in Sydney too...it took me ages to find a suitble product...not that I've used it yet. But there are a few other Aussies here that use Ultratel...cant buy it from Bunnings though. There are specialist providers - call CSR directly and ask for a local supplier. I know there is one in Castle Hill - Sydney insulation or something. Trust me, you wont find it via google

So.... a 100% reduction in energy is only 6 db? Or is there some curve I don't know about. Admittedly I'm very new to this.

That's correct, but that's not the same thing as 100% reduction in transmission of course.

Frank

No!!!!! :D
A decibel is defined as 10 time the log (base 10) of the power ratio.

So a 50% power ratio (50% reduction) = -3dB.
A 25% power ratio (75% reduction) = -6 dB.
A 10% power ratio (90% reduction) = -10 dB.
A 0% power ratio (100% reduction) = -infinity dB.
Etc.

No!!!!! :D
A decibel is defined as 10 time the log (base 10) of the power ratio.

So a 50% power ratio (50% reduction) = -3dB.
A 25% power ratio (75% reduction) = -6 dB.
A 10% power ratio (90% reduction) = -10 dB.
A 0% power ratio (100% reduction) = -infinity dB.
Etc.

Terry,

I'm not following this. Probably because I don't know what is meant by "power ratio". A little help please?

Terry,

I'm not following this. Probably because I don't know what is meant by "power ratio". A little help please?

A change in db is a ratio at any power level. So, for instance, if you have 100 watts and reduce it to 50 watts, that 50% reduction in power is a 3 db difference. Going from 10 watts to 5 watts is also a 3 db difference. So you have to look at the 3 db change in logarithmic land (db) as a power ratio in linear land (watts/volts/spl/whatever).

Did I add mud to the waters?

Hello all,

I have a couple of questions reguarding diffusion.

Below is a picture of "Wooden Cube" Ceiling inserts
The Cubes are 1 1/2 or 2 1/4" deep, and come in sizes of 1/4, 1/2, and 3/4" thick blades

http://www.architecturalsurfaces.net/prodcuts/art/woodcube_sm.jpg

Im looking at using the 2' x 2' "Wooden Cube" panels as the center insets in a 4' x 4' coffered ceiling design. I would end up with 9 of these panels in my ceiling (18.5 x 16.5 room).

So the question is : will these panels offer diffusion benefits.

Second part of the question: Their seems to be a school of thought that Diffusion need to be a min of 10' from the listener.. (if i understand what i have read). Is this an accurate interpretation? If so,, this seems like it would be a deal breaker for diffusion in a lot of rooms, unless placed on the ceiling in the front or rear of the room only. Assuming you would get diffusioin from these panels, would it be detremental to place directly over the listeneing position?

Any feedback would be appreciated.

Thanks
Brad

http://www.architecturalsurfaces.net/prodcuts/art/woodcube_sm.jpg
..
So the question is : will these panels offer diffusion benefits.

No. These will not diffuse sound.

A change in db is a ratio at any power level. So, for instance, if you have 100 watts and reduce it to 50 watts, that 50% reduction in power is a 3 db difference. Going from 10 watts to 5 watts is also a 3 db difference. So you have to look at the 3 db change in logarithmic land (db) as a power ratio in linear land (watts/volts/spl/whatever).

Did I add mud to the waters?

No mud added. Actually, that last bit "(watts/volts/spl/whatever)" answered my question.

Thanks!

Can anyone offer their views on the materials I've listed above?

Thanks again.

Can anyone offer their views on the materials I've listed above?

Thanks again.

Fiberglass or rockwool will outperform foam, esp for bass trapping.

I don't know what vendors might be accessible in Australia, but I assume shipping from the US would be excessive.

I'm not clear how DIY handy you are, or what aesthetic criteria you have, but something like the corner traps that REALTRAPS sells or like the pedestal or corner traps that GIK ACOUSTIC sells would likely be worth imitating, if you are going to build something yourself.

Fiberglass or rockwool will outperform foam, esp for bass trapping.

I don't know what vendors might be accessible in Australia, but I assume shipping from the US would be excessive.

I'm not clear how DIY handy you are, or what aesthetic criteria you have, but something like the corner traps that REALTRAPS sells or like the pedestal or corner traps that GIK ACOUSTIC sells would likely be worth imitating, if you are going to build something yourself.
Well, if they have heating, ventilation and air conditioning in Australia, then they have companies selling the fiberglass we are talking about here. ;)

Fiberglass or rockwool will outperform foam, esp for bass trapping.

I don't know what vendors might be accessible in Australia, but I assume shipping from the US would be excessive.

I'm not clear how DIY handy you are, or what aesthetic criteria you have, but something like the corner traps that REALTRAPS sells or like the pedestal or corner traps that GIK ACOUSTIC sells would likely be worth imitating, if you are going to build something yourself.

Well for now, ready-made foam bass traps like the ones above are appealing on many levels. Apart from not having to build them or fix them to the walls, I could simply buy 2 and comfortably wedge them from floor to ceiling.

I'm sure rockwool, fibreglass or glasswool would perform better for bass, although I'm not sure how much (?)

Following Elil's suggestion , I may use this glasswool material for the 3m x 2.2 x 50mm metre area behind the screen/curtains/speakers...
http://www.bradfordinsulation.com.au/Products/Commerical/HVAC/Ultratel.aspx

It's very dense, quite rigid it should absorb bass nicely, it's quite cheap $30ish for a square metre, and comes two packs of 1500x2400 will do the job.

Yes, glasswool. That's what you want.

Trying to quantify how much better it is than foam, let's say that for the same size, glasswool is twice as useful for bass trapping.

You could use that Bobgold link mentioned above to the exact figure.

Yes, glasswool. That's what you want.

Trying to quantify how much better it is than foam, let's say that for the same size, glasswool is twice as useful for bass trapping.

You could use that Bobgold link mentioned above to the exact figure.

A material like this would seem to be the best of all......?
http://www.acoustica.com.au/hdbatts.html


It seems ideal...
* Polyester, so no flaking
* 48kg/m3 density
* I heard somewhere that polyester has a more consistant density than Rockwool (?)
* Available in 50mm, 75mm and 100mm thicknesses
* White
* Two (or more if layered) 1200 x 600 batts would make a floor-to-ceiling bass trap.
* Available with foil backing
* Pretty cheap - around AU$15 a square metre

What do we think of this compared to the alternatives?

Double up the 100mm batts, and lay that across some corners, and that would likely work well. I didn't do the math, but it does seem like it would work. However, one of the things DIYers like is the semi/rigid nature of the popular Owens Corning stuff that everyone in the US uses. I get the impression that product you reference is not rigid, so that's a lot of work to turn it into panels.

Double up the 100mm batts, and lay that across some corners, and that would likely work well. I didn't do the math, but it does seem like it would work. However, one of the things DIYers like is the semi/rigid nature of the popular Owens Corning stuff that everyone in the US uses. I get the impression that product you reference is not rigid, so that's a lot of work to turn it into panels.


True. I'll see how rigid it is (or isn't) when I go to have a look at the stuff.
The foil backing would help, though.

Acording to the link, it's available in weights of up to 180kg/m3 ! That would be somewhat rigid, methinks!!!
http://www.acoustica.com.au/hdbatts.html

For the record, I've also found a very dense (and probably rigid) rockwool batt...
http://www.bradfordinsulation.com.au/Products/Commerical/HVAC/Rockwool-Duct-liner.aspx


I'm still learning about the wonderful world of traps, but there's an excellent How-to by the legendary Ethan Winer here...
http://www.ethanwiner.com/basstrap.html

He speaks of using a plywood front face for extra effect. One could loosley bond a couple of layers together, and then on to a 2400 high sheet of thin plywood, perhaps with a base plate for a bit of weight at the bottom.

Making a 2400mm high pinewood frame is pretty easy, especially as it comes in that length.

Another option would be to cut a series of triangles and just pile them up - with or without a frame or front face.
In a way, this may be best for me as my front corners are actually more like 110 and 70 degrees, and on the right side, I'd rather have a broader 900mm wide trap anyway.
(Again, click my signature for pics.)

It seems ideal...
* Polyester, so no flaking
* 48kg/m3 density
* I heard somewhere that polyester has a more consistant density than Rockwool (?)
* Available in 50mm, 75mm and 100mm thicknesses
* White
* Two (or more if layered) 1200 x 600 batts would make a floor-to-ceiling bass trap.
* Available with foil backing
* Pretty cheap - around AU$15 a square metre


It'll work fine. You can even leave the foil on it for the corner bass traps or the bass traps behind your head (depending on how far away from your head they are). Make sure you take the foil off for the panels at the first reflection points though.

Frank

It'll work fine

Are the properties of polyester as good for bass trapping as fibre glass even if they have the same density? Also will it work as well for reflection points?

Happy days if it is, this'll save me quite a bit of coin (about 1/3 of the cost).

Are the properties of polyester as good for bass trapping as fibre glass even if they have the same density? Also will it work as well for reflection points?

Happy days if it is, this'll save me quite a bit of coin (about 1/3 of the cost).
Yes. Though it is hard to find polyester fiber material as dense as semi-rigid fiberglass. I've never seen it in the US.

- Terry

Yes. Though it is hard to find polyester fiber material as dense as semi-rigid fiberglass. I've never seen it in the US.

- Terry

Sounds like a 48kg/m3 100mm polyester batt will not be quite as rigid as a 48kg/m3 100mm fibreglass, although its absorbtion prooperties are very similar?

At any rate, that polyester above comes in densities of up to 180kg/m3.
I imagine for the same thickness, that would be pretty rigid, especially with a backing.

Sounds like a 48kg/m3 100mm polyester batt will not be quite as rigid as a 48kg/m3 100mm fibreglass, although its absorbtion prooperties are very similar?

Rigidity actually has nothing to do with acoustic absorption. Since you are in Australia, you are all set! I'd go with the 48kg/m3 polyester batts. They should give performance comparable to Owens Corning 703 (3 pcf) fiberglass.

In the US, we are very fiberglass-based. Owens Corning, a big US company, invented the stuff.

Rigidity actually has nothing to do with acoustic absorption. Since you are in Australia, you are all set! I'd go with the 48kg/m3 polyester batts. They should give performance comparable to Owens Corning 703 (3 pcf) fiberglass.



OK, so density is really the determining factor.

However, if you take two 75mm thick batts, one at 48kg/m3 and the other at 180kg, the 180kg will always provide more absorbtion, yes?

OK, so density is really the determining factor.

However, if you take two 75mm thick batts, one at 48kg/m3 and the other at 180kg, the 180kg will always provide more absorbtion, yes?
No. :)

It's not that simple. Too much thickness of too dense a material (a material with a high acoustic resistivity) may reflect and therefore not absorb high frequencies as well as less thick and dense materials.

And to make matters more complicated, acoustic resistivity does not increase linearly with density. That is, doubling the density does not in general double the resistivity. It is a more complex relationship which is material-specific.

No. :)

It's not that simple. Too much thickness of too dense a material (a material with a high acoustic resistivity) may reflect and therefore not absorb high frequencies as well as less thick and dense materials.

And to make matters more complicated, acoustic resistivity does not increase linearly with density. That is, doubling the density does not in general double the resistivity. It is a more complex relationship which is material-specific.

Okey dokey, then.

Well the first thing I want to do is to make a 2400mm-high, floor-to-ceiling corner trap for the front right.
I want to make it 900mm wide (so it'll go from the curtain at the front to the curtain at the side wall. Again, click my signature.)


I could either....

1. Stack up a series of triangles to make a Toblerone shape

or

2. Make a pinewood frame and add one or two layers (?) of 75mm (?) 48kg/m3 polyester batts.

Other additions, like material and perhaps plywood (?), would follow shortly after.

Any thoughts on the above?
Reducing bass boom is the goal. No great desire to affect the higher frequencies.

Thanks!

Okey dokey, then.

Well the first thing I want to do is to make a 2400mm-high, floor-to-ceiling corner trap for the front right.
I want to make it 900mm wide (so it'll go from the curtain at the front to the curtain at the side wall. Again, click my signature.)


I could either....

1. Stack up a series of triangles to make a Toblerone shape

or

2. Make a pinewood frame and add one or two layers (?) of 75mm (?) 48kg/m3 polyester batts.

Go for the Toblerone.

Go for the Toblerone.

Mmmmmmm...Toblerone.

Frank

Go for the Toblerone.

mmmmmmmm... Toblerone it is.


May as well ask....

50mm / 75mm thick, 48kg/m3 batts with no foil backing are the cheapest.

But 100mm thickness is also available, and densities of up to 180kg/m3.

Is it worth my while getting anything more than 75mm / 48kg ?

Terry was serious, I think; Frank was making a joke but essentially agreeing.

I'm actually thinking about some DIY diffusion for my front wall (under the screen) and perhaps the side wall and/or ceiling. (I'm using some GIK panels under the screen, but might move the to the ceiling -- or a corner for more bass trapping.)

Would a simple shape, repeated, like the triangle chocolate's box really work well? How big should the triangle be? For example, I could get a bunch of 2x2s and rip them in half the long ways, and glue them to thin plywood or luon.

Previously I was thinking I had to get mathematical and fancy. But maybe I was just over complicating things.

Would a simple shape, repeated, like the triangle chocolate's box really work well? How big should the triangle be?
Did you look at the Studiotips SuperChunk corner absorbers I referenced earlier? If not, here's a link:

http://forum.studiotips.com/viewtopic.php?f=8&t=535

They are easy to make, and work great.

- Terry

My mistake. I was speaking of a small triangular shaped ridges spaced close together to create a diffuser, not a large trap.

Something that would be far more DIY easy than something like this:

http://www.auralexelite.com/resources/spacearray_Imag.jpg

For an application like this:

http://www.customaudiodesigns.co.uk/diffusers/trans.jpg

though I am more interested in the front wall, side walls and ceiling that the back wall right now.

I'm actually thinking about some DIY diffusion for my front wall (under the screen) and perhaps the side wall and/or ceiling. (I'm using some GIK panels under the screen, but might move the to the ceiling -- or a corner for more bass trapping.)

Why would you use diffusion on the front wall under the screen? I understand on the side walls, back walls, and ceiling, but I'm not sure what diffusion on the front wall would accomplish?

CJ

Did you look at the Studiotips SuperChunk corner absorbers I referenced earlier? If not, here's a link:

http://forum.studiotips.com/viewtopic.php?f=8&t=535

They are easy to make, and work great.

- Terry
http://peparsplace.com/Pg_23.htm

Why would you use diffusion on the front wall under the screen? I understand on the side walls, back walls, and ceiling, but I'm not sure what diffusion on the front wall would accomplish?

CJ


Seems to be one way to increase the sound stage depth, without pulling the speakers even further into the room (they are already about as far into the room as makes sense).

I'm actually thinking about some DIY diffusion for my front wall (under the screen) and perhaps the side wall and/or ceiling.

Sorry, I missed seeing this. DIY Schroeder diffusers (the ones with variable depth wells) are difficult for DIY construction. Alternatives are:

Slanted wedges -- good for flutter echo between parallel walls
Luan plywood bent into an arc (polycylindrical) - general purpose

The depth will depend on the frequencies you need to diffuse. Larger and deeper extend lower in frequency. I have no idea what your specific acoustical issues are, but typical diffusers are a minimum of 6" deep.

- Terry

Thanks for the ideas. Yes, I was intimidated by the DIY Schroeder diffuser idea.

My room is 12.5ft by 17ft by 8 ft.

I've got a pair of 4inch thick 2x4ft bass traps straddling the rear/side walls, and another pair flat against the front side walls near the corner. (The screen prevents them from straddling the corner.)

At the Left and Right first reflection points I have 2inch 2x5ft fiberglass absorbers. And I have two such panels under the screen, and two such panels on the rear wall, as well.

I'm thinking, instead of buying/making two or three panels for the ceiling, perhaps I have built a diffuser for the front wall, increasing the soundstage depth (especially on two channel music) and move the panels from there to the ceiling.

Hey guys-

I am a two channel guy, but looking for someone to come in and do room acoustics for a mixed use room. Are there any recommended folks in Los Angeles?

I have a 24'x28'x8' room (so large), although 1/3 of it is a dining area. I know some basics about acoustics, but would prefer to bring someone in.

I have read up on ASC---but don't like the full absorption model in other rooms i've heard. Rives does stuff to, but figure since i am in LA, the king of recording studios, there might be a local guy who i would pay to come out, measure, and have a consultation.

Thanks,

KeithR

No. :)

It's not that simple. Too much thickness of too dense a material (a material with a high acoustic resistivity) may reflect and therefore not absorb high frequencies as well as less thick and dense materials.

And to make matters more complicated, acoustic resistivity does not increase linearly with density. That is, doubling the density does not in general double the resistivity. It is a more complex relationship which is material-specific.

Whoa. I wonder if my plan has been wrong then (or not).

I can't get into "true" bass trapping in my room but I've been planning to do the best I can. I've been planning to do as big an aborber as I can put over the screen - 24" wide, 12 feet long, of OFI 48 (essentially like OC 703)...piled up 5" thick.

I also planned to put similar 5" thick piles in the ceiling corners.

Is this the right approach (trying to absorb as low a frequency as I can get to help with mid-bass bloat) or might I end up with reflection rather than absorption? And if I'd end up with reflection, what is the better approach?
Would I add something else in between the OFI 48 layers or something?

Thanks again.

Whoa. I wonder if my plan has been wrong then (or not).

I can't get into "true" bass trapping in my room but I've been planning to do the best I can. I've been planning to do as big an aborber as I can put over the screen - 24" wide, 12 feet long, of OFI 48 (essentially like OC 703)...piled up 5" thick.

I also planned to put similar 5" thick piles in the ceiling corners.

Is this the right approach (trying to absorb as low a frequency as I can get to help with mid-bass bloat) or might I end up with reflection rather than absorption? And if I'd end up with reflection, what is the better approach?
Would I add something else in between the OFI 48 layers or something?

Thanks again.
This plan is just fine, Rich. First of all, since you are interested in absorbing bass, any non-absorption of high frequencies (in the kHz!) is moot. Also, 3 pcf fiberglass does not have too much density, even at 5" thick. You can go as thick as you want with it, again, assuming that you don't want a broadband absorber working efficiently up to the highest frequencies -- to place at early reflection spots, for example.

For the screen wall this is fine as well, because speakers are directional at high frequencies and simply won't generate that much sound rearward. And again, any reasonable thickness of 3 pcf fiberglass (even a foot or two) will still absorb more highs than it reflects.

- Terry

Whew. I sure appreciate your input Terry. Thank you!!!

Is this the right approach (trying to absorb as low a frequency as I can get to help with mid-bass bloat) or might I end up with reflection rather than absorption? And if I'd end up with reflection, what is the better approach?
Would I add something else in between the OFI 48 layers or something?

Like Terry said, you'll be fine...definitely down into the low mids if not lower.

Frank

Looking for some honest opinions on my sound panel setup so far:

I feel like I mounted the front reflection points a bit to high.

Please note, I'm not done, I'm just out of panels (I buy about 2 a month).

Any suggestions?

What do people think about a thick rug for the floor in front?


http://www.silverti.com/pics/HT/front.jpg

http://www.silverti.com/pics/HT/left.jpg

http://www.silverti.com/pics/HT/right.jpg

Instead of the thick rug, put a panel or two on the first reflection points on the ceiling. And then stop and consider whether or how much more you really need. Have you done any measurements?

Looking for some honest opinions on my sound panel setup so far:

I feel like I mounted the front reflection points a bit to high.

Please note, I'm not done, I'm just out of panels (I buy about 2 a month).

Any suggestions?
I think the white/near white walls and ceiling will wash out your picture from light reflected off the screen onto them and reflected back onto the screen. :)

I think the white/near white walls and ceiling will wash out your picture from light reflected off the screen onto them and reflected back onto the screen. :)

Absolutely!

A dedicated room like yours should be as much of a cave as possible.
You'll be staggered by the difference that dark walls make.
If you don't want to paint them, then perhaps do what I did in my previous place and put up curtains and rails for the side walls. This will noticeably help the sound, too.


Ideally, have a dark ceiling, and a dark floor rug too.

I think the white/near white walls and ceiling will wash out your picture from light reflected off the screen onto them and reflected back onto the screen. :)

And all those equipment lights lined up in front aren't great either. I know the equipment is on display, but who wants to see all those lights when watching a movie? Boy... we purists are really raggin' on you, aren't we? :) Here's a pic of my theater. Nuthin' but screen! (The door and trim have since been dealt with.)

EDIT: You can rag on me for the white couches. I just built the house and am feeling mighty poor right now, otherwise I'd get a nice black leather set.

Instead of the thick rug, put a panel or two on the first reflection points on the ceiling. And then stop and consider whether or how much more you really need. Have you done any measurements?

I'd agree...you've got a lot on the front wall, and you should probably shift some to the reflection points. How about the back wall? What's going on back there?

Frank

I think the white/near white walls and ceiling will wash out your picture from light reflected off the screen onto them and reflected back onto the screen. :)

The flash lights it up. The paint is actually a really dark gray. When the lights are out its perfectly black. The carpet is also a pretty dark gray. All trim in the room is flat black.

this picture shows it better (lights are even still on),

This picture also shows that I put sound panels on the floor in "movie mode" to hide the front lights.

http://www.silverti.com/pics/HT/Front2.jpg

And all those equipment lights lined up in front aren't great either. I know the equipment is on display, but who wants to see all those lights when watching a movie? Boy... we purists are really raggin' on you, aren't we? :) Here's a pic of my theater. Nuthin' but screen! (The door and trim have since been dealt with.)

EDIT: You can rag on me for the white couches. I just built the house and am feeling mighty poor right now, otherwise I'd get a nice black leather set.
I'm sure they go well with your shag rug. :p

The flash lights it up. The paint is actually a really dark gray. When the lights are out its perfectly black. The carpet is also a pretty dark gray. All trim in the room is flat black.

this picture shows it better (lights are even still on),

This picture also shows that I put sound panels on the floor in "movie mode" to hide the front lights.

http://www.silverti.com/pics/HT/Front2.jpg
Project an image onto the screen, hit pause and take a flash-free picture. That would be a better test of your wall/ceiling color and whether or not they should be darker.

I'd agree...you've got a lot on the front wall, and you should probably shift some to the reflection points. How about the back wall? What's going on back there?

Frank


The back is the problem right now and the next focus of attention. I want to cover it pretty good. If I stand at my center speaker and "clap" I still get echo from the rear. If I move to my 5 feet over closer to the front reflection points and clap.. I don't get any echo.

Older pic of the back:

http://www.silverti.com/pics/HT/back1.jpg

Newer

http://www.silverti.com/pics/HT/back2.jpg

Project an image onto the screen, hit pause and take a flash-free picture. That would be a better test of your wall/ceiling color and whether or not they should be darker.

These are the best I have. I have always found it hard to take pictures down there (Using my Sony A700 SLR) when the lights are off because the room is dead dark and the image is really bright. One of these has my 46" LCD TV in it. I used to have an LCD TV behind the screen but took it out since I wasn't using it as much as I thought I would. You can see the image reflect of the equipment under the screen.

http://www.silverti.com/pics/HT/image1.jpg

http://www.silverti.com/pics/HT/image2.jpg

These are the best I have. I have always found it hard to take pictures down there (Using my Sony A700 SLR) when the lights are off because the room is dead dark and the image is really bright. One of these has my 46" LCD TV in it. I used to have an LCD TV behind the screen but took it out since I wasn't using it as much as I thought I would. You can see the image reflect of the equipment under the screen.
Yes, but not much off the walls or ceiling. Looks like you've got that under control. :)

What do you think I should do with the rear? I was thinking 4 to 6 panels?

I'm sure they go well with your shag rug. :p

Well! I never! It's NOT a shag rug! :)

I like what you do with the panels in "movie mode". That's a good solution.

I'm sure they go well with your shag rug. :p

Shag rugs have been back "in" for quite a while now! Open any "metropolitan" magazine or attend any design show and you'll see shag rugs
everywhere.

I love them and ordered one for my own HT room. My kids love it, feels awesome, looks funky-cool.

The back is the problem right now and the next focus of attention. I want to cover it pretty good. If I stand at my center speaker and "clap" I still get echo from the rear. If I move to my 5 feet over closer to the front reflection points and clap.. I don't get any echo.

Older pic of the back:

http://www.silverti.com/pics/HT/back1.jpg

Newer

http://www.silverti.com/pics/HT/back2.jpg


My friend, having floorstanding towers like that aiming at the back wall, below ear level out of proper ear-shot to all except those in the back row is just wrong.

I've been there. Trust me... you can do a lot better.

Consider wall-mounted bipole or dipole surrounds around half way down your seating area, and ideally another pair of bipole surrounds at the back for 7.1. That'll be a huge improvement.

The layout with your back wall is tricky, so either ceiling-mount the rears, or wall-mount them to the sides behind the seating area, or stand-mount them.

You can also have just one pair of dual-monopole surrounds (like the Infinity BETA ES250 (http://www.amazon.com/Infinity-BETA-ES250-Surround-speakers/dp/B0006DPPVA) or JBL's P52OWS (http://www.jbl.com/home/products/product_detail.aspx?prod=P52OWS&Language=ENG&Country=us&Region=USA&cat=SSS&ser=PER)) and still go 7.1

In any case, surrounds in your room should be at least a foot above seated ear-level.

The are a couple of dipole-bipole threads here on AVS.
Some excellent speakers include Monitor Audio BFX (http://monitoraudiousa.com/products/bronze-br/brfx/your-speaker), Paradigm's ADP (http://www.paradigm.com/en/paradigm/surrounds-monitor-adp190-model-4-4-1-8.paradigm)surrounds and Axiom's QS8 (http://www.axiomaudio.com/surroundspeakers.html).

My friend, having floorstanding towers like that aiming at the back wall, below ear level out of proper ear-shot to all except those in the back row is just wrong.

I've been there. Trust me... you can do a lot better.

Consider wall-mounted bipole or dipole surrounds around half way down your seating area, and ideally another pair of bipole surrounds at the back for 7.1. That'll be a huge improvement.

The layout with your back wall is tricky, so either ceiling-mount the rears, or wall-mount them to the sides behind the seating area, or stand-mount them.

You can also have just one pair of dual-monopole surrounds (like the Infinity BETA ES250 (http://www.amazon.com/Infinity-BETA-ES250-Surround-speakers/dp/B0006DPPVA) or JBL's P52OWS (http://www.jbl.com/home/products/product_detail.aspx?prod=P52OWS&Language=ENG&Country=us&Region=USA&cat=SSS&ser=PER)) and still go 7.1

In any case, surrounds in your room should be at least a foot above seated ear-level.

The are a couple of dipole-bipole threads here on AVS.
Some excellent speakers include Monitor Audio BFX (http://monitoraudiousa.com/products/bronze-br/brfx/your-speaker), Paradigm's ADP (http://www.paradigm.com/en/paradigm/surrounds-monitor-adp190-model-4-4-1-8.paradigm)surrounds and Axiom's QS8 (http://www.axiomaudio.com/surroundspeakers.html).

HEHEE! Guys, I appreciate all the HT advise but I am *really* just looking for the acoustical parts right now.

Those are the 7.1 channel rears/ In that picture I have turned them towards the rear wall in "workout" mode. They are turned around in "movie" mode.

My 5.1 side speakers are Polk Fxi5's that are mounted up on the wall at a 90 degree angle to the center viewing spot.

As seen in this older picture

http://www.silverti.com/pics/HT/Side.jpg



Please, is there any advise on the rear wall sound panel placing?

Please, is there any advise on the rear wall sound panel placing?

Yep. I'd get the rear corners floor to ceiling with 4" traps, then do maybe two or three 6" traps on the back wall.

Frank

HEHEE! Guys, I appreciate all the HT advise but I am *really* just looking for the acoustical parts right now.

Those are the 7.1 channel rears/ In that picture I have turned them towards the rear wall in "workout" mode. They are turned around in "movie" mode.

My 5.1 side speakers are Polk Fxi5's that are mounted up on the wall at a 90 degree angle to the center viewing spot.

As seen in this older picture



Please, is there any advise on the rear wall sound panel placing?


Ah, I see.

Well it's a little hard to say for sure without listening to the room, but off the batt, I'd say this...

* Your side-wall panels are perhaps a little high. You could try mounting them closer to the listening position, but it isn't too critical.
Ideally, get two rows of panels - one lower down than the current ones, and another higher row.

* As for the back wall, try moving the 3 front-centre traps from your front wall to the back wall and see if you can pick the difference. They'd likely be much better served there. You'll still have two traps at the front, and the projector screen will already be helping somewhat.

* The legendary Ethan Winer (a man who knows more about acoustics than most of us) isn't nearly as fussed about the front wall as the back. Look him up and read through some of his stuff. He's also on YouTube.

* If you're still getting a fair bit of bass-boom - as you'd expect in that room - then more corner traps will always help.

A few pages back, you'll see that I had some questions about bass traps in my room. I resolved to make Toblerone-shaped corner traps, made from stacks of triangular-cut panel (fibreglass, rockwool, polyester, whatever.)

Generally, these will be more effective than just having thinner panels laid against the corners.... and they'll be a damn sight cheaper.

Yep. I'd get the rear corners floor to ceiling with 4" traps, then do maybe two or three 6" traps on the back wall.

Frank

Thx guys

Where would be the best spots for the rear wall panels, up high, centered or down low?

Thx guys

Where would be the best spots for the rear wall panels, up high, centered or down low?
To use a billiards analogy, they would go on the cushion (rear wall) where the ball (sound) would strike going from the LCR speakers to the listeners.

Where would be the best spots for the rear wall panels, up high, centered or down low?

Centered at seated ear height.

--Ethan

To use a billiards analogy, they would go on the cushion (rear wall) where the ball (sound) would strike going from the LCR speakers to the listeners.

Nice! :)

Frank

Nice! :)

Frank
You can use it, Frank. :)

Is it necessary to Treat the entire front wall behind the screen if the Screen covers 2/3rds of the wall. If you trying to stop reflections from rear speakers it seems the mid/highs would hit the screen and not go through it.

Just a question...thanks

Kermie,

I can tell you that my room sounds better with the entire screen wall treated. As a matter of fact, I put up a second layer of 1 inch Linacoustic RC and the sound improved exponentially.

Your mileage may vary.

Centered at seated ear height.

--Ethan

Even with a long extended rear like that? I was thinking that I need the entire rear treated (kind of like the front). The wall is bare right now but it is double walled (with double R19 in it) and double sheet 5/8ths sheet rock.

That rear wall is a good 25' from the listening position. I figured sound waves back there are all over the place and I don't want them bouncing back.

Is that logical at all?

Logical, yes, but not accurate. 25 feet is a long way. Some treatment is useful, like what Ethan suggests. But for anything other than that "first reflection point" your ears/brain will easily differentiate between direct and reflected sound.

Bass trapping, even in a room that large, will probably be (more) worthwhile. That's going to be very thick and spread over corners.

Kermie,

I can tell you that my room sounds better with the entire screen wall treated. As a matter of fact, I put up a second layer of 1 inch Linacoustic RC and the sound improved exponentially.

Your mileage may vary.


Thank you Dan...I was planning on 2" on entire Front wall and Base traps in corners. I will continue to move forward as planned.

Bass trapping, even in a room that large, will probably be (more) worthwhile. That's going to be very thick and spread over corners.

For the bass traps the plan was to get the same 4" thick panels without the wood backing.

I finally got a monster subwoofer and have found the best place for it is along the middle of the back wall. I have superchuck bass traps in the front and cant do corner traps in the back. what i could do is a corner trap on the ceiling directly above the sub, and/or a 6 inch trap placed on the wall directly above the sub. The wall is only 1 drywall layer thick unfortunately and it really moves when the sub is hitting low notes. Any thoughts? And yes I do need to get an spl meter to get some readings.

The wall is only 1 drywall layer thick unfortunately and it really moves when the sub is hitting low notes.
Does it rattle audibly?

Does it rattle audibly?

fortunately no, hopefully wont start either. you can sure feel it though. and the light sconces do rattle so im not sure what to do with them except maybe change them for something rigid.

fortunately no, hopefully wont start either. you can sure feel it though. and the light sconces do rattle so im not sure what to do with them except maybe change them for something rigid.
Yes. Change the sconces or fasten them so they don't rattle. Feeling the wall vibrate is fine.

Rattles typically happen at high decibel levels. They generate non-linear distortion.

- Terry

how do i know whether or not i need more bass traps? what do you think about putting a gik 6" directly above my sub? good/bad? the sub is a monster, a seaton submersive, so im thinking the more traps the better but i havent done measurements as i am not very calibration educated.

fortunately no, hopefully wont start either. you can sure feel it though. and the light sconces do rattle so im not sure what to do with them except maybe change them for something rigid.

Mine's an IB sub with 8 woofers. Even in a 1 year old well built house it makes the structure in the walls and roof creak. I guess there's nothing to do but turn down the volume?

After speaker and listener locations are optimized, I would start out by absorbing each first order reflection for each front speaker on all six surfaces. I would then look at diffusing the first order reflection points for all surround speakers. With a room length well beyond 25' and an opening at the side wall to another room, you probably don't have terrible modal issues. Corner traps in all 8 corners should be a good idea to smooth out existing room modes as well as reverberation times. Have someone clap their hands in front of each speaker as you listen from your primary spot and place treatment (probably absorption in your case) where needed to control any slap echos. From there you'll need to determine if more absorption is needed to control lingering frequencies. The idea is to make the room disappear visually and sonically. Often people use too much mid and high frequency absorption making the room sound too dead above 500Hz. and sloppy below. Be sure to re-calibrate the electronics after physical changes are made.

To use a billiards analogy, they would go on the cushion (rear wall) where the ball (sound) would strike going from the LCR speakers to the listeners.

When I use my laser pointer and mirror trick from my listening postion, I have the speaker well covered at that front refection point (especially the tweeter).

Im actually going to shoot for ceiling mounts now. Im going to use the laser trick to get 2 panels mounted on the ceiling at their reflection points from the center channel. I'll use my 2 2" panels for that (which are currently siting in the front corners as base taps until I get some real base traps.

Hi, I am going to build a home theater as part of finishing my basement. As the the picture shows, the room is 20' by 15', plus bump outs on two sides. The fourth side of the

room (the right side of the drawing) opens to the rest of the basement. I also tried to show locations of the stage (on the right side of the drawing), speakers, subwoofer(s),

and an ajacent finished bathroom.

As a newbie to HT, I've read many, many threads on AVS, but still not sure what I have to do regarding many aspects of acoustic treatment. I plan to spend up to $500.

To start off, my first questions are about the front wall (the wall on right side of the drawing).
1. There is a bump out (4' wide by 2' deep by 8' high) on the screen wall. It's right in the middle of the 15' long wall(red circle 1), and will be right where I plan to put

the center speaker (With grill cloth-covered panel). What kind of treatment should I do to this cavity?
2. Referring to the area labeled by the red circle 2, what kind of materials should I apply at the corner of the stage, where I will be hiding Left, Right speakers and may be

subs?

I am all ears and appreciate any help.

Hi all,
I’m continuing my planning for our new HT. You all have put a lot of knowledge out there for us newbies, so thanks. I hope you can take a look at what I’m thinking and provide any sound treatment advice that you may have.

Specs
• Finished inside dimensions (including false screen wall) = 12’10” x 25’
• Ceiling height = 7’10” for first 11’ from screen (to enclose utilities), 9’ for remaining depth
• West wall and Southwest two small walls = Staggered studs, 5/8” DD + GG
• North, East, and South walls = RSIC-DCO4 isolated 2x4 double walls spaced 2” from concrete wall. Apply 5/8” DD + GG
• Ceiling = Use RSIC-EXTO4. Apply 5/8” DD+GG
• Insulate walls with R13 (plus vapor barrier on concrete walls)
• Screen = 2.35:1 SMX 120”w X 51.1"h X 130.4"diag
• Stage = Sand filled, but not yet sized. Separated from walls.
• Riser = Insulation filled, not yet sized. Separated from walls.
• Door = Safe N Sound exterior door with exterior trim

http://i148.photobucket.com/albums/s18/muffinlina/Theateroptions-2.jpg

1) I plan to put tri corner bass traps in the false wall. But since there are no 90 degree angles in the back of the room is a rear bass trap required? If so, how do you suggest I build it?
2) I’m considering sound absorbing panels on the first reflection point (which is likely to be on the door. Are there any concerns with that?
3) What other suggestions do you have for sound isolation in this room?

Regards, DJ

1) I plan to put tri corner bass traps in the false wall. But since there are no 90 degree angles in the back of the room is a rear bass trap required? If so, how do you suggest I build it?
"Acoustically," why not make the rear square and use superchunk corner traps and acoustically transparent cloth to create the diagonal corners a la your drawing?

Thanks pepar,

That's certainly something to think about. I didn't go that route originally because my thinking is that the rear speakers would be too close to the last row. And other discussions I read said that having the rear wall too close to the seats adds a "boomy" sound. Compromise, compromise, compromise! But which would be the best alternative?

Thanks pepar,

That's certainly something to think about. I didn't go that route originally because my thinking is that the rear speakers would be too close to the last row. And other discussions I read said that having the rear wall too close to the seats adds a "boomy" sound. Compromise, compromise, compromise! But which would be the best alternative?
Yes, all definitely true. My suggestion of triangular traps in the corner (as in the link in my sig) would yield the exact same floor plan and hide big hunky traps that a lot of people find difficult to hide.

If my room is too small to get quality corner traps will soffit traps all the way around work sufficient? I can have corner traps from floor to about 5 feet but above that will be tough with using sconces. In addition to my surrounds being too close to the corners.

Thank you

"Acoustically," why not make the rear square and use superchunk corner traps and acoustically transparent cloth to create the diagonal corners a la your drawing?


Those are foundation walls.

Yeah Big, you're right that they're foundation walls (not so easily moved!).

Maybe KERMIE's question about using soffits for bass traps is another alternative for my HT?

Regards

Those are foundation walls.
The diagonals? Nevermind . . :)

If just the soffit is the case, do you leave the face and the bottom open, then fill with 4" ridged fiberglass?

Thank you

"Acoustically," why not make the rear square and use superchunk corner traps and acoustically transparent cloth to create the diagonal corners a la your drawing?



Hey Pepar,

How do the superchunk corner traps compare to thick corner traps with some air behind them? The type with air behind them are much bigger but if you can accommodate them they provide more bass absorption don't they?

TIA

Chris

Hey Pepar,

How do the superchunk corner traps compare to thick corner traps with some air behind them? The type with air behind them are much bigger but if you can accommodate them they provide more bass absorption don't they?
The solid ones are better, but here is the data (http://forum.studiotips.com/viewtopic.php?f=8&t=536) for you to look at yourself.

How do the superchunk corner traps compare to thick corner traps with some air behind them? The type with air behind them are much bigger but if you can accommodate them they provide more bass absorption don't they?

The testing we had Riverbanks Acoustic Lab certainly indicates that the corner-filling design does out perform the panel straddling the corner design.

Frank

I am soon going to be installing some GIK tri-traps and 244 panels, but before I do I'd like to measure my room's frequency response to know where things are now.

I have a Pioneer SC-05 receiver which has the MCACC with EQ, but it doesn't give enough points of adjustment in the bass frequencies to give me enough information. But I can hear some serious "one note bass" and overall boominess. Room is 26'L x 13'W x 12'H



Only trouble is, I am a complete n00b when it comes to which type of product I should use for this. Can this be done relatively well using a laptop and microphone? If so, could I use the microphone that came with my SC-05 receiver, or is do I need to buy an actual SPL meter for these readings???

Is there any free software that can just take input from a mic and spit out nice detailed graphs? I know I saw a link earlier but forgot to bookmark and now can't find much.

Thanks!
Ryan

I am soon going to be installing some GIK tri-traps and 244 panels, but before I do I'd like to measure my room's frequency response to know where things are now.

I have a Pioneer SC-05 receiver which has the MCACC with EQ, but it doesn't give enough points of adjustment in the bass frequencies to give me enough information. But I can hear some serious "one note bass" and overall boominess. Room is 26'L x 13'W x 12'H



Only trouble is, I am a complete n00b when it comes to which type of product I should use for this. Can this be done relatively well using a laptop and microphone? If so, could I use the microphone that came with my SC-05 receiver, or is do I need to buy an actual SPL meter for these readings???

Is there any free software that can just take input from a mic and spit out nice detailed graphs? I know I saw a link earlier but forgot to bookmark and now can't find much.

Thanks!
Ryan

Prices are very approximate... from memory... just to give you an idea. This stuff is pretty cheap.

I use:

1. Room EQ Wizard is free and GREAT! I run it on Windoze.

2. LinearX M31 calibrated mic. Comes with it's calibration curve you can enter into Room EQ Wizard if you want. About $100

3. Behringer MiniMIC modeling mic pre-amp. I don't use any of the modeling settings, of course. It was just a nice cheap mic pre-amp with an analog VU meter. It's good to 6Hz! About $89

4. Then I got an M-Audio Transit to get the pre-amp output into the laptop's USB port and Room EQ Wizard's test tones into the audio system. About $50

5. Last, I use Behringer's Feedback Destroyer Pro to adjust out those bothersome "humps". It's a multi-band parametric eq that works extremely well for tuning sub-woofers. About $99

Thanks alot for that info! I just got REW 4.11 and it looks like it does more than I'll need.

Just so I'm clear, what is the difference between using a Microphone and an SPL meter when using RoomEQ??? Does an SPL meter also need any kind of pre-amp?

Also, the M-Audio Transit, that is handling both the Mic into the laptop and also allows you to go from mini to RCA???

The Behringer feedback destroyer sounds neat.... but I think I might be able to adjust the EQ to a finer level if I use the RS232 port from my receiver and then install some software but I haven't gotten that far yet :D

2. LinearX M31 calibrated mic. Comes with it's calibration curve you can enter into Room EQ Wizard if you want.
And you definitely should!

Thanks alot for that info! I just got REW 4.11 and it looks like it does more than I'll need.

Just so I'm clear, what is the difference between using a Microphone and an SPL meter when using RoomEQ??? Does an SPL meter also need any kind of pre-amp?
Not exactly sure what you're asking, but REW has SPL measuring function. It does need a standalone SPL meter to calibrate it to reference once at the beginning of the session.

Also, the M-Audio Transit, that is handling both the Mic into the laptop and also allows you to go from mini to RCA???
Technically, no actually, you are using the line in and line out of the "soundcard." The mic's preamp does not pug into a mic input; it goes into the line input. Line output goes to the device/channel being tested.

The Behringer feedback destroyer sounds neat.... but I think I might be able to adjust the EQ to a finer level if I use the RS232 port from my receiver and then install some software but I haven't gotten that far yet :D
What would you be adjusting in your receiver via that RS232 port?

Thanks alot for that info! I just got REW 4.11 and it looks like it does more than I'll need.
More than I need too. Just use what you need and forget the rest. It's like Word or Excel.

The Behringer feedback destroyer sounds neat.... but I think I might be able to adjust the EQ to a finer level if I use the RS232 port from my receiver and then install some software but I haven't gotten that far yet :D
I dunno... I think you'd be hard-pressed to find a finer level of control than 24 parametric eq bands for a subwoofer. But maybe. I have no idea what's in today's "room eq" receivers.

The solid ones are better, but here is the data (http://forum.studiotips.com/viewtopic.php?f=8&t=536) for you to look at yourself.


Thanks Pepar and Frank!

Chris

Not exactly sure what you're asking, but REW has SPL measuring function. It does need a standalone SPL meter to calibrate it to reference once at the beginning of the session.


I am talking about how the HomeTheaterShack guide says you can use a Mic or an SPL meter:

We recommend the Behringer ECM8000 microphone (with a proper preamp) or the Galaxy CM-140 SPL meter for full range measurements. Limit your measurements with the Radio Shack SPL meters to 3KHz.


So you are saying that you NEED an SPL meter for calibration? HTS seems to suggest you can use either/or. Could the entire setup be done just from a mic or SPL meter?

I'm not sure why you need a preamp with a mic, do you also need a preamp with an SPL meter?

I am talking about how the HomeTheaterShack guide says you can use a Mic or an SPL meter:

"We recommend the Behringer ECM8000 microphone (with a proper preamp) or the Galaxy CM-140 SPL meter for full range measurements. Limit your measurements with the Radio Shack SPL meters to 3KHz. "

So you are saying that you NEED an SPL meter for calibration? HTS seems to suggest you can use either/or. Could the entire setup be done just from a mic or SPL meter?
I believe that they are referring to using a Radio Shack SPL meter as a measurement mic. In any case, one needs an SPL meter to calibrate REW to a sound pressure level. Generate a test signal, either with REW or from an external source; held next to the test mic, measure it with an SPL meter and "tell" REW what the level is that it is "seeing" on the measurement mic. If one is actually using the RS meter as a measurement mic, then it will both indicate the SPL and send the signal to REW.

I'm not sure why you need a preamp with a mic, do you also need a preamp with an SPL meter?
The RS meter has a line out that can connect directly to the soundcard's line input. (Mic inputs should NOT be used.) The measurement mics I am familiar with - the EMM8 and the Audyssey Pro mic - need pre-amps because they do not output a line level signal.

I really don't think that they are saying "either or" wrt the RS meter and a calibrated mic when they qualify it with "Limit your measurements with the Radio Shack SPL meters to 3KHz." I got myself into a brouhaha on the Audyssey thread trying to point out the limitations of the RS meter in this application and I don't care to do it here as well. Everybody can use whatever they want to.

So you are saying that you NEED an SPL meter for calibration?

As pepar said, "yes." But Personally, I'm not interested in SPL calibration so I don't bother. I have a tri-amp's system and the Behringer FBD for the subwoofer. I just use the emasurements to flatten and balance things out. Then I turn up the volume to where I want for a particular movie/audience/time of day.

Just recently added absorption panels in my HT, enclosed is a few pictures can someone advise me if it is too high from the floor? Thank you very much.
first 2 photos are the new setup (2X4X1) it also shows the panels below but I took that out, should I put it back? last photo was the old setup. (1 2X4X2) is now on each side of the screen and also added 2 2x4x1 just below the screen hanged rectangular. Any advised would be appreciated.

In the early planning stage of my dedicated HT. The room is 25'x14'. The current plan is a false wall. From the flase wall to the finished back wall is 22'. On the front left wall next to the false wall is a 4'x4' egress window. I'm trying to figure out the best way to cover this window, but not drywall over it completely.

My first thought was to make a removeable drywall block and then put a 4'x4' sound panel over it. Thus covering up the seems from the drywall block. But then I thought, why not just sink the sound panels into the wall. Is this a bad idea?

The picture below is rough mock up (close to scale, but not exact). It was when I had the thought of sound panels covering the wall, not imbeded in the wall. The red x is where the egress window is.

Currently there are not even stud walls up. The picture is just 1 idea done with sketchup.

Any and all thoughts on this would be apprecited. Everything in the room is up for change, except for the beam across the ceiling. The door placement can be moved to any either of the blue Xs. The columns are just an idea and can be ditched.

http://i6.photobucket.com/albums/y243/docwhorocks/theateridea1.jpg

Thanks for any and all input :D

I'm towards the end of my theater build and plan on treating the the whole front wall with linacoustic, the lower side and back wall with linacoustic 44" with polyester batting on the upper wall. I have a front wall "room" that is 4' deep by 12' wide. It is mostly enclosed, much like a closet. Its enclosed on all sides except the right side wall(which will house my components) and the front wall which has a 6-8" wall along the outer edges (top and 2 sides). I am going to do a 120" AT screen and GOM along below the screen down to the stage. In my research about bass traps and room acoustics, I am now wondering that due to the "enclosed" space on the screen wall will bass traps be as big of an issue or have I messed up in my design and do I need to change something now?

I don't totally understand the question, but I can tell you that lack of left-right symmetry is going to be a problem. More here:

How to set up a room (http://www.realtraps.com/art_room-setup.htm)

--Ethan

Hi Ethan, I assume you are referring to my post. As far as the room design, I am stuck with it :( My concern is basically having the front wall that is not fully open acoustically. it has been "boxed in by the 8" walls on the side and top. Will this affect bass response acoustically? I have noticed a huge loss in loudness, but seems to reduce the boominess of the room. Is it the loss of the 3 boundry db increase or do i have more serious acoustic issues here?

P.S. Please don't laugh, I stink at those CAD programs :(

You could build a dividing wall along the right hand side that makes the main space symmetrical. Leave openings to walk into each row of seats.

It won't be perfect symmetry, because the left hand wall will be contiguous and the right hand "wall" won't be. But it will be better than not having the dividing wall. And you have the added benefit of mids+highs seeing the room as symmetrical (good for non-bass frequencies) and the bass finding the gaps and seeing the larger room as not-symmetrical (good for bass frequencies).

I am making a dedicated home theatre in a 12' by 13' (by 8') room. I am planning only one raw of seats and rather simple set-up (no stage or ramp), but want to make sure I am getting best possible picture and sound.

First, few words about personal preferences - I tend to like "dead" rooms with close to no reverb. Also, given that this is a rather small room, and I'll have to put seats close to the rear wall, there is little chance of quality reverb, so I'd rather err on the side of no reverb (not sure how correct my logic is).

So here is my plan:

1. Front wall - completely covered by 2" of Roxul or other mineral wool/board covered by acoustically transparent fabric. Due to space limits, I am not making the stage - the screen will just be attached to the wall over the sound treatment.
2. Rear wall - same as the front + 2 triangular bass traps (superchunks) in the corners
3. Sides - a strip of 2" sound treatment (absorption) along the entire wall, starting about 2 feet from the floor and ending a foot above ear level. non-covered-2 layer drywall everywhere else.
4. Floor - plush carpet on concrete
5. Ceiling - a small spot (something like 2'x3') of the same absorption treatment in the first reflection point and non-covered drywall everywhere else. The ceiling is flat with soffit above the seating area.

Does this make sense? Do I need any diffusion panels? I got an impression diffusion treatment is not useful for such small spaces...

Thanks!

I'd recommend that you double the thickness, and cover only half the wall area you describe.

Focus on the first reflection points.

And if you can quadruple the thickness and cover just a 1/4 of the wall area (while still getting all the first reflection points), that is even better.

You'll avoid killing off the high end, get much more even, broad band, mid-band, and bass absorption.

I'd recommend that you double the thickness, and cover only half the wall area you describe.

Focus on the first reflection points.

And if you can quadruple the thickness and cover just a 1/4 of the wall area (while still getting all the first reflection points), that is even better.

You'll avoid killing off the high end, get much more even, broad band, mid-band, and bass absorption.

So just to make sure I understand it right - you are suggesting 4" of sound treatment on the primary reflection points? I cannot get 8 inches, but I could get, for example, two more superchunk bass traps (for 4 total).

Also, what do you suggest I do with the front and back walls? I'm going for a 7.1 setup.

My concern is basically having the front wall that is not fully open acoustically. it has been "boxed in by the 8" walls on the side and top. Will this affect bass response acoustically?

In all honesty I can't tell, but at least now with your new drawings the situation is perfectly clear. Generally, large open areas are a Good Thing. But lots of insulation as you propose will certainly help further.

--Ethan

So just to make sure I understand it right - you are suggesting 4" of sound treatment on the primary reflection points? I cannot get 8 inches, but I could get, for example, two more superchunk bass traps(for 4 total).

4 inches is great. Much better than 2 inches.

And more of the superchunk style corner bass traps will be useful. It's almost impossible to have too many of those.

Also, what do you suggest I do with the front and back walls? I'm going for a 7.1 setup.

Front and back walls have first reflection points, too. Hit those, but don't just generically cover the whole wall or large swaths of wall.

4
Front and back walls have first reflection points, too. Hit those, but don't just generically cover the whole wall or large swaths of wall.

From what I have gathered from "acoustics 101" from this thread, you should cover the entire front wall (and the side/rear walls completely under ear height). Not true?

Every few pages of this thread someone is asking the same question and we never seem to get anywhere with an agreed conclusion. That's fair enough in some respects as people are entitled to a different view of the world.

BUT, because this has been a constant point of frustration I've followed Dennis' advice and got a copy of Sound Reproduction by Floyd Toole and the somewhat older, Master Handbook fo Acoustics by Everest. They contain more information then you could imagine and back up my old view that text books are better than the internet - just to be clear this isn't a shot at this forum.

So, do yourselves a favour and get a copy of Sound Reproduction and start reading (its very long, I've only read a few chapters of interest so far).

One of the main things I've discovered to date is that many of the treatment options many people use here aren't really that necessary or can lead to poor 2 channel quality (for example) - so you need to be very careful in what you spend your cash on and get something suitable for your specific needs, not that of someone else.

Highly Recommended.

P.S. these books aren't that cheap, but in the overall scheme of things they are nothing and will probably save you some coin in the long run.

Every few pages of this thread someone is asking the same question and we never seem to get anywhere with an agreed conclusion. That's fair enough in some respects as people are entitled to a different view of the world.


That's very true. I think a lot of it has to do with the fact that you have to seriously filter what you read here to. you have to filter the advise since there is a lot of people here that have an economic interest in whats said.

One of the main things I've discovered to date is that many of the treatment options many people use here aren't really that necessary or can lead to poor 2 channel quality (for example)

Well I hope my first reflection absorption panels aren't one of those unnecessary treatment options.

From what I have gathered from "acoustics 101" from this thread, you should cover the entire front wall (and the side/rear walls completely under ear height). Not true?

Neither true nor false. But definitely NOT a cookie cutter approach that works well in all (or even most?) situations.

There are advocates on both sides of the issue. But the scientific literature (nicely summarized in the Toole book mentioned above) would answer your question with the statement "Not true".

Yeah it's definitely true that you can make a room sound too dead. While there's a purity to the sound something just doesn't feel right like that.

Well I hope my first reflection absorption panels aren't one of those unnecessary treatment options.

I dont want to sit here and re-hash Toole's book, nor do I think I have the necessary knowledge to present sections of it that wont provide a biased view when read in isolation to the rest of his work.

Get the book.

Saying that'd I'd think twice about treating a room if you are into Stereo in a big way - I kind of am. But my problem is that I want to design a room with the treatments it needs, but that is hard to determine that until its built!

For example, I think chair rails look very classy with wall paper above. But I cant have a rail if I need to have some sort of treatment haning over it, because that'll look totally stupid. I dont want to put bass traps in later, because I want to wrap mouldings etc around it all to make it just look like an angled wall....so do I need traps or not? should I build soffits as normal or with 600mm 45degree bass traps in the wall/ceiling joint? These are all things I am trying to come to terms with before the room is built. But its becoming abuldantly obvious I'll have to build it - set up the gear, listen and then take it all out and finish decorating it and then put it all back....this I am trying to avoid.

Newer "thinking" encompasses multichannel systems. Some of the older works are from the stereo audio era, and studio acoustics.

4 inches is great. Much better than 2 inches.

And more of the superchunk style corner bass traps will be useful. It's almost impossible to have too many of those...

Front and back walls have first reflection points, too. Hit those, but don't just generically cover the whole wall or large swaths of wall.

Great advice. Rule-of-thumb type information is common and it's good as far as it goes, but it's kinda like axioms and proverbs. They're meant to cover a lot of ground, but context is important. Sometimes it's definitely the right thing to cover all of the front wall; other times it definitely isn't. Each room is it's own context and should be viewed that way. Personally I like to place lots of 4" broad band panels in smaller rooms because they're more efficient...they cover more sonic ground in a more balanced way using fewer panels.

Frank

4 inches is great. Much better than 2 inches.

And more of the superchunk style corner bass traps will be useful. It's almost impossible to have too many of those.



Front and back walls have first reflection points, too. Hit those, but don't just generically cover the whole wall or large swaths of wall.

Should I worry about dispersion panels at all? The room is almost a perfect square (12' x 13') with one row about 3 feet away from the back wall and 7.1 setup.

Thanks

4 inches is great. Much better than 2 inches.
...
Front and back walls have first reflection points, too. Hit those, but don't just generically cover the whole wall or large swaths of wall.
I'm afraid such a strategy for the front wall makes no sense. Main speakers face away from this wall, into the room. Very little middle to high frequency energy is directed at the front wall first reflection points. As for low frequencies (which could potentally cause 1/4 wave cancelation via reflection from these points), a mere 4 inches of porous absorption is not going to help.

I'm afraid such a strategy for the front wall makes no sense. Main speakers face away from this wall, into the room. Very little middle to high frequency energy is directed at the front wall first reflection points. As for low frequencies (which could potentally cause 1/4 wave cancelation via reflection from these points), a mere 4 inches of porous absorption is not going to help.
"Dead End" is dead for multichannel reproduction?

"Dead End" is dead for multichannel reproduction?
Not what I said. :) It's just that the front wall early reflection points have no particular importance for treatment.

Not what I said. :) It's just that the front wall early reflection points have no particular importance for treatment.
Thanks. On a completely different subject then, is LEDE still recommended for multichannel reproduction? ;)

From what I have gathered from "acoustics 101" from this thread, you should cover the entire front wall (and the side/rear walls completely under ear height). Not true?

Not true, and Terry gave some reasons why. However, bass traps on the front wall always help. More here:

Front Wall Absorption (http://www.realtraps.com/art_front-wall.htm)

As for the side walls, having absorption down by the floor is a waste, and not going to at least a foot above ear height leaves too much of the wall bare and reflecting. More here:

Early Reflections (http://www.realtraps.com/rfz.htm)
How to set up a room (http://www.realtraps.com/art_room-setup.htm)

--Ethan

Thanks. On a completely different subject then, is LEDE still recommended for multichannel reproduction? ;)
:)
I didn't know that it ever was. LEDE was a fad for control rooms around a quarter century ago. No acoustic design idea ever fully dies. :D

I'm afraid such a strategy for the front wall makes no sense. Main speakers face away from this wall, into the room.

What about reflection of the sound from rears?

:)
I didn't know that it ever was. LEDE was a fad for control rooms around a quarter century ago. No acoustic design idea ever fully dies. :D
Unfortunately, I built my house about 20 years ago and was still heavily influenced by that scheme when I upgraded my theater 4 years ago. Now I wonder if I should not remove the 2" Linacoustic behind the false wall.

I'm afraid such a strategy for the front wall makes no sense. Main speakers face away from this wall, into the room. Very little middle to high frequency energy is directed at the front wall first reflection points. As for low frequencies (which could potentally cause 1/4 wave cancelation via reflection from these points), a mere 4 inches of porous absorption is not going to help.

Yep, I was conflating two different goals. Earlier I wrote:

"And if you can quadruple the thickness and cover just a 1/4 of the wall area ... that is even better." That'd be an 8 inch panel.

Or a 4 inch panel bridged across a corner at 45degrees would be better than a 4 inch panel flat against the wall.

Hello, looking for some feedback and ideas for treating my room. Currently my bass is AWFUL (polk DSW Pro600), many songs hear like one-note-bass and it just sounds muddy.


Dimensions are about 13'w x 26' L x 12' H. Unfortunately it is a kind of ackward space with all sorts of openings.

So with each picture I'll briefly outline my current treatment thoughts, please let me know if I'm in the right direction. For now I'm using all GIK products in my planning....

Sorry this first pic came out so dark:
http://www.worstkind.com/tv/room3.jpg
Was thinking of using 6 Monster-Bass-traps, 3 in each front corner, stacked floor to ceiling. They would be a few inches from the front L/R speakers.

In addition, (3) 242 panels on the 1st reflection point by the recliner (where the picture is hanging), and I'll need some kind of acoustic curtains on the left. Not much I can do for the fireplace I guess?

Another 242 on the left wall between the two top windows, and (2) 242's on the 1st reflection on the ceiling.


Surround Left:
http://www.worstkind.com/tv/Room1.jpg
Would it be beneficial to use a Tri-Trap up in these top-rear corners??? Or would I be better off with a Monster-Bass-Trap here also???


Surround Right:
http://www.worstkind.com/tv/Room2.jpg
Again, Tri-Trap or Monster-bass in the upper back corner?

Was thinking of putting a single 242 panel on the back wall to soak up the sound, since one whole side is open I dont want uneven echos. Should I use multiple 242s there for that purpose?

Also, was thinking of putting some Tri-Traps in the stair-way ceiling, and possibly a 242 panel by where the banister meets the wall in that photo.

Sorry for what might be poorly constructed post.... I could post back with images depicting where I am thinking of the treatments if its not clear.

Hello, looking for some feedback and ideas for treating my room. Currently my bass is AWFUL (polk DSW Pro600), many songs hear like one-note-bass and it just sounds muddy.Aside from acoustic treatments, if you can figure out a way to get at least 1 band of PEQ in there to tune out the room's primary resonance, you'd notice a huge benefit in solving the one note bass problem. Several subs have this facility. Not sure if there's a simple outboard box available, though. Which AVR are you using? Does it have any sort of EQ for the sub output?

If your system has no EQ for the sub, an option does exist. This thread (http://www.avsforum.com/avs-vb/showthread.php?t=1048461)describes the Anti-mode 8033. Worth a look.

I read the first 20+ pages again (last time was about 1.5 years ago) and it gave me better direction. Looking for a few more suggestions.

Front bass traps: I'm looking at buying 4 more 2' x 4' ATS acoustics panels in bass trap config. They would be a triangle in the corner with their mount kit. They would be 4 inchs thick with no wood backs. I can stack 2 in the corner and they would fit perfectly and look pretty darn clean.

Here is an example where I threw in some of my normal panels for testing. I also put my sub location and bass trap location in the drawing below.

http://www.silverti.com/pics/HT/front.jpg



Here's something different!

I have found that a lot of sound is escaping into my house through my stairs going up (the rest of the room is sealed pretty good since I have double 5/8th sheet rock, double walls and double insulation). I drew this up real fast as an example.

http://i184.photobucket.com/albums/x25/tleavit/stairs.jpg

At the end of the stairs is a solid wood door but it also is not "sealed". For example there is a half inch gap open on the bottom between it and the carpet.

What I was thinking of doing is putting some of the 4" 2' x 4' panels in locations that I marked with the red spray paint to help stop the sound bouncing upstairs. I would consider also lining the entire middle stair wall with linacoustic. I also want to figure out how to seal that door better.

Any advise would be apreciated.

I read the first 20+ pages again (last time was about 1.5 years ago) and it gave me better direction. Looking for a few more suggestions.

Front bass traps: I'm looking at buying 4 more 2' x 4' ATS acoustics panels in bass trap config. They would be a triangle in the corner with their mount kit. They would be 4 inchs thick with no wood backs. I can stack 2 in the corner and they would fit perfectly and look pretty darn clean.

Here is an example where I threw in some of my normal panels for testing. I also put my sub location and bass trap location in the drawing below.

http://www.silverti.com/pics/HT/front.jpg



Here's something different!

I have found that a lot of sound is escaping into my house through my stairs going up (the rest of the room is sealed pretty good since I have double 5/8th sheet rock, double walls and double insulation). I drew this up real fast as an example.

http://i184.photobucket.com/albums/x25/tleavit/stairs.jpg

At the end of the stairs is a solid wood door but it also is not "sealed". For example there is a half inch gap open on the bottom between it and the carpet.

What I was thinking of doing is putting some of the 4" 2' x 4' panels in locations that I marked with the red spray paint to help stop the sound bouncing upstairs. I would consider also lining the entire middle stair wall with linacoustic. I also want to figure out how to seal that door better.

Any advise would be apreciated.

weather stripping and a threshold would be a good place to start.

I initially posted this in the Audyssey thread. It may not be appropriate for this thread because treatments are a final option, if an option at all but at the suggestion of people there, I'm listing it here to see if there are any who have any experience or feedback on this.

Help Please - Sound pressure & Audyssey Trouble-Got an RTA-what to do?

--------------------------------------------------------------------------------

I recently got the Integra DHC 9.9 conviced it was the answer to all my issues with my video and connectivity challenged older Yamaha RXV-1400. Pretty much - it was. But it created a new one.

Now that I've installed the Integra - something painful is happening in the room. It's more prevalent with Multi EQ on, but is present with no EQ whatsoever. After multiple calibrations with two subs from my previously identical set-up except the avr, and reducing the system to a single sub, the room is being pressurized to a painful degree even at very low volumes, with no EQ engaged at all. Audyssey exacerbates the issue. My sub is actually calibrated 3db lower than the other speakers and it still hurts. My wife and I both experience ear pain almost immediately and after a minute or 2, I swallow and my ears pop as if on an airplane. I want to emphasize this isnt' so much a volume issue - it's sound pressure. It doesn't occur on music but I can't even think about watching tv much less a blu ray unless I do the following.

It's not just the sub. To eliminate the issue, I've had to turn the sub off and set my mains at 80hz so nothing below that comes out of my system. Even at that setting, If I engage the eq (not dynamic eq-can't even think about using that) the problem is back even with everything cut off at 80hz.

I have a great contact who was kind enough to let me use their spectrum analyzer. It's an Audio Control SA 3050. I have figured out how to measure each speaker individually and will use the full mono setting to check the summed effect of all speakers.

My question, unless someone has a eureka solution to my issue is: Can I somehow use REW with the RTA to actually get the readings into the computer as opposed to manually logging all of the results. I have a lot of testing to do and it's going to be a ton of data when I look at measuring speakers 7.1, 7.2, 7.3 individually and summed, as well as the inevitable various placements I'll have to experiment with for the sub or subs - whatever works. (Obviously my issue with the Yamaha was not enough bass-thus the 3 subs - I'd like to get down to 2 just to keep headroom but will drop to one if it fixes it)


FYI: I've used the input volume attenuation and other suggestions posted by batpig. No tangible results

Room dimensions: 29' 6" x 22'8" x 7'11" with open doorways on opposite corners of the lenght of the room. Large window and Slider on left & right framing the seating positions.

Equip:

Integra DHC 9.9
Rotel 1095
B&W 803s
B&W 602 S2 (pair for center)
B&W CDM SNT surrounds
SVS 25-31 & 20-39 both tuned to 20hz - this was recommended and approved by Ed at SVS and never caused the problem on the older unit.
Using Old Yamaha to power surrounds til I see if I can fix this before buying an surround amp. This used to be the heart of the system and neither this, nor the previous Yamaha 2090 exhibited this problem with the same room, mains & dual subs. The center & surrounds have changed over the years.

I guess trial and error is the way to go for the RTA & REW.

The RTA only emits wide band pink noise - no sweeps. But I'll start there.
That might be all you need.

I could have something wrong in the setup but I've experimented exhaustively and think I've tried every possible combination of settings to avoid this more demanding path and the possibility of room treatment.
Room treatments are always a good idea and necessary to get one's sound to the next level. But your issue is *so* weird that there must be something wrong other than a room node or two. PAIN?!?!

Check on all the sub notes. Tried with and without processing and am back at no processing, have been for a while.
That is happens without the sub when mains are on large suggests that it is not the sub.

I feel like I'm reading a cliffhanger here, Artzilla! :D

Aside from acoustic treatments, if you can figure out a way to get at least 1 band of PEQ in there to tune out the room's primary resonance, you'd notice a huge benefit in solving the one note bass problem. Several subs have this facility. Not sure if there's a simple outboard box available, though. Which AVR are you using? Does it have any sort of EQ for the sub output?

If your system has no EQ for the sub, an option does exist. This thread (http://www.avsforum.com/avs-vb/showthread.php?t=1048461)describes the Anti-mode 8033. Worth a look.

Thanks. I have a Pioneer Elite SC-05 which does have MCACC.... but as you said it doesnt really seem set up for the sub since there's really only one band for EQ in the bass range, then the next one is over 100hz (cant recall exactly right now).

I got myself a galaxy SPL meter and I am going to try and do some testing with RoomEQ Wizard to see how bad things are.


I see above people talking about sealing doors at the end of hallways... can I ask why? I thought you just didn't want sound to echo off the walls, what harm is it if sound gets past a door??? I have halls, rooms and stairs all leading out of my HT room, none of which I can 'seal up'

That might be all you need.


Room treatments are always a good idea and necessary to get one's sound to the next level. But your issue is *so* weird that there must be something wrong other than a room node or two. PAIN?!?!


That is happens without the sub when mains are on large suggests that it is not the sub.

I feel like I'm reading a cliffhanger here, Artzilla! :D

You are, it's called, Is his wife going to kill him & when? How long does he have? I got lucky with a wife that likes football, Sci-Fi and action movies, and HT, but not being able to watch a movie or tv without this headache has turned her into......well, something else. Truth be told I'm far more bent about it than she is. Talk about expectations being dashed. I just read the praise the unit gets and how thrilled people are with it when they find that secret ingredient after their own brand of troubles for a whilethen "Eureka". I cross my fingers that I'll have my moment.

You're right about it not being the sub, or at least the sub alone. My mains are pretty capable, but they're not subs. Part of the reason for the Integra over the Marantz 8003 was the ability to adjust the spekaer x-overs by pair (And Audyssey XT & Dynamic EQ which make it worse rather than better) so I could run my mains lower than 80hz for the more articulate bass they provide within their comfort zone on music which is easily down to 60 if not 40 depending on individual taste. Make no mistake, I love bass, and prefer to run it a little hot when things are "normal". I was hoping the Integra & Audyssey would fill in the areas where I felt the Yamaha was bright and weak in mid-bass.

In the next hour or three I'm going to check the wiring again and do a quick run through of the speakers all on, full mono, with and without the sub, and post my results to see if they reveal anything.

So let's get this right... when you've made no changes except for replacing the yamaha witht the new AVR, it all goes haywire... and when you go back the problem goes away..

that says it has to be either;
1) the new AVR is so much more capable than the old it's dispalying room/setup problems yuo never knew you had, or
2) a faulty AVR, or
3) a faulty job setting it up...

Not sure what ins/outs you have on the RTA, but I would start by using either the RTA, or preferably (at least in my world) REW, to inject a signal into the Integra's input and read it's preamp output ... make sure that's clean... if not, start looking at what settings affect it in a manner that's advantageous... if you can't find one, it's faulty...

I At the end of the stairs is a solid wood door but it also is not "sealed". For example there is a half inch gap open on the bottom between it and the carpet.

What I was thinking of doing is putting some of the 4" 2' x 4' panels in locations that I marked with the red spray paint to help stop the sound bouncing upstairs. I would consider also lining the entire middle stair wall with linacoustic. I also want to figure out how to seal that door better.

Any advise would be apreciated.

This would help with the door issue:
http://www.soundproofingcompany.com/products/automatic_door_bottom/

CJ

I want to emphasize this isnt' so much a volume issue - it's sound pressure. It doesn't occur on music but I can't even think about watching tv much less a blu ray unless I do the following.


This sounds VERY MUCH like a infra-sonic vibration (2-20Hz) - you cannot hear it, but certain frequencies can play pretty bad tricks with your brain. I did it in a lab, and could get similar symptoms of air pressure or even induce nausea and vertigo.

It is pretty much guaranteed that sounds of this frequency are not mixed into any commercial disks, so the frequency can be created either by the sound system or by the room. My bet would be on the room, taking into account how you could get the same result without a sub and with mains cut off at 80Hz. It is possible that something in the room has a sub-sonic resonance frequency that is excited by the sound system. Try moving things around etc.

This sounds VERY MUCH like a infra-sonic vibration (2-20Hz) - you cannot hear it, but certain frequencies can play pretty bad tricks with your brain. I did it in a lab, and could get similar symptoms of air pressure or even induce nausea and vertigo.

It is pretty much guaranteed that sounds of this frequency are not mixed into any commercial disks, so the frequency can be created either by the sound system or by the room. My bet would be on the room, taking into account how you could get the same result without a sub and with mains cut off at 80Hz. It is possible that something in the room has a sub-sonic resonance frequency that is excited by the sound system. Try moving things around etc.

I would agree with only part of that 2-20Hz not occurring on commercial disks. But there is a distribution of likelyhood ranging from 2-5Hz being completely unlikely to 15-20Hz being fairly likely. Parts of Inside Man rattle my teeth and blur my vision. I'm sure it's lower than 20Hz.

I would agree with only part of that 2-20Hz not occurring on commercial disks. But there is a distribution of likelyhood ranging from 2-5Hz being completely unlikely to 15-20Hz being fairly likely. Parts of Inside Man rattle my teeth and blur my vision. I'm sure it's lower than 20Hz.
From his mains? He said "it" is there with the sub OFF and the mains at LARGE.

From his mains? He said "it" is there with the sub OFF and the mains at LARGE.

The quote I was responding to was this: "It is pretty much guaranteed that sounds of this frequency are not mixed into any commercial disks".

From his mains? He said "it" is there with the sub OFF and the mains at LARGE.
If his mains (or even his sub) are putting out significant sound at 2-5 Hz, I'd like to buy them! :D

If his mains (or even his sub) are putting out significant sound at 2-5 Hz, I'd like to buy them! :D

Again... I was simply responding to the claim about frequency content of commercial disks; that one sentence I quoted above. That's it. That's all. That's where my comment stops. The disk. Frequency content of disks comes well before subs on or off in the signal chain.

So let's get this right... when you've made no changes except for replacing the yamaha witht the new AVR, it all goes haywire... and when you go back the problem goes away..

that says it has to be either;
1) the new AVR is so much more capable than the old it's dispalying room/setup problems yuo never knew you had, or
2) a faulty AVR, or
3) a faulty job setting it up...

Not sure what ins/outs you have on the RTA, but I would start by using either the RTA, or preferably (at least in my world) REW, to inject a signal into the Integra's input and read it's preamp output ... make sure that's clean... if not, start looking at what settings affect it in a manner that's advantageous... if you can't find one, it's faulty...

#1 was my first assumption followed by #3. The jury is still out. I have more work to do. I have not tried reinserting the Yamah. That will happen in the next day or two but I will run thoroughly through the RTA tomorrow.

#1 was my first assumption followed by #3. The jury is still out. I have more work to do. I have not tried reinserting the Yamah. That will happen in the next day or two but I will run thoroughly through the RTA tomorrow.

Have you tried using only 1 of the mains ? If the problems go away it points a
speaker setup issue with the Integra.

A complete factory reset of the Integra may also help. It may have
configuration data that is messed up in NVRAM. You dealer can probably
help you.

If your RTA is capable, I suggest doing spot checks in the 5-15Hz region
to see if there is anything there.

Have you tried using only 1 of the mains ? If the problems go away it points a
speaker setup issue with the Integra.

A complete factory reset of the Integra may also help. It may have
configuration data that is messed up in NVRAM. You dealer can probably
help you.

If your RTA is capable, I suggest doing spot checks in the 5-15Hz region
to see if there is anything there.

The rta cuts off at 25 hz but I've run test tones with no eq and

from 11.22-17.2 It's varies by only 1db with a 3 db jump at 20hz

10 db spike at 22.45hz. where it stays relatively flat until a 13 db hole at 44.9

I get a 5 db spike at 113.1

5-10 db suckouts from 142.5 - 179.6

a 6 db drop at 254hz, and a 14 db drop at 403 hz

6-7 db drop at 570.2.

Does this indicate any sort of inteligible pattern?

FYI: This was run w/dual subs and mains crossed at 60hz or 80hz. Can't remember which but it was pretty flat through the crossover area regardless.