Ethan,

Using your file here is what i found:

http://home.mchsi.com/~fun_pictures/Graphic_Plots.JPG


I read most of what you have on your site but what is this telling me about room treatments?

thank you for your help when you get a chance

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.
What it doesn't seem like is anything that would cause you pain. Could you elaborate a bit on what you think is causing your distress?

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.

I have to agree. That's really not bad at all. What are you hearing that's bothering you?

Frank

I have to agree. That's really not bad at all. What are you hearing that's bothering you?

Frank

I can only describe it as "pressure". It's progressive. My wife notices it immediately and if you sit there a few minutes I end up with a naggin little pain and a ringing in my ear that lasts a while. With me, it's mostly the right ear and my wofe, the left. She sits on the left side of the couch and I'm on the right so it seems they are reflective sounds not direct, that's as close as I've come to isolating anything.

I can't isolate a particular frequency. Since my last post, I've manageg to use the rta and the single band eq on one of my subs to get the bass pretty darn flat all the way up to 160. Sure I've got some 4 db swings in there but for a little placement experimentation and a single band parametric eq - not too bad.

Problem now is, I got a replacement mic from my dealer to see if maybe that could be faulty, plugged it in and I get speaker detect errors. It's not emitting the test tones now. I'm beginning to think this is a buggy unit.

I can only describe it as "pressure". It's progressive. My wife notices it immediately and if you sit there a few minutes I end up with a naggin little pain and a ringing in my ear that lasts a while. With me, it's mostly the right ear and my wofe, the left. She sits on the left side of the couch and I'm on the right so it seems they are reflective sounds not direct, that's as close as I've come to isolating anything.

I can't isolate a particular frequency. Since my last post, I've manageg to use the rta and the single band eq on one of my subs to get the bass pretty darn flat all the way up to 160. Sure I've got some 4 db swings in there but for a little placement experimentation and a single band parametric eq - not too bad.

Problem now is, I got a replacement mic from my dealer to see if maybe that could be faulty, plugged it in and I get speaker detect errors. It's not emitting the test tones now. I'm beginning to think this is a buggy unit.
Got any A/V nut enthusiast friends that you could have over for a listen?

Got any A/V nut enthusiast friends that you could have over for a listen?

In my neighborhood, I'm that nut. The only other AV nut I know is my wife and she's had enough.:D

In my neighborhood, I'm that nut. The only other AV nut I know is my wife
Well somehow I knew you'd say that. :) Where do you live?

Yeah, I'm the only nut who seems to care much at all about this in my circle of friends. I'm in West Boca just north of Fort Lauderdale.

Well, that's a little far for me to trek to help out...

Have you tried putting the yamaha back in?

Well, that's a little far for me to trek to help out...

Have you tried putting the yamaha back in?

Thanks for the consideration regardless. Haven't put the Yamaha back in but I know what it will do. I've had it for years with the same rig. I know it and it's foibles in and out - thuis, my attempt at an upgrade. If I put it back in, I'll never get it back out unless it spontaneously combusts or something without a major battle ropyal woth my wife. Probably something worse than the one we're havign right now over it. I'm not whipped and my wife's not a B---h but this unit and I have just completely worn through her patience. She likes movies as much as I do and getting a pain in the ear every time you try to watch one doesn't contribute to fun or domestic tranquility.

Artzilla,

I am wondering if maxl (of whose msg I made a sarcastic and stupid remark:() may be correct.

You have open doors, which communicate to other rooms. So the effective size of your room is much larger. It is possible that the lowest room mode for this total space is infrasonic -- say, around 10 Hz. This is probably too low for your mic and electronics to measure. But even if your speaker/sub puts out a small amount of energy down there, it can be greatly amplified by the room mode if the total space is well sealed, and you are at one "end" of it.

Note that this "end" doesn't have to be at a linear extreme. Low frequency room modes happily bend around 90 degree angles, and do not have to be in a straight line. This is a common misconception in acoustics.

- Terry

Artzilla,

I am wondering if maxl (of whose msg I made a sarcastic and stupid remark:() may be correct.

You have open doors, which communicate to other rooms. So the effective size of your room is much larger. It is possible that the lowest room mode for this total space is infrasonic -- say, around 10 Hz. This is probably too low for your mic and electronics to measure. But even if your speaker/sub puts out a small amount of energy down there, it can be greatly amplified by the room mode if the total space is well sealed, and you are at one "end" of it.

Note that this "end" doesn't have to be at a linear extreme. Low frequency room modes happily bend around 90 degree angles, and do not have to be in a straight line. This is a common misconception in acoustics.

- Terry

That sounds reasonable because my wife noticed it in the bedroom and the problem is detectable at the other end in the den. I have no doors, so I can't really test it. My subs are rated down to 20 & 25 hz in their native tune. I don't know what kind of rolloff there is below that. Your' theory holds water with me but the odd thing is that I get the same issue when running my mains only with EQ engaged (doesn't happen with no EQ & Mains only). They're B&W 803-s. Very capable, but I douby they're capable of putting out anything that low. I think they're rated to 39hz or something in that range.

Thanks for the consideration regardless. Haven't put the Yamaha back in but I know what it will do. I've had it for years with the same rig. I know it and it's foibles in and out - thuis, my attempt at an upgrade. If I put it back in, I'll never get it back out unless it spontaneously combusts or something without a major battle ropyal woth my wife. Probably something worse than the one we're havign right now over it. I'm not whipped and my wife's not a B---h but this unit and I have just completely worn through her patience. She likes movies as much as I do and getting a pain in the ear every time you try to watch one doesn't contribute to fun or domestic tranquility.

Ca you at least put it "half in" so you can scan what it's outputting, and compare that to a similar scan of the Integra, so you can see if the Integra is putting anything out that could excite room modes that the Yamaha wasn't putting out?

Point being, unless I'm misunderstanding, you only made one change, the AVR, you didn't change the room setup, the speakers, the doors, acoustic treatments, etc...

So first step SHOULD BE to make sure the new component isn't doing anything funky... if it's not putting out test tones, it sounds like it's doing something funky... try a factory reset and/or firmware upgrade... you didn't buy it open box, did you?

Ca you at least put it "half in" so you can scan what it's outputting, and compare that to a similar scan of the Integra, so you can see if the Integra is putting anything out that could excite room modes that the Yamaha wasn't putting out?

Point being, unless I'm misunderstanding, you only made one change, the AVR, you didn't change the room setup, the speakers, the doors, acoustic treatments, etc...

So first step SHOULD BE to make sure the new component isn't doing anything funky... if it's not putting out test tones, it sounds like it's doing something funky... try a factory reset and/or firmware upgrade... you didn't buy it open box, did you?

Certainly a sound approach but I think I've got one better in the works. Since Audyssey failed to initiate the test tones (confirmed by Kal the mic failure alone does not cause this) I have concluded with my dealer that I need a new unit as this one has at least one bug. (Audio that is. It also has the gamma bug on rgb video input) As opposed to beating my head agaisnt the wall with this one, I'm going to pick up a new unit (hopefully this afternoon) and beat my head against that one and see what happens.

Certainly a sound approach but I think I've got one better in the works. Since Audyssey failed to initiate the test tones (confirmed by Kal the mic failure alone does not cause this) I have concluded with my dealer that I need a new unit as this one has at least one bug. (Audio that is. It also has the gamma bug on rgb video input) As opposed to beating my head agaisnt the wall with this one, I'm going to pick up a new unit (hopefully this afternoon) and beat my head against that one and see what happens.

Now ur talkin! Replacement under warranty, I presume?

Now ur talkin! Replacement under warranty, I presume?

Yes, I picked it up at the end of April. I'm assuming any fault in the units would be a warranty replacement with it at 3 years and none of these units being that old yet but my dealer said even that was in question. Not by him, by Integra. I'm hoping this will solve this issue as well as the gamma bug. I had inquired about he gamma bug, even told him before I ordered it "make sure it doesn't have the gamma bug" and of course, it did. Integra, despite at least one memeber on this boards stating that he had the bug, and got a replacement which solved it, denies that they've hear dof it, that the problem exists. Whattcha gonna do?

Um, me personally? That means I'm not going buy Integra. If you bought from an authorized dealer, there should be no question about the warranty if the new unit fixes the problem, and you haven't broken the warranty seal on the unit. Unless they claim it was just set up wrong, which is why we were saying to try a factory reset... and maybe a firmware upgrade... What is this gamma bug of which you speak?

Um, me personally? That means I'm not going buy Integra. If you bought from an authorized dealer, there should be no question about the warranty if the new unit fixes the problem, and you haven't broken the warranty seal on the unit. Unless they claim it was just set up wrong, which is why we were saying to try a factory reset... and maybe a firmware upgrade... What is this gamma bug of which you speak?

I agree. That part is a no brainer. I'll refrain from commenting further because my dealer has always been a stand up guy and a complete overachiever in terms of service, (especially for someone on my budget given the scope ot their company) and he was reluctant to carry the line. He finally bent to pressure from outside sources and started carrying them. These were his comments on delaing with "a big Japanese company". Buyer beware I guess.

As for the gamma bug: If you feed the integra DHC 9.9 an rgb video signal via hdmi (don't know about component) and try to adjust the gamma, it only goes from green to red with negative & positive settings respectively. Change the signal from the same source (in my case the Pioneer BD-05) to a ycrbr 4:4:4, or 4:2:2 signal and the gamma adjustment works as it should.

Using your file here is what i found:

That's actually quite excellent bacause the lowest modes are evenly spaced.

what is this telling me about room treatments?

Nothing really. Mode calculators are meant to design new room dimensions, not advise how to treat an existing room. All rooms need bass traps and absorption at the reflection points. This readout simply tells you that you're starting from a good place, so after treatment you'll end up better than other rooms with less favorable ratios.

--Ethan

That's actually quite excellent bacause the lowest modes are evenly spaced.



Nothing really. Mode calculators are meant to design new room dimensions, not advise how to treat an existing room. All rooms need bass traps and absorption at the reflection points. This readout simply tells you that you're starting from a good place, so after treatment you'll end up better than other rooms with less favorable ratios.

--Ethan

How would you use a mode calculator for an L-shaped room? My room, for instance, has a relatively small (3'x5') alcove at the left rear corner of the room.

CJ

How would you use a mode calculator for an L-shaped room? My room, for instance, has a relatively small (3'x5') alcove at the left rear corner of the room.
You would not. Nor would it be used for my almost-but-not-quite rectangular room.

Hi All,

Long time AVSForum member, short-time "Acoustical Treatment" guy. I just recenly started putting the finishing touches on my room and have some moderate room challenges, that I'd like some advice on.

Room is 26 x 16. Below are some pictures that show my setup and some of the challenges. Room configuration is set up for 7.1. Fairly deep. There is an area to the left of the viewing area that is a fairly open space. Don't know how much sound is escaping here. What I DO KNOW, is that when I clap my hands, there is an echo coming from that area.

Please do not tell me to build a wall. Not really an option. Anyone have ideas of what I can do in terms of other treatments and panels tho?

Feedback welcome. Thx!

http://chriskir.smugmug.com/photos/592604109_JpABn-XL.jpg
http://chriskir.smugmug.com/photos/592604180_q9CVb-XL.jpg
http://chriskir.smugmug.com/photos/592604807_qGHfG-XL.jpg
http://chriskir.smugmug.com/photos/594004749_E2Azu-XL.jpg
http://chriskir.smugmug.com/photos/594004215_MQq5Y-XL.jpg
http://chriskir.smugmug.com/photos/594004348_D5obt-XL.jpg

eiger,

Your room appears to have no soft, acoustically absorptive surfaces other than the furniture. The rug, while well placed, seems too thin to do much of anything. This makes for way too "live" a space.

Get several 2" thick acoustic panels, and spread them around the walls just about anywhere (though don't fix them permanently, so that they can be moved later). Don't worry about bass traps or covering first reflection points just yet. Your room has more fundamental issues!

- Terry

Anyone have ideas of what I can do in terms of other treatments and panels tho?

Besides Terry's always-good advice, I suggest you move some of the stuff that's now in corners and put bass traps there. A room like that needs at least four bass traps, and even more is advisable. Music is much more than just mid and high frequencies, and the entire range needs to be treated including bass frequencies. As a point of reference, I have 51 panels in my 25 by 16 foot living room home theater. You don't need that many for great sound! But you definitely need more than what you have now. :D

--Ethan

Please do not tell me to build a wall. Not really an option. Anyone have ideas of what I can do in terms of other treatments and panels tho?

If this were my room, I'd do two things:

1) 4 or 6 inch thick panel traps straddling each corner, floor to ceiling if possible, to help the bass response.

2) 2 or 4 inch think wall panels at the first reflection points -- though as noted above, throwing them anywhere in the room would be useful given the current situation.

Here's a good read: http://www.realtraps.com/art_room-setup.htm

You are on the right track, with your thinking that you need acoustic panels. And the advice in the two posts above will get you a long way towards a solution.

--

By the way, that's a nice space you have to work with.

hi guys. received my panels from ATS they are the micro suede ones in wine color.

questions

o i have these in the right place? want to make sure before i put them up... cause its a pain in the ass

http://images.blu-ray.com/htgallery/24380_full.jpg

http://images.blu-ray.com/htgallery/24310_full.jpg

http://images.blu-ray.com/htgallery/24311_full.jpg

hi guys. received my panels from ATS they are the micro suede ones in wine color.

questions

o i have these in the right place? want to make sure before i put them up... cause its a pain in the ass
Are you asking if they look good there or if they are helping your room acoustics 'cause they are totally different questions. :)

A friend of mine has a few of these DIY base traps that he made for the corners of his room and 2 on the sides of his room. they are about 54" tall and 21 " wide covering in black fabric. Do you think these are effective for Bass Traps?

http://home.mchsi.com/~fun_pictures/untitled.JPG

do i have these in the right place? want to make sure before i put them up... cause its a pain in the ass

No. http://www.realtraps.com/art_room-setup.htm though it looks like you'll have trouble placing them in the most effective spots. So what you've chosen may be best.

Do you think these are effective for Bass Traps?

They probably help some, but that doesn't look to me like a particularly good way to make a bass trap.

--Ethan

Installed my ceiling panels. Did the old laser pointer / mirror trick to get the exact location to all 3 front speakers.

http://www.silverti.com/pics/HT/Ceiling.JPG

Reran Audyssey
http://www.silverti.com/pics/HT/DSC00700.JPG
http://www.silverti.com/pics/HT/DSC00701.JPG
http://www.silverti.com/pics/HT/DSC00702.JPG

tleavit

there is no way those LCRs are capable of 20Hz and even if they play at 80Hz it is probably with more distortion/compression than your sub. Set them to small or whatever your receivers equivalent is. Usually 'full band' is called 'large' - but 'full band' is actually a better name because this is a crossover control. What it means is all of the frequencies are sent to the LCRs with none of them sent to the sub - in other words - these frequencies are either not played at all because they are below your LCR range or they are not played well at all because the sub can do better. And if I misunderstand and "full band" means the sub shares the bottom octaves of the LCR's - then the latter comment still applies.

It does requiring properly balancing sub and LCR levels - do it right a plucked bass will sound like it is on the LCR stage even though the fundamental is played by the sub.

Also a panel above the screen and some black velvet on the white case will seriously cut back on the ceiling glare - may not think it is distracting now - but you will realize it was once you fix it!

Reran Audyssey
http://www.silverti.com/pics/HT/DSC00700.JPG
I know this is not what you're on this thread for, but you did change your speakers - ALL of them - from Full Band to a crossover around 80Hz, didn't you?

I know this is not what you're on this thread for, but you did change your speakers - ALL of them - from Full Band to a crossover around 80Hz, didn't you?

Yup! I usually change them right back to the Onkyo 805's THX recomendation of 80. I had just taken those raw pictures right after I ran it. I find it funny that *every* time I run Aud, it sets them back to Full and drops my Sub WAY down. In this cae, it wasn't as bad, in times before it would go like -20db to -25db on my sub.

Also a panel above the screen and some black velvet on the white case will seriously cut back on the ceiling glare - may not think it is distracting now - but you will realize it was once you fix it!

Thanks! Hahahah, thats been on my wifes "to do list" for 1.5 years now!

You could threaten to use her sewing machine and make a case wrap yourself - that will get her motivated to do it soon as she sees you start threading the bobbin - cause you will be doing it all wrong!

So Audyssey sets it up wrong by default?!

You could threaten to use her sewing machine and make a case wrap yourself - that will get her motivated to do it soon as she sees you start threading the bobbin - cause you will be doing it all wrong!

So Audyssey sets it up wrong by default?!

Ya, every time sets my speakers to full since I bought it 2 years ago.

So Audyssey sets it up wrong by default?!

Ya, every time sets my speakers to full since I bought it 2 years ago.

Fine point: Audyssey measures the response. It is the decision of the particular AVR/prepro manufacturer to define a specific FR as full and that varies a lot from one to another. The Audyssey EQ (one of the stand-alone units) is more reasonable, imho, in making this determination.

I’ve read through the choices regarding sound proofing soffits and dead vent systems (thanks John H.). But I was wondering if I would get decent isolation if I built a “backer box” around the HVAC vent (similar to what is used with recessed lights, but with DD + GG, and not cement board)?

I would load up the gap between the flex duct and backer box with Silenseal or similar. The remainder of the duct work would be behind DD+GG. Sound would still travel down the duct, but I’ll try to S shape it to reduce the reflections.

Thoughts?

Artzilla,

I am wondering if maxl (of whose msg I made a sarcastic and stupid remark:() may be correct.

You have open doors, which communicate to other rooms. So the effective size of your room is much larger. It is possible that the lowest room mode for this total space is infrasonic -- say, around 10 Hz. This is probably too low for your mic and electronics to measure. But even if your speaker/sub puts out a small amount of energy down there, it can be greatly amplified by the room mode if the total space is well sealed, and you are at one "end" of it.

Note that this "end" doesn't have to be at a linear extreme. Low frequency room modes happily bend around 90 degree angles, and do not have to be in a straight line. This is a common misconception in acoustics.

- Terry

I think you hit it Terry, or at least part of it. I'm dead center of the total space and found that I can feel it in my office even running just the mains - no sub. O got a tripod and I'm moving the seating are froward and trying variable mic positions at Chris's suggestion and different sub placements (again) with the doors to 2 of the rooms closed to see what I get.

Sorry if this has been asked before but after reading +50 pages and some searching my eyes are killing me.

Does anyone have any links to lower wall treatment construction using something like Insul-Shield?

I am not familiar with that material can you just cover it in GOM or does it need a frame.

Thanks

However you can get absorbing materials in the right places is fine. But covering the very bottom of the side walls is not useful unless you're using very thick materials. In that case you're making bass traps, not reflection absorbers.

Reflections occur at specific places, and those are where the treatment should go. Much 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

Ethan,

Is really the main reason for NOT doing the bottom half is the risk of making the room too dead or is there much more at risk here?

^^^ Well, mostly it's just a waste because little sound reflects off the walls down that low.

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan

Hey Ethan,

Great help as usual!

Could you give some parameters of "small" rooms?

My room is 27' x 15' x 8' - does that qualify for small?

Thanks much. :)

Hey Ethan,

Great help as usual!

Could you give some parameters of "small" rooms?

My room is 27' x 15' x 8' - does that qualify for small?

Thanks much. :)
"a room the size you'll find in most homes"

Could you give some parameters of "small" rooms?
If you move 2' and the sound changes, it's a small room. Your room will be a small room.

^^^ Well, mostly it's just a waste because little sound reflects off the walls down that low.

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan

I was just going to ask the same question regarding making a room dead. My bottom half of the wall has Carpet and Underlay which is divided by skirting( actually it was more aesthetic purposes). I have the room treatments in place which were placed by a certified HAA ( these guys specialize in room treatments and room calibrations over here in Western Australia). I was going to cover the top half of the walls with Acoustic wall tiles to deadned the room. Do you think that is wise decision or is there other products to use.

These are ones im talking about:
Fonic Acoustic Tiles are specially designed and tested to improve the frequency response and decay time of mid to high frequencies in Recording Studios, Home Theatres and Public spaces. They are typically used on walls and ceilings at reflection points to reduce interference and flutter echoes.

My bottom half of the wall has Carpet and Underlay ... I was going to cover the top half of the walls with Acoustic wall tiles to deadned the room.

That's not a good idea because you don't want or need to make all of the walls absorbent. Not only is that much surface coverage not a good idea, but the materials you propose are not thick enough. The general goal in room treatment is to have decay times that are more or less uniform across the audible range. Thin materials absorb only higher frequencies. So the room is too dead sounding and the bass still rattles around and is boomy etc. The graph below is from my recent video Hearing is Believing (http://www.realtraps.com/video_hearing.htm), showing how extensive diffusion, coupled with absorption, helps make the decay times more uniform.

--Ethan

Ethan is not entirely correct, nor is he entirely incorrect either. There are two purposes for the use of absorption in a playback space. One is to solve direct acoustical issues. For example, SBIR when speakers are near a boundary, back reflections from an AT screen, or, in some cases, to knock down the effect of early reflections (usually diffusion is more useful). In this case, the placement of the absorptive treatments becomes part and parcel of their performance.

The second reason is to reduce the overall reverberation time in the room. In this case, the position of the absorptive material is less important than its very presence in the room. For this purpose, ear height and below would work.

In actual practice, you may absolutely want absorptive materials to stay out of early reflection points. An example would be the use of diffusors to expand sound stage width, depth or to enhance the surround channels. At the same time, absorption needs to be placed in the room to reduce reverberation time. This would be a real case where absorptive panels in less than obvious locations is required.

That's not a good idea because you don't want or need to make all of the walls absorbent. Not only is that much surface coverage not a good idea, but the materials you propose are not thick enough. The general goal in room treatment is to have decay times that are more or less uniform across the audible range. Thin materials absorb only higher frequencies. So the room is too dead sounding and the bass still rattles around and is boomy etc. The graph below is from my recent video Hearing is Believing (http://www.realtraps.com/video_hearing.htm), showing how extensive diffusion, coupled with absorption, helps make the decay times more uniform.

--Ethan

Thank you for your response I will leave it as it is then.

"a room the size you'll find in most homes"
Caught that in Ethan's original post, but wondered if there were some general parameters for "small" like cubic feet, etc. But, thanks for the reply. :)

If you move 2' and the sound changes, it's a small room. Your room will be a small room.
Ah, that makes sense in practice. It is true, at least of bass in my room. :)

Thanks for the clarifications, though I'm still curious if there are some numbers to put to "small" or "large" which would help establish whether a room should be damped-down vs. left more natural.

When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.

Two Questions:

1. What makes a good "membrane" to cover corner bass traps in the rear

2. Why do you use it on the bottom of walls (like FSK)?

When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.

Ha, ha! Not always. I had a buddy (lifestyles too different to maintain friendship) who build a 3 story concert hall with a replica of some old-school European pipe organ as part of his ranch house. It was the darndest thing to walk from a nice, but definitely NOT McMansion house into this incredibly ornate concert hall. Stanford used his facilities for a while after the Loma Prieta earthquake damaged their organ recital hall.

Ha, ha! Not always. I had a buddy (lifestyles too different to maintain friendship) who build a 3 story concert hall with a replica of some old-school European pipe organ as part of his ranch house. It was the darndest thing to walk from a nice, but definitely NOT McMansion house into this incredibly ornate concert hall. Stanford used his facilities for a while after the Loma Prieta earthquake damaged their organ recital hall.
Well now, that *would* be a concert hall then, wouldn't it? ;)

The second reason is to reduce the overall reverberation time in the room. In this case, the position of the absorptive material is less important than its very presence in the room. For this purpose, ear height and below would work.

Good point Dennis, ands this brings up a related issue. In my experience treating "normal" furnished rooms, there's less need for overall reverb reduction. Once absorption has been placed at the reflection points, and in corners for bass trapping, that's often enough. But you are correct that all treatment is not necessarily position-specific.

--Ethan

When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.

Well I certainly don't have a McMansion, eh! Thanks. :)

Caught that in Ethan's original post, but wondered if there were some general parameters for "small" like cubic feet, etc. But, thanks for the reply. :)

Everest says 2500Ft3. Dennis' answer was the right one from a practical standpoint though.

Frank

All -

Does anyone have experience with the panels from Ready Acoustics? Quality?

On their website I see "ReadyTraps" panels and "Chamelon C2" panels. Both of these are for mid to high frequencies. The ReadyTraps are significantly cheaper and looks like you can get a bundle.

Anyone know the differences between these models? I'm looking to address my side and front walls so guessing this is the right area I need to be looking if I'm not planning DIY components.

Posted my room configuration a couple pages back. Thx!

All -

Does anyone have experience with the panels from Ready Acoustics? Quality?

On their website I see "ReadyTraps" panels and "Chamelon C2" panels. Both of these are for mid to high frequencies. The ReadyTraps are significantly cheaper and looks like you can get a bundle.

Anyone know the differences between these models? I'm looking to address my side and front walls so guessing this is the right area I need to be looking if I'm not planning DIY components.

Posted my room configuration a couple pages back. Thx!



After reviewing the test data and materials from both, I compared the price of the roughly equivalent models from Ready Acoustics and GIK Acoustics and chose GIK. Before I completed my purchase, however, I took them up on their offer of a free phone consultation to discuss my room and needs (based on photos I sent them). That was very helpful in terms of getting the most impact for the limited budget I had.

But Ready Acoustics has some DIY options, and some construction methods that GIK doesn't offer. So it's not a easy question to answer.

I've also used Real Traps in my room and found the construction/fit/finish to be superior to the competition. It was, however, a little too "industrial" looking for the lady of the house. If you factor in re-sale value, and/or like the solid look, Real Traps is worth considering.

I think all of these (and some other) reputable brands will give you good results, if you intelligently choose which products you buy, and if you carefully select their placement in your home for the right impact.

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


Hi erkq/Pepar,

Sorry to bug you about this again but I just finally ran some measurements last night with my Galaxy CM140 SPL meter and REW using my Laptop.

Unfortunately my laptop only has a Mic in... no line in. So I dont thinnk the curves I got mean much, as its only saying ~45-50db until I hit the 1khz range, then it gets to the 75db area. And this is with my subwoofer turned up to room-shaking levels. And I did calibrate things to the proper level beforehand.


But I am still confused about what the M-Audio Transit does. In the quoted post you said you're going Mic-Preamp-> Transit -> USB.

So would the M-Audio transit allow me to bypass the laptops soundcard somehow? Or do I need to lug down my desktop machine to get a line input?

What Pepar said in this post seems to contradict what erkq said:

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.

Hi erkq/Pepar,

Sorry to bug you about this again but I just finally ran some measurements last night with my Galaxy CM140 SPL meter and REW using my Laptop.

Unfortunately my laptop only has a Mic in... no line in. So I dont thinnk the curves I got mean much, as its only saying ~45-50db until I hit the 1khz range, then it gets to the 75db area. And this is with my subwoofer turned up to room-shaking levels. And I did calibrate things to the proper level beforehand.


But I am still confused about what the M-Audio Transit does. In the quoted post you said you're going Mic-Preamp-> Transit -> USB.

So would the M-Audio transit allow me to bypass the laptops soundcard somehow? Or do I need to lug down my desktop machine to get a line input?

Thanks!
Ryan
I picked up an M-Audio MobilePre USB on ebay for ~$80. Not familiar with the Transit, but a quick visit to their site suggests that it might work. With the stereo line in and stereo line out - as opposed to discrete connectors for each channel - you need to look at your 3-pole-to-whatever adapter to make sure that you are using the same channel for both in and out.

Yes, any measurements you made with your laptop sound are throwaways. :) Onboard laptop audio solutions lack the necessary bi-directionality which is why external "soundcards" are needed. I know that there are Firewire interface units, but most use USB. Firewire is more "pro" and that usually means it is more sophisticated and more $$$.

If you are using a mic preamp in addition to the USB soundcard, the mic preamp needs to plug into a line input. One of the reasons I bought the MobilePre USB is so that I could plug a mic into the mic input and do away with the mic's preamp. I've just learned that I am not supposed to do that, but that is another subject entirely and is unrelated to your question. :)

With the stereo line in and stereo line out - as opposed to discrete connectors for each channel - you need to look at your 3-pole-to-whatever adapter to make sure that you are using the same channel for both in and out.


Thanks for the reply.

Do you mean making sure that both in/out are using L or R??

I am planning on doing everything at just 1/8" mini. I have a Mini-to-RCA cable so I have separate L and R cables going into the receiver.

Do you still think I need a separate adapter or could I just reverse the RCA cables if it doesn't work? And to be clear, is this a 'works or doesn't work' thing, or are we talking about innacurate measurements?

Also not sure exactly what a 3-pole adapter is, I couldn't find it on google, only standard Y adapters. Are you talking about something that would separate stereo into separate L/R channels? Do they even make that for mini?

If you are using a mic preamp in addition to the USB soundcard, the mic preamp needs to plug into a line input.



Nope, no preamp for me since I am using an SPL meter... Am I confused? Do I still need a preamp with a Galaxy Cm140 SPL meter?

Thanks for the reply.

Do you mean making sure that both in/out are using L or R??

I am planning on doing everything at just 1/8" mini. I have a Mini-to-RCA cable so I have separate L and R cables going into the receiver.

Do you still think I need a separate adapter or could I just reverse the RCA cables if it doesn't work? And to be clear, is this a 'works or doesn't work' thing, or are we talking about innacurate measurements?

Also not sure exactly what a 3-pole adapter is, I couldn't find it on google, only standard Y adapters. Are you talking about something that would separate stereo into separate L/R channels? Do they even make that for mini?
For using measuring software like REW, pick Left or Right, and use that channel's input and that channel's output. If you have mono 1/8" minis, then they will only use one of the channels - I forget if it is left or right - so you won't need to do anything else but plug in. If your minis go to left and right RCA phono plugs, you do need to pick a channel to use.

Mono 1/8" minis are 2-pole ("tip-and-sleeve" in old jargon - two circuits, one hot and one ground), stereo minis are 3-pole ("ring, tip-and-sleeve" - three circuits, one left, one right and one ground).

Nope, no preamp for me since I am using an SPL meter... Am I confused? Do I still need a preamp with a Galaxy Cm140 SPL meter?
Then you have a line level output and need to plug into a line level input. There is a preamp built into the SPL meter.

I've also used Real Traps in my room and found the construction/fit/finish to be superior to the competition. It was, however, a little too "industrial" looking for the lady of the house. If you factor in re-sale value, and/or like the solid look, Real Traps is worth considering.

Thanks very much Nathan. In case you're not aware, we have some newer products that are more "spouse friendly" than our usual panels, including a bass traps disguised as a large planter.

--Ethan

Just FIY: I got the Creative SB X-Fi USB soundcard and worked with REW without even installing the drivers. It was the only decent one that BestBuy had in stock so I took a chance and it seems fine.

It didn't specify whether it was full duplex or not, but it did work with REW. However, my baby daughter was sleeping so I had to do the measurement at super-low-volume. Even so, the results look better than before using the laptop's mic input. I'll probably have to wait until this weekend to take measurements at the right volume though.

My neighbor insists that these louvered shutters from an old barn house that was torn down work very well as diffusers.

he has about 8-10 of them across the back half of the room on his ceiling and back wall. They are on top of 1" rigid fiberglass and all covered in black GOM. I have not been in a room of his size with or without them to compare. I think it sound good but...

he used them because they were free and it only took up 2" of total depth

every other one is opened (angled) forward/backward, up/down depending on ceiling or back wall.

https://www.invitinghome.com/store/images/T/011-louvered-shutters-01.jpg

any thoughts

Better than a bare wall, ie, better than not having them. But more depth, varied depth, and varied slant would be even better.

Just FIY: I got the Creative SB X-Fi USB soundcard and worked with REW without even installing the drivers. It was the only decent one that BestBuy had in stock so I took a chance and it seems fine.

It didn't specify whether it was full duplex or not,

It is.

Everest says 2500Ft3. Dennis' answer was the right one from a practical standpoint though.

Frank
Ah, that's helpful, Frank. Thanks much...

Hi,

Does anyone know what type of screws to use with Isomax? I am doing a ceiling sound isolation and already nailed 1/8"MLV to the joists. Now it is time to screw the hat tracks with Isomax clips but I cannot figure out which screw to use for the clips and for the sheetrock.. I will have two layers of Type C Gypsum Board. One is 1/2 inch, the other is a 5/8
Thanks

My neighbor insists that these louvered shutters from an old barn house that was torn down work very well as diffusers.

I wonder if he's ever actually heard real diffusors. :D

Ask your neighbor to look at this video:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

Then, if he's capable of recording things, ask him to do a similar test and assess what he hears. My guess is his louvers will sound more like the bare wood partition than the QRD diffusor.

--Ethan

Hey,

I'm keep wanting to pick up a box of the Certainteed Acoustaboard tiles that marc_stan advertises on the forum, but can't convince myself to do it.

Has anyone tried using these tiles for wall applications at reflection points? They aren't the most attractive things out there, but are definitely more in line with my budget. I would like to know if they can be wrapped in cloth of my choosing and possibly trimmed on the edges to create a bevel of sorts.

Thanks,

snudley

I wonder if he's ever actually heard real diffusors. :D

Ask your neighbor to look at this video:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

Then, if he's capable of recording things, ask him to do a similar test and assess what he hears. My guess is his louvers will sound more like the bare wood partition than the QRD diffusor.

--Ethan


If you only have 2 inches to work with on the back wall (maybe 3) what would be the best solution for diffusion

If you only have 2 inches to work with on the back wall (maybe 3) what would be the best solution for diffusion

A three-inch deep diffusor is better than a bare wall. But it depends on the distance from the listener's head to that wall. If it's like a foot or less I'd probably use absorption instead of diffusion.

--Ethan

A three-inch deep diffusor is better than a bare wall. But it depends on the distance from the listener's head to that wall. If it's like a foot or less I'd probably use absorption instead of diffusion.

--Ethan

The back row will be about 2 feet and the first row will be about 7 feet. There will not be many times the back row will be filled with people though..

There are also rear surround speakers in back on a 12 foot wide wall

^^^ In that case a diffusor six inches deep would be fine.

--Ethan

Ethan,

is something like this effective above the first reflection and seating area of a "small" room. (12x18)


http://www.ethanwiner.com/BTPic-2.jpg

I'm not Ethan but here's the general idea: Depending on what the material actually is, and how thick it is, and the relation to the speakers and seats, it could be a good absorption method.

I'm curious about how my room is responding to base. Room is 30x17.5x9' so I have 4725 cubic feet.

I have a 15" servo Velodyne and a 15" Klipsch sub. After moving them all over the room, I ended up with them both as end tables to my middle row and firing forward into the room. I'm getting what I might call "almost resonable performance" whatever that is. :)

I have a preference for above average base and just can't accomplish it in this room with the equipment I have.

The room is unfinished. It is sheetrocked and has linacoustic down the side walls and on the full screen wall. It also has 703 triangular base traps in both the front corners, floor to ceiling. However, the ceiling is not yet sheetrocked. So the ceiling is open rafters that have insulation in them. The insulation is roughly 6" thick then there is 12" or so of air space and then the subfloor for the main level of the house. I got to thinking that the entire ceiling is currently very much like a large base trap...isn't it?

So my question is: Am I just traping all the base in the ceiling? or at least enough of it to take the "umph" out of my subs?

I'm fishing for some reassurance that sheetrocking the ceiling is going to make a difference for me.

Thanks for any input.

is something like this effective above the first reflection and seating area of a "small" room. (12x18)

You bet. That photos shows the ceiling in my home studio, and I have something similar in my 25 by 16 living room.

--Ethan

I'm curious about how my room is responding to base. Room is 30x17.5x9' so I have 4725 cubic feet.

I have a 15" servo Velodyne and a 15" Klipsch sub. After moving them all over the room, I ended up with them both as end tables to my middle row and firing forward into the room. I'm getting what I might call "almost resonable performance" whatever that is. :)

I have a preference for above average base and just can't accomplish it in this room with the equipment I have.

The room is unfinished. It is sheetrocked and has linacoustic down the side walls and on the full screen wall. It also has 703 triangular base traps in both the front corners, floor to ceiling. However, the ceiling is not yet sheetrocked. So the ceiling is open rafters that have insulation in them. The insulation is roughly 6" thick then there is 12" or so of air space and then the subfloor for the main level of the house. I got to thinking that the entire ceiling is currently very much like a large base trap...isn't it?

So my question is: Am I just traping all the base in the ceiling? or at least enough of it to take the "umph" out of my subs?

I'm fishing for some reassurance that sheetrocking the ceiling is going to make a difference for me.

Thanks for any input.




Yes, sheet rock on the ceiling will make a difference. You also need to remember that you don't have the door in place yet.

Something I learned when placing my subs is to start at opposite corners measuring out 1/5 or 1/3 the length of the room and about 8 inches from the wall.

Am I just traping all the base in the ceiling? or at least enough of it to take the "umph" out of my subs?

You might misunderstand the principle. Bass traps generally increase the perceived level of bass in a room because they absorb the reflections that cause nulls.

I'm fishing for some reassurance that sheetrocking the ceiling is going to make a difference for me.

Adding sheet rock will likely make the sound worse because you'll be covering whatever amount of absorption you have now. So then you'll need to add more absorption under the sheet rock.

--Ethan

So my question is: Am I just traping all the base in the ceiling? or at least enough of it to take the "umph" out of my subs?

While you're unfinished ceiling probably is making a difference, it's probably making a positive impact and not a negative one. Bass trapping won't have a subtractive effect on low end the way you're thinking it will; it will even out the peaks and bring up the valleys some, but it's never going to turn a +10 peak into a -10 valley no matter what you do.

I think the lack of bass response really has more to do with the size and shape of the room itself...you may just need more bass trapping. I don't know that putting up sheet rock is going to "help" at all. It'll just create another hard, reflective surface...you're almost certainly getting better low end response with the unfinished ceiling than you would with a 9' sheet rock ceiling or something.

Frank

Ethan, Dan, Frank, thanks for the input. I suppose I don't understand exactly what's happening. But I do trust in what you guys have to say.

So assuming I get the room finished you're saying that adding more bass trapping may start to help?

Will dropping some cash on a volkswagon sized sub help !?!?! I'd be willing to do something like a Danley, Submersive or Ed A7-900 Of course, after treating the room. I was starting to wonder if something like that was needed for my size room anyway.

you're saying that adding more bass trapping may start to help?

Yes, of course. Not sure how deeply you want to get into this, but there are a ton of non-sales articles and videos on my company's site that explain all aspects of small room acoustics:

RealTraps Articles (http://www.realtraps.com/articles.htm)
RealTraps Videos (http://www.realtraps.com/videos.htm)

Will dropping some cash on a volkswagon sized sub help !?!?!

Maybe, but it will not help as much as finding the correct acoustic solution.

--Ethan

So assuming I get the room finished you're saying that adding more bass trapping may start to help?

The corners were the right start, but the back wall can be the culprit for some of the deepest nulls and highest peaks in the room. Some more trapping in the right places will probably help.

Frank

This thread spans 6 years and 170 pages which is cool. However, it is becoming harder and harder to find a good summary of things that are must do's and things that are good to do. Does anyone have a link to something good like that?

For me - the HT has to be up and running within a month... The room is there, dry-walls are in and paint is in. Cut-outs are there for the speakers. Those things aren't getting moved now. Speakers might move in the future.

What I am doing next is putting up a false wall up front to put the screen on. What I got from the first post here is to cover the
FRONT WALL: Acoustical treatment (1" Insul-Shield) floor-to-ceiling

I guess this still stands correct 7 years later

Then I put the false wall up in front of that. put in the speakers and frame around them. Around that I have been told to put Guilford acoustical fabric.

Everything after this point can be altered going forward. I can put the panels on the sides up etc. So considering that I have an existing room with carpet is there something else that "isn't to late" but that I really should do before I do anything else?

Thanks!

Thanks Ethan / Frank. Since my posting I've borrowed a second sub and it has gone a long way to solving my issues. In fact, I'm quite pleased except for the middle two seats in my front row. There is a terrible null right in that location. I'm going to get further along in construction and then revisit the acoustic treatment. I'm open to adding base traps in the rear of the room, and have the place for them.

Right now the placement of both subs is in the middle of the room as end tables to the middle row. My "master plan" was to have them behind the AT screen, but that's just not giving me the performance I want. At least not with my current treatments. :(

What I am doing next is putting up a false wall up front to put the screen on. What I got from the first post here is to cover the
FRONT WALL: Acoustical treatment (1" Insul-Shield) floor-to-ceiling

I guess this still stands correct 7 years later

Sometimes. :D

I find that there is no "one size fits all" treatment plan. Sometimes I use an absorptive front wall and sometimes I don't. The requirements of different rooms vary.

An important goal for any room treatment is to achieve relatively uniform reverberation times (RT60s) over the major range of audio frequencies. Traditionally in architectural acoustics, the classic Sabine or Eyring equation is used for prediction. Here is a calculator for this purpose written by Chris Whealy:
http://www.whealy.com/acoustics/ControlRoom.html

I favor the more modern (but difficult) ray tracing method, which requires building a 3D CAD model.

Of course, many people just make a guess at room treatment. :eek::D

- Terry

Terry

Thanks for the post that is a really neat calculator. I am guessing Wall 1 is the front wall -- correct? Came up with

User defined absorbant wall surface
Plasterboard on frame
50% each

Not even sure what to do with that information - lol

I favor the more modern (but difficult) ray tracing method, which requires building a 3D CAD model.

Of course, many people just make a guess at room treatment. :eek::D

- Terry

Is there any low-cost (or free) software that does the ray tracing method? Is an AutoCAD 3D model sufficient?

Thanks,
CJ

Is there any low-cost (or free) software that does the ray tracing method? Is an AutoCAD 3D model sufficient?

Thanks,
CJHere are two aids:
http://www.avsforum.com/avs-vb/showthread.php?t=822273
http://www.avsforum.com/avs-vb/showthread.php?p=9615620#post9615620

Of course, many people just make a guess at room treatment. :eek::D


I took a guess to hold me over while I read up on the subject. What I did with the screen wall (I have an AT screen) and reflection points is effective but I now find sloppy mic'ing really annoying, and there's a lot of it. I find that even in the same scene a character's dialog comes from different recording sessions that have different mic distances (very common), different reverberation, and even (less common) different frequency content. The sudden change is so obvious it take me out of the story. Even my g'friend notices.

This thread spans 6 years and 170 pages which is cool. However, it is becoming harder and harder to find a good summary of things that are must do's and things that are good to do. Does anyone have a link to something good like that?

Yes, this is much better:

Acoustics FAQ (http://www.ethanwiner.com/acoustics.html)

What I got from the first post here is to cover the
FRONT WALL: Acoustical treatment (1" Insul-Shield) floor-to-ceiling

I disagree, as explained in detail here:

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

So considering that I have an existing room with carpet is there something else that "isn't to late" but that I really should do before I do anything else?

You need bass traps.

--Ethan

Is there any low-cost (or free) software that does the ray tracing method? Is an AutoCAD 3D model sufficient?

Thanks,
CJ
Unfortunately, ray tracing software is very expensive. It's designed for high-end architectural acoustics. All such packages (I think) will import AutoCAD DXF files when created and formatted appropriately. Each specific CAD layer maps to an acoustic material with defined absorption and diffusion.

EASE 4.2 ($2200) plus AURA ($1000) is one of the lower priced packages whose performance is as good as any in the world. You need AURA for full ray tracing functionality. And there's still a relatively steep learning curve.

But you can get pretty close with just the Eyring equation, and Chris Whealy's free spreadsheet for this. If the room geometry and distribution of absorption is relatively uniform, and you don't need to model diffusion, the two methods yield the same numbers.

- Terry

Terry

Thanks for the post that is a really neat calculator. I am guessing Wall 1 is the front wall -- correct?

Actually, it doesn't matter. The formulas (Eyring, Sabine, Fitzroy, etc.) compute overall reverberation times for the room. These don't vary much with room position. Though again, ray tracing will provide differences where there are any.

Came up with

User defined absorbant wall surface
Plasterboard on frame
50% each

Not even sure what to do with that information - lol
I recommend the beginner's acoustics book that everyone else does: Everest's Master Handbook of Acoustics (http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071360972).

- Terry

I recommend the beginner's acoustics book that everyone else does: Everest's Master Handbook of Acoustics (http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071360972).

Great book to start with...accessible but fairly thorough.

Frank

Has anyone used GOM Thin Loop Fabric (hook and loop) for their theater?...Just curious. It seems as it would make a great acoustic material covering.

In actual practice, you may absolutely want absorptive materials to stay out of early reflection points.

This comment seems to have gone unnoticed and that the "put absorption at first reflection points" conventional wisdom seems to still be alive and well, despite Dennis's occasional comments like above and also Floyd Toole's recent book which published his research and blind listening test and studies where he wrote:

"We are left, though, with a problem: how to explain why the often mentioned comb filtering engendered by early reflections is not a problem. None of the listeners heard it, or at least didn't comment on it except to say that they prefer sounds with reflections. . . . If there is a subjective response to comb filtering, it is that it appears to have a beneficial effect. (p. 140)

As far as imaging and reflections, his whole chapter 8 is about it and the conclusion is that first reflections help imaging. Specifically he wrote that

"When stereo listening tests were done in the two versions of the room [with and without side wall absorption], it was found that the condition with absorbing side walls was prefered for monitoring the recording process and examining audio products, whereas reflective side walls were preferred when listeners were simply 'enjoying the music.' As might be expected, reflective side walls resulted in a 'broadening of the sound image.'" (p. 116).

Why is absorption at first reflections still such a dogma of acoustic design in this thread, despite real evidence and informed guidance to the contrary?

As far as imaging and reflections, his whole chapter 8 is about it and the conclusion is that first reflections help imaging. Specifically he wrote that

"When stereo listening tests were done in the two versions of the room [with and without side wall absorption], it was found that the condition with absorbing side walls was prefered for monitoring the recording process and examining audio products, whereas reflective side walls were preferred when listeners were simply 'enjoying the music.' As might be expected, reflective side walls resulted in a 'broadening of the sound image.'" (p. 116).

Why is absorption at first reflections still such a dogma of acoustic design in this thread, despite real evidence and informed guidance to the contrary?

I have read somewhere, maybe Toole's book or somewhere on this forum, that the typical absorber put at first reflection points is at such a shallow angle of incidence to the sound waves that they act more as reflectors than absorbers.

Question: THe passage you have quoted above is about stereo music. Does it hold for multichannel?

This comment seems to have gone unnoticed and that the "put absorption at first reflection points" conventional wisdom seems to still be alive and well, despite Dennis's occasional comments like above and also Floyd Toole's recent book which published his research and blind listening test and studies where he wrote:

"We are left, though, with a problem: how to explain why the often mentioned comb filtering engendered by early reflections is not a problem. None of the listeners heard it, or at least didn't comment on it except to say that they prefer sounds with reflections. . . . If there is a subjective response to comb filtering, it is that it appears to have a beneficial effect. (p. 140)

As far as imaging and reflections, his whole chapter 8 is about it and the conclusion is that first reflections help imaging. Specifically he wrote that

"When stereo listening tests were done in the two versions of the room [with and without side wall absorption], it was found that the condition with absorbing side walls was prefered for monitoring the recording process and examining audio products, whereas reflective side walls were preferred when listeners were simply 'enjoying the music.' As might be expected, reflective side walls resulted in a 'broadening of the sound image.'" (p. 116).

Why is absorption at first reflections still such a dogma of acoustic design in this thread, despite real evidence and informed guidance to the contrary?
For home theater/cinema, why would we want the sound image broader than it was in the mixdown studio? And, especially for those of us with LCR behind an AT screen, why would we want the image wider than the image? And if that is desirable, companies such as Audyssey are working on mathmatically deriving discrete "wide" and "height" channels from the information already in the soundtracks. It makes more sense to me to place speakers for these channels to enlarge the image in a consistent manner than to rely upon varying room acoustics.

Just my $.02.

- Jeff

Here are two aids:
http://www.avsforum.com/avs-vb/showthread.php?t=822273
http://www.avsforum.com/avs-vb/showthread.php?p=9615620#post9615620

Thanks, Kal. I'm familiar with those. I think that what Terry was talking about was a program that simulates playing a range of sounds and will model how they interact with each other and the room boundaries.

Unfortunately, ray tracing software is very expensive. It's designed for high-end architectural acoustics. All such packages (I think) will import AutoCAD DXF files when created and formatted appropriately. Each specific CAD layer maps to an acoustic material with defined absorption and diffusion.

EASE 4.2 ($2200) plus AURA ($1000) is one of the lower priced packages whose performance is as good as any in the world. You need AURA for full ray tracing functionality. And there's still a relatively steep learning curve.

But you can get pretty close with just the Eyring equation, and Chris Whealy's free spreadsheet for this. If the room geometry and distribution of absorption is relatively uniform, and you don't need to model diffusion, the two methods yield the same numbers.

- Terry

Thanks, Terry. It looks like I'll stick with the spreadsheet for now!

CJ

Why is absorption at first reflections still such a dogma of acoustic design in this thread, despite real evidence and informed guidance to the contrary?
The culprit would be Floyd Toole. :) His classic 1988 paper with Sean Olive, The Detection of Reflections in Typical Rooms (http://www.aes.org/e-lib/browse.cfm?elib=4725), was the first to quantify image-shifting caused by early reflections. It led to the early reflection limits adopted in 1998 EBU Technical Recommendation 3276, "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic," and its 1999 Supplement, "Listening Conditions for the assessment of sound programme material: multichannel sound."

After doing a fair amount of research & analysis, I decided to go w/ DIY acoustical panels for my difficult “live” 16’ w x 11’ d x 8’ h room w/ 4 openings.

My 5.1 HT/ audio system: av123 525 towers & center, Paradigm surrounds, Rythmik F12G subwoofer, Denon avr-1909 w/ Audyssey, Oppo BDP-83 blu-ray, Pio 4280HD plasma.

Total material costs for OC-703 2” thk 4' x 8'- 64 ft2 frk backing panels panels thru local insulation contractor, 11 yds. burlap fabric covering on sale at Hobby Lobby, 2 cans spray adhesive, & fastener hardware was $133.

My total time to make/ mount (5) 2” early reflection panels (3 panels were 24” x 36” to mount above 2’ h bookshelves/ cabinets), & (2) 4” bass traps incl. material purchases was about 20 hrs. or so.

I thought the panels turned out pretty darn good, but believe me, I have a much finer appreciation for RealTraps & GIK Acoustic panel costs (DIY fabrication is somewhat difficult, messy & back-breaking). Wood or metal frames definitely would give a better fit/ finish vs. folded burlap ends (I wrapped like a Xmas present & glued flat). I can of course add wood frames later, but wanted to try & keep the panels lighter for simpler hanging purposes while maintaining 1.5” gap from walls for 2” panels.

Performance-wise, I was truly floored. My problematic room was tamed dramatically w/ acoustical panels installed & a couple small rugs strategically placed. MUCH finer detail, nuance, delicate vocals were immediately evident. Bass was less boomy, much tighter. Of course it is a different sound than I am accustomed to since previously I had sound waves bouncing all over the place, but once the ears/ brain adjust, it’s a dramatic improvement. Only problem I have is that I want to crank up the volume, & Rat Shack SPL meter keeps telling me I’m listening about 6 to 8 dB louder than before.:eek:

Many thanks to those on this thread, GIK Acoustics articles, RealTrap articles & particularly Ethan Winer, whose “Rigid Fiberglss Density Tests” article was instrumental (pun intended) in the methods I employed for my particular situation.

Edit: Attached are pics of my modest attempt @ DIY acoustical panels (which look far better than pics show). I’m well aware that I have a severely compromised room layout. Factoring in WAF & all, I did the best I could w/ what I had to work with... ie. before: 0 panels, after: 5 early reflection panels (2 panels directly behind rear wall bookshelves) & 2 bass traps.

PS, sub is behind blue recliner @ back wall corner. Front wall no panels.... yet.;)

After doing a fair amount of research & analysis, I decided to go w/ DIY acoustical panels for my difficult “live” 16’ w x 11’ d x 8’ h room w/ 4 openings.

My 5.1 HT/ audio system: av123 525 towers & center, Paradigm surrounds, Rythmik F12G subwoofer, Denon avr-1909 w/ Audyssey, Oppo BDP-83 blu-ray, Pio 4280HD plasma.

Total material costs for OC-703 2” thk 4' x 8'- 64 ft2 frk backing panels panels thru local insulation contractor, 11 yds. burlap fabric covering on sale at Hobby Lobby, 2 cans spray adhesive, & fastener hardware was $133.

My total time to make/ mount (5) 2” early reflection panels (3 panels were 24” x 36” to mount above 2’ h bookshelves/ cabinets), & (2) 4” bass traps incl. material purchases was about 20 hrs. or so.

I thought the panels turned out pretty darn good, but believe me, I have a much finer appreciation for RealTraps & GIK Acoustic panel costs (DIY fabrication is somewhat difficult, messy & back-breaking). Wood or metal frames definitely would give a better fit/ finish vs. folded burlap ends (I wrapped like a Xmas present & glued flat). I can of course add wood frames later, but wanted to try & keep the panels lighter for simpler hanging purposes while maintaining 1.5” gap from walls for 2” panels.

Performance-wise, I was truly floored. My problematic room was tamed dramatically w/ acoustical panels installed & a couple small rugs strategically placed. MUCH finer detail, nuance, delicate vocals were immediately evident. Bass was less boomy, much tighter. Of course it is a different sound than I am accustomed to since previously I had sound waves bouncing all over the place, but once the ears/ brain adjust, it’s a dramatic improvement. Only problem I have is that I want to crank up the volume, & Rat Shack SPL meter keeps telling me I’m listening about 6 to 8 dB louder than before.:eek:

Many thanks to those on this thread, GIK Acoustics articles, RealTrap articles & particularly Ethan Winer, whose “Rigid Fiberglss Density Tests” article was instrumental (pun intended) in the methods I employed for my particular situation.

Pics!!! :)

Pics!!! :)I knew that was coming the second I hit the "reply" button. :D I'll try to take a couple pics tonight & edit my post.

Pics!!! :)

+1 for DIY acoustic panel porn. DIYAPP for us industry folks.

Frank

I knew that was coming the second I hit the "reply" button. :D I'll try to take a couple pics tonight & edit my post.

Looking forward to them, rhcorolla!

I'm at that stage of things myself and have 10 panels of JM spinglass 3" thick, so I'm looking opinions about what I should do with them that will give me the most bang (or should I say least boomy-ness) with my 10 panels!

http://i532.photobucket.com/albums/ee324/allredp/TheaterFloorPlanner.jpg

BTW, the sub position is under advisement as I'm figuring out how to best use my new toy: Mark Seaton's amazing SubMersive-1! :) So far, without EQ or Audyssey, this thing is really something--especially for music.

As I figure it I have two main options with a third possibility as well considering I only have 10 panels.

Option 1: triangle cut the panels into the classic super-chunk corner trap (17" x 17" x 24"). At 3" thick I can stack them on top of each other to form one room corner floor to ceiling.

Option 2: I can double the panels up to make two 6" thick panels to straddle 2 corners floor-ceiling.

(both options use 8 of my 10 panels, leaving me with options for first reflections or back wall treatment with the remaining 2 panels).

Or the other possibility is to triangle cut chunks of the same size and fill my floor/back wall intersection for 12' directly behind my seating position.

So, it is either 1 corner filled with a super-chunk, or 2 corners covered with panels, or the back wall/floor filled with 12' of super-chunk.

Help much appreciated!

ADDITION:

I have 3" mineralwool panels completely covering behind my AT screen with beveled cut-out for my center speaker. FWIW, I've kept about 1" of space between the mineral wool and the wall creating basically 4" of absorption.
http://i532.photobucket.com/albums/ee324/allredp/ATmineralwooltreatment3inchesthick.jpg http://i532.photobucket.com/albums/ee324/allredp/ATmineralwoolbeveledforCenter.jpg

Why is absorption at first reflections still such a dogma of acoustic design in this thread, despite real evidence and informed guidance to the contrary?

Very simple: There's no accounting for taste. :D

To me, the improvement from having absorption at reflection points is so incredibly obvious that I can't imagine anyone who has heard it both ways disagreeing. Yet some disagree anyway. They are definitely in the minority of people who have heard both. Maybe in a really large room where the reflection points are ten feet away or farther, absorption may not matter as much. In that case the reflections might be "first" reflections, but they won't be "early."

Have you heard it both ways? If not, try it yourself and see what you think. Even a couple of folded over bath towels will absorb enough to make an informed decision. Another way to hear the difference is to watch my recent video Hearing is Believing (http://www.realtraps.com/video_hearing.htm). The first audible comparison is a smallish room that's fully treated versus no treatment. Ignore the difference in bass clarity and just focus on the mids and highs.

--Ethan

Because for some of us, once you start listening critically, you never truly stop... once you learn to pick out flaws, you hear them everywhere you go...

Because for some of us, once you start listening critically, you never truly stop... once you learn to pick out flaws, you hear them everywhere you go...
One must know when - and how - to exit evaluation mode and just relax and enjoy.

One must know when - and how - to exit evaluation mode and just relax and enjoy.

A worthy goal to be sure, but more difficult for some than for others.

Quote:
Originally Posted by Dennis Erskine http://images.avsforum.com/avs-images/buttons/viewpost.gif (http://www.avsforum.com/avs-vb/showthread.php?p=16886782#post16886782)
In actual practice, you may absolutely want absorptive materials to stay out of early reflection points.
This comment seems to have gone unnoticed and that the "put absorption at first reflection points" conventional wisdom seems to still be alive and well, despite Dennis's occasional comments like above...

I think his comment is somewhat ambiguous. He is not saying that you never want absorption, or that you never want some sort of treatment at reflective points. He is saying that there are some cases where you don't and that it depends on the room. In my case, due to the dispersion patterns of my particular speakers, he recommended diffusion at the first reflection points.

CJ

Looking forward to them, rhcorolla!

I'm at that stage of things myself and have 10 panels of JM spinglass 3" thick, so I'm looking opinions about what I should do with them that will give me the most bang (or should I say least boomy-ness) with my 10 panels!

http://i532.photobucket.com/albums/ee324/allredp/TheaterFloorPlanner.jpg

BTW, the sub position is under advisement as I'm figuring out how to best use my new toy: Mark Seaton's amazing SubMersive-1! :) So far, without EQ or Audyssey, this thing is really something--especially for music.

As I figure it I have two main options with a third possibility as well considering I only have 10 panels.

Option 1: triangle cut the panels into the classic super-chunk corner trap (17" x 17" x 24"). At 3" thick I can stack them on top of each other to form one room corner floor to ceiling.

Option 2: I can double the panels up to make two 6" thick panels to straddle 2 corners floor-ceiling.

(both options use 8 of my 10 panels, leaving me with options for first reflections or back wall treatment with the remaining 2 panels).

Or the other possibility is to triangle cut chunks of the same size and fill my floor/back wall intersection for 12' directly behind my seating position.

So, it is either 1 corner filled with a super-chunk, or 2 corners covered with panels, or the back wall/floor filled with 12' of super-chunk.

Help much appreciated!

ADDITION:

I have 3" mineralwool panels completely covering behind my AT screen with beveled cut-out for my center speaker. FWIW, I've kept about 1" of space between the mineral wool and the wall creating basically 4" of absorption.
http://i532.photobucket.com/albums/ee324/allredp/ATmineralwooltreatment3inchesthick.jpg http://i532.photobucket.com/albums/ee324/allredp/ATmineralwoolbeveledforCenter.jpg

Any thoughts on which option would maximize my 10--3" x 2' x 4' panels the best for bass-trapping?

Much obliged!

Any thoughts on which option would maximize my 10--3" x 2' x 4' panels the best for bass-trapping?

Much obliged!allrepdp, Have you read Ethan Winer's excellent article "Rigid Fiberglass Density Tests"?

http://www.ethanwiner.com/density/density.html

Testing OC-703 w/ frk-backing pretty much indicates more panels is better versus half as many/ twice as thick.

Everything I have read though says 4" minimum for bass traps, & the thicker the better.

Hard to know where to draw the line, isn't it? So many variables/ caveats/etc.. I figure it's all good, esp. compared to untreated walls. :D

I was wondering how you guys hung your panels, whether it be fish wire, steel wire, d-hooks.

I was wondering how you guys hung your panels, whether it be fish wire, steel wire, d-hooks.
Small angle brackets for me.

I was wondering how you guys hung your panels, whether it be fish wire, steel wire, d-hooks.Rotofast mounts of different types: http://www.rotofast.com/

allrepdp, Have you read Ethan Winer's excellent article "Rigid Fiberglass Density Tests"?

http://www.ethanwiner.com/density/density.html

Testing OC-703 w/ frk-backing pretty much indicates more panels is better versus half as many/ twice as thick.

Everything I have read though says 4" minimum for bass traps, & the thicker the better.

Hard to know where to draw the line, isn't it? So many variables/ caveats/etc.. I figure it's all good, esp. compared to untreated walls. :D

Thanks for the link--more reading, eh?! And here I thought I was on summer break! :D

Thanks for the link--more reading, eh?!

That's the hidden cost of DIY. :D

--Ethan

Rotofast mounts of different types: http://www.rotofast.com/

How do you get an air gap with those mounts?

I don't think you can.

How do you get an air gap with those mounts? I bought some plastic pucks from Home Depot for the 1" spacing. For greater spacing, I made up spacers by drilling out appropriate lengths of 1.5" dowel (closet clothes bar stock) and using longer screws but decided not to use them.

The culprit would be Floyd Toole. :) His classic 1988 paper with Sean Olive, The Detection of Reflections in Typical Rooms (http://www.aes.org/e-lib/browse.cfm?elib=4725), was the first to quantify image-shifting caused by early reflections. It led to the early reflection limits adopted in 1998 EBU Technical Recommendation 3276, "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic," and its 1999 Supplement, "Listening Conditions for the assessment of sound programme material: multichannel sound."

From the abstract to that paper, it doesn't seem like he was suggesting absorption at first reflections points:


"Reflected sounds influence the timbre and spatial character of live and reproduced sounds. Most investigations of reflections have focused on the performance of live sounds in large halls. Current interest in the acoustical interactions of rooms, loudspeakers, and listeners, requires further and possibly more relevant data than has been available. In this study, the effects of reflected sounds were examined as they would occur in stereophonic reproduction in rooms of domestic or control-room size. Thresholds were determined as a function of level relative to the direct sound, the angle of incidence, spectrum, the temporal form of the signal and reverberation. The relationships between audible effects and measurements, such as ETC and frequency response, are discussed."

When he later reports on blind tests of listener preference in his recent book, he finds that blind test listeners prefer the first order reflections to absorption at that point. I don't believe Toole tested diffusion at first reflection points which seems to be what some acoustic designers often recommend.

Re multichannel: Floyd discusses multichannel quite a bit -- his whole final chapters where he gives specific recommendations are based on multichannel rooms and he still maintains lateral/early reflections are never harmful b/c they are swamped by any actual surround content, and to the extent that there isn't any surround content (i.e., during portions that are essentially stereo) the lateral reflections are beneficial.

Here are few relevant quotes:

"The locations of the first side-wall reflections at the front of the room are specified as areas for optional treatment. Leaving these areas as flat wall surfaces provides an open and spacious soundstage for those customers who listen in stereo. In television and movies these reflections will "soften" the image of the commonly dominant center channel. Well-designed wide-dispersion front loudspeakers will generally sound better in the presence of lateral reflections. When multiple channels are operating simultaneously, these reflections are swamped by the recorded sounds and become neutral factors. So, the effects of these side-wall reflections range from neutral to slightly beneficial. In any event, they are not large effects, so the choice can be left to the designer."

"In professional environments, like recording control rooms, it has been common practice to absorb these side-wall reflections from the front loudspeakers. As discussed in Chapter 8, most recreational listeners have voted that they enjoy them in stereo reproduction. In a multichannel context, the matter is open for discussion. If the surround channels are active, it is probable that the modest spatial contributions of these front-channel reflections will be masked. If only the front channels, especially the center channel, are active, it is possible that a small spatial effect may be beneficial. "

and also,

"The most common problem in custom home theaters is that they are too 'dead.' In conversation, voices sound muffled, and more than the usual amount of vocal effort is required. It is not a relaxing situation. However, I know of designers who have done this deliberately to make the theater seem 'special.'"

Toole also mentions Lexicon and THX surround processing and suggests that those surround processing modes sound better in part because they add their own "artificial" reflections to the sound from the front speakers -- in a sense duplicating and even amplifying those first reflections that some go to great lengths to abolish with absorption at first reflections.

Toole did blind tests that showed people preferred first reflections to absorption.

Has anyone done similar blind tests that show that people prefer absorption at first reflections?

and note, you should test just the difference in absorption at first reflection or not -- you shouldn't test the difference between some absorption and no absorption; i.e., to test, don't just put absorption up at first reflection and then take it out of the room. Test the room with equivalent overall absorption the room, but in one case with absorption at first reflection and the other case with the same absorption somewhere else in the room so you are testing just the variable of first order absorption with equivalent overall absorption/reverb in the room (and not just testing two different overall absorption/reverb levels).

. . .As discussed in Chapter 8, most recreational listeners have voted that they enjoy them in stereo reproduction. In a multichannel context, the matter is open for discussion. If the surround channels are active, it is probable that the modest spatial contributions of these front-channel reflections will be masked. If only the front channels, especially the center channel, are active, it is possible that a small spatial effect may be beneficial. "
Many/Most of us here have home theaters with 5.1/7.1 systems with a predominance of usage being cinema. It seems that when this first reflection point absorption issue is being argued discussed, 5.1/7.1 cinema use is ignored, or it is conflated with 2-channel music reproduction. I do not need blind tests to tell me that my theater's performance improved dramatically with the addition of absorbers at the first reflection points.

From the abstract to that paper, it doesn't seem like he was suggesting absorption at first reflections points:

You have to read the entire paper, not just the abstract. Treatment is not discussed. This is psychoacoustics research.

From the paper:


In a few experiments, a second kind of threshold was determined. Called the image-shift threshold, this was the reflection level at which there was a just-discernable shift in the location or size of the principal auditory image.

to test, don't just put absorption up at first reflection and then take it out of the room. Test the room with equivalent overall absorption the room, but in one case with absorption at first reflection and the other case with the same absorption somewhere else in the room so you are testing just the variable of first order absorption with equivalent overall absorption/reverb in the room (and not just testing two different overall absorption/reverb levels).

Issue with doing this is anywhere you put the absorption, it becomes a second variable in the test... to null that out you have to run multiple tests with putting that absorption in a myriad of different places...

I'm more inclined to say, if you're hearing something that's bothering you, that you can trace to FRP, treat it. But if not, it's POSSIBLE an "If it ain't broke don't fix it" attitude is preferable... but I'd sure like to hear more debate...

Of course then we get down to, when he says listener "prefer" it, what kind of profile do these listeners fall into... obviuosly they can discern the difference, but... similar to those people who don't care how accurate the bass is as long as it's LOUD, are these people who want it to sound spacious, even if that spaciousness is incoherent? I know I know, read the whole paper, not just the abstract...:o

You have to read the entire paper, not just the abstract. Treatment is not discussed. This is psychoacoustics research.

From the paper: Quote:

In a few experiments, a second kind of threshold was determined. Called the image-shift threshold, this was the reflection level at which there was a just-discernable shift in the location or size of the principal auditory image.



I don't know the context of this quote, it seems to simply say that first reflection absorption (or not) just barely shifts the image.

If anything, since the shift is "just-discernable" that suggests that the effect (whether good or bad) is very minor.

In any case, despite whatever this old paper may or may not conclude, in Toole's very recent and authoritative book the message is pretty clear: based on the evidence from blind tests (and those that read the book would know that the test panel was not random listeners), and the opinion of a very well-informed expert, and explained in very reasonable and persuasive terms, first order lateral reflection absorption is of no value in multi-channel setups and is harmful in stereo setups.

He does mention exceptions to this for 1) speakers with poor off-axis response and 2) professional mixing environments where engineers who are working, rather than trying to enjoy the sound, want to listen to the speaker source directly.

Also he does make clear that diffusion, sub location and number, general absorption and especially bass trapping in a room are all very important. But if you read the book you can't help but come to the conclusion that all the fuss with mirrors and protractors and cool-looking reflection-plotting applets does more harm than good.

. . the message is pretty clear: based on the evidence from blind tests and the opinion of a very well-informed expert, and explained in very reasonable and persuasive terms, the opinion of a very well-informed expert, first order lateral reflection absorption is of no value in multi-channel setups . .

if you read the book you can't help but come to the conclusion that all the fuss with mirrors and protractors and cool-looking reflection-plotting applets does more harm than good.
In spite of how clear the message is, some seem to conclude what they want to conclude. :rolleyes: ;)

And that is exactly how this issue always plays out whenever it comes up.

If room Acoustics intrests you I highly recommend Floyd E Toole's latest book Sound Reproduction loudspeakers and rooms..

It is more biased towards surround sound & Home theater setups speaker layout and how to deal with room acoustics & related issues, it give's A different perspective to other related books I have read..

IMO The problem with room Acoustics, as with other complexed specialized fields there is A lot of biased snake oil and misinfomation out there, you cant believe every thing you read or hear rather listen to all sides keeping an open mined and research as much as you can or just hire A pro with A proven back ground like Terry Montlick :D....

Cheers...

From the abstract to that paper, it doesn't seem like he was suggesting absorption at first reflections points:

Toole did blind tests that showed people preferred first reflections to absorption.

Has anyone done similar blind tests that show that people prefer absorption at first reflections?

and note, you should test just the difference in absorption at first reflection or not -- you shouldn't test the difference between some absorption and no absorption; i.e., to test, don't just put absorption up at first reflection and then take it out of the room. Test the room with equivalent overall absorption the room, but in one case with absorption at first reflection and the other case with the same absorption somewhere else in the room so you are testing just the variable of first order absorption with equivalent overall absorption/reverb in the room (and not just testing two different overall absorption/reverb levels).

I don't think anyone has done a specific experiment where they added and removed the first lateral reflection produced from a loudspeaker in a room and asked listeners which one they preferred. The paper that Floyd and I wrote on reflections was focussed on measuring the absolute detection thresholds of the first lateral reflection, and their various effects (image shift, spaciousness, echo) -- not preference. Most of the evidence that people prefer the first lateral reflection is based on concert hall data, and stereo/mono loudspeaker tests that show that wider dispersion loudspeakers are preferred over narrower ones -- all other things being equal (good on and off-axis response, smooth DI ).

The closest experiment I know is one I at NRC in the anechoic chamber (1985) where I simulated the ceiling and wall reflections produced from a stereo playback system in typical listening room. People rated the fidelity/preference of different music programs reproduced in stereo, with and without the first reflections added. On average, people preferred the music reproduction with the lateral reflections included. I did not include the other room reflections in the simulation so the ecological validity of the results is somewhat lacking.

The best sound field simulation of a loudspeaker in a listening room I know was the Archimedes project done in Denmark around 1990. They simulated many of the early reflections in an IEC listening room using multiple loudspeakers surrounding the listener. Unfortunately, the results did not include a measure of what listeners preferred, rather it focused on which individual reflections were audible. Rather sad that more wasn't learned given the potential opportunities afforded with such a setup. http://www.aes.org/e-lib/browse.cfm?elib=7673

I don't think anyone has done a specific experiment where they added and removed the first lateral reflection produced from a loudspeaker in a room and asked listeners which one they preferred.

[snip]

Unfortunately, the results did not include a measure of what listeners preferred, rather it focused on which individual reflections were audible. Rather sad that more wasn't learned given the potential opportunities afforded with such a setup. http://www.aes.org/e-lib/browse.cfm?elib=7673 What a drag. Now we have to leave the question of preference up to the individual...:rolleyes:

I don't think anyone has done a specific experiment where they added and removed the first lateral reflection produced from a loudspeaker in a room and asked listeners which one they preferred. The paper that Floyd and I wrote on reflections was focussed on measuring the absolute detection thresholds of the first lateral reflection, and their various effects (image shift, spaciousness, echo) -- not preference. Most of the evidence that people prefer the first lateral reflection is based on concert hall data, and stereo/mono loudspeaker tests that show that wider dispersion loudspeakers are preferred over narrower ones -- all other things being equal (good on and off-axis response, smooth DI ).

The closest experiment I know is one I did an experiment at NRC in the anechoic chamber (1985) where I simulated the ceiling and wall reflections produced from a stereo playback system in typical listening room. People rated the fidelity/preference of different music programs reproduced in stereo, with and without the first reflections added. On average, people preferred the music reproduction with the lateral reflections included. I did not include the other room reflections in the simulation so the ecological validity of the results is somewhat lacking.

The best sound field simulation of a loudspeaker in a listening room I know was the Archimedes project done in Denmark around 1990. They simulated many of the early reflections in an IEC listening room using multiple loudspeakers surrounding the listener. Unfortunately, the results did not include a measure of what listeners preferred, rather it focused on which individual reflections were audible. Rather sad that more wasn't learned given the potential opportunities afforded with such a setup. http://www.aes.org/e-lib/browse.cfm?elib=7673
Thank you for your post. THANK YOU!

Yes, thank you so much for joining the conversation, Sean!

I was incorrect when I stated that your early reflection research led to the EBU reflection recommendations. Floyd set me straight -- that he didn't think that this research had anything to do with the recommendations. This makes a lot of sense, since the EBU considers only the first 15 ms, while your research covered the first 80 ms.

Regards,
Terry

Yes, thank you so much for joining the conversation, Sean!

I was incorrect when I stated that your early reflection research led to the EBU reflection recommendations. Floyd set me straight -- that he didn't think that this research had anything to do with the recommendations. This makes a lot of sense, since the EBU considers only the first 15 ms, while your research covered the first 80 ms.

Regards,
Terry

Hi Terry,
Thanks. Yes, I think you're correct. The EBU recommendation also said you only need to attenuate the early reflections > 1 kHz, which doesn't make the reflection much less audible but does make it colored. The people who wrote the standard have admitted they did the best job given what knowledge they had at the time , which was apparently very little ;)

He does mention exceptions to this for 1) speakers with poor off-axis response and 2) professional mixing environments where engineers who are working, rather than trying to enjoy the sound, want to listen to the speaker source directly.

Toole at the most extends engineers the benefit of doubt that they may be overly sensitized to reflections compared to the non-pro. He doesn't endorse their habits. On the contrary he leans the other way.

Regarding poor off axis speakers, Toole writes:

"....wide dispersion loudspeakers with what would appear to be compromised sound quality are given a higher sound quality and spatial quality ratings than a narrow dispersion loudspeaker with potentially superior sound quality... listeners appeared to prefer the sound from wide dispersion loudspeakers with somewhat colored off-axis behavior to the sound from a narrow dispersion loudspeaker with less colored off-axis behavior. In the years since then, it has been shown that improving the smoothness of the off-axis radiated sound pushes the subjective ratings even further up, so it is something not to be neglected."

This doesn't contradict zmisst since Toole does not address uniformly terrible off-axis performance in this section. But I hope it sheds light on the topic.

So just think about it. What do you do when using just a couple inch thick absorbers at first reflection points? You attenuate the amplitude of reflections making the loudspeaker essentially behave as a narrow dispersion design.Ouch. Furthermore, you worsen the tonal coloration of the loudspeaker. Ouch. That's what's called a double whammy.

Tumara Baap

If "most of the evidence that people prefer the first lateral reflection is based on concert hall data, and stereo/mono loudspeaker tests that show that wider dispersion loudspeakers are preferred over narrower ones", can it be safely inferred that the preference would hold for multichannel systems reproducing cinema soundtracks as well? Until there is the experiment that Tonmeister2008 said has never been done "where they added and removed the first lateral reflection produced from a loudspeaker in a room and asked listeners which one they preferred" people will extrapolate for multichannel systems and draw their conclusions based on the way they were leaning in the first place.

Why hasn't this testing ever been done? Why hasn't this subject been updated for modern home theaters?

If "most of the evidence that people prefer the first lateral reflection is based on concert hall data, and stereo/mono loudspeaker tests that show that wider dispersion loudspeakers are preferred over narrower ones", can it be safely inferred that the preference would hold for multichannel systems reproducing cinema soundtracks as well? Until there is the experiment that Tonmeister2008 said has never been done "where they added and removed the first lateral reflection produced from a loudspeaker in a room and asked listeners which one they preferred" people will extrapolate for multichannel systems and draw their conclusions based on the way they were leaning in the first place.

Why hasn't this testing ever been done? Why hasn't this subject been updated for modern home theaters?

Good question: why haven't more people done psychoacoustic experiments to learn what the optimal acoustical treatment of the room should be for multichannel music and film/TV broadcast? One reason is that doing a listening experiment that manipulates the acoustical treatment in a controlled manner is challenging. I think binaural room scanning (http://seanolive.blogspot.com/2009/03/binaural-room-scanning-powerful-tool.html) (BRS) is a solution for that problem. BRS allows you in sequence to binaurally scan the room acoustically treated in various ways, and later play them back over head-tracking headphones permitting double blind multiple comparisons among the different room treatments in very controlled way.

We have such a device - and we have a multichannel setup in a room (http://seanolive.blogspot.com/2009/05/harman-international-reference.html) that we can easily vary its acoustical treatment.

It's on my list of research projects. I'm just looking for a PhD student or an acoustical treatment company that might be willing to sponsor it... :)

It's on my list of research projects. I'm just looking for a PhD student or an acoustical treatment company that might be willing to sponsor it... :)
The cynic in me questions whether or not acoustical treatment companies may not have a vested interest in leaving it up in the air if FRP absorption is a good thing. ;)

The cynic in me questions whether or not acoustical treatment companies may not have a vested interest in leaving it up in the air if FRP absorption is a good thing. ;)

Yes, that thought too has crossed my mind. It may explain why I've had no luck finding a sponsor so far...:)

We have broadband diffusers and absorbers in our room, and just purchased some RPG Modex Plate absorbers (http://www.rpginc.com/products/modexplate/index.htm) for a problematic room that had walls that were too stiff (2 layers of drywall)- so I don't think the acoustical treatment companies that build legitimate products need to worry.

It's just a question of how what type and much acoustical treatment you need, how broadband should it be, and where is the best place to put it -- based on results of psychoacoustic experiments. Those are scientific questions that need to be answered.

We have broadband diffusers and absorbers in our room, and just purchased some RPG Modex Plate absorbers (http://www.rpginc.com/products/modexplate/index.htm) for a problematic room that had walls that were too stiff (2 layers of drywall)- so I don't think the acoustical treatment companies that build legitimate products need to worry.



Wow, those look expensive! But what a brilliant concept!

The cynic in me questions whether or not acoustical treatment companies may not have a vested interest in leaving it up in the air if FRP absorption is a good thing. ;)

LOL, if only! :D

We have about zero influence on the industry. Nobody gives a crap about acoustic treatment. It's all gear, more gear, and yet more gear. No bass? Buy another sub. Still not enough bass? Then buy two more subs! Still not happy? Buy a sub equalizer. :D

I laughed at Roger's suggestion that it's a shame we have to let people decide for themselves what they like. As I explained in another forum just this morning, there's also the issue of an "educated" listener. Many people could make the right decision if they had extended listening time in a good sounding and well-treated room. But look at the high-end audio dealer showrooms. All gear, little or no treatment. So even if you have $100k to drop on a system, its still really difficult to find a place where you can listen to a treated room and learn over time why treatment makes the sound so much better. :mad:

I'm in the wrong business. If I wanted to get rich I'd be selling gear. :D

--Ethan

LOL, if only! :D

We have about zero influence on the industry. Nobody gives a crap about acoustic treatment. It's all gear, more gear, and yet more gear. No bass? Buy another sub. Still not enough bass? Then buy two more subs! Still not happy? Buy a sub equalizer. :D

I laughed at Roger's suggestion that it's a shame we have to let people decide for themselves what they like. As I explained in another forum just this morning, there's also the issue of an "educated" listener. Many people could make the right decision if they had extended listening time in a good sounding and well-treated room. But look at the high-end audio dealer showrooms. All gear, little or no treatment. So even if you have $100k to drop on a system, its still really difficult to find a place where you can listen to a treated room and learn over time why treatment makes the sound so much better. :mad:

I'm in the wrong business. If I wanted to get rich I'd be selling gear. :D

--Ethan
A fellow HT enthusiast and I went about 2 years ago to a dealer in the Reading area to hear a $150,000 Marantz system that was traveling around the country. "Underwhelming" got a new meaning that day; the sound was a mile high, but an inch deep. The showroom was carpeted, but otherwise all glass and drywall. WTF? Were we expected to be swayed by the price tag? Unfortunately, I'm sure some were.

Gear is a commodity, acoustical treatments are a specialty. I have great respect for you and Terry and all of the others on this thread that make a living at the latter.

Buy another sub.
No, no, no. Buy 5000 subs!

No, no, no. Buy 5000 subs!

:D:D:D

Frank

Ok...some anal dude just busted my chops via email on that. The actual purchase would be 4999 since there's already one sub in the room. Jeeze people.

Ok...some anal dude just busted my chops via email on that. The actual purchase would be 4999 since there's already one sub in the room. Jeeze people.

Gotta tell us who that was so I can put him on an ignore list...

Hi, I'm new to the AVS Forum and to the discussion of room treatments. Have been reading this forum for the last couple of days and find it very interesting and also very confusing. I've been to several web pages offering different treatments but haven't seen any discussion on this forum regarding the Cathedral Sound Room Dampening Panels. Different idea, these panels mount in the upper corners where the walls meet the ceiling, are only 11 x 16 x 2 and only cost $179. for a pair. They claim they are better than the 4'-6' panels at treating standing waves and have a primary effect on mid-base and deep-base response below 200 Hz. They deal with something called the "Venturi Effect" I can't post the site (Newbie) but you can search Google and find them through Ultrasystem.
There also a couple of reviews that seem to indicate they work very well. Does anyone have any experience with these or has tried them? Thanks.
--Ron

haven't seen any discussion on this forum regarding the Cathedral Sound Room Dampening Panels ... Does anyone have any experience with these or has tried them?

Yes, I tested them and they don't work for various reasons including their size which is way too small to have any effect on bass frequencies. Proof below. The top graph pair shows the room with and without the panels. No change. The second graph pair shows the room with three half-filled garbage cans as a "control," and that actually did improve the room a little. The photo below shows one of the garbage cans.

--Ethan

http://www.ethanwiner.com/cathedral/cathedral.gif

http://www.ethanwiner.com/cathedral/garbage.gif

http://www.ethanwiner.com/cathedral/garbage1.jpg

Yes, I tested them and they don't work for various reasons including their size which is way too small to have any effect on bass frequencies. Proof below. The top graph pair shows the room with and without the panels. No change.
...
http://www.ethanwiner.com/cathedral/cathedral.gif

I see a big change in the second low frequency resonance at around 70 Hz, Ethan. The upper graph resonance (with panels?) damps out more quickly, by more than 50 ms over the 28 dB decay range. There are other differences, but this is the most obvious one.

I'm not suggesting that this constitutes proof that these panels work. Only that I do see a change in the two graphs.

- Terry

Interesting to note that these were "recommended" by Robert Deutsch of "Stereophile" and highly recommended by Moreno Mitchell of "Stereo Times" The site selling them also includes a Tech. Info. page with their own graph showing a marked reduction in standing waves under 40Hz. This can be found at ultrasystem.com and then linking to the Cathedral Sound acoustic page. I can't post the page until I have more posts. Thanks for the info.
---Ron

I'm not suggesting that this constitutes proof that these panels work. Only that I do see a change in the two graphs.

Agreed, though that hardly makes them what I'd consider "effective." Especially compared to the garbage cans that had much more effect and at many more of the peak frequencies.

--Ethan

Interesting to note that these were "recommended" by Robert Deutsch of "Stereophile" and highly recommended by Moreno Mitchell of "Stereo Times"

Well, hi-fi reviewers recommend all kinds of things that science-minded folks know is nonsense. Like replacement power supply fuses, cable elevators, and a "demagnetizer" for your vinyl records and CDs.

The site selling them also includes a Tech. Info. page with their own graph showing a marked reduction in standing waves under 40Hz ... I can't post the page

Here you go:

http://www.ultrasystem.com/usfeaturedPanelsTechInfo.html

I'll go out on a limb and call BS because I know my tests are valid, and I have no evidence that their's are valid. Initially, they had a third party test their panels, and the "with" graphs were exactly the same as the "without" graphs except the overall level was different. So it seemed that the ringing was reduced with the panels even though nothing changed. I had several email exchanges with some of the Cathedral people, and they admitted to me they have no idea how to test their own products. That's why they sent them to me to test! Anyway, this is what used to be on the Cathedral Panels web site:

http://www.ethanwiner.com/cathedral.gif

If they don't even know how to run room measuring software, how could they have done "extensive scientific investigation" in the first place? :D

The new graph is not believable either because nothing that size could make the improvement shown, even if it absorbed 100 percent at 40 Hz and below. Unless they had maybe 40 of them in the room.

IMO, people who sell stuff like this should not even try to use "science" to make their points. They should stick with the usual subjective prose you see for $1,000 replacement AC power cords and bags of magic pebbles.

--Ethan

Ok...some anal dude just busted my chops via email on that. The actual purchase would be 4999 since there's already one sub in the room. Jeeze people.

Wow....how funny.

Frank

If they don't even know how to run room measuring software, how could they have done "extensive scientific investigation" in the first place? :D

The new graph is not believable either because nothing that size could make the improvement shown, even if it absorbed 100 percent at 40 Hz and below. Unless they had maybe 40 of them in the room.

IMO, people who sell stuff like this should not even try to use "science" to make their points. They should stick with the usual subjective prose you see for $1,000 replacement AC power cords and bags of magic pebbles.

--Ethan[/QUOTE]

Thanks for taking the time to respond, Ethan. As a newbie, that's exactly why I asked about these panels ... appreciate it!
--Ron

The new graph is not believable either because nothing that size could make the improvement shown, even if it absorbed 100 percent at 40 Hz and below. Unless they had maybe 40 of them in the room.

+1. That's just not credible at all.

Frank

Thanks for taking the time to respond, Ethan. As a newbie, that's exactly why I asked about these panels ... appreciate it!

There are many "acoustic" products that are way too small to possibly be useful. This is one of the most egregious examples because it's so expensive ($3,500):

http://www.synergisticresearch.com/?p=195

Common sense tells us that something the size of a golf ball cannot possibly affect room acoustics, yet people buy them anyway. Then they post in audio forums how much better the sound became. :D

--Ethan

Ethan;

Kind of like 10K$ speaker wires :-)

Magnets, warmth and liquidity... magical thinking comes to room treatment.

Kind of like 10K$ speaker wires :-)

So you're saying they *don't* work? ;)

The example Ethan posted above is one of my favorites.

Frank

Common sense tells us that something the size of a golf ball cannot possibly affect room acoustics, yet people buy them anyway. Well, you could stick them in your ears!

Well, you could stick them in your ears!

Yep...firmly duct tape them to both sides of your head. :D

Frank

No, no, no. Buy 5000 subs!

Dennis I know you are kidding but I thought I would let people in on the joke who don't know the background.

Todd Welti simulated in Matlab the effect of 5,000 subs versus 4 subs on reducing the seat-to-seat variance in the predicted low frequency magnitude response, after a manufacturer suggested that everyone needs 5000 subs for a perfect in-room response at every seat. There is a point of diminishing returns in controlling room modes through destructive interference after adding 4 subwoofers. But for the high-end, discerning, sociable audiophile with many friends (probably an oxymoron), 5,000 subs will probably be the only satisfactory solution for multiple seat listening rooms --- as long as they are Harman subs, of course :)
The AES paper is here (http://www.aes.org/e-lib/download.cfm?ID=13680&name=harman):

I've been looking at trying to aesthetically incorporate wooden membrane absorbers as the inner panels in a wainscot.

However the information here:
http://www.ethanwiner.com/basstrap.html
seems to size the panels at ~ 2'x8'

My question is, if the panels were only 2' x 4' (wainscot insert) would they still be effective at helping to tame the lower bass?

Ie will the reduced diaphragm size inhibit vibrations to the point that the panel is ineffective

Thanks
Brad

if the panels were only 2' x 4' (wainscot insert) would they still be effective at helping to tame the lower bass?

Yes, they'll work, and will be exactly half as effective as traps twice as tall having twice the surface area. If they were only 1 foot square, that might restrict the panel motion enough to not work well. But at 2x4 the wood is large enough to flex and absorb.

--Ethan

So you're saying they *don't* work? ;)

The example Ethan posted above is one of my favorites.

Frank

I just checked out that link - and am shaking my head at what I have been missing; Tesla cable, Tibetan "singing" prayer bowls....?

Priceless....What was that famous WC Fields quote? "There's one born every minute"?

I just checked out that link - and am shaking my head at what I have been missing; Tesla cable, Tibetan "singing" prayer bowls....?

Priceless....What was that famous WC Fields quote? "There's one born every minute"?
That was P.T. at least according to the urban myth.

Pepar,

You are correct. My bad...

But for the high-end, discerning, sociable audiophile with many friends (probably an oxymoron)...

:D:D:D

I think I just wet myself a little.

Frank

What was that famous WC Fields quote?

It was ... edited to socially acceptable standards ...

"Don't drink the water my boy, fish **** in it."

That was P.T. at least according to the urban myth.

Yup. But Fields did say, "You can't cheat an honest man. Never give a sucker an even break or smarten up a chump," in his movie with part of this quote as the title.

Though OT, one of my favorite Fields quotes is from "The Bank Dick."

Fields (as Egbert Sousé): "Was I in here last night and did I spend a twenty dollar bill?"
Bartender (played by sometimes Stooge Shemp Howard): "Yeah."
Fields (breathing a sigh of relief): "What a load that is off my mind. I thought I'd lost it."

:D

and don't forget "Who put this lemonade in my lemonade?"

More apt I think is that WC had a movie called "Never Give A Sucker An Even Break." So as long we're selling you 10K cables, we might as well sell you the signing bowls, too.

Yup. But Fields did say, "You can't cheat an honest man. Never give a sucker an even break or smarten up a chump," in his movie with part of this quote as the title.
Well, Terry, you smarten a lot of us chumps on this thread. :)

I knew WC would fit in here ...

Well, Terry, you smarten a lot of us chumps on this thread. :)
Thanks, pepar. :)

The AES paper is here: (http://www.aes.org/tmpFiles/elib/20090826/13680.pdf)I think that link has expired. No?

The paper may still be found on the Harman site.

The paper may still be found on the Harman site.I would find that unusual, as AES does not allow open distribution of their copyrighted papers. Harman may have cooked an alternative paper with similar content, however. Mayhaps, do you have a link? Harman's website is pretty extensive, yet gives zero hits for a search on "Welti."

BTW, I have the paper, but I cannot post it, either. Just wanted to make a ref to it in another thread.

I would find that unusual, as AES does not allow open distribution of their copyrighted papers. Harman may have cooked an alternative paper with similar content, however. Mayhaps, do you have a link? Harman's website is pretty extensive, yet gives zero hits for a search on "Welti."

BTW, I have the paper, but I cannot post it, either. Just wanted to make a ref to it in another thread.

Hi Roger,

I couldn't find any papers by searching their website, but I found this "hidden" summary paper by googling.

Subwoofers: Optimum Number and Locations (http://www.harman.com/wp/pdf/multsubs.pdf)

Larry

That's strange, I read that paper from that site Thursday.

The "paper" that Larry found, is not the original from the site. I have that one but if Harman has taken it down, I'm not about to go sending in about.

So guys...suck it up...pay for the AES paper. Perhaps if enough buy it mine and Roger's dues will go down.

I think that link has expired. No?

You're right: that link is dead. This link (http://www.aes.org/e-lib/download.cfm?ID=13680&name=harman) for the Welti-Devantier paper on subwoofer optimization works for me. If it doesn't work, go the Technology Section (http://www.harman.com/about_harman/technology_leadership.aspx)of Harman's web site, click on the link "Scientific Publications" under the header "Technology Leadership" and you will find 20 AES papers written by Harman scientists and engineers that you can download for free.

We negotiated a yearly fee with AES that allows us to have audiophiles download these 20 papers. I am in the process of updating this list of 20 papers for the upcoming year - so if there are any Harman AES papers you'd like to see posted - let me know.

You're right: that link is dead. This link (http://www.aes.org/e-lib/download.cfm?ID=13680&name=harman) for the Welti-Devantier paper on subwoofer optimization works for me. If it doesn't work, go the Technology Section (http://www.harman.com/about_harman/technology_leadership.aspx)of Harman's web site, click on the link "Scientific Publications" under the header "Technology Leadership" and you will find 20 AES papers written by Harman scientists and engineers that you can download for free.

We negotiated a yearly fee with AES that allows us to have audiophiles download these 20 papers. I am in the process of updating this list of 20 papers for the upcoming year - so if there are any Harman AES papers you'd like to see posted - let me know.

Thanks a lot for the link Sean - and for allowing these interesting paper downloads, great reading!!!

Ray

We negotiated a yearly fee with AES that allows us to have audiophiles download these 20 papers.Much appreciated. Truly.

Wow, Sean, that's great! Thanks for the link.

CJ

I have some GIK Tri-Traps that I need to hang up in the corners overhead. I'm still trying to decide how to mount them.

The acousticalsurfaces.com website has pictures of some clips they call "EC Clips / EZ Clips" but they do not offer them for sale from their storefront that I can see.

http://www.acousticalsurfaces.com/fabric_panel/art/wall_clips/wall_bar_large.jpg

http://www.acousticalsurfaces.com/fabric_panel/art/wall_clips/panel_clips_lg.jpg

These look EXACTLY like what I want, but I cannot find any products that look similar either googling or at the hardware store.

Can somebody help me out? Is there a generic name for this type of metal clip system? Should be pretty easy to find right?

Any other creative ways of suspending a tri-trap overhead? They will still be oriented vertically but there will be nothing underneath. I think two clips like the ones above on either side would work well.... if I can find them.

ok I found something similar here, but looks like it will push things further off the wall than the one from acousticalsurfaces:

http://zbarhanger.com/7to50zbarha.html

might just call acousticalsurfaces and see if theyll sell just the hanger.

Look at these:

http://www.monarchmetal.com/pages/panelclip.html

Looking for some advice given my theater room's smallish size / plans.
It is 12 x 17.5 x 8 with a 11" sofit around the back and side walls. Sheetrocked all around including ceiling. Under my kitchen addition surrounded with concrete walls except for a 36" doorway into the main part of the basement. 2 rows of seating, rear about 1 foot from the rear wall, front 6.5 from rear wall.

I was planning on a 7.2 TRIAD silver in-wall system that will likely run around $9K. Will I be able to realize the potentially better sound over say a more affordable inwall speaker system that costs half that (e.g. Atlantic Technology)?
Am concerned that equalization and acoustic room treatements won't be enough...

Thanks in advance for your thoughts here.
Mike

Only one suggestion: Put a thick absorber on the rear wall behind the heads of the people in the rear row. Or eliminate the rear row. :)

Can somebody help me out? Is there a generic name for this type of metal clip system? Should be pretty easy to find right?


They seem fairly similar in concept to a french cleat. Same with the other ones you and Terry posted as well. No clue if they're exactly the same or not though.

http://www.hooksandlattice.com/cleat-hangers.html

They seem fairly similar in concept to a french cleat. Same with the other ones you and Terry posted as well. No clue if they're exactly the same or not though.

http://www.hooksandlattice.com/cleat-hangers.html

Why not just use some split battens? cheaper, easier to install/get level

I was planning on a 7.2 TRIAD silver in-wall system that will likely run around $9K. Will I be able to realize the potentially better sound over say a more affordable inwall speaker system that costs half that (e.g. Atlantic Technology)?
Am concerned that equalization and acoustic room treatements won't be enough... I'd be hard pressed to tell you that the Atlantic IWCB-626s wouldn't serve just as well as the Triads in this case. They both are in boxes, and that's essential.

Your room is a virtual clone of mine (diagram at the bottom of this post (http://www.avsforum.com/avs-vb/showpost.php?p=16916242&postcount=2)). 11.5' x 17' x 8' with soffits all round, 13" riser, rear ears 27" from rear wall, front ears 6.5' from rear. I avoided using recliners so I could keep the seat rows a little closer.

I went with four B&W CWM8180 as their driver compliment better matched the Aerials up front, and I built the back boxes. Not sure I'd do that again, but they do sound great, running zero EQ on the rears.

any forum members have experience about these decorative sound absorbers, they look quite nice but I'm not sure of their acoustic performance for 2-channel music; seems to be used for classrooms and workspaces for reducing echo, flutter and clarify voice


I am thinking about this in a 12x10x8 room and mostly on the ceiling...

From that site:

Designed to be used as lightweight sound absorber in the upper frequency range (500 Hz and above).

Stereo and home theater rooms need absorption that is effective all the way down to the bass range, so those panels are not suitable.

--Ethan

any forum members have experience about these decorative sound absorbers, they look quite nice but I'm not sure of their acoustic performance for 2-channel music; seems to be used for classrooms and workspaces for reducing echo, flutter and clarify voice


I am thinking about this in a 12x10x8 room and mostly on the ceiling...
These (http://realtraps.com/p_roomkits.htm) will work. :)

Yes, they'll work, and will be exactly half as effective as traps twice as tall having twice the surface area. If they were only 1 foot square, that might restrict the panel motion enough to not work well. But at 2x4 the wood is large enough to flex and absorb.

--Ethan

Ethan.. thanks tons for the reply.

When you say it will be 1/2 as effective.. is it safe to assume that it means it aborbs 1/2 the "Amount" ie.. 2 X 2x4 membranes are as effective as 1 2x8.
Or does this mean that it is only effective in 1/2 frequency the range?

Sorry for being dense.:o
Brad

Hello Acoustic experts and enthusiasts. I need your help!
I have created a thread with my situation, pics, ect and could use some acoustic treatment advice.
http://www.avsforum.com/avs-vb/showthread.php?p=17115283#post17115283

When you say it will be 1/2 as effective.. is it safe to assume that it means it aborbs 1/2 the "Amount" ie.. 2 X 2x4 membranes are as effective as 1 2x8. Or does this mean that it is only effective in 1/2 frequency the range? Sorry for being dense.:o

Actually, that's a great question and not dense at all. You'll have half the total amount of sabins in the room, where one sabin (unit of absorption) is equal to a one square foot open window. There is some overlap though. By having only half the absorption you'll have less affect on the lowest frequencies. Related, I once did a comparison of 12 traps three inches thick, versus only six traps that were each six inches thick. I was interested mainly in the role of material density on absorption, and this comparison was just an extra test for fun. The results are here if you care:

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

I'll give away the ending: 12 thinner traps worked better and to a lower frequency.

--Ethan

ok I found something similar here, but looks like it will push things further off the wall than the one from acousticalsurfaces:

http://zbarhanger.com/7to50zbarha.html

might just call acousticalsurfaces and see if theyll sell just the hanger.

Lowes has the Hangman products.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=56378-37672-122373&lpage=none

The beauty of the french cleat with a full angle is that if you mount it to the object correctly the angle can pull the item tight to the wall with it's weight.

From that site:



Stereo and home theater rooms need absorption that is effective all the way down to the bass range, so those panels are not suitable.

--Ethan

thanks Ethan

I've been looking at diffusion+absorption treatments for the ceiling that looks nice, have you tested the Bastoni ceiling panels, the idea looks like it may work :

http://www.asc-hifi.com/in-celing-bastoni.htm

geoff

A quick question:

I am trying to determine what to do with my front corners for bass traps. The 17" sided (24" across) super chunks would be too big as the space is limited. So:

- Can I make one with 12" sides (17" across)? Will that be very ineffective to make it even not worth it?

- Will I get better results by just hanging bass trap panels on the two adjacent walls?

Thanks.

have you tested the Bastoni ceiling panels

No, but even if I did I wouldn't comment because it's not appropriate for me to talk about products from a competing vendor. I can tell you that ASC is a top notch company who makes great stuff.

--Ethan

The 17" sided (24" across) super chunks would be too big as the space is limited.

Anything is better than nothing, but it's common to angle panels a little off 45 degrees to make then fit. Or put a panel flat on the wall near the corner.

--Ethan

No, but even if I did I wouldn't comment because it's not appropriate for me to talk about products from a competing vendor. I can tell you that ASC is a top notch company who makes great stuff.

--Ethan

An expert, who doles out his knowledge, and classy too?

Applause.:)

I am working through the details of my acoustic treatments for my 12x17.5x8 dedicated theater room. One item that I've read in several threads is the use of the riser as a bass trap by stuffing the riser "bays" with acoustic material and then drilling holes (2" mentioned) in the end of each bay facing the screen.
Possibly also leaving a few inches uncovered by plywood at the wall/riser corner boundary.

How effective is such a riser trap, and is it a broadband bass trap or one that is tuned to control the frequency that's absorbed based on the hole sizes and locations? If tuned, how would one translate resonant frequencies to hole size?

Thanks in advance for the feedback
Mike

I am working through the details of my acoustic treatments for my 12x17.5x8 dedicated theater room. One item that I've read in several threads is the use of the riser as a bass trap by stuffing the riser "bays" with acoustic material and then drilling holes (2" mentioned) in the end of each bay facing the screen.
Possibly also leaving a few inches uncovered by plywood at the wall/riser corner boundary.

How effective is such a riser trap, and is it a broadband bass trap or one that is tuned to control the frequency that's absorbed based on the hole sizes and locations? If tuned, how would one translate resonant frequencies to hole size?

Thanks in advance for the feedback
MikeWhat your talking about is A Helmholtz Resonator tuned for the low freq's AKA bass trap.. These type of traps are'nt broadband by nature but you can design them to work over an acceptable bandwidth or just add more aimed at different freq...

These type of treatments are good for fine tuning such as ultra low freq absorbtion/room modes, but it is better to first treat the room with BroadBand absorbtion, say in the corners on the rear wall and first reflection points inc ceiling ...

Hope this helps,
Cheers....

Without getting into drilling holes and such into the riser I would like to know if in general you would fill any such structure with fiberglass?

Definitely! If you look at my thread, there are plans for the construction of a riser from an article written by Dennis Erskine. I've also thrown in a few additions that have come up in the years since the article was written.

CJ

One item that I've read in several threads is the use of the riser as a bass trap by stuffing the riser "bays" with acoustic material and then drilling holes (2" mentioned) in the end of each bay facing the screen. Possibly also leaving a few inches uncovered by plywood at the wall/riser corner boundary.

How effective is such a riser trap, and is it a broadband bass trap or one that is tuned to control the frequency that's absorbed based on the hole sizes and locations? If tuned, how would one translate resonant frequencies to hole size?You might ask Dennis Erskine about this, as it is one of his specialties. Here's (http://www.avsforum.com/avs-vb/showpost.php?p=9156798&postcount=47) just one example.

Hi all,

I’m in the process of doing some “light” remodeling in my finished basement to accommodate a 2 channel audio/home theater setup. I have a very old “popcorn” drop ceiling that I want to replace with either standard commercial or residential Armstrong ceiling tiles. They seem to come in a variety of NRCs, from 0.4 to 0.65 (they also have some high absorption acoustic tiles that I am not considering). Given that my basement is fully carpeted, I was concerned about making the room too dead if I installed ceiling tiles that have a high absorption factor. I seem to recall that some people on this forum recommend against treating a ceiling. My basement is about 16’ x 17’ and it is “busy”, bookshelves, etc. Other than the front wall, I won’t have too many flat, bare surfaces. I just don’t want to make a mistake by ordering tiles that have too much of an absorption coefficient. Thanks in advance for any feedback!

You want as much absorption as possible at the ceiling reflection points. Elsewhere on the ceiling matters less. However, high absorption at bass frequencies is good around the perimeter, near the wall-ceiling corners above the grid.

Making a room dead is not as big a risk as making it dead at only mid and high frequencies.

--Ethan

No, but even if I did I wouldn't comment because it's not appropriate for me to talk about products from a competing vendor. I can tell you that ASC is a top notch company who makes great stuff.

--Ethan

my architect suggests that I do a double gypsum ceiling with space between with fibreglass stuffed inside, this seems to be a primarily sound insulation technique and the absorption I see are typically not very high in the 200-500 Hz range, would I be wasting money (it'll cost around $1300 USD) ?

after reading around a bit, I appreciate more and more polycylinder diffusors, especially spherical like ones as they seem to work in quite a few directions and wide angles like 120 degrees (e.g. Saturn); if I find a shape that is visually acceptable I want to end up going this way...

You want as much absorption as possible at the ceiling reflection points. Elsewhere on the ceiling matters less. However, high absorption at bass frequencies is good around the perimeter, near the wall-ceiling corners above the grid.

Making a room dead is not as big a risk as making it dead at only mid and high frequencies.

--Ethan

Thanks Ethan. So if I proceed with replacing the entire ceiling with 0.5 NRC (let's say) ceiling tiles and also take care of the corners, it would generally be ok? Not too much absorption throughout?

my architect suggests that I do a double gypsum ceiling with space between with fibreglass stuffed inside... would I be wasting money (it'll cost around $1300 USD)?

I'm not much of an isolation expert so I'll let others comment. But do you even need sound isolation? Generally, construction that increases sound isolation makes the bass response worse inside the room. So unless you have sleepy and/or crying babies elsewhere in the house, I'd skip the extra isolation and put the funds into better acoustics inside the room.

after reading around a bit, I appreciate more and more polycylinder diffusors, especially spherical like ones as they seem to work in quite a few directions and wide angles like 120 degrees

I'm not a fan of polys, at least not in most home-sized rooms. I think they're more useful in much larger spaces. For smaller rooms I always recommend QRD type diffusors. This video lets you hear a variety of surface types close-up:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

--Ethan

So if I proceed with replacing the entire ceiling with 0.5 NRC (let's say) ceiling tiles and also take care of the corners, it would generally be ok? Not too much absorption throughout?

It seems to me a better solution is to use a lesser amount of highly absorbing materials. The problem with "semi-absorbing" materials is the absorption may not be uniform across the audible range.

--Ethan

It seems to me a better solution is to use a lesser amount of highly absorbing materials. The problem with "semi-absorbing" materials is the absorption may not be uniform across the audible range.

--Ethan

ok, very useful advice, thank you.

I'm not much of an isolation expert so I'll let others comment. But do you even need sound isolation? Generally, construction that increases sound isolation makes the bass response worse inside the room. So unless you have sleepy and/or crying babies elsewhere in the house, I'd skip the extra isolation and put the funds into better acoustics inside the room.



I'm not a fan of polys, at least not in most home-sized rooms. I think they're more useful in much larger spaces. For smaller rooms I always recommend QRD type diffusors. This video lets you hear a variety of surface types close-up:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

--Ethan You make An Exellent point Ethan, that Floyd Toole makes mention in his new book as well about the not so well documented down side of room isolation IE: 2/3 layers of dry wall, as it can have an adverse effect on the low freq response due to the walls being made stiff/rigid.. Thus more $$$ then needed for Acoustic treatment & the same can be said for concrete walls....

Cheers...

I'm not a fan of polys, at least not in most home-sized rooms. I think they're more useful in much larger spaces. For smaller rooms I always recommend QRD type diffusors. This video lets you hear a variety of surface types close-up:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

--Ethan

Hi Ethan,

I cannot access your video at the moment....stupid work firewalls. Would you mind explaining breifly why you dont like polys in smaller rooms and why QRD is better. Or alternatively point me to a reference I can look up/read that might explain it.

I had more or less decided on polys for my room (mainly becuase they look good and are easy to make :) ), I would very much appreciate your views.

Also, if QRD's are the way to go, is DIY considered at all possible or just too hard for the "simple minded" to get right?

Many thanks,
Elill

Nothing is perfict inc Quadratic Residue Diffuser's but What makes well designed QRD diffusers superior to Polys is the favorable uniform pattern in which QRD's diffuse/scatter compared to poly's...

DIY 1D QRD's are of course possible but keep in mined that there are many different types of sequences of numbers 7 prime 11 prime, 13 prime, 17 prime,and then there are 2D primitive root "skyline's" and so on..

Small 1D shallow 7 prime seed diffusors are usefull for mid/high freq, taming flutter Echo.
If you wanted to diffuse A very wide freq range using standard QRD, the QRD Diffusor would be huge some wells as deep as 6ft or more.. This is where Wide band Diffractal type diffusors are the better choice in A smaller room due to there smaller compact size but are extremely complexed to make....

I must admit having made some 1D's myself, Good QRD's are very time consuming complexed to construct... I look & construct them like they are A prosition instrument, but I have made 7 prime QRD's and wideband 13prime 7" deep x30" wide x 4ft 2" high (Abffusors) Absorbtion and Diffusion in one ...

Cheers...

Nothing is perfict inc Quadratic Residue Diffuser's but What makes well designed QRD diffusers superior to Polys is the favorable uniform pattern in which QRD's diffuse/scatter compared to poly's...

This is what I thought for a long time. The theory of Schroeder diffusers is so elegant, they perform well, and they look so cool. ;)

However, there are two factors that ultimately limit diffuser performance -- depth and regular periodicity. The first controls the lowest frequency they can scatter, and the second the uniformity of diffusion and the absence of "lobing."

But guess what? These issues are the same for both polycylindrical diffusers and Schroeder diffusers. And if you look at the performance of an individual poly vs. and individual QRD or other Schroeder diffuser, a poly or similar convex curve covers a wider frequency range and is more uniform at normal incidence. Depending on the circumstances, I recommend both types in my consulting practice.

- Terry

This is what I thought for a long time. The theory of Schroeder diffusers is so elegant, they perform well, and they look so cool. ;)

However, there are two factors that ultimately limit diffuser performance -- depth and regular periodicity. The first controls the lowest frequency they can scatter, and the second the uniformity of diffusion and the absence of "lobing."
How low is diffusion needed in rooms the size of the typical home theater?

Would you mind explaining breifly why you dont like polys in smaller rooms and why QRD is better. Or alternatively point me to a reference I can look up/read that might explain it.

This is something you really need to hear for yourself. If you just read articles, or look at scattering data, polys look like they'd do a fine job. And they do scatter sound. But they don't reduce the hollow boxy sound of comb filtering nearly as well IMO. It seems to me the real value of QRD diffusors is the staggered reflection times due to the varying well depths more than the actual scattering.

When you get home you can see the All About Diffusion (http://www.realtraps.com/video_diffusors.htm) video. Another video that's closely related and worth watching / hearing is Hearing is Believing (http://www.realtraps.com/video_hearing.htm).

--Ethan

Jeff Hedback wrote a great article (http://www.gikacoustics.com/news_060109.html) on diffusion that addresses some of these questions pretty directly.

Frank

Anything is better than nothing, but it's common to angle panels a little off 45 degrees to make then fit. Or put a panel flat on the wall near the corner.

--Ethan

Ethan, are you saying that these would work to cut a 2' x 4' of rigid so that one side doesn't stick out as far into the room?

http://home.mchsi.com/~fun_pictures/Bass_Trap.JPG

This is something you really need to hear for yourself. If you just read articles, or look at scattering data, polys look like they'd do a fine job. And they do scatter sound. But they don't reduce the hollow boxy sound of comb filtering nearly as well IMO. It seems to me the real value of QRD diffusors is the staggered reflection times due to the varying well depths more than the actual scattering.

When you get home you can see the All About Diffusion (http://www.realtraps.com/video_diffusors.htm) video. Another video that's closely related and worth watching / hearing is Hearing is Believing (http://www.realtraps.com/video_hearing.htm).

--Ethan

Jeff Hedback wrote a great article (http://www.gikacoustics.com/news_060109.html) on diffusion that addresses some of these questions pretty directly.

Frank

This is a most useful discussion, thankyou both.

I need to pull my finger out and start working up detailed plans. Once this is done and I start my new construction thread. I'd be delighted if you can provide more "feedback" at this point.

In the interim I'm going to have to find somewhere that has both types of diffusers to experiment with....unfortunately it seems to be a cottage industry in Sydney.

Sorry, am I missing something about diffusion on the bass end ? From reading Ethan's article, very low frequency diffusion seems to miss the point, as bass response polar plot shows < 500 Hz the speaker is really omnidirectional ? (I am excluding room mode issues for now)

An acoustic consultant that I'm talking to, has this to say about Poly versus QRD diffusion for ceiling deployment (I'm in a 10'x18' room, sitting on the 18' side :

"... due to their (QRD diffusors) dependence on phase relationships, QRDs tend to exhibit beaming effects at higher frequencies, where more sound energy is reflected at certain sets of angles. These frequencies in turn depend on their design and construction. The most common applications are in the rear wall of a studio control room, which is normally some distance behind the listening position or in the front wall behind the speakers. The beaming effect is less pronounced at this distance from the QRD and it still gives an overall sense of diffusion after considering the direct sound from the speaker and other room reflections.

However, when suspended from the ceiling of a small apartment, the listener is closer to the QRD in relation to the speaker and beaming effects may still be prominent. This can potentially give rise to a sound-field that will vary significantly with position.

A 'Polycylindrical diffusor' relies on a curved surface to provide treble diffusion. While it may be a less efficient diffuser at certain frequencies, its effects are more even across the frequency range and less dependent on distance from the listener. It also provides more bass absorption in the sub-250Hz range, which is important for an apartment with limited space and a comfortable listening environment can be achieved with less of the potential issues of QRDs. If you are only going to get ceiling panels, Polycydrindrical are a more well-rounded solution.

Diffusion is only one aspect of room acoustics. A room with excessive diffusion will also lose some of the "liveliness" and "sense of space" that comes from well-controlled reflection patterns. This is less desirable in a studio control room where the emphasis is on accurate spatial reproduction for monitoring purposes, especially where stereo mixing is being carried out, but these qualities make for a better listening room."

Ethan, are you saying that these would work to cut a 2' x 4' of rigid so that one side doesn't stick out as far into the room?

I wouldn't use less fiberglass. All I meant is to change the angle as needed to avoid a door or window. A 24" wide panel straddling a corner impinges about 19 inches in both directions. If you change the angle it will extend less in one direction and more in the other.

--Ethan

This is a most useful discussion, thankyou both.

I need to pull my finger out and start working up detailed plans. Once this is done and I start my new construction thread. I'd be delighted if you can provide more "feedback" at this point.

In the interim I'm going to have to find somewhere that has both types of diffusers to experiment with....unfortunately it seems to be a cottage industry in Sydney. The larger QRDs/Abffusors I built go for around $2000au each here in Auss for A simmlar commercially built RPG Abffusor...

Looking for some advice on where to purchase materials. I live in central New Jersey and have no problems driving an hour or 2 for a good price.

I'll be looking to purchase about 150 square feet of 4" OC703, 60 square feet of 2" OC703, and 80 square feet of 1" linacoustic.

I found a web site, readyacoustics.com that sells the OC703 for $80 for 3 2x4 sheets of 4" and $80 for 6 2x4 sheets of 2". Are those good prices?

Thanks
Mike

Looking for some advice on where to purchase materials. I live in central New Jersey and have no problems driving an hour or 2 for a good price.

I'll be looking to purchase about 150 square feet of 4" OC703, 60 square feet of 2" OC703, and 80 square feet of 1" linacoustic.

I found a web site, readyacoustics.com that sells the OC703 for $80 for 3 2x4 sheets of 4" and $80 for 6 2x4 sheets of 2". Are those good prices?

Thanks
Mike
http://www.spi-co.com/directory.html

These are insulation products from the HVAC/construction world. Once the word "acoustics" is attached to them, the price goes up. Contact the branch closest to you and get a quote to compare.

I wouldn't use less fiberglass. All I meant is to change the angle as needed to avoid a door or window. A 24" wide panel straddling a corner impinges about 19 inches in both directions. If you change the angle it will extend less in one direction and more in the other.

--Ethan

Ethan, that was kind of what I was checking on. If I cut a 2' x 4' piece in those angles and stack them where one side is short then the other I think we are on the same page.

thanks

^^^ Ah, okay, you mean apply the same "angle theory" to a solid fill design. Yes, that's great.

--Ethan

I have a large living room, the dimensions are approximately 20 feet by 25 feet. The ceilings are vaulted, and approximately 15 feet tall at the top. My dining room is directly attached to the back of the room and open, so it extends another 12 feet, and is around 15 feet wide. All of the flooring is porcelain tile. The walls are covered with wood paneling that has been painted over. The ceiling is sheetrock.

As you can see, all of these factors contribute to a very live, reverberant space. I recently purchased the house, and before I moved any furniture in, it was pretty much an echo chamber in my living room. Now, with furniture and a rug, it is slightly better, but still way too reverberant for serious music/movies listening.

I was planning on making some absorbers out of either R19 or R30 fiberglass. Basically I would take a 4'x8' sheet of 1/4" mdf, and frame it about 4 inches tall, then stuff it full of fiberglass, and cover it with fabric. I would mount them to the ceiling (which is a popcorn ceiling so anything looks better than that), and the side walls.

Would 4 of these make a big difference? I would probably need to install some bass traps too, but I would like to get rid of the terrible echo first.

Just a quick note on a homemade bass trap(s) I did ("made" is too strong of a word). I haven't been thrilled with the (lack of) effect of some of the commercially available traps. I purchased bales of non-itch, cellulose insullation designed to be blown into ceiling cavities. The bales are wrapped in plastic, and relatively dense; they were about 11.39 per at home depot (I'm sure there are better prices available). They weigh about 15 or 20 pounds each, and are about 25" x 15" x 18" (not exact -- from memory) I taped the seams on the bales, then stacked them angled across the front and rear corners in my room, and obscured them. I measured quite a significant difference on bass down to about 40 hz. The only mode it didn't help with was the one I have at 18hz, but I'm not surprised about that. Net cost was about $70. WAF was good once they were obscured, as this is a semi-dedicated room. I'm pretty sure it would get a no-go in the living room. :=)

pix?

I posted this as a separate thread, but I guess it belongs in here...

AFter searching the archives for answers, I came up short. The older threads seem to deal with insulation rather than room acoustics.

Why do people recommend OSB vs. plywood for floating subfloor, besides the price? And what about cement reinforced gypsum floor boards?

My concerns are low freq absorbtion (room acoustics) as well as sound insulation.

My construction thoughts are (attic HT room above bedrooms - ceilings below are decoupled from joists):

1.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2" wood
- GG
- 1/2" wood
- carpet

OR

2.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2 " cement reinforced gypsum boards
- GG
- 1/2 " cement reinforced gypsum boards
- carpet

Thoughts on Gypsum vs. wood:
Gypsum boards are heavier thus better for low freq insulation, however also less flexible and therefor less absorbing (I think?). In other words, I might have an acoustic penalty for getting better sound insulation...?

Thoughts on OSB vs. plywood:
OSB is cheaper and a little heavier, thus better sound insulation; however, I read somewhere that the multiple layers in plywood creates better absorbtion and less low freq resonans, thus better low freq room acoustics...?

Thoughts on T&G OSB/plywood vs. non-T&G:
Using T&G osb/plywood makes it easier to lay vs. screwing the two layers of OSB/plywood together (GG in between) and using acoustic chalk to seal the seams. However, wouldn't it make the top layer (T&G) act as one big resonater rather than many smaller plates- and isn't that worse for room acoustics?

I appreciate any answer and help, but please state your knowledge level vs. hearsay :) (i.e. DE or BP answers will hold higher value to me :D)

Added::
My local wood supplier said today that he wouldn't recommend plywood for any kind of floating floor/subfloor, due to the tension in the wood. He said it would be difficult to control it - even if using T&G plywood. He recommended using chipboard as it is completely dead. Any thoughts on this issue?


Thanks!!!!

Jacob
Attic HT in progress

Does FSK or Scrim make a difference if it is on the back wall behind seating?

^^^ Yes, you do not want anything reflective on a wall that's right behind listeners.

--Ethan

Sorry guys, should have stated my question better.

Does FSK or Scrim make a difference if it is on the bottom half of the back wall behind seating but below ear level.

^^^ Below ear level is a good place for FRK/FSK because that gives more bass absorption in the wall-floor corner.

--Ethan

I posted this as a separate thread, but I guess it belongs in here...

AFter searching the archives for answers, I came up short. The older threads seem to deal with insulation rather than room acoustics.

Why do people recommend OSB vs. plywood for floating subfloor, besides the price? And what about cement reinforced gypsum floor boards?

My concerns are low freq absorbtion (room acoustics) as well as sound insulation.

My construction thoughts are (attic HT room above bedrooms - ceilings below are decoupled from joists):

1.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2" wood
- GG
- 1/2" wood
- carpet

OR

2.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- (GG??)
- 1/2 " cement reinforced gypsum boards
- GG
- 1/2 " cement reinforced gypsum boards
- carpet

Thoughts on Gypsum vs. wood:
Gypsum boards are heavier thus better for low freq insulation, however also less flexible and therefor less absorbing (I think?). In other words, I might have an acoustic penalty for getting better sound insulation...?

Thoughts on OSB vs. plywood:
OSB is cheaper and a little heavier, thus better sound insulation; however, I read somewhere that the multiple layers in plywood creates better absorbtion and less low freq resonans, thus better low freq room acoustics...?

Thoughts on T&G OSB/plywood vs. non-T&G:
Using T&G osb/plywood makes it easier to lay vs. screwing the two layers of OSB/plywood together (GG in between) and using acoustic chalk to seal the seams. However, wouldn't it make the top layer (T&G) act as one big resonater rather than many smaller plates- and isn't that worse for room acoustics?

I appreciate any answer and help.

Added::
My local wood supplier said today that he wouldn't recommend plywood for any kind of floating floor/subfloor, due to the tension in the wood. He said it would be difficult to control it - even if using T&G plywood. He recommended using chipboard as it is completely dead. Any thoughts on this issue?


Thanks!!!!

Jacob
Attic HT in progress

Please, if anyone have good advice on this acoustic issue, I would really appreciate it!
I would like to have the floor done this week, so I need to make a decision soon.

Thanks!!

Jacob

Please, if anyone have good advice on this acoustic issue, I would really appreciate it!
I would like to have the floor done this week, so I need to make a decision soon.

Thanks!!

Jacob

You are right in wondering whether better isolation means worse acoustics in the room. Or, rather, you are right that that is the trade off. Once you have stopped noise from coming into the room, further isolation to reduce all vibrations from leaving the room tend to make the room itself less ideal, acoustically.

Hey folks,

I am employing various strategies at cutting down light reflections from my wall back to my projection screen. Most of the room is dark; the wall is light and pretty reflective (no, I can't paint it for various reasons). I'm using curtains to cover a lot of the wall are when watching a movie. However I still have a large reflection point on the wall right were my surround speaker is sitting.

What I'd like to do is use a roller shade hidden up in the ceiling above that portion of the wall, and pull it down when watching a movie. However that would be pulling the shade material right over the surround speaker. Therefore I'm looking for an acoustically transparent shade material.

Any suggestions?

I took a look at a local shade store and some of their black semi-transparent shades seem very promising: dark enough to cut down the light walls. The material isn't made to be speaker-grill-like per se, but it is a very open weave, more open than most speaker grill cloth I've seen, and in the "speak-through" and "blow through" test appears to me to be very transparent.
Think it will work, or is there some more fiddly factors that go into a speaker grill clothe/acoustic cloth that makes them better?

There's also the question of the fact the speaker would end up with two sets of "grill cloth" in front of it (the one it comes with and the shade that will drop in front of it). Ought I expect muffled sound at all?

Thanks,

You are right in wondering whether better isolation means worse acoustics in the room. Or, rather, you are right that that is the trade off. Once you have stopped noise from coming into the room, further isolation to reduce all vibrations from leaving the room tend to make the room itself less ideal, acoustically.
Thanks! That still leaves me in the dark on choosing subfloor material.. :(

Jacob

Lacking an opinion from a pro, personally, I would use option 1 with T&G OSB and no Green Glue between the rubber and first layer of OSB.

1.
- wooden planks subfloor on the joists (cavities filled with rockwool)
- rubbermat 10 mm (~3/8") (isolgomma R10, european brand)
- 1/2" T&G OSB
- GG
- 1/2" T&G OSB
- carpet