Acoustical Treatments Master Thread [Text View] - Page 29

mtbdudex

02-01-11, 04:29 AM

Has anyone ever used stone as a diffusing medium? I have some left over from a fireplace and could use it in a strip on my rear wall if it would be beneficial. This is the only pic I could find:

http://i182.photobucket.com/albums/x67/srp001/stone.jpg

Also, if making soffit bass traps, with 1/2" sheetrock covering loose insulation should I cut vents in or leave it sealed?

Stone would be better than a flat wall, but to be predictably effective would need to have bigger peaks and valleys than in that photo. That looks like a visual flourish but not an effective sound treatment.

You want something much thinner than half inch Sheetrock covering a bass trap. Examples: fabric, foil, paper. If you look at some of the build threads here you'll see some creative solutions. Example, one whole side is left unsheetrocked and is covered with fabric.

That won't work very well for various reasons, mostly because there's not enough depth. More here:

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

A soffit as you describe will not work as a bass trap because sheet rock is too dense to let bass waves pass through to the insulation inside. You need to make a wood frame, then stretch fabric (or staple cardboard) to the frame.

--Ethan

Kinda related, while doing tile work in my basement I saw these in the store and they reminded me of the diffusers I was reading about while doing some of my acoustic research 1+ year ago.
Yea, they look like them somewhat but depth is too shallow and I'm sure their pattern does not follow some 7th order function...
Wonder how heavy they'd be if built "properly".....100's lbs?
http://lh5.ggpht.com/_FqTNmgNQHz8/S2NZwRXcUSI/AAAAAAAAKWk/I1QwmehX8OI/s640/0129201000390.jpg http://lh5.ggpht.com/_FqTNmgNQHz8/S2NZwhxb15I/AAAAAAAAKWk/nKnfy8UkYVs/s400/0129201000400.jpg

Since I'm in a log home I was looking for some more natural/organic material for diffusors than the metal/plastic ones I've come across.
Some of those commercial wood ones are really neat looking, and with science behind them.
http://www.rpginc.com/products/hemiffusorw1/hem_img/main_hem_image.jpg http://www.silentsource.com/images/qrd734L.jpg

The DIY wood ones seem like lots of work....(this is from a 3 year old thread with Ethan also in it, http://recording.org/studio-construction-and-acoustics-forum/34687-diffusors-manufacturer-comparisons.html)
http://www.icixsound.com/vb/icixnation/images/202_79.jpg

mtbdudex

02-01-11, 05:10 AM

hey mtbdudex, thanks so much for sharing.

i noticed that you only wrapped the OC703 only, instead of the whole frame.

how did you keep the OC in the frame, so it doesn't fall out? i see 2 back panels support, but how about the front?

I've been thinking to make a separate thread on the DIY construction methods of hanging acoustic panels, currently none exist, I've searched AVS forum.
Just these for Fabric frames, which are integrated as part of the wall itself, not hanging and locatable to where only needed.
(these are great threads btw for those whole wall coverage methods)
Fabric Frames - GPowers Thread (http://www.avsforum.com/avs-vb/showthread.php?t=487747&highlight=fabric+frames)
Another Fabric Frame Thread - Canvas Stretcher Bars (http://www.avsforum.com/avs-vb/showthread.php?t=768967&highlight=fabric+frames)

I'll start it later, and others can then add their methods there.
IMO, this "Master treatments" thread is more for the theory, science, and practical application for acoustics of your particular room situation/issue, not the DIY construction methods, that will clutter it too much.

Having separate DIY construction technique thread will keep that ready for others to grasp as well, this 100's pages thread can be overwhelming at times.

Dennis Erskine

02-01-11, 06:11 AM

You certainly do not want the back wall "dead" if you have surround speakers back there. The extent to which that wall is treated, and exactly with what, is dependent upon many factors ... distance from speakers, distance from nearest row, available height for rear speaker installation, overall decay rate by frequency in the room, where are the side surrounds (and type), etc.

smokarz

02-01-11, 10:55 AM

I've been thinking to make a separate thread on the DIY construction methods of hanging acoustic panels, currently none exist, I've searched AVS forum.
Just these for Fabric frames, which are integrated as part of the wall itself, not hanging and locatable to where only needed.
(these are great threads btw for those whole wall coverage methods)
Fabric Frames - GPowers Thread (http://www.avsforum.com/avs-vb/showthread.php?t=487747&highlight=fabric+frames)
Another Fabric Frame Thread - Canvas Stretcher Bars (http://www.avsforum.com/avs-vb/showthread.php?t=768967&highlight=fabric+frames)

I'll start it later, and others can then add their methods there.
IMO, this "Master treatments" thread is more for the theory, science, and practical application for acoustics of your particular room situation/issue, not the DIY construction methods, that will clutter it too much.

Having separate DIY construction technique thread will keep that ready for others to grasp as well, this 100's pages thread can be overwhelming at times.

great idea.

i agreed this is probably not the right thread for diy panels, and frankly the size of this thread and its content is overwhelming for people looking for diy materials.

please post link when you get a chance to getting around on creating this new thread.

thanks

Jay5298

02-01-11, 02:29 PM

Jay ... no. Measurements are required since the room has the bigger impact. Positioning counts, seating locations count, etc.

...of course cavities have to be deadened which is different from the LEDE adopted in early two channel, free standing arrangements.

THX is talking about baffle walls and the cavity behind the baffle is deadened to avoid resonance. There's also the SBIR notch issue to be cautious about.

Okay, well I guess I'll wait to hear from Mike about what to do with my room. I still think I'm safe to put corner bass traps in though.

Thanks

Ethan Winer

02-01-11, 02:36 PM

I was wondering has anyone used these kits for treating their theatre room, are these appropriate or are they setup only to work for a recording studio?

I don't see enough detail there to know what's included, but it's better to work with a treatment manufacturer directly who will guide you and make sure you get what's most appropriate for your specific room. In my experience, few resellers understand acoustic treatment well enough to advise specific products and placement etc.

--Ethan

nathan_h

02-01-11, 03:54 PM

Hi Guys,

Couldn't see this mentioned in the thread, but I was wondering has anyone used these kits for treating their theatre room, are these appropriate or are they setup only to work for a recording studio?

http://vintagemicrophone.com/JShop/product.php?xProd=58&jssCart=0c57f9c23c1d7f9cd6d2fb22c7b3c64d

Cheers,

Matt

Heck, for that price spend a few hundred bucks for a pro to come measure your room and tell you what to get and where to place it. Overall you'll likely spend less, and get a better (ie, perfect fit) solution.

EDIT: At the very least, Ethan's suggestion to have one of the expert vendors advise you is worthwhile. No cost for those remote consults, though it's of course polite to purchase at least some of what they sell.

Johnnydc

02-03-11, 03:25 PM

Hello everyone. I am a newbie to the site and was told to come to this thread for a good response. First, I am turning a large frog into a dedicated theater room (except for a few pieces of excercise equiptment that the wife has to keep in there). I would love to see some pics and get advice from some theater room owners that did a great job at "faking luxury" using some sort of curtains on all the walls for the "theater look", and of course for the benefit of sound dampening (doesn't have to be red velvet, can be any color and any material...I'm really looking for a cheap way to get the best theater look). I am thinking of running painted black dowels down the ceiling of the entire room, and using simple clearance curtains from Lowes that will reach the floor. There are so many responses on where to put curtains as well. here's my set up: rectangular room, entrance to room has large built ins where 50 Panasonic will be mounted, subs in bottom niches (large niches). do i put curtains over this stuff as well?? do I put it along all walls and in back?? There is a double window in the back of the room. This will be a 7.2 system (maybe 7.1 depending on the response I get from the sub-heads).
I have a 2 sub question as well , but will be posting it in the sub forums unless I have any subbies on this forum.
Basically here's my equiptment: Harmon kardon reciever, 50 panasonic plasma, 1 jbl powered 8sub, 1 veladyne powered 8, sony and jbl satalite speakers for front, mid, rear, and sony center channel.

mtbdudex

02-03-11, 09:58 PM

Here is the thread I just started in this same forum, called DIY construction methods of hang-able acoustic panels (not fixed frames) (http://www.avsforum.com/avs-vb/showthread.php?t=1312693)

I'd like others who make DIY hang-able acoustic panels, whether absorption, diffusion, reflection, etc. to also feel free to add your construction techniques/methods there.
>>We need to learn from you!

I've been thinking to make a separate thread on the DIY construction methods of hanging acoustic panels, currently none exist, I've searched AVS forum.
Just these for Fabric frames, which are integrated as part of the wall itself, not hanging and locatable to where only needed.
(these are great threads btw for those whole wall coverage methods)
Fabric Frames - GPowers Thread (http://www.avsforum.com/avs-vb/showthread.php?t=487747&highlight=fabric+frames)
Another Fabric Frame Thread - Canvas Stretcher Bars (http://www.avsforum.com/avs-vb/showthread.php?t=768967&highlight=fabric+frames)

I'll start it later, and others can then add their methods there.
IMO, this "Master treatments" thread is more for the theory, science, and practical application for acoustics of your particular room situation/issue, not the DIY construction methods, that will clutter it too much.

Having separate DIY construction technique thread will keep that ready for others to grasp as well, this 100's pages thread can be overwhelming at times.

great idea.

i agreed this is probably not the right thread for diy panels, and frankly the size of this thread and its content is overwhelming for people looking for diy materials.

please post link when you get a chance to getting around on creating this new thread.

thanks

Bills Fan

02-05-11, 12:50 PM

Looking for a reccomendation for a company to install a LCD TV and run the wires behind the wall.

pepar

02-05-11, 01:12 PM

Looking for a reccomendation for a company to install a LCD TV and run the wires behind the wall.
Had you considered posting this in a thread more closely related to installing an LCD and running wires inside the wall? Include a location, too. "Bills Fan" might say it, but you could be a translpant as well.

Tolstoi

02-06-11, 08:19 AM

I currently through a threads on construction projects to say how peoples did it. Doing this I came up with questions related to soundproofing.

1) I want to use tubing to be used a cables channels between the rack and near each speakers. I saw that almost all setup pass their tubing through the ceiling. I was planning to pass my tubing under the floor to try to get shorter cable runs. Soundproofing wise is their a benefit of method was to other?

2) Does the soffit add anything acoustic wise or are they strictly there for cosmetic reasons? Do they need to be symmetrical?

3) One of my walls is made of 2x6 on which I am using sound clips and hat channels. What should I do soundproofing wise with that extra 2" compare with 2x4 structure? Increase the 1" air space between the R13 pink insulation and gypsum? Increase the pink insulation thickness to 5"1/2?

dallaslistener

02-07-11, 10:11 AM

Hey Guys,

My wife and I built a fairly large dedicated HT a couple of years ago. At the time we hired an acoustics "consultant" to help with the design and construction. He provided a set of plans and after it was too late, we discovered that many of the "acoustical" tricks he had recommended had been mis-communicated to our builder in the beginning and it was too late to implement most of them. Things such as built in corner bass traps and soffit diffusers and so on and so on. In addition, they would have made the aesthetics of the theater horrible. When challenged by myself and the builder, it became obvious that the guy had sub contracted the whole design and drawing set to someone else and he really didn't know what he was talking about. There were actually two aspects to the construction, the sound proofing / isolation of the room from the rest of the house and the interior acoustical treatment. We got the isolation stuff right from the start. But the interior treatment stuff didn't get implemented.

At first pass, the room seems to sound pretty good but I would really like to take some analytical measurements and begin experimenting with acoustical treatments. So my question is what instrumentation do I acquire? Computer? Software? Mics? Etc? This may have been covered already and if so I apologize for repeating. Just point me to the right thread. I have a EE degree so I'm not scared of the in depth technical stuff. I've also been a lifelong "audiophile" for what that's worth - if anything :-)

Thanks
Dale Troutt
Frisco TX

Ethan Winer

02-07-11, 11:09 AM

what instrumentation do I acquire?

Here's my standard list of room measuring links:

Room EQ Wizard, Windows and Linux and Mac OSX 10.4+, Freeware (http://www.hometheatershack.com/roomeq/)
ETF, Windows, $150 (http://www.etfacoustic.com)
FuzzMeasure, Mac, $150 (http://www.fuzzmeasure.com)
Room Measuring Primer (http://www.realtraps.com/art_measuring.htm)
Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

--Ethan

pepar

02-07-11, 12:40 PM

Laptop, USB sound "card" or preamp, Room EQ Wizard and a calibrated mic. But it will be the time needed to get around the learning curve .. or "curb" depending on how well you assimilate. But even then with measurements in your hand you may not know what they mean. I don't mean to dissuede you, but you have a bit of a daunting task ahead.

You might consider a design service like the one offered here by AVS (http://shop.avscience.com/Design-Services_c_27.html) or Dennis Erskine.

Also, acoustical treatment vendors such as Ethan Winer and GIK Acoustics offer design recommendations as part of their customer service.

erkq

02-07-11, 01:47 PM

I have a "flutter" echo in the back of my theater. Fortunately it doesn't seem to get activated by the speakers. I just unscientifically covered the walls with 1" black-faced fiberboards and it went away with great audio clarity. But talk of "over damping" got me to experiment with positioning absorption using the "mirror test". The results are again very clear and satisfactory, but if I go to the back of the theater and even utter a "sss" I hear the flutter echo.

The room is a little complicated back there. The 6' wide projection booth juts out a foot creating a 1' deep 6' wide alcove on one side (I'd like to eventually use for a huge bass trap) and a 4.5' entryway on the other. Not only that, but the ceiling starts at 12' and pitches up to 17' about midway to the screen.

So there could be lots of places the flutter echo is occurring. I'd like to measure the flutter's period because that would give me the dimension to look for. How can I do that? A 'scope might be good but I don't have one. Can REW do this? I have that, a laptop and a calibrated mic. Is it worth setting those up and playing with available measurements and graphs?

Iusteve

02-07-11, 05:39 PM

A while back I asked if it was a good/bad idea to use OC 703 and fabric on all vertical surfaces in my theater and was told not to do so. So my next simple question without asking for a too complex answer. Is it ok to use OC 703 and fabric on both side walls to chair rail height or basicially 4ft? Also what about the rear wall? Chair rail or floor to ceiling?

dallaslistener

02-07-11, 08:17 PM

erkq

02-07-11, 08:25 PM

Ethan,

Thanks so much for the recommendations. I am a MAC computer guy primarily. I have a MAC Book Air and a MAC Desktop (both a couple of years old) and I've been thinking about buying a Mini to hook up to the Theater. My question is will REW do all the same stuff as FuzzMeasure or do I need to get both. Will I be giving up anything significant by not going Windows? Also, where do I buy one of the recommended mics and will I need an external mic preamp with a MAC? If so, which one and where to buy?

Thanks Again
Dale

I'm not Ethan but I settled on a LinearX M31 calibrated mic. It comes with its response curve both on paper and on a mini-cd. You can enter the curve into REW, but the it's so flat it hardly seems worth it.

I used a Behringer Mini-Mic Modelling Pre-Amp. Just set the "effects" to neutral. It seemed to be the best deal for an ultra-wide band flat pre-amp. There is a procedure to have it measure itself via a loop, but it's hardly worth it to find the -1dB points when the room response is so much more variable.

They're each around $125 or so.

I forget where I got them. I can look it up if you are interested.

dallaslistener

02-07-11, 08:45 PM

ERKG,

Thanks. I Googled them and found a few places to buy them. Did you use a MAC or PC?

Dale

erkq

02-07-11, 09:04 PM

ERKG,

Thanks. I Googled them and found a few places to buy them. Did you use a MAC or PC?

Dale

Unfortunately a PC. I run HCFA on it too. It's a pretty slick little test rig.

dallaslistener

02-07-11, 09:35 PM

HCFA? I'm not familiar with that. If I get a MAC Mini, how much memory do I need for these apps?

erkq

02-07-11, 09:47 PM

HCFA? I'm not familiar with that. If I get a MAC Mini, how much memory do I need for these apps?
HCFA is a very good free color calibration system. It's really OT here. I was just adding to why I use a PC.

You don't need much memory. Most of your memory load will be running the OS. These are pretty simple programs in comparison to the bloatware Microsoft gives us. Would you be running Bootcamp or Parallels on the Mini? Has anyone else here done that? It should work... I just don't know from experience.

systemlayers

02-07-11, 10:57 PM

Hi everyone been reading this thread intently - definitely not ready to pull the gun anytime soon but i've been looking into obtaining some rigid fiberglass in Edmonton Canada.
I found this large distributer and their rigid fiberglass:
http://www.crossroadsci.com/PRODUCTS/ProductCatalog/RigidFiberglassBoard/tabid/73/Default.aspx
It seems to have similar sound coefficients and thickness to the owens corning 703 will this be sufficient or should i search elsewhere/more?

mtbdudex

02-08-11, 12:15 AM

This past weekend continuing with improving the HT acoustics, I put (6) sheets of 2" thick 2' x 4' Roxul Rockboard on my screen to make is a "dead zone" instead of a resonance/reflection zone.
Dennis E suggested this to me almost 2 years ago, was on my "to do" list, finally did it this weekend.
http://www.atsacoustics.com/item--Roxul-Rockboard-60-Case-of-6--RB60.html
This is a case of 6 pieces of 24 x 48 x 2 inch Rockboard 60 manufactured by Roxul. It is rigid mineral wool board similar to Owens Corning 705 at a density of 6 pounds per cubic foot.
I used Roxul Rockboard instead of OC705 because I am NOT going to cover it, so did not want itchy stuff.

This is on back of my DIY screen, there is a controlled 3/4" gap to the DW laminate screen via the metal plates I added for supporting, secured the panels by suspended ceiling 14ga wire.
https://lh5.googleusercontent.com/_FqTNmgNQHz8/TVDMlQb3JEI/AAAAAAAAMFw/LncrBIXSX0c/s400/_MG_4199.jpg

Final product done and secured, the outside portion has (2) 2" thick 2 ' x 4' pieces fitting, the inside (1) due to screen curve allows more on outside.
https://lh4.googleusercontent.com/_FqTNmgNQHz8/TVDMlo0FmGI/AAAAAAAAMF0/MlVKzxbf0Y0/s400/_MG_4511.jpg

It's also with about a 3" air gap to the wall now.
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVDX07rjSMI/AAAAAAAAMGQ/nDYi2ah2Oe0/s400/_MG_4563.jpg

screen hung, btw It's also 50 lbs heavier.....my wife complained I'm "slaving her" with all this heavy lifting.:
https://lh5.googleusercontent.com/_FqTNmgNQHz8/TVDX1LfIoVI/AAAAAAAAMGU/GSYG1BJ0U5I/s640/_MG_4569.jpg
(that's my acoustic cloud I'm making just today, it was not there when I did the Audyessy re-run)

I immediately could tell improved bass, I've not taken REW plots yet, but I did re-run my Audyessy and it shows how its EQ is applied, look at the before/after for the center channel!
Yes, I was very careful about having my mic in repeatable positions as well for before/after check..
Plus, before Audyessy always set my Paradigm 9 mains Frt RH/LH to large, but the huge CC-390 center to small, now it also was set to Large, indicating it recognized it's lower freq potential better with the improved acoustics.
Note: The front of the center channel is about 29" from the back wall, that's as far as I could put it "in room" on the shelf I made, the mains are similar, plus 24" off the side walls.
Before...................................................... .......After:
https://lh6.googleusercontent.com/_FqTNmgNQHz8/TUlz_iAS18I/AAAAAAAAMC0/QbTkzm_w9l8/s288/_MG_4083%20After%20side%20wall.jpg https://lh4.googleusercontent.com/_FqTNmgNQHz8/TVDMmEKnjQI/AAAAAAAAMF8/SiQ09q916Os/s288/_MG_4531.jpg

Iusteve

02-08-11, 04:18 AM

My question got buried so I figured I would attempt one more time

A while back I asked if it was a good/bad idea to use OC 703 and fabric on all vertical surfaces in my theater and was told not to do so. So my next simple question without asking for a too complex answer. Is it ok to use OC 703 and fabric on both side walls to chair rail height or basicially 4ft? Also what about the rear wall? Chair rail or floor to ceiling?

Brad Horstkotte

02-08-11, 08:14 AM

The best answer is "it depends", and requires acoustic measurement. However, many have followed that general approach (floor to just above ear level on side and rear walls) and are happy with it.

erkq

02-08-11, 10:11 AM

The best answer is "it depends", and requires acoustic measurement. However, many have followed that general approach (floor to just above ear level on side and rear walls) and are happy with it.

How does this jibe with the "mirror test" which is how my room is configured now? It turned out to be wall coverage from just in from of the screen to almost parallel with the last seating position for that right speaker to left rear listener reflection. The covering goes up to 70" to cover the positions on the riser. I figured a little over-coverage was OK to make sure the reflections were "gotten". So much of the walls are left bare I figured I'd have enough "liveness". It sounds good... intelligibility is very good.

pepar

02-08-11, 10:31 AM

erkq

02-08-11, 10:42 AM

Or maybe no one has an answer:

I have a "flutter" echo in the back of my theater. Fortunately it doesn't seem to get activated by the speakers. I just unscientifically covered the walls with 1" black-faced fiberboards and it went away with great audio clarity. But talk of "over damping" got me to experiment with positioning absorption using the "mirror test". The results are again very clear and satisfactory, but if I go to the back of the theater and even utter a "sss" I hear the flutter echo.

The room is a little complicated back there. The 6' wide projection booth juts out a foot creating a 1' deep 6' wide alcove on one side (I'd like to eventually use for a huge bass trap) and a 4.5' entryway on the other. Not only that, but the ceiling starts at 12' and pitches up to 17' about midway to the screen.

So there could be lots of places the flutter echo is occurring. I'd like to measure the flutter's period because that would give me the dimension to look for. How can I do that? A 'scope might be good but I don't have one. Can REW do this? I have that, a laptop and a calibrated mic. Is it worth setting those up and playing with available measurements and graphs?

mtbdudex

02-08-11, 10:46 AM

How does this jibe with the "mirror test" which is how my room is configured now? It turned out to be wall coverage from just in from of the screen to almost parallel with the last seating position for that right speaker to left rear listener reflection. The covering goes up to 70" to cover the positions on the riser. I figured a little over-coverage was OK to make sure the reflections were "gotten". So much of the walls are left bare I figured I'd have enough "liveness". It sounds good... intelligibility is very good.

It doesn't. And I can tell you that I regret covering floor-to-ear level with carpet, an idea that I got 10-15 years ago from an acoustic handbook. My system sounds very good, dialog intelligibility is perfect regardless of the level of the dialog or the level of the rest of sounds.

But my room also seems a bit dead and I am looking at swapping the absorption at the first reflection points for diffusion. "Thinking" has changed, and so must I.

Jeff

fwiw, I calculated my desired RT60 for 0.5 sec, now I am in process of putting that absorption at first reflection points (side walls done, ceiling in progress), this way there was some science behind it.

Panels Added Resulting Reverb Time - RT60
Square Feet Count 125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz
Baseline drywall + carpet 0 sq.ft. 0 panels 0.4 1.09 1.34 0.77 0.48 0.42
treated with 6 side wall 2" and 6 ceiling 4" panels 96 sq.ft. 12 panels 0.38 0.64 0.56 0.42 0.31 0.29

I'm sure you guys have read this by Ethan W?.
http://www.realtraps.com/rfz.htm

I can't say how mine will turn out, but with some rationale of following a method, I can so far see good results as each phase goes on.

[edit]
hey erkq, hopefully Ethan or Terry or another expert will chime in for your Q

pepar

02-08-11, 11:16 AM

nathan_h

02-08-11, 11:40 AM

nathan_h

02-08-11, 11:42 AM

Ethan Winer

02-08-11, 12:13 PM

will REW do all the same stuff as FuzzMeasure or do I need to get both.

If REW works on your particular Mac then that's all you need.

where do I buy one of the recommended mics and will I need an external mic preamp with a MAC? If so, which one and where to buy?

I don't know if your Mac has a preamp, but my Room Measuring Primer (http://www.realtraps.com/art_measuring.htm) shows hardware that will work. Or buy the microphone and sound card from a dealer who knows Macs, and they'll know what to suggest. There are tons of good vendors such as Sweetwater and Vintage King and Musician's Friend and American Musical.

--Ethan

erkq

02-08-11, 12:16 PM

As I understand it, flutter echo happens between two parallel reflective surfaces. I'm sure you knew that ... :) ... and I would also think they'd be easy to spot?

Yes. The complexity of the room gives several possibilities for reflecting parallel surfaces. I guess I could just experiment and see what REW will tell me as nathan_h suggests. It's just hard to hang stuff 17' up, so I wanted to try to cut down on the possibilities before I start climbing the ladder.

pepar

02-08-11, 12:46 PM

Yes. The complexity of the room gives several possibilities for reflecting parallel surfaces. I guess I could just experiment and see what REW will tell me as nathan_h suggests. It's just hard to hang stuff 17' up, so I wanted to try to cut down on the possibilities before I start climbing the ladder.
I don't know how measurement software would identify the surfaces. I've always been able to find the culprits with my ears a few finger snaps. Yours sound like they are ... inconvenient, but the same process still applies .. snap your fingers and listen. It should be obvious which two surfaces are causing the echo.

erkq

02-08-11, 12:48 PM

I don't know how measurement software would identify the surfaces. I've always been able to find the culprits with my ears a few finger snaps.

The period of the flutter would tell me the distance between the surfaces. That would point to specific surface pairs that have that distance between them.

All I can tell with my ears is that it's somewhere in the back of the room.

pepar

02-08-11, 01:00 PM

The period of the flutter would tell me the distance between the surfaces. That would point to specific surface pairs that have that distance between them.

All I can tell with my ears is that it's somewhere in the back of the room.
:)

Front/back? Left/right? Up/down?

Ethan Winer

02-08-11, 03:15 PM

I don't know how measurement software would identify the surfaces.

The Impulse Response (or Energy / Time) display shows individual reflections and their arrival time. So you can figure the distance of a reflecting surface. I don't use that feature much, but I might if the alternative was climbing 17 feet up on a ladder!

--Ethan

erkq

02-08-11, 03:49 PM

:)

Front/back? Left/right? Up/down?

It's hard to tell, and that's my problem. There are 3 sets of parallel surfaces I suspect. I don't suspect the floor/ceiling surfaces because of a 6/12 pitch to ceiling.

erkq

02-08-11, 03:51 PM

The Impulse Response (or Energy / Time) display shows individual reflections and their arrival time. So you can figure the distance of a reflecting surface. I don't use that feature much, but I might if the alternative was climbing 17 feet up on a ladder!

--Ethan

That's what I'm looking for. Thanks. It seems it's worth playing with REW then.

dallaslistener

02-08-11, 06:47 PM

Ethan,

Thanks so much for the info. One more question - is basic mic calibration adequate or do I need the "premium" calibration?

Regards
Dale

smokarz

02-09-11, 09:04 AM

can anyone share some diy tips for constructing corner bass traps with OC 703? thanks

Kal Rubinson

02-09-11, 09:26 AM

can anyone share some diy tips for constructing corner bass traps with OC 703? thanks
Best: http://forum.studiotips.com/viewtopic.php?t=535

pepar

02-09-11, 09:43 AM

can anyone share some diy tips for constructing corner bass traps with OC 703? thanks
Enter here (http://forum.studiotips.com/viewforum.php?f=8&sid=03c9368e5d6963885d4f6998da03deef) and you get an overview.

myfipie

02-09-11, 10:28 AM

can anyone share some diy tips for constructing corner bass traps with OC 703? thanks

The main thing you want to do is
1) Make them 4" or thicker
2) Make sure to keep the back open. As in do not cover with wood or anything rigid.
From there you can just frame them up with wood and cover with fabric.

The other option is to cut the fiberglass to 24"x17" triangles and stack them floor to ceiling, then put a false fabric wall in front of that.

smokarz

02-09-11, 11:52 AM

The main thing you want to do is
1) Make them 4" or thicker
2) Make sure to keep the back open. As in do not cover with wood or anything rigid.
From there you can just frame them up with wood and cover with fabric.

The other option is to cut the fiberglass to 24"x17" triangles and stack them floor to ceiling, then put a false fabric wall in front of that.

thanks, i was asking specifically about corner bass trap.

cutting the OC 703 into triangles, and stack them up. but what are people doing? are they building triangle frames to house these stacks of OC 703?

smokarz

02-09-11, 12:24 PM

Best: http://forum.studiotips.com/viewtopic.php?t=535

Enter here (http://forum.studiotips.com/viewforum.php?f=8&sid=03c9368e5d6963885d4f6998da03deef) and you get an overview.

thanks, but looking for details diy instructions for corner bass.

pepar

02-09-11, 12:29 PM

thanks, i was asking specifically about corner bass trap.

cutting the OC 703 into triangles, and stack them up. but what are people doing? are they building triangle frames to house these stacks of OC 703?
For a hidden trap, you could do it this way (http://www.peparsplace.com/pg23.html). For an exposed trap, my idea is to use angle brackets bent into a 45 degree and mounted "inside" the retaining slats with a cover panel made and velcro'd onto the slats.

That is up next for me ... more superchunk traps in the rear of my theater.

Jeff

pepar

02-09-11, 12:30 PM

thanks, but looking for details diy instructions for corner bass.
Well, "corner" traps can be the panels straddling the corner or they can be the filled, chunk style. Your original post didn't specify any design in particular so I linked to both styles with comparative test data.

nathan_h

02-09-11, 12:32 PM

Ethan Winer

02-09-11, 12:35 PM

is basic mic calibration adequate or do I need the "premium" calibration?

Most likely you don't need any calibration. This shows a comparison of microphones at widely varying price points:

Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

--Ethan

pepar

02-09-11, 12:44 PM

Most likely you don't need any calibration. This shows a comparison of microphones at widely varying price points:

Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

--Ethan
I must compliment you on the wealth of useful information that you have put together and placed on your website.

Jeff

erkq

02-09-11, 12:46 PM

Most likely you don't need any calibration. This shows a comparison of microphones at widely varying price points:

Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

--Ethan

The LinearX I used came with a response graph and included each individual piece of equipment used in the measurement and when it was due for its next calibration.

Basically it shows Ethan is right. It is 1/4 dB down at 10Hz, 1/2 dB down at 25kHz and 1/3 dB up from 20Hz to 300Hz. I mean... so what? That is an insignificant level of precision when measuring a room. But I entered the curve into REW just for fun.

smokarz

02-09-11, 12:46 PM

pauleyc

02-09-11, 01:27 PM

For a hidden trap, you could do it this way (http://www.peparsplace.com/pg23.html). For an exposed trap, my idea is to use angle brackets bent into a 45 degree and mounted "inside" the retaining slats with a cover panel made and velcro'd onto the slats.

That is up next for me ... more superchunk traps in the rear of my theater.

Jeff

Jeff - thanks for the link to your example. I'm getting some bass 'build up' in the second row of my home theater (pictures in link below) and I was thinking about doing the same 'super chunk' design in the rear two corners. All these are under the soffit and out of the way so functionality won't be compromised. I could probably do corners in the front as well since black on black disappears in a dark HT environment. So I may try that as well. I keep hearing you can't have too many bass traps ;)

For the rear corners, I was thinking just left/right verticals w/ a 45 cut and maybe use your vertical wire idea if the OC703 isn't sturdy enough to stand on its own. Then its just a simple face frame grille. Here's an idea I plan to use ... before you fabric wrap the face frame, clamp it in place, drill a hole all the way through and then gluing a dowel in the face frame (or vertical nailers) so that you have a secure mount. I've had issues with Velcro and heavy panels.

Great info .. also thanks to Ethan - I've been reading a lot on your sight and even checked out a few of your youtube videos. While there is a lot of science behind it .. I get the impression that you can just keep adding with 'minimal' ill effects? (strictly speaking m-ch/HT)??

http://www.avsforum.com/avs-vb/showthread.php?t=1299530

pepar

02-09-11, 01:41 PM

thanks, i thought i saw that before.

my "chunky" corner bass trap will be exposed. so i am thinking perhaps some sort of frame wrapped with fabric?

just trying to find some visual image of what people have done.
The only thing that keeps a cover from being fastened to the slats that hold the horizontal trap are the 1x2 hunks that hold the slats in place. Make them thin metal brackets internally mounted and that obstruction disappears. I'm sure that there are other designs that would work, but that's where I am headed.

For the cover, I will make something like this (http://www.peparsplace.com/pg4.html). My edge pieces will be cut at a 45 degree angle to snug up to the wall as close as possible.

pepar

02-09-11, 01:50 PM

Jeff - thanks for the link to your example. I'm getting some bass 'build up' in the second row of my home theater (pictures in link below) and I was thinking about doing the same 'super chunk' design in the rear two corners. All these are under the soffit and out of the way so functionality won't be compromised. I could probably do corners in the front as well since black on black disappears in a dark HT environment. So I may try that as well. I keep hearing you can't have too many bass traps ;)

For the rear corners, I was thinking just left/right verticals w/ a 45 cut and maybe use your vertical wire idea if the OC703 isn't sturdy enough to stand on its own. Then its just a simple face frame grille. Here's an idea I plan to use ... before you fabric wrap the face frame, clamp it in place, drill a hole all the way through and then gluing a dowel in the face frame (or vertical nailers) so that you have a secure mount. I've had issues with Velcro and heavy panels.

To hold the vertical stack of 703 in place and give me something to fasten the covers to, I will use the slats. The wires were a down and dirty solution that was perfect for the hidden traps.

Brad Horstkotte

02-09-11, 02:04 PM

For my superchunks, I simply used drywall screws and liquid nails to affix 2 2x2s at 17" from the corners - then the triangles just stack in. Will staple a fabric face to the edges of the 2x2s. An easy approach if you're installing them permanently (vs a moveable trap).

fotto

02-09-11, 02:22 PM

I did just as Brad suggests for my front corner superchunks (hidden behind false screen wall). For my rear ones, I did a bit different:

http://i625.photobucket.com/albums/tt333/feotto/reartrap1.jpg

http://i625.photobucket.com/albums/tt333/feotto/reartrap2.jpg

http://i625.photobucket.com/albums/tt333/feotto/reartrap5.jpg

http://i625.photobucket.com/albums/tt333/feotto/panels5.jpg

pauleyc

02-09-11, 02:44 PM

Now I'm excited .. this is going to be a fairly easy project (in the scheme of things) thanks to the great info here. Now if I could just find a source in NoVA for OC703.

foto - Thanks for the pictures. Gave me some good ideas.

Jeff - What are your frames made out of? They are small. Any warping issues?

pepar

02-09-11, 03:04 PM

Jeff - What are your frames made out of? They are small. Any warping issues?
Poplar 1x2 ripped in half. Poplar is used for moldings because of its stability, but usually residences do not have large swings in relative humidity anyway. Plus the front of the theater is black and dark with no prominent "net fit" locations. My rear traps will not have the advantage of being hid.

Jeff

myfipie

02-09-11, 03:33 PM

Johnnydc

02-09-11, 03:35 PM

**********ACOUSTIC EXPERTS PLEASE READ ***********
First, (B) is wrong. Virtually every surface is a first reflective surface (speaking of walls). "B" is actually treating those early reflections which meet the listener's ears within a time frame described by Helmut Haas (further researched by Toole and Olive). Depending upon the delay due to the longer path to the ear will result in the sound being perceived as a distortion, or echo. As well, sounds reflecting off a surface suffer timbre shift. Next, you don't care a twit about "early reflections" that don't intersect the listening position.

The 'early reflections' technique is more typically found in two channel playback environments where higher reverberation times in the room are required to make up for the absence of surround channels (or intelligent surround processing techniques).

Dennis, or anyone else who has acoustical treatment knowledge PLEASE read this and reply. I don't have it in my budget to professionally treat my new home theater room, but this is what I can do in my budget and want to know:
1. will MY SOLUTION do ANYTHING
2. What is the best layout for the curtains.
My SOLUTION: http://www.walmart.com/ip/Montego-Woven-Texture-Grommet-48-x-84-Panel-Mocha/13269330
Put these regular curtain panels with grommets on rods (regular 50x 102 panels spread enough to have a deep wave as shown in pics) spaced all along the side and back walls of my theater room with about 1 foot of space between each curtain panel (maybe for a sconce light or neat piece of artwork). Room is about 18x20+ room window in back and one door, front is built in shelves where plasma will be.
WILL THESE DO ANYTHING...SEEMS LIKE THE FOLDS WOULD STOP WAVES FROM BOUNCING AROUND IF NOTHING ELSE AND CATCH SOME SOUND. Please give me your sound advice. I think it will "look" great, but I won't spend even that amount of money (probably $200+) if it won't help the sound.

pepar

02-09-11, 03:36 PM

See if you have a SPI in your area.
Northern VA? Yes, "Lancaster" ... PA .. :) according to their site. ;)

Actually, the Winfield, WV location might be closer ..

pauleyc

02-09-11, 03:40 PM

See if you have a SPI in your area.

Northern VA? Yes, "Lancaster" ... PA .. :) according to their site. ;)

Actually, the Winfield, WV location might be closer ..

Lancaster is an easy drive (1.5hrs). I take my kids up there to Dutch Wonderland (good times). Winfield is close to where I grew up but is >7hrs from the WashDC area. While I get back home often, I don't think my wife and kids want to travel with that much OC703 in the van :D

Johnnydc

02-09-11, 03:47 PM

Hey guys, is my post, 7067 going to get lost here? any ideas for me? Just wondering if there is a more appropriate place for it or should I start a new thread.

PTAaron

02-09-11, 04:11 PM

Hey guys, is my post, 7067 going to get lost here? any ideas for me? Just wondering if there is a more appropriate place for it or should I start a new thread.

There is a good chance that it will take longer than 15 minutes for someone to be able to reply to your post - I would give it at least a day, and if it gets buried start your own thread.

pepar

02-09-11, 05:42 PM

erkq

02-09-11, 06:32 PM

Curtains are window treatments, not acoustical treatments. Will they do *something?* Yes, something, but not anything meaningful. On the positive side, a few won't hurt.

And mocha is such a lovely color.

Yes. I favorited that page. I want to do acoustic treatment and then cover it with drapes that pass the "breath" test. I like the ones he found.

Johnnydc

02-09-11, 09:01 PM

erkq

02-09-11, 09:06 PM

They are by far the cheapest, neatest ones that I have found. So, If I get two sets for each rod, would that do the trick? Also, how about the placement question...hang them with about a foot of wall space showing between each one (mostly to save money)?
PS, ERKQ, if you decide to get them in the next few days, let me know how they look and get some pics.

I don't think it would "do the trick". If you are using the wrong tool, using 2 wrong tools won't make it work.

I have some more work to do on my sound treatment before I get the coverings so it will be a while. But thanks for the link! I'll have to show it to my girlfriend. It really looks nice.

systemlayers

02-09-11, 09:40 PM

nathan_h

02-09-11, 09:44 PM

They are by far the cheapest, neatest ones that I have found. So, If I get two sets for each rod, would that do the trick? Also, how about the placement question...hang them with about a foot of wall space showing between each one (mostly to save money)?
PS, ERKQ, if you decide to get them in the next few days, let me know how they look and get some pics.

In case it wasn't clear: these curtains will have no real acoustic benefit. If you place something substantial behind them like thick fiberglass panels of the kind discussed in this thread you'll be on to something. This isn't meant to be rude but just clear.

Brad Horstkotte

02-10-11, 12:47 AM

Anyone? Help would really be appreciated

Looks like they OEM CertainTeed product - they have a line of products actually called "OEM 300" and the like - if it's that, you're good to go. Unfortunately the link to the non-FSK leads to the FSK specs, so can't tell for sure.

systemlayers

02-10-11, 07:35 AM

Looks like they OEM CertainTeed product - they have a line of products actually called "OEM 300" and the like - if it's that, you're good to go. Unfortunately the link to the non-FSK leads to the FSK specs, so can't tell for sure.

Hm yeah they also carry mineral wool products including Roxul AFB.
I know it seems like most in this thread go with fiberglass but rigid mineral wool is just as good correct?
Is it more expensive generally?
Total noobie thanks for the help :)

Brad Horstkotte

02-10-11, 08:35 AM

I used 3" Roxul AFB for my SuperChunks, it was much cheaper locally for me, and has very similar specs to OC 703. Quite easy to work with too, using an electric carving knife.

DIYHomeTheater

02-10-11, 08:44 AM

There are a fair number of not so expensive speakers which exhibit excellent sound quality ... Atlantic Technology, Triad are among them.

I called Atlantic Technology and asked for their off-axis test measurements for their flagship fronts. They claimed that they are 'proprietary'. Dennis, I thought that you had once said that any company that does not share these results is the one to avoid (or something similar?).

Dennis Erskine

02-10-11, 08:53 AM

Yup...I said that and I'm sticking to that story. On the other hand, I know what it is for their THX stuff. The rest, well ...

myfipie

02-10-11, 09:09 AM

Hm yeah they also carry mineral wool products including Roxul AFB.
I know it seems like most in this thread go with fiberglass but rigid mineral wool is just as good correct?
Is it more expensive generally?
Total noobie thanks for the help :)

Mineral wool should be less expensive (density to density comparison). Mineral wool will work fine but keep in mind that you will need to build a frame for the panels as mineral wool is not as rigid as rigid fiberglass. If you are not a master carpenter :D then I would stick with the rigid fiberglass. We work with both here so I have first and experience with both.

DIYHomeTheater

02-10-11, 09:26 AM

Yup...I said that and I'm sticking to that story. On the other hand, I know what it is for their THX stuff. The rest, well ...
I am sorry, but I didn't quite understand your response. Are you suggesting that 'Yes, companies who don't reveal their off-axis test data are to be avoided, BUT you still recommend AT because you are very pleased with their THX performance?' Thank you.

Johnnydc

02-10-11, 12:50 PM

In case it wasn't clear: these curtains will have no real acoustic benefit. If you place something substantial behind them like thick fiberglass panels of the kind discussed in this thread you'll be on to something. This isn't meant to be rude but just clear.

No problem, and I like the feedback. My main goal is not to deaden the sound heard from other parts of the house, but to keep the sound quality in the room at it's best and on a very low budget (wife isn't 100% on board with this yet). I thought the curtains would quiet the inside of the room and stop reflection from the side and rear walls.

erkq

02-10-11, 01:29 PM

No problem, and I like the feedback. My main goal is not to deaden the sound heard from other parts of the house, but to keep the sound quality in the room at it's best and on a very low budget (wife isn't 100% on board with this yet). I thought the curtains would quiet the inside of the room and stop reflection from the side and rear walls.

This isn't just the wrong tool from the sound isolation standpoint, it's the wrong tool from the room treatment standpoint too.

Ethan Winer

02-10-11, 01:38 PM

I must compliment you on the wealth of useful information that you have put together and placed on your website.

Thanks very much Jeff.

thanks to Ethan - I've been reading a lot on your sight and even checked out a few of your youtube videos. While there is a lot of science behind it .. I get the impression that you can just keep adding with 'minimal' ill effects? (strictly speaking m-ch/HT)??

Not sure what you're asking. Adding what with minimal effects? Bass traps?

--Ethan

pauleyc

02-10-11, 03:23 PM

Not sure what you're asking. Adding what with minimal effects? Bass traps?
--Ethan

Sorry my question wasn't clear ... I got from one of you videos that most rooms will benefit from absorption and you seem to indicate that you couldn't, under normal circumstances, 'over' do it. My question is more of when would adding more bass traps have a negative effect on a home theater environmnet (multichannel, not 2-ch). I have the ability to "super chunk" all four corners of my HT and wanted to understand if it can be over-done.

Brad Horstkotte

02-10-11, 03:42 PM

Chunk em and don't look back.

nathan_h

02-11-11, 01:45 AM

No problem, and I like the feedback. My main goal is not to deaden the sound heard from other parts of the house, but to keep the sound quality in the room at it's best and on a very low budget (wife isn't 100% on board with this yet). I thought the curtains would quiet the inside of the room and stop reflection from the side and rear walls.

Sorry this is what we are saying: curtains won't do that for you. You need something porous but more importantly with considerably more mass.

How "handy" are you? What's your budget? Folks may have suggestions to get you started on effective solutions based on that data.

nathan_h

02-11-11, 01:47 AM

Sorry my question wasn't clear ... I got from one of you videos that most rooms will benefit from absorption and you seem to indicate that you couldn't, under normal circumstances, 'over' do it. My question is more of when would adding more bass traps have a negative effect on a home theater environmnet (multichannel, not 2-ch). I have the ability to "super chunk" all four corners of my HT and wanted to understand if it can be over-done.

It is possible to over absorb but what you are proposing is going to be far more beneficial than problematic. You are covering very little wall space but you are making it super thick and putting it where it will have maximum bass impact.

I agree with the advice to do it and don't look back.

myfipie

02-11-11, 07:15 AM

Sorry my question wasn't clear ... I got from one of you videos that most rooms will benefit from absorption and you seem to indicate that you couldn't, under normal circumstances, 'over' do it. My question is more of when would adding more bass traps have a negative effect on a home theater environmnet (multichannel, not 2-ch). I have the ability to "super chunk" all four corners of my HT and wanted to understand if it can be over-done.

In theory you could over absorb low end but in the real world it is not going to happen. By the time you put traps in every corner (wall to wall, ceiling to wall and floor to wall corners) I still believe the low end would just continue to become better. There is though a point of diminishing returns but that is really dependent on our room. All and all in most smaller rooms, if you cover all wall to wall corners you are not hitting the thresh hold of diminishing returns.

scoobygt68

02-11-11, 09:16 AM

I've recently installed some bass traps and acoustic panels and I had a question about speaker placement near acoustic panels/bass traps. My fronts/center have rear ports and are fairly close to the acoustic panels and bass traps. In one corner i have my right speaker only about 10 inches away from the bass traps straddling the corner floor to ceiling. My center is also about 10 inches away from the acoustic panel that is up against the wall between the floor and my projector screen. My question is do i need to move the speakers further away from the treatments since they have rear firing ports?

nathan_h

02-11-11, 10:59 AM

NicksHitachi

02-11-11, 02:49 PM

Ok so I built some bass traps a while ago looking at some of the designs found on here. I think I may have made a mistake, I removed the vapor barriers when I sandwiched them together to get 4".

Ive been reading about poly barriers and backings which I did not know anything about when I made the last design. I plan on redoing them for my current theater build.

I was wondering if I should add some layer of poly or backing back?
Has anyone tried using rigid fiberglass as a backing like VCT tile?
Here are some pics of the old build how could I improve these?

http://i174.photobucket.com/albums/w100/nottaway/Home%20theater%20projects/100_0049.jpg

http://i174.photobucket.com/albums/w100/nottaway/Home%20theater%20projects/100_0050.jpg

http://i174.photobucket.com/albums/w100/nottaway/Home%20theater%20projects/100_0051.jpg

http://i174.photobucket.com/albums/w100/nottaway/Home%20theater%20projects/100_0052.jpg

pepar

02-11-11, 02:54 PM

Stretch the covering tighter?

NicksHitachi

02-11-11, 02:57 PM

Stretch the covering tighter?

Haha, OK better performance wise. They're going behind a screen wall anyways.:rolleyes:

pepar

02-11-11, 03:02 PM

Had you ever checked the acoustical properties at http://www.bobgolds.com/AbsorptionCoefficients.htm?

Brad Horstkotte

02-11-11, 03:07 PM

Not sure what the batting is for - to support the fiberglass (create airspace behind) and keep fibers in (front)?

As for poly - for what? Kind of lost there. You can put kraft paper (or the faced side of faced fiberglass) on the outside face to reflect highs; but unless your room is already overobsorbed, it might not matter.

Johnnydc

02-12-11, 08:53 PM

Sorry this is what we are saying: curtains won't do that for you. You need something porous but more importantly with considerably more mass.

How "handy" are you? What's your budget? Folks may have suggestions to get you started on effective solutions based on that data.

OK, I'm fairly handy but time is a major problem for me right now. Here's a good question:
***IF YOU HAD A NEW THEATER ROOM AND YOU HAD $200-250, HOW WOULD YOU TREAT THE WALLS TO ASSURE YOU GET THE BEST SOUND QUALITY IN THE ROOM?
(6- satellite speakers, 2- 8' powered subs, center channel, 7.2 receiver)

Brad Horstkotte

02-12-11, 09:22 PM

I'd either sink it into bass traps - or do nothing until I've listened to it for a while and determined what audio issues need addressing.

nathan_h

02-12-11, 09:25 PM

I'm not sure if you can get enough mass for that budget to do much good bass trapping.

So I would attack slap echo, comb filtering, and imaging.

If you have time to build yourself, you could probably put together good bass trapping AND build what I am suggesting you buy, but if you have no time and $200 ish to spend, I'd get:

http://www.gikacoustics.com/gik_242.html

which come three in a box, and with shipping should be within your budget.

(There are a few other sources for similar panels at a similar price, but I wanted to just cut to the chase with one of the vendors we know is reliable.)

I would place one at the left reflection point and one at the right reflection point (do a search in this thread for "mirror method"). And I would place one on the wall behind my head.

----

If you post a picture or three of your room, and note the dimensions of your room, there may be some more ideas that people have.

----

If you are near a major metropolitan area, watch craigs list and ebay and audiogon for people selling their acoustic treatments. You'll get stuff for half price, easy, if you are patient.

nathan_h

02-12-11, 09:30 PM

Dennis Erskine

02-13-11, 05:22 AM

I am sorry, but I didn't quite understand your response. Are you suggesting that 'Yes, companies who don't reveal their off-axis test data are to be avoided, BUT you still recommend AT because you are very pleased with their THX performance?' Thank you.
No. Not exactly. There are two issues here. The first is that a company who will not reveal their performance (or cannot because they don't know) is possibly not wanting you to know the performance of the product they are trying to sell. The second is, with AT, and with respect to their THX certified products, they have taken the time, energy and money to have an independent third party test their products, examine the product's engineering, and to make the modifications necessary in order to certify the products meet the established criteria to pass certification and are suitable for their intended purpose. In the case of speakers, there is nothing proprietary with respect to the speaker's response, polar radiation, plots, etc. What could be considered proprietary is how they achieved that performance.

NicksHitachi

02-13-11, 08:48 AM

Those should be fine as is.

Thanks, I'll probably pretty them up..... Anybody thought of incorporating high density fiberglass(VCt) in the trap for mass?

pepar

02-13-11, 09:59 AM

Jay5298

02-14-11, 09:16 AM

I finally started building my bass traps. I bought some 6lb density board from Knauf that I thought was the unfaced insulation, but when I opened the boxes they were the FSK faced board. My thought was to build the front traps without the facing as I don't think I should need that up front. The back traps however I think would benefit from the facing based on my surrounds. I have Paradigm ADP-590's in the back as well as the sides. These speakers fire more laterally than diagonally based on their design. My traps will be in their line of fire so to speak so I think using the FSK on these rear traps would be a good idea. What do you guys think?

Haps

02-14-11, 06:14 PM

kevinzoe

02-14-11, 07:13 PM

Sheesh this thread is a monster. I keep coming back to it and working thru more of it and re-reading and "peeling layers of understanding" off that knowledge onion.

13.5x21 room with 10.5 ceilings. From what I've gleaned so far I would benefit from:

1) Corner bass traps. 2 Front corners floor to ceiling. 2 rear corners floor to ceiling. More would be better. Looking for best bang for the DIY buck. If I can find it in Ontario then OC703 4 inch across the corners. Or cut into triangles and stacked in corner frame. Cover with black speaker fabric.

I'm concerned about sourcing the material. Are there other more common alternatives? Is hitting the 4 corners floor to ceiling a good start?

2) Wall treatments. Right now 1st reflection points. 2'x4' covered panel attached to wall. 2 4" thick panels behind back row. Also a(size unknown) panel on ceiling at "mirror test" reflection point.

Am I moving in the right direction? Is this a good start or am I missing the mark?

Hi Haps,
By Ontario, I'm assuming you mean the CDN province. If so, then call General Insulators in Mississauga at (866) 459-1323. They delivered my Owins Corning 701 insulation for my bass traps. OC701 is less costly than 703 and does the same job. It's only at the frequency extremes when there's a performance difference of any real tangible amount.

I would recommend you read Dr Floyd Toole's book and also the textbook by F Alton Everest to educate yourself on what goes where. I would recommend thicker than 4" if you can do it. 4" is the bare minimum and remember to put an ample air space behind the traps to lower the frequency that it'll absorb to.

Jay5298

02-14-11, 07:37 PM

Anybody?

nathan_h

02-14-11, 10:21 PM

Anybody?

Either way is workable and neither would be bad.

myfipie

02-15-11, 08:27 AM

1) Corner bass traps. 2 Front corners floor to ceiling. 2 rear corners floor to ceiling. More would be better. Looking for best bang for the DIY buck. If I can find it in Ontario then OC703 4 inch across the corners. Or cut into triangles and stacked in corner frame. Cover with black speaker fabric.

I would go with cutting into triangles as this will reach lower frequencies.

erkq

02-15-11, 10:26 AM

What about rectangular bass traps? Is there anything inherently superior about the triangular shape except it fits in a corner, that thing most rooms have 4 of? What if I have a 1' deep 6' wide alcove at one side of the back of my theater? Would filling it completely, floor to ceiling, with OC 703 (or 701) be better than a triangular corner trap?

mtbdudex

02-15-11, 10:48 AM

Ethan/Glenn/Dennis/Terry/et all experts;

My DIY corner bass traps are in process of being finished.

Simply, what is "appropriate" material to block mid-hi freq on them?
In reality, any material you can't breath thru will work fine for mid-hi freq blockage, is that a correct statement?
I recall some people may have used plastic, so whatever the DIY person has around is ok?

In the below I had this brown utility paper handy so used that, I'll be putting the fabric over them either tonight or Wed night, depends on how much time I have after putting the kids to bed...

thx for your advice. Love this thread.

un-blocked
https://lh6.googleusercontent.com/_FqTNmgNQHz8/TVo1P_pk4II/AAAAAAAAMNo/GbaHQwT_Iys/s400/_MG_4843.jpg
vs blocked.
https://lh5.googleusercontent.com/_FqTNmgNQHz8/TVo1QGGOy_I/AAAAAAAAMNs/8E439lnZPhQ/s400/_MG_4878.jpg

Learning Q:
Is that because the mid-hi freq size is larger than the blocking item, in this case a 48" high x 34" wide "wall" ?
So it will "pass" waves greater than 34" (below 400hz-approx) on the width axis and 48" (below 300hz-approx) on the height axis?
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVqrrRPHDRI/AAAAAAAAMOM/ipJ5rDmmjsE/s400/WavelengthVsFreq_feet_air.JPG

Ethan Winer

02-15-11, 11:38 AM

My traps will be in their line of fire so to speak so I think using the FSK on these rear traps would be a good idea. What do you guys think?

Corner bass traps work best with a facing. Just because sound reaches a trap doesn't mean it's at a reflection point. Reflection points are the only places not to use traps with a facing.

--Ethan

Ethan Winer

02-15-11, 11:39 AM

what is "appropriate" material to block mid-hi freq on them?

Thin cardboard, thick paper, plastic wrap - it's all good.

--Ethan

Jay5298

02-15-11, 01:39 PM

Corner bass traps work best with a facing. Just because sound reaches a trap doesn't mean it's at a reflection point. Reflection points are the only places not to use traps with a facing.

--Ethan

Ethan,
I peeled the facing off the insulation I'm using in the front, so I could put it back on with spray adhesive I'm assuming? Does it make sense to use the facing on the front traps though? Don't I want to absorb some of the mids and highs from my front speakers? Also, the facing is shiny silver, I'm afraid when I wrap them with GOM it will show, is it okay to spray paint the surface black?

Jay5298

02-15-11, 06:42 PM

Maybe I should stop trying to over think all of this and just build the damn bass traps and listen to how it sounds with them in place. What do you guys think about that?:eek:

pepar

02-15-11, 06:43 PM

You can never be too rich, too thin or have too many corner bass traps.

erkq

02-15-11, 06:50 PM

pepar

02-15-11, 06:53 PM

What about RECTANGULAR bass traps??? :) Someone's got to know...
I seem to remember reading that the material "beyond" the triangle adds very little performance and would be better deployed as more lineal feet of "single" triangle traps.

NicksHitachi

02-15-11, 07:38 PM

How big to make the triangles?

erkq

02-15-11, 07:51 PM

I seem to remember reading that the material "beyond" the triangle adds very little performance and would be better deployed as more lineal feet of "single" triangle traps.

Thanks! Good to know.

mtbdudex

02-15-11, 10:08 PM

Maybe I should stop trying to over think all of this and just build the damn bass traps and listen to how it sounds with them in place. What do you guys think about that?:eek:

+1 agreed, just buy 2 boxes of 2" 2' x 4' OC705 (6 sheets/box) if you are going 8 feet high with 17x17x24 triangles, or 4 boxes if going for the "biggies" 24 x 24 x 34" triangles.
Measure room (freq wise, freq plot & RT60 baseline), and then...for the OC705 Measure em (dim wise), whack em, stack em, cover em (if you want to block hi freq do so before the cover) then re-measure room with treatments in.

Ready - set - go!

smokarz

02-15-11, 11:47 PM

i don't have space for the triangle chunks on my front walls....

what about building 4" thick panel of OC703 and place them in the corner, does that work for bass trapping?

pepar

02-16-11, 01:49 AM

How about at the wall/ceiling "corner?"

pepar

02-16-11, 01:55 AM

i don't have space for the triangle chunks on my front walls....

what about building 4" thick panel of OC703 and place them in the corner, does that work for bass trapping?

A panel "straddling" the corner works.

Jay5298

02-16-11, 08:41 AM

Okay, unfortunately I still have one more question. Is it okay to spray paint the FRK foil on the insulation so it doesn't show thru the GOM fabric?

pepar

02-16-11, 08:44 AM

Okay, unfortuately I still have one more question. Is it okay to spray paint the FRK foil on the insulation so it doesn't show thru the GOM fabric?
I can't see how that would change the acoustical properties of the foil, but what paint is going to adhere to it and not crack over time? That foil will be flexing from the energy that strikes it.

Just throwing that out there ....

Jeff

Jay5298

02-16-11, 08:58 AM

I can't see how that would change the acoustical properties of the foil, but what paint is going to adhere to it and not crack over time? That foil will be flexing from the energy that strikes it.

Just throwing that out there ....

Jeff

Good point. I guess I will see if the GOM shows thru first and go from there.
Thanks

smokarz

02-16-11, 09:01 AM

How about at the wall/ceiling "corner?"

A panel "straddling" the corner works.

thanks, i was thinking of 2 24"x48" OC703 4" thick panels at the front corners (bottom)

and 2 24"x24" 2" OC703 on the top corners.

NicksHitachi

02-16-11, 09:01 AM

Which would be the better performer?

4" OC703 2'x4' panel straddling corner

or

12"X12"X24" superchunks approx 64" tall(coverage from two 2"OC703 panels cut up into super chunks)

Jay5298

02-16-11, 10:11 AM

Well, the foil shows thru. I sprayed a section and it doesn't adhere very well. What about flipping the foil over so the plain side is up? Any problem doing this? I may just scratch the whole FRK facing and go without if it's to much of a pain.

nathan_h

02-16-11, 10:42 AM

Flipping the foil is fine as long as it still is on the outside (not against the wall).

pepar

02-16-11, 11:17 AM

Which would be the better performer?

4" OC703 2'x4' panel straddling corner

or

12"X12"X24" superchunks approx 64" tall(coverage from two 2"OC703 panels cut up into super chunks)
There's some test data on the StudioTips Forum, but it seems to be down right now. (You probably mean 17x17x24 as that is the result of cutting a 2' x 4' panel into eight triangles.) I seem to remember the chunk outperforming the panel . ... but that might have been the 34" face triangle resulting from cutting the 2' x 4' panel into FOUR triangles. Keep checking back at http://www.forum.studiotips.com.

Jeff

Jay5298

02-16-11, 11:40 AM

Flipping the foil is fine as long as it still is on the outside (not against the wall).

Cool, Thanks.

NicksHitachi

02-16-11, 12:30 PM

There's some test data on the StudioTips Forum, but it seems to be down right now. (You probably mean 17x17x24 as that is the result of cutting a 2' x 4' panel into eight triangles.) I seem to remember the chunk outperforming the panel . ... but that might have been the 34" face triangle resulting from cutting the 2' x 4' panel into FOUR triangles. Keep checking back at http://www.forum.studiotips.com.

Jeff

OK, I gather then that cutting the 2x4 panel into 16 1x1x2 triangles would be inferior..... Right? Cutting in this fashion would yield approx the same vertical corner coverage as two 2" 2x4 panels straddling the corner, which is why I'm comparing the smaller triangles and smaller super chunks.....

smokarz

02-16-11, 12:52 PM

pepar

02-16-11, 01:12 PM

OK, I gather then that cutting the 2x4 panel into 16 1x1x2 triangles would be inferior..... Right?
Cutting a 24" x 48" sheet into sixteen triangles would yield 12" x 12" x 17" triangles.

I didn't even stay at a Holiday Inn Express last night, but my *guess* is that the straddling 2' x 4' panel would be more effective than the 16-triangle size from the same sheet. You really need to do the 8-triangle cut to get deeper absorption.

Unless you don't have the space, you need to bite the bullet and use the 8-cut size. As a DIY project, these are still way more economical than commercial products.

If I would have had the space, I would have used the 4-cut size.

Jeff

NicksHitachi

02-16-11, 01:49 PM

Cutting a 24" x 48" sheet into sixteen triangles would yield 12" x 12" x 17" triangles.

I didn't even stay at a Holiday Inn Express last night, but my *guess* is that the straddling 2' x 4' panel would be more effective than the 16-triangle size from the same sheet. You really need to do the 8-triangle cut to get deeper absorption.

Unless you don't have the space, you need to bite the bullet and use the 8-cut size. As a DIY project, these are still way more economical than commercial products.

If I would have had the space, I would have used the 4-cut size.

Jeff

DUH! yeah I was not thinking A2+B2=C2. I'm gonna dig a bit more to see if there has been some direct comparisons made. Like you however I think the panel would probably perform better. I think i read somewhere that the incremental increase in performance went down after about 4" thickness and therefore the loss in coverage(width) in the corner would not be compensated for with increasing the depth.

Thanks for the response!

smokarz

02-16-11, 03:32 PM

Brad Horstkotte

02-16-11, 04:16 PM

Also, if budget is more of a constraint than space, you may be able to locate alternatives to OC 703 that are available locally cheaper, and work just as well. In my case, I used Roxul AFB, and the cost was about half what it would have cost for OC 703.

Brad Horstkotte

02-16-11, 04:16 PM

Flipping the foil is fine as long as it still is on the outside (not against the wall).

Or leave the FRK in place, and add a thin layer of something over it. I was thinking black plastic, but not sure about the flammability, maybe there's something better and cheap. Black polyethylene sheeting?

I'm in the same boat BTW, I have FRK side of rigid insulation facing down in my soffit, and will have to address the same issue as you when I get to covering it with fabric.

Brad Horstkotte

02-16-11, 05:47 PM

ok guys,

i finally put up twelve 24"x48" panels in a 13'x24' room. is this too much?

i got 4 on the right wall, 5 on the left wall, and 3 in the back wall.....

nothing on front wall or ceiling yet.

Only way to tell for sure would be to measure.

I ran Bob Gold's room mode calculator, thinking that a ballpark number of required Sabins (unit of absorption) could help you - but really it doesn't, since you don't know how many Sabins you're starting with (carpet, furniture, humans all absorb). Well anyway, assuming 8' ceiling height, it said 549 Sabins required to achieve RT60. For reference, 12 2'x4' panels is 96 square feet, if they were 100% absorptive, that would be 96 Sabins. So unless you've got a ton of squishy furniture and people in the room, I think you're probably fine. You've covered 96 square feet of a possible 592 square feet of wall space, only about 16%. Many HTs cover ~50%.

Someone check my math... ;)

KERMIE

02-16-11, 07:50 PM

Ethan,

I have a question regarding your test tone files I downloaded.

I set my crossovers on my AVR to 80Hz for my L/C/R speakers, Sides and Rears for 7.1.

For some strange reason the test tones below that crossover plays on my Center Channel loud down to 20 Hz with little regards to my Crossover. All other speakers start dropping off nicely and disappear as I go below 60-65 hz. I am concerned that for movies that my crossover is not working and LF is going to ruin my center channel.

Is anyone experiencing this or doest the "Center Channel" just react differently?

Thanks in advance for any assistance.

Brad Horstkotte

02-16-11, 11:48 PM

Maybe your center is set to "large", and the rest are set to small?

KERMIE

02-17-11, 07:35 AM

Brad Horstkotte

02-17-11, 08:35 AM

I guess with that receiver, it would be under Speaker Configuration -> Full Band - just in case you didn't check there

Jay5298

02-17-11, 10:18 AM

Or leave the FRK in place, and add a thin layer of something over it. I was thinking black plastic, but not sure about the flammability, maybe there's something better and cheap. Black polyethylene sheeting?

I'm in the same boat BTW, I have FRK side of rigid insulation facing down in my soffit, and will have to address the same issue as you when I get to covering it with fabric.

Brad,
I peeled the FRK foil off the insulation and then flipped it over and re-attached it with spray adhesive. Worked great, and now it doesn't show thru the GOM.

Jay5298

02-17-11, 10:28 AM

Okay, once again I'm over thinking things as I always do. I built one corner bass trap. I used 2 pieces of 705 stacked to make a 4" thick panel and then cut the ends at a 45 degree angle so they would fit flush in the corner. I then built a frame from floor to soffit filled it with the insulation and hung it up. Looks great but now I'm wondering if there is a performance difference between this design and a typical rectangle trap straddling the corner. I attached a drawing of what I'm talking about. Technically when you look at the drawing the 24" in the rectangle trap is from corner to corner. The trapezoid design the 24" is from corner to corner also, but the back of the panel surface area is less, I think mine was about 15". So the air gap from the back of the rectangle trap is deeper than the trapezoid design. The trapezoid design is sort of like the superchunk style(although not as deep)and the rectangle style. I think it should perform similar to the rectangle design, I just have my doubts now. Why can't I just do something without second guessing myself all the time

Brad Horstkotte

02-17-11, 10:49 AM

Shouldn't be significantly different - you could get a little more by stuffing the cavity behind with fluffy insulation (heard that one from bpape way back somewhere in this thread).

Edit: my mistake, it wasn't actually bpape, it was TamaraBaap - but it sounded logical to me: http://www.avsforum.com/avs-vb/showthread.php?p=8119356#post8119356

erkq

02-17-11, 12:01 PM

Its an Integra 70.1 and it doesn't have that option. There is only crossover points for each. I double checked and it is crossed over at 80 like all the other 6 speakers. When I turn off my subs and run 20-60 Hz test tones the sound comes out of center and not any other speaker. Very strange to me

As a work-around to protect your speaker for the short term, you could put a big capacitor in series and an inductor in parallel. Values depend on your speaker's impedance. There are lots of on-line calculators for this. That would get you a 12dB/octave roll-off. It would also introduce insertion loss and phase shift like any other simple filter, but at least it would protect against over-excursion while you figure out how to fix it for real.

mtbdudex

02-17-11, 12:39 PM

Okay, once again I'm over thinking things as I always do.

Jay - I do it also many times, that's good - up to a point.

I'm sure you've seen Ethan W page?
http://www.ethanwiner.com/acoustics.html#air%20gap
The % diff in gap to wall is so small either way, whatever works....
Picts from that page:
http://www.ethanwiner.com/sinewave.gif
http://www.ethanwiner.com/airgap.gif

So, what's the difference in gap to wall and from this chart how much freq did you "miss" covering?
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVqrrRPHDRI/AAAAAAAAMOM/ipJ5rDmmjsE/WavelengthVsFreq_feet_air.JPG

did you take before/after measurements?

Jay5298

02-17-11, 12:49 PM

Jay - I do it also many times, that's good - up to a point.

I'm sure you've seen Ethan W page?
http://www.ethanwiner.com/acoustics.html#air%20gap
The % diff in gap to wall is so small either way, whatever works....
Picts from that page:
http://www.ethanwiner.com/sinewave.gif
http://www.ethanwiner.com/airgap.gif

So, what's the difference in gap to wall and from this chart how much freq did you "miss" covering?
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVqrrRPHDRI/AAAAAAAAMOM/ipJ5rDmmjsE/WavelengthVsFreq_feet_air.JPG

did you take before/after measurements?

I did not take any measurements, I don't have a laptop computer. I guess I will just let my ears be the judge.

mtbdudex

02-17-11, 01:27 PM

I did not take any measurements, I don't have a laptop computer. I guess I will just let my ears be the judge.

Honestly I could immediately notice the side wall panels and their 1st reflection effect when I put those up.
The bass traps are noticable vs w/o, but also more subtle, guess it all depends on your room issue(s) and qty of bass traps/etc, size, etc.
(plus I have the riser bass trap already and the ceiling cloud which is 12" suspended and helping bass somewhat, so I've had incremental treatments added prior to my corner traps, therefore mine is not a true "no bass trap" vs "bass trap" comparision)

Ethan Winer

02-17-11, 01:34 PM

For some strange reason the test tones below that crossover plays on my Center Channel loud down to 20 Hz with little regards to my Crossover.

Others already gave you the right answer - it's most likely a receiver setting.

--Ethan

dallaslistener

02-20-11, 06:09 PM

OK Guys,

I've set up all the recommended equipment and I'm using REW and getting an error message which I don't understand - "impulse peak is not where it should be, the measurement may have been corrupted". What do I do now? Also, the spl graph dips way down below the -60db limit at 2khz and up. Any body know what's wrong?

mtbdudex

02-21-11, 01:27 PM

Ethan/Terry/Dennis;

Have you guys used this product , ECOUSTIMAC Eco Friendly DIY Insulation (4 lbs/ft) 48"x24"x2" (http://www.acoustimac.com/index.php/diy-acoustic-materials/acoustic-insulation-material/ecoinsul422.html) , as alternative to OC705 for Bass traps?

It came up in my DIY panel build thread, http://www.avsforum.com/avs-vb/showthread.php?p=20037070#post20037070

I'm ready to buy 3 cases of the 2" 2' x 4' sheet, but want to know if you've used it prior and feedback if any.

I called their tech support and asked who their 3rd party test company is, he said http://riverbank.alionscience.com/

Seems like a legit product.

Copy and past from the DIY panel build thread:
Well looking at the data it sure seems to have much better low freq absorption characteristics....
http://www.acoustimac.com/index.php/diy-acoustic-materials/acoustic-insulation-material/ecoinsul422.html
Sound Absorption Coefficients (1/3 Octave Band Center Frequencies. HZ)

Hz
100 125 250 500 1000 2000 4000
2" Thickness 0.38 .39 .63 1.18 1.11 1.06 1.09

An even greener alternative to cotton insulation:

Cotton insulation works as well as its fiberglass counterparts, however this material can be prone to mold and is not as biodegradable and recyclable as cellulose which is made from recycled newspapers and cardboard products.

Better Performance than Fiberglass!

Oh yes, it’s true! This cellulose based insulation has even higher absorption coefficients than our standard insulation material, so not only is it more eco-friendly, it also outperforms its fiberglass and mineral wool counterparts hands down.

Freq 125 HZ 250 HZ 500 HZ 1000 HZ 2000 HZ 4000 HZ NRC
OC-703 (2") 0.17 0.86 1.14 1.07 1.02 0.98 1.00

Freq 125 HZ 250 HZ 500 HZ 1000 HZ 2000 HZ 4000 HZ NRC
OC-705 0.16 0.71 1.02 1.01 0.99 0.99 0.95

and when you compare the online price of 705 to this ....so you get your cake (better low freq absorption) and get to eat it too (lower cost/6 pcs).....I need more 705, now I'll re-think that and consider this.
Thx for posting!
(Bruce - let me know what they say about cutting it, if a serrated bread knife does it same as thru OC703/705 that would be nice.)

For their ECOUSTIMAC line, has there been 3rd party testing to confirm their claims?
I'd hate to be 1st on the block in avs community to use them.....I wonder if Ethan W/Dennis E/others have used their product.....

NicksHitachi

02-21-11, 01:45 PM

Dennis Erskine

02-21-11, 02:08 PM

Riverbank .... excellent lab.

This can be used for your bass trap (don't know how you intend to fabricate, where it will be placed). As a single layer, not much of a trap at all. This stuff could over absorb your high frequencies so you'd want to put 3 mil poly sheeting over the top of the first layer.

mtbdudex

02-21-11, 05:19 PM

If you average the 1st three absorption coefficients you'll see the fiberglass is still the better absorber overall. Sure it looks like it does more at 125 but compare their respective progressive absorbances........
I'll be using this as a Bass trap, so I'm more concerned with the 100hz, 125hz performance, even the 250hz perf is very close.

Riverbank .... excellent lab.

This can be used for your bass trap (don't know how you intend to fabricate, where it will be placed). As a single layer, not much of a trap at all. This stuff could over absorb your high frequencies so you'd want to put 3 mil poly sheeting over the top of the first layer.

Dennis;
I used OC705 24"x24"x34" superchunk stack 4' high floor-to-mid room on both rear corners of my HT, as currently done, they have kraft paper in front to block mid-hi freq, I plan on doing that for the upper ones also.
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVyLKSNRs_I/AAAAAAAAMSs/C8ADA7EQRiI/s640/_MG_4928.jpg

My next step in bass traps is this ECOUSTIMAC Eco Friendly Insulation will be in a 24"x24"x34" trapezoid shaped to a 17" x 17" x 24" superchunk stack ceiling down 2'.

With this products performance "superior" to OC705 in the low freq region, what advantage is there in using OC705 for a bass trap?
(except possible you can get OC705 locally for lower cost)
Pict show the image:

Plan B:
I'll call this the "Trapezoid wedgie bass trap", consists of smaller triangles 17" x 17" x 24" blending into the biggie 24" x 24" x 34" to get more low freq absorption.
The thd rod will be hidden inside the bass trap except will show on the bottom.
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TWDwBxFDClI/AAAAAAAAMVU/Ns8OkkQC__A/s800/_MG_4998_sketch.jpg

I'm 90% going with Plan B, I think it will look nicer up there and the hidden rods is better for the upper location.
Unless I move those sconces full 24" x 24" x 34" size won't fit.

btw, not all the Star Trek stuff will stay there, it will be de-cluttered, just showing my kids some of the stuff I had back in the day.
And YES, those Star Wars glasses are original Burger King glasses from the early 1980's, and those are genuine Apollo 13 glasses as well.

Jay5298

02-21-11, 10:20 PM

Well I've pretty much given up on the professional companies giving me any help. Sorry if I'm offending anyone. I submitted my pics and dimensions to 2 companies. One never responded with any information and the other is too busy with a high end client to help me. I called another local company, we played phone tag for a while and then nothing.:rolleyes: So I guess I'm on my own. I have almost completed my corner bass traps, just one more to build. I read some but not all of F. Alton Everest's Master Handbook of Acoustics. Some stuff I understood and some was just too technical. He talks about controling the early reflections form the floor and ceiling first and then deciding what to do with the lateral or wall reflections last. Explaining that the direct sound from the speakers arrives first then the floor then the ceiling and then the lateral or wall reflections next, as well as other reflections. I now understand why it was said that I would lose all the envelopment in the room if I covered the side walls with too much absorbtion. You still need to have some sense of spaciousness to the room. I forgot I have an old PC in my basement that I could use to take some measurements. So the question is, if I didn't want to hook up the computer, buy the mics and other stuff to take the measurements. Is the approach of treating the floor(I already have carpet) then the ceiling and then deciding what to do with the walls a good start?

Brad Horstkotte

02-21-11, 11:45 PM

pepar

02-22-11, 08:29 AM

Jay5298

02-22-11, 06:43 PM

FWIW, the absorber that made the biggest difference in my room was the one on the rear wall. Context .. 21' long, rear (and main) row of seats is ~7' from the rear wall making the first reflection about 14ms delayed from the direct sound.

I think my room would benefit from some rear absorption as well. When I sit in the middle 2 seats in the front row the bass sounds good. The seats directly behind sound boomy. The seats on either side don't sound as bad I think because of the columns which are made of wood and have insulation inside them. What type of insulation and how thick are your rear absobers?

Jay5298

02-22-11, 06:50 PM

I would think whether ceiling or side walls are the priority would depend on speaker location (which is closer) and dispersion (how much energy is fired horizontally and vertically. Personally, I'm not prioritizing the ceiling at least initially - mainly because it's a hassle.

My main speakers are only about 2 feet from the side walls so I probably hear those reflections first I would think. Your right I really don't want to put anything on my ceiling either if I don't have to. The question is how thick should the panels be on the side walls, so I still get some sense of spaciousness.

Dennis Erskine

02-22-11, 07:04 PM

pepar

02-22-11, 07:16 PM

I think my room would benefit from some rear absorption as well. When I sit in the middle 2 seats in the front row the bass sounds good. The seats directly behind sound boomy. The seats on either side don't sound as bad I think because of the columns which are made of wood and have insulation inside them. What type of insulation and how thick are your rear absobers?
2" of Owens Corning SelectSound Black. It is sized to only catch the first reflections from LCR. The rest of the rear wall is plaster.

Jay5298

02-22-11, 07:30 PM

You're not going to get "spaciousness" by putting absorption all over (particularily at the early reflection locations). Diffusers or Ab-fusors would be better.

For the speakers being less than 3.5' away from wall, you need some serious absorption near the speaker itself...the effect is called SBIR or Speaker Boundary Interference Response.

Dennis, I appreciate you giving me the name of the company out here in Colorado. He just apparently doesn't have time right now. You say serious absorption. Are you talking behind the speaker for the cabinet reflection on the front wall, or the side wall as well. My bass traps are pretty close to front speakers so they should absorb some of the reflections. I want to find the "happy medium" if possible to absorb the reflections but not make it too dead sounding. I have read briefly about SBIR, but not too much.

nathan_h

02-22-11, 07:38 PM

You're not going to get "spaciousness" by putting absorption all over (particularily at the early reflection locations). Diffusers or Ab-fusors would be better.

For the speakers being less than 3.5' away from wall, you need some serious absorption near the speaker itself...the effect is called SBIR or Speaker Boundary Interference Response.

Instead of absorption, one could use diffusion instead, right? (I think that's what the first half of your response means.)

Or are you saying that at that short distance diffusion isn't an option, but one really has to use absorption (and it should be thicker than one might usually select)?

Jay5298

02-22-11, 08:22 PM

Looking at the picture of the front of my room I think the only place I'm going to be able to absorb the reflections from SBIR are on the side walls. My bass traps almost come to the edge of the screen about 6 inches away I think. So they should help somewhat.

NicksHitachi

02-23-11, 06:59 AM

You're not going to get "spaciousness" by putting absorption all over (particularily at the early reflection locations). Diffusers or Ab-fusors would be better.

For the speakers being less than 3.5' away from wall, you need some serious absorption near the speaker itself...the effect is called SBIR or Speaker Boundary Interference Response.

Interesting, I always thought most rooms needed absorption at the early reflection points and that it was hard to over absorb unless you got crazy with it..... Hmmmmmm.

So what's wrong with these statements?

1. Front wall should be dead
2. Bass trap as many "corners" as is practical
3. Absorption at primary reflection points
4. Absorption behind all point sources

These were the take home messages I had gleaned, are they incorrect?

Kal Rubinson

02-23-11, 08:21 AM

It is easy to over-absorb the treble in the effort to use a sufficient amount of bass trapping since passive absorbtion is generally much more efficient as the frequency rises. Thus, if you are going to use a lot of bass trapping, consider using traps with reflective skins for some proportion of them.

NicksHitachi

02-23-11, 09:04 AM

Anyone know of a "rule of thumb" as to what the proportion of absorptive area to reflective area might get one in the ball park?

In other words it would be most helpful to get in the ballpark with some "general" proportion and fine tune each space from there. There must be a good starting ratio, although not golden or absolute for each room, which would I think be helpful in this thread.

FOH

02-23-11, 09:09 AM

The attached pic in post #7171 doesn't appear to be on the verge of overly damped. IMO, the room would likely benefit from sidewall reflection points being attenuated as much as possible. A nice, simple 4"-6" absorber spaced somewhat off the wall would certainly address potential destructive interference, if care was taken with placement.

If there is only one row of seating, it's likely that one or two panels per side would cover it.

Good luck

nathan_h

02-23-11, 09:37 AM

Interesting, I always thought most rooms needed absorption at the early reflection points and that it was hard to over absorb unless you got crazy with it..... Hmmmmmm.

So what's wrong with these statements?

1. Front wall should be dead
2. Bass trap as many "corners" as is practical
3. Absorption at primary reflection points
4. Absorption behind all point sources

These were the take home messages I had gleaned, are they incorrect?

1) Not the whole thing. Concentrate on reflection points.
2) Yes. Note: the caveat to cover with a thin layer of plastic sheeting (or paper or foil) is a good one to avoid over absorbing/damping the room.
3) Yes.
4) Probably not necessary, maybe overdoing it.

---

I do still wonder whether Dennis meant that diffusion should not be used on a wall close to a speaker, or whether I was misreading his post.

FOH

02-23-11, 10:15 AM

Interesting, I always thought most rooms needed absorption at the early reflection points

Absolutely

Beginning with diffractive elements at the speaker, continuing to the earliest reflection points at the adjacent surfaces.

So what's wrong with these statements?

1. Front wall should be dead
2. Bass trap as many "corners" as is practical
3. Absorption at primary reflection points
4. Absorption behind all point sources

In my experience, front wall treatment should depend on the room balance.

Bass trapping can be extensive, however, balance can be maintained with FRK, or similar covering if needed. Besides, traps are somewhat more effective when employed with some type of paper or plastic covering. Also, they're best when spaced at 1/4 wavelength from the surface.

In my experience, absorption at the early reflection points is very important. If these points are left untreated, imaging suffers, smearing of transients results, and undesirable destructive coloration occurs. It is true that lateral diffusion results in spaciousness, and this can be maintained, but not at the expense of the earliest first reflections. Additionally, ceilings can be treated aggressively with absorption. We're overwhelmingly more suited to delineate lateral energy, and ceiling reflectivity does little but be destructive between the speakers and listener.

Also, back wall treatments can certainly vary, depending on proximity to the listeners. The closer the wall, generally absorption treatments would be the route. Further away, a nice diffuse mix, with some serious bass trap elements would generally be effective.

Additionally, I'd stay away from "flavor of the month" trends that seem to be so prevalent these days. Watch the RT 60, and move slowly and deliberately with each treatment, be it diffusion, absorption, or whatever. Be mindful that LCR mains, and their respective directivity need to be given strong consideration, and any treatment after the earliest lateral reflections are damped, needs to be done in concert with the mains polar pattern, and the LP.

Just my 2 cents:)

Listen, measure, experiment, listen

NicksHitachi

02-23-11, 10:15 AM

1) Not the whole thing. Concentrate on reflection points.
2) Yes. Note: the caveat to cover with a thin layer of plastic sheeting (or paper or foil) is a good one to avoid over absorbing/damping the room.
3) Yes.
4) Probably not necessary, maybe overdoing it.

---

I do still wonder whether Dennis meant that diffusion should not be used on a wall close to a speaker, or whether I was misreading his post.

I took it to mean that for speakers that close to a boundary, diffusion would not be as effective....... I think for diffusion to work it has to be sufficiently distant to the point source..... Right?

FOH

02-23-11, 10:22 AM

Diffusion works regardless how close. However, in my experience, in this situation it's important to have absorption in that location.

nathan_h

02-23-11, 10:56 AM

I took it to mean that for speakers that close to a boundary, diffusion would not be as effective....... I think for diffusion to work it has to be sufficiently distant to the point source..... Right?

Diffusion works regardless how close. However, in my experience, in this situation it's important to have absorption in that location.

This is why I hope Dennis clarifies his comment(s), since two people can look at those comments, filter through their experience, and reach different conclusions. :p

mtbdudex

02-23-11, 11:38 AM

Listen, measure, experiment, listen

great "sound" advice. :rolleyes:

I'd modify slightly:

Initially (n=0):
Plan(n=n+1), listenBaseline (n=n+1), measureBaseline (n=n+1), experiment [add treatment(s)] (n=n+1), listenChange (n=n+1), measureChange (n=n+1)

Repeat cycle until:
-your $$'s run out
-your time limit is reached
-your brain gets tired
-the WAF is way past
-your non-HT friends stop calling you
-your kids forget your name
-n = 10, unless you have OCD and then the skies the limit

Heck, you might even reach acoustic nirviana and accept that fact and move onto other things......

FOH

02-23-11, 12:34 PM

This is why I hope Dennis clarifies his comment(s), since two people can look at those comments, filter through their experience, and reach different conclusions. :p

Generally, a proper diffuser's effectiveness is a function of the frequencies involved, not distance.

Now relative size, that metric must include distance. A 4'x4' diffuser immediately adjacent to someone playing violin, has a different impact than the same person playing violin and the diffuser 20' away. The relative size is different.

Ethan demonstrates a diffuser's properties adjacent to the diffuser. The diffuser is just as effective of a diffuser when it's 20' away, it's still a good diffuser, but the relative size due to proximity changes.

So a bigger room needs more diffuser panels than a small room, however they're no less effective a diffuser.

Ethan Winer

02-23-11, 12:47 PM

^^^ Good explanation.

--Ethan

Dennis Erskine

02-23-11, 05:03 PM

This is why I hope Dennis clarifies his comment(s), since two people can look at those comments, filter through their experience, and reach different conclusions.

What comments?

nathan_h

02-23-11, 05:17 PM

What comments?

You're not going to get "spaciousness" by putting absorption all over (particularily at the early reflection locations). Diffusers or Ab-fusors would be better.

For the speakers being less than 3.5' away from wall, you need some serious absorption near the speaker itself...the effect is called SBIR or Speaker Boundary Interference Response.

Instead of absorption, one could use diffusion instead, right? (I think that's what the first half of your response means.)

Or are you saying that at that short distance diffusion isn't an option, but one really has to use absorption (and it should be thicker than one might usually select)?

Milt99

02-23-11, 08:43 PM

Just an FYI,
All of the links to the studiotips website are pau.
The links to the forum within the website itself are dead as well.

rgoolio32

02-23-11, 09:04 PM

Hey Im building a HT in my basement and I am newbie at acoustical treatments I have read over the countless literature regarding treatments and understand the basics. But as always I think other opnions would be helpful.

(Ceilings are 7.6 feet)

Attached is a schematic of my HT

I was wondering where I should place panels (OC 703 with GOM Fabric) since it is a 7.1 I will have reflection on the front back and side walls. Also the back speakers are off center to the screen due to the weird shape of the room, and are centered on the back wall.

do you guys have any suggestion? full wall panels? half panels? where you think I should place them?

-RG

Dennis Erskine

02-24-11, 05:03 AM

Or are you saying that at that short distance diffusion isn't an option, but one really has to use absorption (and it should be thicker than one might usually select)?

No, for that specific issue, there are two problems. The first is the SBIR due to the speakers' proximity to the walls. That issue is best solved by absorption. The second issue is spaciousness which is better solved with diffusion or a combination of diffusion and absorption.

nathan_h

02-25-11, 01:01 AM

No, for that specific issue, there are two problems. The first is the SBIR due to the speakers' proximity to the walls. That issue is best solved by absorption. The second issue is spaciousness which is better solved with diffusion or a combination of diffusion and absorption.

Interesting. I thought SBIR happens in all rooms and that it's a matter of speaker placement (different distances from front and side walls, for example) that solves it.

I guess in the OP's situation (and many domestic rooms) the solution might be absorption behind the speaker on the screen wall and diffusion at the lateral first reflection points.

dunkman23

02-25-11, 02:27 AM

Brad Horstkotte

02-25-11, 09:14 AM

Nope - sound treatments address the character of the sound in the room, but do nothing to affect sound transmission between the room and outside the room.

nathan_h

02-25-11, 09:36 AM

hey guys. I was thinking about getting 2 24x48x4 panels from ATS acoustics. However what I am trying to do is dampening the noise of my system. My HT room is towards to front of my house, and people can hear the subwoofer from the driveway. If i put 2 panels in the back of the room, will it quiet down my room from the outside? as well as improve the sound? my room is 20 x 16 with 9 feet ceilings

As noted above, those panels won't help.

But there is a small possibility that an isolation riser like an Auralex Gramma may help a bit. It's not going to silence things but depending on why one can hear the sub outside, it may reduce that. It's the $50 experiment I would recommend.

Otherwise you're probably looking at a construction project of significant proportions (adding mass and or decoupling walls, floor, ceiling; replacing windows and doors; etc.).

dunkman23

02-25-11, 09:38 AM

^ ok thanks......those ideas help!

im going to put a post up and see if i get more ideas.

erkq

02-25-11, 10:08 AM

Otherwise you're probably looking at a construction project of significant proportions (adding mass and or decoupling walls, floor, ceiling; replacing windows and doors; etc.).

Coupled with a Green Glue sandwich. GG works well at lower frequencies. You can usually forgo added mass (except for the additional sheet of drywall) and decoupling.

nathan_h

02-25-11, 10:52 AM

Coupled with a Green Glue sandwich. GG works well at lower frequencies. You can usually forgo added mass (except for the additional sheet of drywall) and decoupling.

Very true, unless the sound path is that the sub is rattling the floor and that is what is transmitting the sound that the OP is hearing outside.

erkq

02-25-11, 10:59 AM

Very true, unless the sound path is that the sub is rattling the floor and that is what is transmitting the sound that the OP is hearing outside.

I've been curious about this. Can you put GG between two layers of subfloor? Or, does GG HAVE to go between something with a smoother surface like drywall?

nathan_h

02-25-11, 01:29 PM

Their web site has more info that I have digested, but I could see that possibly working, if one was ready to "rebuild" the floor.

Still I think that, short of a construction project, the thing to try is the $50 isolator and see if that helps enough.

02-25-11, 09:12 PM

I've been curious about this. Can you put GG between two layers of subfloor? Or, does GG HAVE to go between something with a smoother surface like drywall?

I have had really good luck with GG between two layers of a subfloor under my hardwood floors.

Read about my experience here:

http://www.avsforum.com/avs-vb/showthread.php?t=1136101

erkq

02-25-11, 09:25 PM

I have had really good luck with GG between two layers of a subfloor under my hardwood floors.

Read about my experience here:

http://www.avsforum.com/avs-vb/showthread.php?t=1136101

Thanks! GG acting as a bass trap makes total sense.

Tireman1

02-26-11, 05:45 PM

Ethan,

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems? The reflection shows through the GOM 701 at some angles.

Thanks,

nathan_h

02-26-11, 08:08 PM

No problem.

DIYHomeTheater

02-26-11, 10:30 PM

I'm not saying to make your room totally dead. But there's a good amount of leeway with this, and generally more absorption leads to cleaner sound that is more realistic and lifelike.

--Ethan

Ethan:

You have stated that you use 38 traps in your living room. How big is each trap? Does a trap that goes from floor to ceiling in a corner count as a single trap or a combination of several?

For 1st reflection absorption in a home theater, you seem to recommend 2" rigid fiberglass. Dennis Erskine seems to recommend 1" on the grounds that 2" may be too deadening. Have I understood your position accurately? What is appropriate thickness for side reflection? This is where the art takes over from the science
perhaps. Or perhaps, your personal preference for a music listening room vice Dennis' for home theaters dictate different treatments? For example, you are no fan of dipole surrounds, but I am sure that Dennis would not want a good home theater without them.

My planned theater is rectangular (28' deep, 18' wide at screen, 16' wide at rear row, and 8.5' high ceilings) with a carpet floor. I will follow your advice on traps and 1st reflection treatment. Should I consider ceiling reflection absorption as well if my floor will be carpeted? (For what it is worth, I plan to use Atlantic Technology speakers and the manufacturer tells me that their 8200 THX model is designed to not have much significant vertical dispersion (ie. towards the ceiling))

Also, given my 28' long room, I am planning on putting a sub towards the rear vice front to put it closer to the listening position for greater effect. (I'll bass trap all corners). Is rear positioning OK or is the front preferred? Putting it in the front would mean requiring more power to drive it I think. Closer to seating would require less. Edit: I came across this article: http://www.realtraps.com/art_sub-placement.htm Will read it in full

Thanks

DIYHomeTheater

02-27-11, 09:06 AM

Most rooms have 12 corners! :D

--Ethan

Ethan:

Do you mean 12 'edges'? I consider a corner to be where the walls/ceiling or walls/floor meet. So, 12 edges and 8 corners. Correct?

DIYHomeTheater

02-27-11, 10:33 AM

FSK is good for corner bass traps, but not for absorbers at reflection points. More here:

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

--Ethan
Very useful. How and why does FRK affect absorption? It is such a thin layer that I thought it would have no effect! But, it does.

DIYHomeTheater

02-27-11, 10:38 AM

However, you could apply a new facing to what is now the front surface of the entire trap, which is really all those 2-inch edges. That not only reduces absorption at higher frequencies, but increases bass absorption too.

--Ethan
Why does adding facing INCREASE bass absorption?

nathan_h

02-27-11, 10:39 AM

Ethan:

You have stated that you use 38 traps in your living room. How big is each trap? Does a trap that goes from floor to ceiling in a corner count as a single trap or a combination of several?

Check out the photos and videos of his room on his site. Each trap is 2' X 4' except some at corners that are 2'x2' iirc.

For 1st reflection absorption in a home theater, you seem to recommend 2" rigid fiberglass. Dennis Erskine seems to recommend 1" on the grounds that 2" may be too deadening. Have I understood your position accurately? What is appropriate thickness for side reflection? This is where the art takes over from the science
perhaps. Or perhaps, your personal preference for a music listening room vice Dennis' for home theaters dictate different treatments? For example, you are no fan of dipole surrounds, but I am sure that Dennis would not want a good home theater without them.

I would be very surprised if Dennis at any time said 2'' is less good than 1'' for side panel thickness. That would contradict every measurement I have seen.

One might reasonably argue that sometimes diffusion is better than absorption but essentially never that one wants thinner absorption.

My planned theater is rectangular (28' deep, 18' wide at screen, 16' wide at rear row, and 8.5' high ceilings) with a carpet floor. I will follow your advice on traps and 1st reflection treatment. Should I consider ceiling reflection absorption as well if my floor will be carpeted? (For what it is worth, I plan to use Atlantic Technology speakers and the manufacturer tells me that their 8200 THX model is designed to not have much significant vertical dispersion (ie. towards the ceiling))

Also, given my 28' long room, I am planning on putting a sub towards the rear vice front to put it closer to the listening position for greater effect. (I'll bass trap all corners). Is rear positioning OK or is the front preferred? Putting it in the front would mean requiring more power to drive it I think. Closer to seating would require less. Edit: I came across this article: http://www.realtraps.com/art_sub-placement.htm Will read it in full

Thanks

That's gonna be a nice space! You should consider starting a dedicated build thread with photos and details of the plan and progress. You'll get lots of good encouragement and maybe some good advice :)

about sub placement: Unless you are sitting next to a sub for tactile reasons, placement close or far is not the key. The key is how the sub interacts with the room modes. It is going to have to "fill" the room ("pressurize" it). Placement should be determined by where it sounds best when doing that. A quick search on the "crawling" method for sub placement will show you what I am talking about.

nathan_h

02-27-11, 10:41 AM

Ethan:

Do you mean 12 'edges'? I consider a corner to be where the walls/ceiling or walls/floor meet. So, 12 edges and 8 corners. Correct?

Yep.

Brad Horstkotte

02-27-11, 10:43 AM

FRK = Foil Reinforced Kraft paper (a.k.a. FSK = Foil Scrim Kraft paper, a.k.a. Scrim) - it has a thin layer of metallic foil (thin but not very porous).

DIYHomeTheater

02-27-11, 12:21 PM

I would be very surprised if Dennis at any time said 2'' is less good than 1'' for side panel thickness. That would contradict every measurement I have seen.

One might reasonably argue that sometimes diffusion is better than absorption but essentially never that one wants thinner absorption.

That's gonna be a nice space! You should consider starting a dedicated build thread with photos and details of the plan and progress. You'll get lots of good encouragement and maybe some good advice :)

Nathan:

Thanks. I recall reading that suggestion from Dennis Erskine on this thread. Check this post from him (http://www.avsforum.com/avs-vb/showthread.php?p=2177054&highlight=absorptive#post2177054)
It is post #6 on this thread.

My build thread is on my signature below. If you look at the voting button that I have established, the naysayers and cheering squad are about evenly split

nathan_h

02-27-11, 01:05 PM

Nathan:

Thanks. I recall reading that suggestion from Dennis Erskine on this thread. Check this post from him (http://www.avsforum.com/avs-vb/showthread.php?p=2177054&highlight=absorptive#post2177054)
It is post #6 on this thread.

My build thread is on my signature below. If you look at the voting button that I have established, the naysayers and cheering squad are about evenly split

I'm gonna say, in context, Dennis was talking about very large areas (full front wall and side wall all around up to ear level) being problematic (=leaving one open to absorbing too much). Stick with less coverage (eg, first reflection points) and thick panels at those points, for more reliable results.

Nice build thread! That's gonna be a great space.

The thread poll is pretty general, so it's not clear what the pro and con votes indicate....

Ethan Winer

02-27-11, 01:06 PM

You have stated that you use 38 traps in your living room. How big is each trap? Does a trap that goes from floor to ceiling in a corner count as a single trap or a combination of several?

Actually, I have 55 panels now. :eek:

The photos below are fairly recent, and Yes, I think I'm done!

For 1st reflection absorption in a home theater, you seem to recommend 2" rigid fiberglass.

The thicker the better, always. First reflections are mainly a mid/high frequency issue, but more bass trapping from using even thicker panels is always welcome. A panel thicker doesn't absorb more per se. Rather, it extends the same absorption to lower frequencies. So while even one inch thick is adequate, thicker is only better. And Yes, absorbing ceiling reflections is important too for most speaker types.

--Ethan

http://www.realtraps.com/cust_ht5.jpg

http://www.realtraps.com/megatraps.jpg

Ethan Winer

02-27-11, 01:07 PM

Do you mean 12 'edges'? I consider a corner to be where the walls/ceiling or walls/floor meet. So, 12 edges and 8 corners. Correct?

There are four corners where each wall meets another wall, four more where each wall meets the ceiling, and four more where each wall meets the floor. I'm talking about "normal" corners, not tri-corners where three boundaries meet. There are eight of those in a rectangle room.

--Ethan

Ethan Winer

02-27-11, 01:10 PM

Why does adding facing INCREASE bass absorption?

The membrane vibrates when sound waves strike it, and the fiberglass the membrane is bonded to damps that vibration.

--Ethan

DIYHomeTheater

02-27-11, 01:57 PM

The membrane vibrates when sound waves strike it, and the fiberglass the membrane is bonded to damps that vibration.

--Ethan

Thanks for your answers. Should the membrane be facing into the room or away from it? I would think the latter, right?

nathan_h

02-27-11, 02:21 PM

Into the room.

DIYHomeTheater

02-27-11, 03:03 PM

* Diffusion can be used on the front wall behind dipole speakers if the listener prefers more ambience, but wants to avoid the small-room boxy sound often caused by leaving those early reflections untreated.

--Ethan

I am confused. Dipoles are used as side and rear surrounds on the side and rear walls, respectively. Where is the 'front wall behind dipole speakers'?

vinyl

02-27-11, 03:18 PM

I am confused. Dipoles are used as side and rear surrounds on the side and rear walls, respectively. Where is the 'front wall behind dipole speakers'?
http://i159.photobucket.com/albums/t130/VinylSpinner/MaggieSide.jpg
Dipole speakers with mostly diffused front wall.

nathan_h

02-27-11, 04:49 PM

That's a sexy picture. What brand/model are those diffusers?

vinyl

02-27-11, 05:07 PM

What brand/model are those diffusers?

Auralex Acoustics: T’Fusors / Q’Fusors

DIYHomeTheater

02-27-11, 06:01 PM

Ethan:

How does one fashion a theater seat riser into a bass trap? Is it effective? Thanks for all the education that your website provides.

How would you modify your recommendations here for placing the LCR behind an acoustically transparent screen? Would you still toe-in the speakers?

mtbdudex

02-27-11, 09:04 PM

Ethan:

How does one fashion a theater seat riser into a bass trap? Is it effective?

Ethan W gave me advice on that for my riser, read here:
riser: Broadband bass trap (http://www.avsforum.com/avs-vb/showthread.php?t=1103345)
(Based upon Dennis E work/articles also.)

Is it effective? Yes - every bass trap helps.

DIYHomeTheater

02-27-11, 09:51 PM

Ethan:
Is an air gap recommended for the absorbers at the 1st reflection points, or can the absorber be mounted right against the wall? Thanks

Mtbdudex, Vinyl: Thanks for your responses.

Mtbdudex: What is the theory behind the design of risers as absorbers?

I found this article (http://www.audioholics.com/tweaks/do-it-yourself-diy-topics/multifunction-theater-seat-riser) on risers as bass traps: http://www.audioholics.com/tweaks/do-it-yourself-diy-topics/multifunction-theater-seat-riser. Elsewhere I found a critique of this design that essentially said that front facing holes are not quite as effective as 1/4" x 48" slits on the top of the decking.

nathan_h

02-27-11, 11:41 PM

Air gaps help increase the range of frequencies that are impacted by a trap -- typically a good thing when that means more bass is trapped -- hence the emphasis on "broad band" treatments...

DIYHomeTheater

02-28-11, 07:14 AM

Air gaps help increase the range of frequencies that are impacted by a trap -- typically a good thing when that means more bass is trapped -- hence the emphasis on "broad band" treatments...
Nathan:
So, you would recommend a gap for the 1st reflection points as well? If so, how much? What is the point of diminishing returns from a gap (if any)? Thanks

mtbdudex

02-28-11, 07:49 AM

Mtbdudex: What is the theory behind the design of risers as absorbers?

I found this article (http://www.audioholics.com/tweaks/do-it-yourself-diy-topics/multifunction-theater-seat-riser) on risers as bass traps: http://www.audioholics.com/tweaks/do-it-yourself-diy-topics/multifunction-theater-seat-riser. Elsewhere I found a critique of this design that essentially said that front facing holes are not quite as effective as 1/4" x 48" slits on the top of the decking.

http://www.avsforum.com/avs-vb/showthread.php?p=20007129#post20007129
Yes I read your link, (Good Read Actually) I didnt catch on though about you doing it wrong initially, now I get it. Are the vents on the top absolutely required then? I would assume they are. I am now thinking 2 x 10 around the edges and 2 x 6 in the middle.

As Ethan W taught me, yes, for an effective broadband bass trap you need all those, as much as possible.
At first, I cut just a few 4" x 14", then more, and finally all along the perimeter.

There are some more advanced analysis that people have done where they know (via analysis and/or room measurement confirmation) a room mode will be an issue, and have turned the riser into a Helmholtz absorber via cutting specific width/length slit(s) in the riser....
I've read about that and visited a persons who's HT had that done for him.
However, for laypeople like us going the safe route with a broadband bass trap is the easiest and surest method.

DIYHomeTheater

02-28-11, 09:00 AM

[QUOTE=Ethan Winer;20071042]Actually, I have 55 panels now. :eek:

The photos below are fairly recent, and Yes, I think I'm done!

The thicker the better, always. First reflections are mainly a mid/high frequency issue, but more bass trapping from using even thicker panels is always welcome. A panel thicker doesn't absorb more per se. Rather, it extends the same absorption to lower frequencies. So while even one inch thick is adequate, thicker is only better. And Yes, absorbing ceiling reflections is important too for most speaker types.

--Ethan

Ethan:
With all this treatment what does the frequency response at your listening position look like?

nathan_h

02-28-11, 12:08 PM

Nathan:
So, you would recommend a gap for the 1st reflection points as well? If so, how much? What is the point of diminishing returns from a gap (if any)? Thanks

Rule of thumb rather than science I can cite is the gap should not be thicker than the panel itself, and in practice is often 1 or 2 inches for a 2 to 4 inch thick panel.

That said, in ceiling installations people often leave an even bigger gap, and in corner straddling installations of course the gap is bigger, so there is no reason to shy away from using the space if you have it.

Ethan Winer

02-28-11, 12:31 PM

With all this treatment what does the frequency response at your listening position look like?

Given how terrible the LF response and ringing are in most rooms, I think mine is very good. This is an older plot, from before I added the last round of traps:

http://www.realtraps.com/ethan-ht.gif

Tireman1

02-28-11, 02:55 PM

Ethan,

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems? The reflection shows through the GOM 701 at some angles.

Thanks,

pepar

02-28-11, 03:30 PM

Ethan,

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems? The reflection shows through the GOM 701 at some angles.

Thanks,
I'd be concerned that the "dust" would come off and become airborne. I'm pretty sure that it will not adhere. And the foil will definitely flex.

Something to ponder. :)

Jeff

DIYHomeTheater

02-28-11, 05:49 PM

Given how terrible the LF response and ringing are in most rooms, I think mine is very good. This is an older plot, from before I added the last round of traps:

Ethan:
That looks great! Thx

DIYHomeTheater

02-28-11, 07:19 PM

Ethan
What are your thoughts on using risers as additional bass traps?
Thanks

mtbdudex

02-28-11, 07:20 PM

Ethan,

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems? The reflection shows through the GOM 701 at some angles.

Thanks,

Can you cover the foil with something else you might have on hand, like kraft paper?
That's what I did on my bass traps
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVyLJAv-ckI/AAAAAAAAMSc/u3bBdV1Csqk/s400/_MG_4919.jpg https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVyLHvlw8yI/AAAAAAAAMSE/D8WpiZV0wMs/s400/_MG_4905.jpg

myfipie

03-01-11, 07:33 AM

Can you cover the foil with something else you might have on hand, like kraft paper?
That's what I did on my bass traps
https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVyLJAv-ckI/AAAAAAAAMSc/u3bBdV1Csqk/s400/_MG_4919.jpg https://lh3.googleusercontent.com/_FqTNmgNQHz8/TVyLHvlw8yI/AAAAAAAAMSE/D8WpiZV0wMs/s400/_MG_4905.jpg

Oh yes craft paper will work just fine. Another thing you can use is something like 80# card stock (the paper used for most business cards).

Glenn

dunkman23

03-01-11, 09:31 AM

will having acoustic panels just in the rear wall of my HT help my sound?

Jay5298

03-01-11, 10:44 AM

Well, I finally finished my bass traps. I don't have any measuring equipment so I can't show you how they have helped on a graph. To my "naked" ear they seem to have helped even out the bass around the room and things seem a little tighter. I watched "The Town" last night and the deep bass scenes sounded great. I think my next project will be to add some panels on the side walls. Probably 2" thick and maybe only two at the most on each side. I don't have a very good camera, so the pictures are sort of dim.

NicksHitachi

03-01-11, 10:57 AM

nathan_h

03-01-11, 11:14 AM

will having acoustic panels just in the rear wall of my HT help my sound?

Yes. Obviously, a few more in key spots would also help more, but if that's all you can do, it is worth it, sure.

nathan_h

03-01-11, 11:16 AM

mtbdudex

03-01-11, 12:00 PM

Well, I finally finished my bass traps.

Looks good Jay!

Ethan Winer

03-01-11, 12:50 PM

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems?

Other than Jeff's concern, which I've never seen happen, thin paint is fine. Of course, be sure the shiny foil is perfectly clean and dry before you paint it.

--Ethan

Ethan Winer

03-01-11, 12:53 PM

What are your thoughts on using risers as additional bass traps?

I've never done that so I have no strong opinion. I'm not sure that a riser is the best place for a bass trap, though more bass trapping can only help. I can tell you for sure that the more conventional trap locations are very important.

--Ethan

pepar

03-01-11, 01:22 PM

DIYHomeTheater, I can tell you that my riser was built to allow the future installation of a bass transducer .. 2x12 frame w/2x10 "joists" .. but it was not necessary. It has a fortuitous sympathetic springy "whomp" at about 25Hz. I'm sure that means it is absorbing at and around that frequency, but I wouldn't know how to place any values on it.

Jeff

Jay5298

03-01-11, 02:30 PM

Ethan,

Have the 705 foil out in some areas. Would a light dusting of flat spray paint cause any problems? The reflection shows through the GOM 701 at some angles.

Thanks,

It may be too late, but I removed the foil and then flipped it so the plain side was up and re-attached it with spray adhesive.

Jay5298

03-01-11, 02:41 PM

What are the dimensions of your room?

The worst dimensions possible, 8ft ceiling(actually 7ft,10in.) 16 1/2 ft wide, 24 ft deep. I was stuck with the low ceiling so when I plugged in the numbers with the recommended ratios I didn't like the dimensions it gave me. I built the room based on the screen size I wanted, and the number of seats. I wanted to be able to just walk into the room with a 3 foot isle on each side. Not only for ease of moving around but so the side seats wouldn't be too close to the surround speakers. I also didn't want to sit too close to the screen. If I did some measurements it probably wouldn't look good but it sounds pretty good to me.

dunkman23

03-01-11, 03:02 PM

Yes. Obviously, a few more in key spots would also help more, but if that's all you can do, it is worth it, sure.

i was looking to make 24x 48 sized ones. But im debating if i should do 2 or 4 inch ones.. what would u recommend

pauleyc

03-01-11, 09:46 PM

So I have a non-HT acoustics question, so slightly off topic. A few years ago we built a home on a piece of lakefront property we had, and at the time we wanted all hardwood in the main living space. The main space is a causal family room, dinning and kitchen combination. The issue is that the room is very LIVE. I would guess the room is 25 x 30 and as you can see it's pretty much hard surface after hard surface. It so bad that it's difficult to listen to the tv and nearly impossible if others are having conversations elsewhere in the room. I'm looking for ideas on how to tame the room a little. We originally didn't want curtains because we didn't want to take away from the views however I'm beginning to think heavy drapes, even if they are never closed. Also, the back wall that you can't see (on the left) is a fairly large flat surface. I was thinking a few 2x48x2" panels along that wall. There aren't a lot of other big wall spaces. Any thoughts or suggestions? See pic.

Brad Horstkotte

03-01-11, 10:38 PM

A large area rug would help, but of course would cover up some of the hardwood.

Dennis Erskine

03-02-11, 05:47 AM

How much you will to spend to fix this?

DIYHomeTheater

03-02-11, 06:44 AM