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Acoustical Treatments Master Thread

2M views 15K replies 2K participants last post by  nathan_h 
#1 ·
OK, this seems straightforward from searching AVS and studying theater wall treatment...


FRONT WALL: Acoustical treatment (1" Insul-Shield) floor-to-ceiling.

CEILING: No acoustical treatment - none, nada.

FLOOR: Thick, plush carpet is fine.


But here's where it gets confusing, and I need help...


SIDEWALLS

A) Acoustical treatment (1" Insul-Shield) from floor to ear-height (44"), with 16oz polyester batting above.

--or--

B) Acoustical treatment (1" Insul-Shield) from floor-to-ceiling on all 1st reflective surfaces.


These 2 theories seem to contradict each other. So which is it?



BTW, for those searching for Insul-Shield type product, here are the substitutes which seem to have identical acoustical absorption ratings:


Owens Corning Select Sound Black Acoustic Board

Owens Corning Fiberglas 703 Series duct insulation.

Johns Manville Insul-Shield

Johns Manville Linacoustic Permacoate rolls.

Certainteed Certpro Acoustaboard Black

Knauf Duct board EI-475

Knauf Duct liner EM


...personally, I found the Knauf EI-475 easiest to find (4' x 10' sheets @ $40) from a general heating and air conditioning company.
 
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#9,156 ·

Quote:
Originally Posted by GIK Acoustics  /t/255432/acoustical-treatments-master-thread/9150#post_22544700


GrasaDeCastor,

So it seems you have two problems:

1. Dialogue isn't as present as you would like.

2. Higher frequencies are causing ear fatigue.

The first problem is due to low frequency issues, usually around the 80-150 Hz range. I would make two suggestions to help clear this up:

Step one - Try to get the sub in the most optimal position. I would disconnect Audyssey, and put in a DVD or CD with dialogue that seems to be thin or not as present. Crawl your subwoofer around until you are able to get some more presence in dialogue. Reconnect Audyssey and have a listen from there. If you've already found the absolute optimal sub position, then just go on to the second step.

Step two - bass traps. For ranges of 80-150 Hz a few different types of absorbers work well. From the tests we have done on our 244, it has a great absorption coefficient at 80 Hz when straddling a corner, and it absorbs very well above that as well. Or, you could use some wall mounted panels, though they won't have as strong of a presence at 80 Hz (still very effective, though, for dialogue frequencies)

The second problem, as you suggested, is likely due to room acoustics. The particular phenomenon you described is actually known as "flutter echo". Luckily, it is one of the easiest problems to treat, as relatively thin treatment is usually substantial. Flutter echo happens between two parallel hard surfaces in the room. This means that while treating your ceiling will help with first reflections and reverb reduction, there shouldn't be much flutter echo between your ceiling and your floor since they are not parallel at all. Also, staggered treatment will be most effective at combating flutter echo. For example, if one wall was 100% treated with absorption, and the parallel wall to it was completely untreated, there would be no flutter echo. So, having treatment staggered (ie. parallel to a blank area on the wall) will result in more flutter echo reduction than if treatment was parallel with more treatment. However, this can skew stereo image - so I would recommend this on the ceiling, front, or back wall, but not the sidewalls.

Another phenomenon that can cause ear fatigue is simply loud early reflections. Early reflections are the first reflections that come from a boundary, typically right after the direct sound hits your ears. This can result in unpleasant sounds, and easily ear fatigue (as you will hear every loud transient multiple times, instead of once). Treating your first reflection points on the ceiling, as well as the sidewalls can help cut down these reflections to a much smaller level, allowing you to hear what comes out of the speakers, instead of what's bouncing off your walls. This is why something like Audyssey cannot correct all room problems, as no matter what comes out of the speakers, there will always be harmful reflections.

Considering treating your reflection points will already help combat some echo, I would recommend doing that first. If you wish to combine bass trapping with your flutter treatment, making or buying thicker absorbers (4" to 8" thick) will help treat both the low end and the high end. Perhaps a few panels on the ceiling, a few on the sidewalls, and some on the front or back wall should give you a very good start without breaking the bank. From there you can decide if your room needs more treatment, or if fits your needs and rids of the fatigue.

Please let me know if you have any questions!

Alexander,


Thank you for taking the time to write that up! That is exactly the kind of information I was looking for. I made it over to your site that you linked in another post and it looks like next month when the budget permits I will be ordering some of the 242 acoustic panels. Your post and your site are both a fount of information and can't say enough how much I appreciate you breaking it down in layman's terms like that for me. I'll start with a few of the acoustic panels as you suggest, re-listen and see if I feel like it needs more treatment, possibly a couple of corner bass traps, and take it from there. In the mean time I've ordered a 30ft sub cable so I can play with that until I get some panels.


Thanks again!

GrasaDeCastor
 
#9,159 ·
I stacked my triangles between 2x2s on each side, to keep them into place - 2x2s screwed and liquid nailed to the walls:




Then fabric can be stapled to the 2x2s.
 
#9,160 ·
I'm sure Brad/Pepar/myself - among others - have posted this answer 4-5-6 times...Mo-ichi-do


Stack them low and high, with shelf top is possible, details in this link:
http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames/30#post_20007037








also stacking floor/ceiling, this simple pict should help visualize different approach:



to give this:





I'd like to add;

For big corner bass traps like these shown you can use HD/Lowes Pink fluffy instead of the more expensive/denser stuff I used - and get better performance, it's related to the gas flow resistivity....there are posts in this thread that explain it so I won't re-hash those here.
 
#9,162 ·

Quote:
Originally Posted by mtbdudex  /t/255432/acoustical-treatments-master-thread/9150#post_22551423


I'm sure Brad/Pepar/myself - among others - have posted this answer 4-5-6 times...Mo-ichi-do

Stack them low and high, with shelf top is possible, details in this link:
http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames/30#post_20007037




also stacking floor/ceiling, this simple pict should help visualize different approach:


to give this:



I'd like to add;

For big corner bass traps like these shown you can use HD/Lowes Pink fluffy instead of the more expensive/denser stuff I used - and get better performance, it's related to the gas flow resistivity....there are posts in this thread that explain it so I won't re-hash those here.

Any of the pink fluffy stuff or should I look for something specific.


Thanks for the help going to try to make a few this week.
 
#9,163 ·

Quote:
Originally Posted by cuzed2  /t/255432/acoustical-treatments-master-thread/9150#post_22551524

Quote:
Originally Posted by mtbdudex  /t/255432/acoustical-treatments-master-thread/9150#post_22551423



mtbdudex;

Any more details on how you shaped/constructed these bad-boys (the ones in the upper corners)?

In my signature there is a link for my DIY acoustic treatments thread. I can't repost that from iPhone.


Have fun making yours



Sent from my 32GB iPhone4 using Tapatalk
 
#9,166 ·
Yup
 
#9,168 ·

Quote:
Originally Posted by Holiday121  /t/255432/acoustical-treatments-master-thread/9150#post_22552601


Wow that's cheap compared to the Roxul

Yes it certainly is! It will work great for very thick traps. Theoretically, the Roxul should be a small bit better until about 18" thick, where the pink fluffy will start to become a small bit better. The small advantage should not make much of a real world difference with 4 floor to ceiling traps though.
 
#9,169 ·

Quote:
Originally Posted by GrasaDeCastor  /t/255432/acoustical-treatments-master-thread/9150#post_22546593


Alexander,

Thank you for taking the time to write that up! That is exactly the kind of information I was looking for. I made it over to your site that you linked in another post and it looks like next month when the budget permits I will be ordering some of the 242 acoustic panels. Your post and your site are both a fount of information and can't say enough how much I appreciate you breaking it down in layman's terms like that for me. I'll start with a few of the acoustic panels as you suggest, re-listen and see if I feel like it needs more treatment, possibly a couple of corner bass traps, and take it from there. In the mean time I've ordered a 30ft sub cable so I can play with that until I get some panels.

Thanks again!

GrasaDeCastor

Wonderful!


I would suggest the 244s instead of the 242s considering you have some problems in dialogue (and the price difference for doubling the thickness is pretty minuet)


Glad I was able to help.
 
#9,174 ·
#9,176 ·
Ok I picked up a few rolls iof this today.

http://m.homedepot.com/p/Owens-Corning-EcoTouch-R-30-Unfaced-9-1-2-in-x-15-in-x-25-ft-Continuous-Roll-Insulation-RU70/202585906/


Just unroll them and cut into triangles? I was reading some people leavd plastic on. I am going from floor to ceiling so all atleast 86 inches plus in height.


Going to go with a 24 in front .


So if I do cut then into triangles should I compress them down or just lay on top?



Also I need to pick up some fabric from Joann fabrics tommorow. Anything in particular I should look for? From what I read that you should be able to blow through the material. Or does this not matter when it comes to corner bass traps
 
#9,177 ·

Quote:
Originally Posted by Holiday121  /t/255432/acoustical-treatments-master-thread/9150#post_22555174


Ok I picked up a few rolls iof this today.

http://m.homedepot.com/p/Owens-Corning-EcoTouch-R-30-Unfaced-9-1-2-in-x-15-in-x-25-ft-Continuous-Roll-Insulation-RU70/202585906/


Just unroll them and cut into triangles? I was reading some people leavd plastic on. I am going from floor to ceiling so all atleast 86 inches plus in height.


Going to go with a 24 in front .


So if I do cut then into triangles should I compress them down or just lay on top?



Also I need to pick up some fabric from Joann fabrics tommorow. Anything in particular I should look for? From what I read that you should be able to blow through the material. Or does this not matter when it comes to corner bass traps

Can you re-think and go with 34" front? What is limiting you to 24" front?

Bigger is better for broadband bass traps.


This will show you one pink fluffy build method, from http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames/120#post_22131618
Quote:
Originally Posted by Eric2000  /t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames/120#post_22131618


Hi guys,


I've been following a number of the acoustics threads here for a while, though I haven't been very active on the AVS forums. Mike suggested that I share some of my work on room acoustics with everyone here, so here are my corner bass traps:


I followed a similar construction technique that Mike posted for his corner bass traps, but made mine from pink fluffy R-19 instead and wrapped the fabric around the outside of the threaded rod. Here is the photo journey:


My traps are 24x24x34 inch triangles, are about 3.5 feet tall, and probably weigh less than 10lbs each. Since I need access to one of the corners for a doorway, I made them stackable and moveable. I started by cutting triangles, drilling holes for the threaded rod, and inserting T-Nuts for the sides that stack on one another:



Then I cut 23" squares of insulation, cut them diagonally for triangles, and clipped off the corners so they fit snugly between the threaded rods:




A wire mesh made from separated Cat5 wire goes between each layer to keep the insulation from sagging over time. The numbered arrows indicate the direction of winding the wire to support the insulation. A bead of solder keeps the wire from unwinding. Each layer of insulation is about 5" thick.



Here is the first one all stacked up. You can see the supportive wire mesh wrapped around the threaded rod on each side:



And then with the Kraft paper glued to the front with spray adhesive:



Then, turn the trap upside down to affix the cloth wrapping - a two-pack of curtains from the giant W for $15. Each pack is enough for two traps.



The cloth is stapled to the underside of the top plate to prevent sagging over time:



When the fabric is fully secured to the top panel, turn the trap right side up again and pull the fabric around to the back. Trim off the excess and then just pull it tight and use a desk stapler to hold the fabric together in the back:



The staples produce a few ripples in the sides, but you won't see those once you put it in the corner. The front looks nice and clean:



Here is a closer shot of two of them stacked together:



And finally, the entire back half of the theater. With a few bean bag chairs up front, we can comfortably seat 10-12 people. The colors are a little off from a combination of CFL and flash lighting:



Below are the before and after REW plots. The purple trace is the original measurement with no traps and no EQ. The yellow trace is the difference made by the bass traps alone. The traps took 5dB off of the room-induced peak at 45Hz without sacrificing anything else in the audible range:



This is the original waterfall plot made by REW - no traps, no other corrections - just a mess with room modes at 45Hz and 90Hz:



And here is the waterfall plot after ONLY the traps are put in place. I was surprised by how much of a difference the traps made in the decay:



After several days of tweaking the parametric equalizer with the traps in place and a first order high-pass filter in place, here is my "final" room response curve - flat from 7Hz to 100Hz, plus/minus 3dB :'( The peak at 105Hz won't ever really happen because the preamp crosses the LFE channel at 60Hz.



And the "final" waterfall plot - nice and smooth. If I adjust the waterfall graphing limits in REW, the entire response curve is down by 20dB within the first 100-120ms with the exception of a 2-3dB narrow bump at about 23Hz. I am really pleased with this result:



It sounds great! The EQ and high-pass filter reduce (but don't eliminate) the incidence of amp clipping, but still provide enough punch to cause visitors to literally jump up from the couch :p


All of my other projects are on my web page, which I think is linked in my signature.


Eric
 
#9,179 ·
Kraft paper is the brown paper backing used on faced insulation - also the brown paper of "brown paper packages tied up with strings." It is one of your favorite things, because it reflects high frequency sound while being transparent to mid and low frequency sound. Since highs are so easy to absorb (you and your furniture absorb them), reflecting them back into the room can be important to maintaining the spectral balance of reflected sound in the room.
 
#9,180 ·

Quote:
Originally Posted by HopefulFred  /t/255432/acoustical-treatments-master-thread/9150#post_22555301


Kraft paper is the brown paper backing used on faced insulation - also the brown paper of "brown paper packages tied up with strings." It is one of your favorite things, because it reflects high frequency sound while being transparent to mid and low frequency sound. Since highs are so easy to absorb (you and your furniture absorb them), reflecting them back into the room can be important to maintaining the spectral balance of reflected sound in the room.


Thanks for the info. Do you buy it in rolls at Home Depot,
 
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