DIY construction methods of hang-able acoustic panels & moveable Corner traps (not fixed frames) - Page 6 - AVS Forum
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Old 03-10-2014, 06:48 AM
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Originally Posted by mtbdudex View Post

jkasanic - you are really going big and deep!
You've got an AT screen, and false wall, and behind that you desire to suck up low freq, got it.

For the RH and LH ones, Could you put 2 x 4 strips at the top, 3 like I show in dark blue, and then "hang" the un-faced R-30 by simply clamping it to the 2x4 by say thin 1 x 2 wood strip that is pre-drilled and use coarse drywall screw?
In my mind that seems easy and doable. Go full length ceiling to floor.
Same for area between your LCR, above your LCR just cut the pink fluffy slightly above them.



Somewhere years ago I saw someone do similar with thick cotton shoddy, really deep on front wall.

 

I suppose I could hang it in 9" thick strips as you've shown.  My current concept is to fill these burlap sacks with pink fluffy and hang the top one from the wall and the bottom one from the top one:

 

 

I was a little concerned about only having one layer of GOM (my false wall fabric panels) between the audience and the insulation and the burlap works well to keep the fibers contained.  If compression is a concern (I won't get my pink fluffy until later this week) then I was thinking I could somehow attach the strips to the top surface of the burlap, basically achieving the same result as you've shown.

 

Just to give you an idea of my raw bass response (C+Sub with and without Audyssey no smoothing 0-300Hz):

 

 

Audyssey does a pretty good job taming the 30Hz peak so my goal has really been just to give it a better starting point from which to work its magic.  I don't expect to have a lot of impact on the 30Hz peak but if I can smooth out the even more critical 50-300Hz region then I will have achieved most of my goal.  Part II will be creating sound symmetry (I have two door openings on the right side of the room) as well as taming contra-lateral reflections and then after listening for a while I'll decide what I want to do (if anything) about any remaining high gain early ipsilateral reflections.  There's a couple different schools of thought on these so I figured I'd get the room to the point described earlier and then just listen for myself with some known content.  I should also state that my room is 95% used for movies and the 5% that I use for music is mixed between stereo and multi-channel discs.

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Old 04-24-2014, 06:33 AM
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I posted this in an other thread. But have yet to receive any responses. This thread seems more geared to DIYers so hopefully I will get some help here.

 

 

Now that I have my bass traps done. I am ready to move on to panels. But I have a few questions. First and foremost is regarding something that I read. It said that for first reflection points. Anything less than a 4" thick panel will do more harm than good. As it will result in a muffled sound. Due to it only being  able to absorb upper part of the spectrum leaving the bass and mids in tact. Is that true?

 

Depending on that answer. I need to keep these panels as unobtrusive as possible. I was going to do 2" thick 2'x4' panels of Roxul Safe and Sound with a 1" space behind. Would I be better off with a 3" thick panel with no space? I am trying to limit myself to 3" of protrusion into the room as to not upset my wife too much. But if it really needs to be 4" (with or without space behind?) I will have to renegotiate with here.

 

Lastly should all absorbers on the front wall have a reflective face? Or is that only for the corner traps? Then the rest of the room (side walls and back wall) should be full range (no paper face)? Is that correct. This is only for walls no saddles will be used.

 

Regards,

James

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Old 04-24-2014, 07:04 AM
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Quote:
Originally Posted by James004 View Post
 

I posted this in an other thread. But have yet to receive any responses. This thread seems more geared to DIYers so hopefully I will get some help here.

 

 

Now that I have my bass traps done. I am ready to move on to panels. But I have a few questions. First and foremost is regarding something that I read. It said that for first reflection points. Anything less than a 4" thick panel will do more harm than good. As it will result in a muffled sound. Due to it only being  able to absorb upper part of the spectrum leaving the bass and mids in tact. Is that true?

 

Depending on that answer. I need to keep these panels as unobtrusive as possible. I was going to do 2" thick 2'x4' panels of Roxul Safe and Sound with a 1" space behind. Would I be better off with a 3" thick panel with no space? I am trying to limit myself to 3" of protrusion into the room as to not upset my wife too much. But if it really needs to be 4" (with or without space behind?) I will have to renegotiate with here.

 

Lastly should all absorbers on the front wall have a reflective face? Or is that only for the corner traps? Then the rest of the room (side walls and back wall) should be full range (no paper face)? Is that correct. This is only for walls no saddles will be used.

 

Regards,

James

 

In order to properly treat your reflections, you should use some measuring gear (e.g. USB mic and REW gets you in the game for around $100) and plot some band-limited ETC measurements.  Once you know which frequencies the reflections are strongest then you can better determine the material and thickness of your treatments.  The ETC's will also help you discover which surfaces are reflecting the sound as sometimes the most harmful are not just the first reflection points of your side walls.

 

Here's a calculator to help you determine the effectiveness of your treatments depending on material (for air resistivity), thickness and air gap:

 

http://www.acousticmodelling.com/porous.php

 

I took a stab at filling in the measurements but I'm guessing the air resistivity will vary somewhat based on the thickness of the Roxul (and type, I used AFB).  It shows the solid 3" would go deeper which makes sense since your air gap should be similar to your treatment thickness for maximum effect:

 

 

This basically tells you that if 3" is your max then you're better off using 3" of material rather than 2" with a 1" air gap (assuming everything else is constant).  You might want to double check my numbers if you're looking for "absolute" values in the chart as I was just trying to illustrate the difference.

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Old 04-24-2014, 07:55 AM
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Quote:
Originally Posted by jkasanic View Post
 

 

In order to properly treat your reflections, you should use some measuring gear (e.g. USB mic and REW gets you in the game for around $100) and plot some band-limited ETC measurements.  Once you know which frequencies the reflections are strongest then you can better determine the material and thickness of your treatments.  The ETC's will also help you discover which surfaces are reflecting the sound as sometimes the most harmful are not just the first reflection points of your side walls.

 

This basically tells you that if 3" is your max then you're better off using 3" of material rather than 2" with a 1" air gap (assuming everything else is constant).  You might want to double check my numbers if you're looking for "absolute" values in the chart as I was just trying to illustrate the difference.

Thank you. My gut was telling me 3" no gap was better than 2"+1"air gap. Thank you for confirming that.

 

I do have REW set up and would love to get some measurements to post. Since I now have the corner bass traps installed. But I have an 18 mo son who loves to touch everything daddy touches and the test tones would wake him during his naps. So I am stuck at this point. I think I will go buy some more 3" Roxul today and hope that I can sneak some measurements in before building any panels.

 

What about reflective faces on the front wall panels? Or is that dependent on the REW results? What about the back wall. Is it pretty safe to assume two horizontal 2'x4' panels (no paper face) at head height behind my couch?

 

Thanks in advance,

James

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Old 04-24-2014, 08:07 AM
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Quote:
Originally Posted by James004 View Post
 
Quote:
Originally Posted by jkasanic View Post
 

 

In order to properly treat your reflections, you should use some measuring gear (e.g. USB mic and REW gets you in the game for around $100) and plot some band-limited ETC measurements.  Once you know which frequencies the reflections are strongest then you can better determine the material and thickness of your treatments.  The ETC's will also help you discover which surfaces are reflecting the sound as sometimes the most harmful are not just the first reflection points of your side walls.

 

This basically tells you that if 3" is your max then you're better off using 3" of material rather than 2" with a 1" air gap (assuming everything else is constant).  You might want to double check my numbers if you're looking for "absolute" values in the chart as I was just trying to illustrate the difference.

Thank you. My gut was telling me 3" no gap was better than 2"+1"air gap. Thank you for confirming that.

 

I do have REW set up and would love to get some measurements to post. Since I now have the corner bass traps installed. But I have an 18 mo son who loves to touch everything daddy touches and the test tones would wake him during his naps. So I am stuck at this point. I think I will go buy some more 3" Roxul today and hope that I can sneak some measurements in before building any panels.

 

What about reflective faces on the front wall panels? Or is that dependent on the REW results? What about the back wall. Is it pretty safe to assume two horizontal 2'x4' panels (no paper face) at head height behind my couch?

 

Thanks in advance,

James

 

I'm following a similar path as you.  I've just installed corner bass traps as well.  I went deep as shown a couple posts above and I'm trying to finish some more traps for the front wall.  I was surprised that I didn't see as much benefit in my decay times with just the corner traps installed.  I did seem some smoothing of my FR (pre-Audyssey) in the 60-160Hz range but a large peak at 30Hz from a room mode was hardly affected.

 

Anyway, my next step is to start installing treatments in-room.  I don't have any (baby) constraints yet so I'm taking a very systematic approach to minimize the overall number of treatments yet optimize their size and placement.  The great thing about REW is you can run a full range sweep and then slice the data a million different ways.  If I were you, I'd try to get at least one full range sweep of your left, center and right (with and without subwoofer engaged) as well as the combined response of your L+R+Sub for analysis in the 15-300Hz region.  The individual sweeps can then be used to do those band-limited ETC's I mentioned above.  There's some discussion on this in the REW thread as well.

 

I can't really comment on how effective your approach would be without measurements.  Every room is different and what works for some may not work for others.  If you have more details on your room layout and want to post some FR sweeps, waterfalls, spectrograms and ETC's then I would suggest you head over to the REW thread where you'll get a lot more input on how best to treat your room using the measurements as a guide.

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Old 04-24-2014, 12:10 PM
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It is definitely time to do some measurements. I will post them in the REW thread.

 

My only question remaining for now then is. Are there any locations other than the corner bass traps where a paper face would be used?

 

James

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Old 06-24-2014, 10:27 AM
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For all those using pink fluffy or OC703 in your corner traps and panels, did it have a really strong chemical smell at first? Does this ever go away, or is it trapped in your theater room for good? As a quick test of my need for corner traps, I stacked lots of those pink fluffy R-30 round bales (still in original packaging) in the front corners of my dedicated room. It seemed to improve the REW waterfall, but the smell was just too much, so I moved them all back to the garage. Now trying to figure out what material I'm going to use as I start building corner traps and wall panels. Would the denim Ultratouch have less of a smell since it's "greener"?
Thanks!
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Old 06-24-2014, 02:53 PM
 
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Quote:
Originally Posted by mcnewt View Post
For all those using pink fluffy or OC703 in your corner traps and panels, did it have a really strong chemical smell at first? Does this ever go away, or is it trapped in your theater room for good? As a quick test of my need for corner traps, I stacked lots of those pink fluffy R-30 round bales (still in original packaging) in the front corners of my dedicated room. It seemed to improve the REW waterfall, but the smell was just too much, so I moved them all back to the garage. Now trying to figure out what material I'm going to use as I start building corner traps and wall panels. Would the denim Ultratouch have less of a smell since it's "greener"?
Thanks!

try roxul safe and sound insulation .. most home depots up north..
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Old 06-26-2014, 11:43 PM
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Sorry, posted in the wrong thread.

Last edited by likelinus; 06-27-2014 at 08:17 AM.
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Old 08-11-2014, 11:43 AM
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Originally Posted by mtbdudex View Post

Having used the simulation software for the 1st reflection points, transferred those locations via blue tape onto the ceiling.
Confirmed their accuracy with 1' x 4' mirror and my wife....she was on ladder holding the mirror flat to the ceiling while I was the one sitting in the chair analyzing
Then, with the build wood box, get exact mtg locations via blue tape and much measurement/cross checking.
Where did you get the simulation software for first reflection location?

tia,
Ron

Denon 4520ci, (3) JBL 2360As/EV DHA-1s, (3) 1/4 Pie bass bins, MiniDSP 2x4s, (4) Klipsch HIPs, (2) Klipsch KP3002s, PS3, XBox 360, (3) Intel NUCs, Monoprice Redmere, Monster HTPS7000, 2 SUPER SPUD subs, Panasonic AE8000us SeymourAV 180 (195" diagonal) scope screen, Yamaha P7000s (for the subs), (2) Yamaha P2500s amps for the front (3) bass bins.
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Old 10-01-2014, 09:04 PM - Thread Starter
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Where did you get the simulation software for first reflection location?

tia,
Ron
Sorry late answer, I missed this...

Look here, post 245, I know it works under WinXP....not sure Win7 or later....
*free* software to help determine your first reflection points
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Old 10-01-2014, 11:11 PM
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Sorry late answer, I missed this...

Look here, post 245, I know it works under WinXP....not sure Win7 or later....
*free* software to help determine your first reflection points
Thanks, I got it working in Win 7... How do you get it to display strictly a floor plan so you can measure... All I have been able to get is the 3d plan, and then it is difficult to see exactly what the measurements are.

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Old 10-02-2014, 05:49 AM - Thread Starter
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Going from memory here.
When you input the dimensions of your room, for me in feet, it overlays grids in 2 foot increments.
Not sure if you can change that to finer resolution, you can input dimensions to the inch.
For plan view,side view, etc.
I was able to do that, either by direct button that gave that or rotate the view till it was how you wanted....
Sorry it's been a while since I actually did it.


Via Mikes brain/thumb interface, LLAP
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Old 10-10-2014, 04:24 PM
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Bumping a really good quality thread.

-

"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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Old 11-04-2014, 12:54 AM
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So I've been reading all this speaker porn on this site and Gearslutz. (my wife thinks that's funny) I want to tighten up the resonances/room modes/reverberation in the bottom end. The frequency response I can fix with REW and my Behringer Feedback Destroyer Pro DSP1124P, but the Waterfall plots are ugly.


My plan is to construct corner traps as depicted below, using my mad Power Point skilz. I'll start with 2' x 4' bats of Roxul Safe 'n Sound, cut off the corners 1' in, and place those pieces on the back (top of the picture) to create the shape shown. Overall dimensions will be 4' wide by 3' deep, at the point in the corner, from floor to ceiling. I think I want it to be mobile, so I may mount casters on the plywood bottom. I still have to work out most of the construction details. I have time, as these will go into my house when I retire from the Army.


My question is, given that I'm not so worried about smoothing the FR in this application, will this (reasonably) effectively tame that waterfall? My room is pretty big, so I can get away with three of these monsters in the corners. Is Safe 'n Sound the best for this application (40kg/cu. m.?) Do I want to leave an air gap between the wall and the trap? Can I use 1/8" hardboard for backing on the sides against the wall?
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Old 11-04-2014, 07:38 AM
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Quote:
Originally Posted by crossrh View Post
So I've been reading all this speaker porn on this site and Gearslutz. (my wife thinks that's funny) I want to tighten up the resonances/room modes/reverberation in the bottom end. The frequency response I can fix with REW and my Behringer Feedback Destroyer Pro DSP1124P, but the Waterfall plots are ugly.


My plan is to construct corner traps as depicted below, using my mad Power Point skilz. I'll start with 2' x 4' bats of Roxul Safe 'n Sound, cut off the corners 1' in, and place those pieces on the back (top of the picture) to create the shape shown. Overall dimensions will be 4' wide by 3' deep, at the point in the corner, from floor to ceiling. I think I want it to be mobile, so I may mount casters on the plywood bottom. I still have to work out most of the construction details. I have time, as these will go into my house when I retire from the Army.


My question is, given that I'm not so worried about smoothing the FR in this application, will this (reasonably) effectively tame that waterfall? My room is pretty big, so I can get away with three of these monsters in the corners. Is Safe 'n Sound the best for this application (40kg/cu. m.?) Do I want to leave an air gap between the wall and the trap? Can I use 1/8" hardboard for backing on the sides against the wall?
I just installed about 90 cu ft of pink fluffy in the form of 7 square soffit style bass traps 23"x23"x42"(see a few posts above). I concentrated on the soundstage since I have a false front wall. What I found (in my particular room) was that my frequency response was affected more than my bass resonance. My bass resonance wasn't nearly as bad as yours though so I would expect to see more improvement in the time domain with your setup. I also think that just concentrating my traps on the front soundstage altered the energy balance in the room and exposed some other issues that may have been hidden due to reflective energy (just a hypothesis at this point). In any case, I did some extensive research on constructing the best bass traps to maximize the performancerice ratio. My research indicated that square style traps would be more effective than triangular all things equal. HST, if WAF is a factor or your corner traps are in-room then the triangular style are not a bad tradeoff for better aesthetics. Will be interested to see some before and after waterfalls. I'd also use the Spectrogram to compare. Good luck!
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Old 11-05-2014, 05:47 PM
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I was reading this article from 1998, and the last paragraph in the Modes section says:


"These modes decay at different rates, so to damp a mode, absorbing material must be placed in an area of high pressure. For example, to damp a mode produced by two opposite walls, the absorbent material must be placed on one of the walls, rather than on the floor or ceiling."


http://www.soundonsound.com/sos/jul9...coustics1.html


That made me wonder if there were different techniques for attenuating a frequency versus absorbing a room mode. I've been hearing (no pun intended; let me know when that gets old) that we should leave an air gap between the absorbent material and the wall. Does this apply in both of the above-mentioned cases?


Also, I'd like to try building some Helmholtz resonators.


http://www.audioholics.com/room-acou...onant-absorber


Does anybody know where the Excel spreadsheet is for the calculations, or have any other tips? The link in the article is dead.
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Old 11-06-2014, 07:00 AM
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Quote:
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That made me wonder if there were different techniques for attenuating a frequency versus absorbing a room mode. I've been hearing (no pun intended; let me know when that gets old) that we should leave an air gap between the absorbent material and the wall. Does this apply in both of the above-mentioned cases?
Air gaps are typically used to improve the absorption coefficient when dealing with panels or traps that are thinner in nature and the air gap is at least equal to or greater than the thickness of the panel. For example, a 1" thick panel of OC703 with a 1" air gap can perform nearly as well as a 2" thick panel (see 1st attached image) and noticeably better than a 1" panel with no gap (see 2nd attached image).

Bass traps need to be very thick to absorb lower frequencies so typically (of course, it depends on the material you are using) an air gap is not used with these type of traps. Hope this helps.
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Last edited by jkasanic; 11-06-2014 at 07:09 AM.
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