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DIY construction methods of hang-able acoustic panels & moveable Corner traps (not fixed frames) - Page 5

post #121 of 151
agreed ^^

mtx,
when you did your last round w/ the cloud - was the cloud positioned directly above the listening position or was it at the ceiling reflection point?
post #122 of 151
Thread Starter 
Quote:
Originally Posted by localhost127 View Post

agreed ^^

mtx,
when you did your last round w/ the cloud - was the cloud positioned directly above the listening position or was it at the ceiling reflection point?

Both actually, I have 5 sheets of 2" OC703 un-used, put 2 on the cloud for the 1st row ceiling reflection point and 3 on the cloud for the 2nd row ceiling reflection point.

The 2nd cloud is directly over the 1st row seat positions, below is accurate layour showing that.

post #123 of 151
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:
287

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:
390


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.
400

Here is the first one all stacked up. You can see the supportive wire mesh wrapped around the threaded rod on each side:
516

And then with the Kraft paper glued to the front with spray adhesive:
529

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.
400

The cloth is stapled to the underside of the top plate to prevent sagging over time:
291

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:
550

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:
528

Here is a closer shot of two of them stacked together:
600

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:
326

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:
329

This is the original waterfall plot made by REW - no traps, no other corrections - just a mess with room modes at 45Hz and 90Hz:
443

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:
447

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.
449

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:
443

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
Edited by Eric2000 - 6/14/12 at 9:32am
post #124 of 151
That's good work, Eric. I think that is the first implementations of the pink fluffy bass damper I've seen detailed out (mine uses fluffy but has a foam core so I only have one thickness of fluffy which requires no support--but is probably less optimal). I've seen suggestions to use bird netting to support the layers but the wire thing is easier for this type of construction and definitely inexpensive. I've built some boxes with several horizontal layers of fluffy but they aren't really tall enough to need support for each layer.

Do you have before and/or after sweeps for a variety of listening positions?

And could you post a 0-300Hz waterfall taken with one of the mains and the subs on? I'm interested to see what really happens to that 105Hz thing in real life (among other things).

Just saw your question Mike:
Quote:
side comment/inquiry:
While we use 1/12 octave smoothing to see bass issues clearly and decide how to address them, do our ears "hear" that tight or is 1/3 octave smoothing representative of what our ears hear??

I'd guess the answer is that it depends on the source material. Yes, it's said that we only "hear" in 1/3-octave bands, but by the same token I personally don't think it's too difficult to hear individual bass notes at half-tone intervals. I suspect the 1/3-octave research was done with filtered noise or some methodology that didn't provide all that much possibility for frequency-volume selectivity for the ears. I bet a walking bassline that changed volume a lot would be pretty noticeable. And if you check out the wiki entry for piano key frequencies, they go down to ~27 Hz with pretty small frequency spacing. I do think the specifications for monitoring environments specify 1/3 octave filtering for their judgments -- and I think that is fine for overall tonal balance. But I'd have to go digging around to find enough information to really have a great answer and would be interested to hear if you have gotten any answers from people who are better schooled than I, LOL. Anyway my feeling is that 1/3 makes complete sense above the Schroeder frequency where our ears are good at removing comb filtering effects, but might not be tight enough below it. However since the octaves also get smaller down low... I guess I could be way out in left field, as it were, on that.
post #125 of 151
I've seen the suggestion for bird netting as well. I have some, but don't have a good idea how I would have used it to support the insulation between each layer and still have it look neat. The wire just seemed easier and more straight forward. I don't have any sweeps for other locations. Most of the time, it's just my wife and I and we both fit in the sweet spot cool.gif

I also didn't do any measurements with the mains and the sub together. Just after I took all of my measuring equipment down, I thought of both 1) measurements at other seats and 2) integration with mains - go figure. Due to the layout of my equipment (most of it is in the room on the back-side of the screen wall) it is a major project to rig the IB for measurement and adjustment again. I'll eventually get around to it, but it's not likely to be anytime soon.

The sub is an IB that is mounted two feet behind the screen wall and the mains sit about 3-4 feet out from the screen wall, so I suspect that same peak at 105Hz won't happen with the mains. I need to do some crossover tweaks to my center channel at some point, so I do plan to measure the mains before too long.
Edited by Eric2000 - 6/14/12 at 11:19am
post #126 of 151
Thread Starter 
Thx for posting here Eric.
Others, look at Eric's sig link, his various DIY projects are really sweet!
post #127 of 151
Again Eric, nice implementation of the pink fluffy,....nice time domain results cool.gif
post #128 of 151
mind the compression of the insulation; low GFR material should be loosely filled. have fun!
post #129 of 151
whoollllyyy begggeezzuss...eek.gif
post #130 of 151
This may be a dumb question but...Is there an reason why hang-able acoustic panels are nearly always 2'x4' other than convenience of the available material sizes? Meaning is the some wave length reason?

I realize the size works nicely to cover a reflection point in relation to seating position and speaker position. But than again so could other sizes.

I have a specific situation that I'd like more of a 2x3 horizontal panel to work in my design.
post #131 of 151
Thread Starter 
by using measurements (microphone + software) and ETC you can determine the appropriate amount of material for treatments and where to apply them.
In general, for absorber treatments 4" material (OC703/equiv) + 4" air gap is the baseline for absorption down to 300hz - this way you don't EQ the sound, then the needed height/width can be deduced via ETC analysis.
(there are threads here on how to do that)

Real world: What happens is the std HVAC product sizes of 2 x 4 seem to "work" for most situtations w/o over absorbing when is applied where truly needed, hence you see most treatments follow that.

I've seen rooms where people though only apply where the ETC showed......
post #132 of 151
Nicely done DIY!!
post #133 of 151
Great Post Guys!

Thanks for the info it will save me alot of trial & error.

Now its time to get building! smile.gif
Edited by Davide Feltrin - 4/1/13 at 2:28am
post #134 of 151
Question. I plan to make broadband panels and bass traps. I can get 4 inch mineral wool with density of 8 pcf. I know greater the density better bass absorption, but is it going to hurt my broadband absorption?
post #135 of 151
Thread Starter 
Quote:
Originally Posted by mp5475 View Post

Question. I plan to make broadband panels and bass traps. I can get 4 inch mineral wool with density of 8 pcf. I know greater the density better bass absorption, but is it going to hurt my broadband absorption?

In simplistic terms the greater density stuff typically has less higher freq absorption than the less dense material, so possible it will hurt your broadband absorption.
There are charts that quantify that for you.
http://www.bobgolds.com/AbsorptionCoefficients.htm

For bass specific traps, say 250hz and below, if you go the big superchunk route (34" face side) consider pink fluffy instead of the dense material.
That's discussed earlier in this thread.
post #136 of 151
Thx for the info. According to that website, 4 inch 8 pcf mineral wool has pretty good broad band absorption.
post #137 of 151
Quote:
Originally Posted by mp5475 View Post

Thx for the info. According to that website, 4 inch 8 pcf mineral wool has pretty good broad band absorption.

The values given by manufacturers for materials are random-incidence (diffuse field) coefficients, which are noticeably higher than the absorption of a single-incidence situation. Diffuse-field coefficients are not generally applicable in small-room acoustics. You need single-incidence measurements or estimates from the angles you intend the absorbers to work at, which are not as easy to come by. More info in Toole, p.474 and figure 21.9. Probably the best free way available today to estimate what you might really see for single incidence is to use the Whealy calculator and find the gas flow resistivity for the proposed material. There is a thread on gearslutz attempting to collate all the flow resistivity values available in once place which is probably the easiest way to get an estimate for a proposed material. Of course testing in-situ with the ETC method that mtb described also works.

You could probably consider the random incidence coefficients a hint; some data (even if only obliquely applicable) is better than no data of course.

"I know greater the density better bass absorption, but is it going to hurt my broadband absorption?"

Greater density = "better" bass absorption (assuming better means higher, or moar) is not really the case. I strongly suspect 8 pcf is overly dense, but since I haven't looked into absorption of rockwool that much I can't really say what might be better (if you are sticking to rockwool for whatever reason - without knowing your design limitations there's really no way for someone else to make suggestions).
post #138 of 151
Quote:
Originally Posted by mtbdudex View Post


Quilting Weight Cotton: $18/yard ($16.20 with designer discount)


100% cotton fabric with a soft hand, easy to sew


* 42" wide printable area (107 cm)

* 3.2 oz per square yard

* 78x 76 threads per inch

* Appropriate for quilting, appliqué, shirting, blouses, dresses, children's clothing

* Estimated shrinkage 3%

* Wash on delicate setting, warm or cool using phosphate-free detergent


Hi

Great info!
However, I'm looking at the sunflower site, and I can't find an exact match to the description shown above.
I find:
Basic Combed Cotton: $17.50/yard ($15.75 with designer discount)

100% combed cotton fabric, made from ring-spun yarn


42" wide printable area (107 cm)
3.2 oz per square yard
Thread count: 78 x 76
Appropriate for quilting, appliqué, shirting, dresses, children's clothing, and home decor.
Estimated shrinkage: 3.5% in length and 2% in width
Machine wash warm or cool on a gentle/delicate setting, using phosphate-free detergent.

And

Kona® Cotton: Premium Quilting Weight: $18/yd ($16.20 with designer discount)

100% cotton fabric with a soft hand, easy to sew


42" wide printable area (107 cm)
4.5 oz per square yard
Thread count: 60 x 60
Appropriate for quilting, appliqué, shirting, dresses, children's clothing, and home decor.
Estimated shrinkage: 2% in length and 3% in width
Machine wash warm or cool on a gentle/delicate setting, using phosphate-free detergent.

But what you have used seems to be something else. From the available fabrics, is anyone recommended to use?
http://www.spoonflower.com/spoonflower_fabrics
post #139 of 151
Thread Starter 
Nick did a great write up in the spoonflower thread on latest fabric choices, http://www.avsforum.com/t/1316623/diy-custom-printed-movie-poster-acoustic-panels-cheap/540#post_23974499

11/20/13 at 3:13pm
Quote:
Originally Posted by nickbuol View Post

Quote:
Originally Posted by SeekingNirvana View Post

I'm thinking of doing some panels like the ones in this thread. I would be using some of my own photos takin with a Cannon t1i. Before I get to far into it though I have some questions....

Has anyone done any before and after measurements using REW?

How are you guys finding the reflection points? Are you just placing them were they look best?

I've read the last few pages and see some discussion on fabrics. Has there been a clear winner as far as acoustic transparency and print quality?

Since this thread is about the fabric and not the panel functionality or placement, those topics are best for the Acoustical Treatments Master Thread so that we don't turn this thread into another acoustical treatment thread.

HOWEVER, I can tell you this that my room acoustics improved DRAMATICALLY with my panels, but they are not my only acoustical treatments, and my theater was purpose built from the ground up. I tried to follow all of the "golden rules" for things like ideal seating placement for room harmonics to reduce peaks and nulls, proper amount of treatments knowing that a single panel isn't going to necessarily solve anything. For people that have never done first reflection point measurements are in for a surprise when trying to account for more than 1 seat.

Here is what I started seeing when I started measuring for my seats. Each piece of tape represents a FRP for one of the seats. I started working on the back row and just stopped because doing multiple seats wasn't helping. I went back to the seat that I sit in the most, and then looked to cover up as many other pieces of tape as possible with the one panel. Dispersing the panels somewhat even throughout the room does help, but getting those FRP for the ones closest to the speakers themselves are probably the most critical.



Others with common spaces (non-dedicated) or other things may or may not have as much success, but it depends on what the rest of their room has in it, on it, etc. That is why acoustical treatments are so complex. Every room is different.

I will make this statement. Of all of the things that I've done for my room, from bass traps, to treating the front wall, to adding a second sub (when the first one is a great quality and plenty loud), the biggest improvement was adding the panels to my side wall and a thicker one on my back wall. Hands down, best thing I've ever done in there, or at least the most noticeable for significantly improving dialog intelligibility, surround accuracy, and tightening the bass.

In my opinion, the Performance Knit is the best choice for color depth, cleanliness of the fabric (the threads are fine and even, vs. the larger, and more un-even thickness of the Kona Cotton), and ability to get the creases and wrinkles out. It does, however, take a little care to make sure that any lettering is even, but that is easy. Just stretch a little more where needed to pull some areas down, and bam... Done. If you are crooked with the Kona, it doesn't stretch and will need to have staples removed and the fabric re-applied. Not bashing the Kona and it was the "go to" fabric for a long time. The Performance Knit is a newer product for Spoonflower. Oh, it also allows more sound to pass through it based off of even simple blow tests, but the Kona tested out great too (in a post somewhere near the beginning of this thread. A negative for the Performance Knit is that any printed lettering can seem to bleed a little. Just not quite as crisp, however this should only be noticeable from up close looking side-by-side with other fabrics.

Again, that is my opinion. I think that people will be very happy with either the Performance Knit, or the new Kona Cotton Ultra (which uses the same enhanced printing as the Performance Knit to get deeper colors than the original "washed out" Kona Cotton). The Performance Knit is stretchier and smoother, the Kona is a little more "textured" and stiff. Pluses and minuses for both.
post #140 of 151
Hey. Thanks for the repost. I love when information gets shared.

Don't forget some of the other posts about the fabric:
Kona Cotton vs. Performance Knit comparison #1

AND

More comparisons...

AND

Stretch tests...

AND

Staple tests...

AND the latest side by side photo test.

Spoonflower Kona Cotton, Kona Cotton Ultra, Performance Knit comparison

Kona Cotton Ultra and Performance Knit are the two to look at.

I went with Performance Knit forthe better colors, installation flexability (literally, its ability to stretch more made it easy to "fix" anything that wasn't aligned quite right), and its acoustical properties seemed to be better, thought probably only noticable using test equipment and I would bet that the humar ear wouldn't tell a difference between the Performance Knit and the Kona Cotton Ultra. I also like the "smoother" look of the Peformance knit vs. the rougher texture of the Kona.
Edited by nickbuol - 12/3/13 at 12:59pm
post #141 of 151
Can someone help me understand the proper thickness of OC 703 and the proper amount of space behind the OC 703 and the wall. I am curious about this for both bass traps in the corner and primary reflection points on the walls.

I intend to use a fixed frame design with a 3" thick border and one layer of 2" OC 703. I will then offset these from the walls with thin rubber feet. Does this idea seem to make sense? I see a lot of folks using 2 layers of OC 703, is this only appropriate for corner base traps? I would rather not have panels that are too thick on my walls since I don't want to make the room feel too much smaller. Also for cloud panels is one layer of OC 703 acceptable?

Thank you
post #142 of 151
Thread Starter 
Without getting into acoustic theory, see bottom of post 1 here if you want more education, too thin and you EQ the sound when trying to absorb your 1st reflections.

Side wall , go 4" thick, that can be 2" absorber plus 2" air gap, or 4" total thickness. This will get most of the freq above the Fs transition freq.
For ceiling, where you may have more room target should be 4" absorber plus 4" air gap.

Only place where needed, not random, see mirror trick in post 1.

Sound energy is a good thing, your task is to manage it correctly.

Look at the DIY corner traps also.
Link in post 1.


Via my iPhone 5s using Tapatalk
Edited by mtbdudex - 12/3/13 at 4:32pm
post #143 of 151
Thanks for the input. I would like to 1x4 poplar for my frames. 1x4 is likely a little bit less than 4" is that 2" behind the panel really that critical? It seems that some folks use 1x3 which would give less than 1" behind the rigid- could you explain what the drawback to this is?

Also what about using 1x4 but using a router to cut slots in the side of the frame to allow for side absorption. Has anyone tried something like this?

Also for corner traps I fully intend to have those as well. What diameter of threaded rod are people using? Also for a base trap what is the ideal material for absorption and why does everyone use the kraft paper- what's wrong with absorbing high frequencies in the corners as well?

Thanks
post #144 of 151
Thread Starter 
Quote:
Originally Posted by carter840 View Post

Thanks for the input. I would like to 1x4 poplar for my frames. 1x4 is likely a little bit less than 4" is that 2" behind the panel really that critical? It seems that some folks use 1x3 which would give less than 1" behind the rigid- could you explain what the drawback to this is?

Also what about using 1x4 but using a router to cut slots in the side of the frame to allow for side absorption. Has anyone tried something like this?

Also for corner traps I fully intend to have those as well. What diameter of threaded rod are people using? Also for a base trap what is the ideal material for absorption and why does everyone use the kraft paper- what's wrong with absorbing high frequencies in the corners as well?

Thanks

I won't go into 1/4 wavelength theory here - look at Ethan Winer site or others, suffice to say panels can be designed and applied to take advantage of that.
Hence when I say you will "EQ" the sound, you will only absorb so much of the Freq above Fs based on your panel design and absorber material choice.
Using 1 x 4 wood (which is 3 1/2 thick) vs a full 4" off the wall, nothing to lose sleep over wink.gif
Example below should explain to you visually and with table.
Of course, then your material of choice has it's absorber properties over different freq ranges, but that's topic of another thread.
Can you grasp when I call a acoustic panel "thin" not so good, it's not absorbing down low enough......
Acoustic%2520treatment%2520material%2520plus%2520airgap%2520explain.jpg

and that relates to what you hear with your ears
Interactive-Frequency-Chart.jpg

Definitely routering side slots in the frame will increase your absorption, and reduce possible un-wanted reflections off that frame itself. Yes, I've seen others do it.
Honestly if I go the full 4" thick absorber and 4" air gap, then I will router my side frames to increase the absorption.

Corner traps: The thd dia for the rods are in this thread, did you read it? I did spec what I used in that post, sorry don't know off the top of my head. If you make full corner traps like I did, use pink fluffy. If you make straddle the corner traps, then OC705 for bass traps.
People cover them because sound energy is a good thing, we want to manage it correctly, and over-absorbing is not ideal either, sound reflections give ambiance(sp?) and spaciousness feel to the room.
The cover will reflect the mids-highs back into the room.
post #145 of 151
Thank you for your insight. I did read you post and also looked back to see what diameter rod you used, but I wasn't able to find that info- I will look again. Milling slots in the sides could be difficult in terms of time and equipment. I'll try and think of a solid method and post back with results.
post #146 of 151
Thread Starter 

DIY construction methods of hang-able acoustic panels & moveable Corner traps...

Take a trial piece and router it then stop then again - multiple slots in the side, sorta leaves ribs then, I've seen on gearslutz some do it that way.


Via my iPhone 5s using Tapatalk
post #147 of 151
Thread Starter 
See what localhost127 did with his, maybe that is easiest for you?
Quote:
Originally Posted by mtbdudex View Post

-localhost127 built his own side wall 4" thick 2' x 4' panels with exposed sides for more absorption , post # 86 here http://www.avsforum.com/avs-vb/showthread.php?p=20271296#post20271296




Quote:
Originally Posted by carter840 View Post

Thank you for your insight. I did read you post and also looked back to see what diameter rod you used, but I wasn't able to find that info- I will look again. Milling slots in the sides could be difficult in terms of time and equipment. I'll try and think of a solid method and post back with results.
post #148 of 151

great info thanks

post #149 of 151

Looking for a little guidance on soffit style corner bass traps.  I was originally planning to build some of the style Eric2000 describes above.  Then I decided that I would get more benefit from square/rectangle style traps since they will be behind a false wall that houses my LCR and subwoofer.  This is a crude sketch of the soundstage as planned:

 

 

There are 7 traps that are approx. 23" x 23" x 42" in size and 5 smaller traps approx. 18" x 18" x 42".  The concept I'm working on to attach the traps and avoid compression of the R-30 pink fluffy (raw insulaton that's 9" thick in a roll of 25' so 2x + 5" slit for the larger traps and 2x for smaller traps) is to make "socks" out of burlap and hang from the back wall.  I'm wondering if I should be concerned about sag causing compression over time and reducing the overall impact as I'm trying to have an effect below 50 Hz?  I've read on other sites that 3.5' or 42" is about the max before the material starts compressing on itself.  Do others agree?  I'm trying to avoid the wood frames from Eric2000's design to maximize the absorption.  The burlap sock is basically just to keep the insulation tidy and provide a means to hang it to the drywall (so I don't need paper backed material).  Any other thoughts or suggestions?  I'm also planning to fill in some of the other open spaces shown as I have a real issue in my space with echoes and long decay times.

post #150 of 151
Thread Starter 
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.
Edited by mtbdudex - 3/8/14 at 3:03pm
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