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Acoustical Treatments Master Thread - Page 312

post #9331 of 10165
Quote:
Originally Posted by pepar View Post

So, then it is likely only aesthetic and "green" .. it is reclaimed wood ... and it absorbs.

Thanks for your insights.

Jeff

Seems to be, yes. A great cause and effect!
Quote:
Originally Posted by angryht View Post

I have a question regarding ceiling treatments. I believe that I'm getting quite a bit of reflection from the ceiling from the center speaker. I have some 1" thick linacoustic and my plan was to build a frame 4' by 4' (out of 1" x 2" furring strips) and stretch some black ponte fabric (speaker grill fabric) over it. Then I was going to set the 1" linacoustic in the frame and hang it from the ceiling using hooks and eyes. I would not be covering the entire ceiling just the sections as determined by the mirror test. Does this make sense? I realize the ponte is not fire resistant but I would not be covering an entire wall or ceiling and there are not any lights on the ceiling, just wall sconces.

Yep - that would do the trick!

Something to keep in mind: Even though a 48" x 48" piece of 1" thick Linacoustic isn't terribly heavy, your panel will likely sag a lot if you don't add any cross braces. Its almost impossible to stretch fabric tight enough on a 48" x 48" frame to hold it up. A brace down both directions in the center should be enough. Having that said, its probably possible to do without cross braces - but you'll likely get much better results with the cross braces.

Also, you could double up the Linacoustic so you have a 2" thin panel instead, which will absorb to a lower frequency. Hanging it down from the ceiling a couple inches will also help in the same retrospect.
post #9332 of 10165
Quote:
Originally Posted by Dennis Erskine View Post


Do not place a subwoofer such that the driver is aimed into the seating locations (in a residential sized room). If you do, you should place a 1" thick piece of 1.5 PCF fiberglass in front of the driver. Sometimes it requires 2".
FOH...let's avoid this terminology. Perhaps better as where the x.x wave length is longer than the room dimension. There is too much misunderstanding about "bass not fitting into a room".

 

I placed my two subs in the middle of the side walls of my listening position as suggested by Toole!

post #9333 of 10165

On an other not can I use my fireplace as a bass trap I never use it to much pollution :(

post #9334 of 10165
Quote:
Originally Posted by wse View Post

On an other not can I use my fireplace as a bass trap I never use it to much pollution frown.gif

Of course you can, but there may be better places to trap in the room as well. Do you have your corners treated at all?
post #9335 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

Something to keep in mind: Even though a 48" x 48" piece of 1" thick Linacoustic isn't terribly heavy, your panel will likely sag a lot if you don't add any cross braces. Its almost impossible to stretch fabric tight enough on a 48" x 48" frame to hold it up. A brace down both directions in the center should be enough. Having that said, its probably possible to do without cross braces - but you'll likely get much better results with the cross braces.
You certainly got that right. I built the frame and stretched the fabric as tight as I could and stapled it to the opposite side as the frame. I even broke one of the sides and had to replace it. I was expecting a little sagging due to the weight of the linacoustic and I got some (about 1 inch in the middle). If I put in braces in the from the center of each side to the opposite side, I would still need to staple to the exposed side to gain any benefit from the bracing, right? That was what I was trying to avoid but maybe 4' by 4' is too large. I probably should have built 2' by 2' frames. Otherwise I would need to staple the fabric to the braces and maybe paint the exposed staples. I suppose I could use velcro to stick the underside of the fabric to the braces. Is that typical? That way I could double up the linacoustic and hang it about an inch from the ceiling as you suggested. I really appreciate your input!
post #9336 of 10165
Quote:
Originally Posted by angryht View Post

If I put in braces in the from the center of each side to the opposite side, I would still need to staple to the exposed side to gain any benefit from the bracing, right?

Well, this depends. If the sagging was from the fabric and you just weren't able to pull tight enough, then yes, you'd need to staple the side showing the room (or you might be able to use adhesive). But if the sag was due to the Linacoustic and NOT the fabric, then the cross brace would hold the Linacoustic up so the fabric wouldn't sag.
Quote:
Originally Posted by angryht View Post

That was what I was trying to avoid but maybe 4' by 4' is too large. I probably should have built 2' by 2' frames.

24 x 48 frames still work quite well since one of the sides is 24". This means the whole thing will still be quite tight. I've even built some 4' x 8' traps that don't sag, but I didn't have the same problems as I built a fabric frame out of 1x2s that I inserted into the main 4' x 8' frame, which gave me a lot more freedom to mend the fabric around to get it tight.
Quote:
Originally Posted by angryht View Post

Otherwise I would need to staple the fabric to the braces and maybe paint the exposed staples.

This is an option. Depending on how wide your cross braces are, you might be able to use spray adhesive. Just spray it on the bottom of the cross brace and along the path the crossbrace would meet on the fabric, insert it into the frame above the fabric (on a flat surface, obviously). You can add your Linacoustic in to give it a bit of weight to help the adhesive set.
Quote:
Originally Posted by angryht View Post

Otherwise I would need to staple the fabric to the braces and maybe paint the exposed staples. I suppose I could use velcro to stick the underside of the fabric to the braces. Is that typical?

Not sure about it being "typical" but it might work. Not really the person to ask though, as I'm not an experienced user of velcro. biggrin.gif
post #9337 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

Well, this depends. If the sagging was from the fabric and you just weren't able to pull tight enough, then yes, you'd need to staple the side showing the room (or you might be able to use adhesive). But if the sag was due to the Linacoustic and NOT the fabric, then the cross brace would hold the Linacoustic up so the fabric wouldn't sag.

Okay, forgive me for getting too far into the weeds on this one, and thank you for the help.

The fabric is pulled tight enough so that there is no sag when the Linacoustic is not being suspended by the frame/fabric. When the Linacoustic is placed on the fabric, there is a sag. So, I think what you are saying by 'if the sagging is from the fabric and you weren't able to pull tigh enough', is that the sag is from the fact that the fabric is not tight enough to prevent the sag. - Gosh, when I type it like that it seems intuitively obvious that is what you meant. And the reason that it is not as tight as it could be is because there is a lack of bracing which prevents pulling tight enough to get it even tighter. So, one option would be to remove the fabric, insert the cross braces and then reinstall the fabric tight enough (fingers crossed) that there is no sag. Otherwise, do you mean to put in the cross braces and have the Linacoustic to be placed over that part of the frame?
Quote:
24 x 48 frames still work quite well since one of the sides is 24". This means the whole thing will still be quite tight. I've even built some 4' x 8' traps that don't sag, but I didn't have the same problems as I built a fabric frame out of 1x2s that I inserted into the main 4' x 8' frame, which gave me a lot more freedom to mend the fabric around to get it tight.

I'm not sure I understand this approach. Does that mean that you first built a frame 4' x 8' then made smaller fabric covered frames to fit inside them? Just trying to picture it.
post #9338 of 10165
I think I understand what you're asking and I think you've got it, but let me clarify anyways.

The cross brace can be used in two ways: to hold the JM up and/or to hold the fabric up.

If the fabric doesn't sag without the JM, then insert the cross braces so it holds up the JM and it won't make your fabric sag.

If the fabric sags anyways, then you can affix the fabric to the cross braces by staples or adhesive, whatever you choose, and it will still provide support to hold up the insulation as well.

Edit: I should clarify that the cross braces need to be actually attached to the outer frame, not simply "sitting" in. I think this caused the confusion.

Quote:
Originally Posted by angryht View Post

I'm not sure I understand this approach. Does that mean that you first built a frame 4' x 8' then made smaller fabric covered frames to fit inside them? Just trying to picture it.
I made one 4' x 8' frame (with crossbraces) that had the fabric wrapped around it, and that was inserted inside a slightly bigger than 4' x 8' frame. So yes, what you said is correct, only that it was one large inside frame instead of multiple smaller frames. Though, many small ones would also work in this circumstance.

A last option can be to use appearance grade finished wood or molding to do a 4 window frame. You could fix this to the outside of the frame/fabric which will hold both the JM and fabric up (and look pretty cool too, but obviously be more work and more cost)
Edited by GIK Acoustics - 1/24/13 at 11:43am
post #9339 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

The cross brace can be used in two ways: to hold the JM up and/or to hold the fabric up.

If the fabric doesn't sag without the JM, then insert the cross braces so it holds up the JM and it won't make your fabric sag.

Clarified! And quite well I might add.
Quote:
Edit: I should clarify that the cross braces need to be actually attached to the outer frame, not simply "sitting" in. I think this caused the confusion.
I made one 4' x 8' frame (with crossbraces) that had the fabric wrapped around it, and that was inserted inside a slightly bigger than 4' x 8' frame. So yes, what you said is correct, only that it was one large inside frame instead of multiple smaller frames. Though, many small ones would also work in this circumstance.

Got it.
Quote:
A last option can be to use appearance grade finished wood or molding to do a 4 window frame. You could fix this to the outside of the frame/fabric which will hold both the JM and fabric up (and look pretty cool too, but obviously be more work and more cost)
I like that idea to dress it up a bit. I have linacoustic on my walls and I've been meaning to cover it with fabric, but I haven't yet.

On another note: Previously, I had cut my Linacoustic RC (1" thick) into triangles and just set them (superchunk style - triangles stacked against each other) along the floor to wall corners and from floor to about 3 or 4 feet up. The triangles are about 10" by 10" by whatever the hypotenuse (~14"). I always thought that those would be somewhat effective bass traps but since they were not wrapped in fabric, I did not like them because they 'shed' fiberglass a lot. I have since removed them from the room and I am now wondering about wrapping them in fabric. Since the Linacoustic has very little stiffness, I imagine it that this would require a triangular frame on each end (thin plywood or even fur 1"x2" in a triangle) and some type of straight piece to attach the fabric to. Long story short, would it be more effective to double or even quadruple the 1" Linacoustic in a frame to straddle corner? I've seen that most people like to use the OC 700 Series for this because of the stiffness. I have looked at bobgolds.com to check the coefficients for the materials, just wondering about doubling them up and their effectiveness in bass trapping (the Linacoustic that is).
post #9340 of 10165
I thought I'd share my some build pictures of my N31+6 panel. Built with 3/16" gatorboard and hot glue. The cavities will be filled with OC703. Should be finished and installed tonight on the back wall! Hopefully will turn my little room into a concert hall. smile.gif


post #9341 of 10165
How many dozens of feet are there between this assembly on the back wall and the nearest listening position?
post #9342 of 10165
Quote:
Originally Posted by Dennis Erskine View Post

How many dozens of feet are there between this assembly on the back wall and the nearest listening position?

dozens?

with what looks to be approx 7" max well depth only requires approx ~4' 2" to be considered in far-field.

+/- error from the mkI eyeball.
Edited by localhost127 - 1/25/13 at 5:23am
post #9343 of 10165
Quote:
Originally Posted by HaroldKumar View Post

I thought I'd share my some build pictures of my N31+6 panel. Built with 3/16" gatorboard and hot glue. The cavities will be filled with OC703. Should be finished and installed tonight on the back wall! Hopefully will turn my little room into a concert hall. smile.gif

looking great! no need to fill the cavities with expensive oc703 - pink fluffy will do (cheaper and easier to stuff); just to limit resonance within the cavities.

make sure the wells/air-gaps/cracks are fully sealed to limit unwanted absorption!
post #9344 of 10165
Quote:
Originally Posted by localhost127 View Post

dozens?

with what looks to be approx 7" max well depth only requires approx ~4' 2" to be considered in far-field.

+/- error from the mkI eyeball.

Good eye! yes, 7" well depth, and you nailed the 4'2. here's the plan in QRDude:



Diffuse to 812 hz, scatter 406 hz. My seating postition is 6 feet.

My carpenter did an amazing job, all the depths are accurate and it's attractive. The black gator board works well. Very solid feeling, yet it's only 15 lbs if that. Cedar frame looks and smells good. smile.gif

I will post some listening impressions soon.

Correction: weight is about 40 lbs.
Edited by HaroldKumar - 1/26/13 at 10:05am
post #9345 of 10165
wicked.

HT or 2channel setup?

you could always bring the QRD out from the rear wall 1.5ft or so and construct a false wall from the QRD and make the rest of the rear wall (around and behind the QRD) a giant porous LF absorber filled with pink fluffy attic insulation for additional LF absorption.
post #9346 of 10165
Quote:
Originally Posted by localhost127 View Post

wicked.

HT or 2channel setup?

you could always bring the QRD out from the rear wall 1.5ft or so and construct a false wall from the QRD and make the rest of the rear wall (around and behind the QRD) a giant porous LF absorber filled with pink fluffy attic insulation for additional LF absorption.

It's HT, but using 50/50 music. Music is 2.1x3 using Oppo 105 analog outs. That's a good suggestion on the back wall but I don't want to give up that much space in an already small room and I'm eating up 2.5 feet of the front wall with AT screen. I am going to soon do a retractable so the screen is out of way for music listening. For bass traps I straddle 4" OC703 on corners where I can and also ceiling to walls. I'm going to be doing some tidying up and paint and spackle this weekend. After that I'll get some pictures.
post #9347 of 10165
Quote:
Originally Posted by angryht View Post

On another note: Previously, I had cut my Linacoustic RC (1" thick) into triangles and just set them (superchunk style - triangles stacked against each other) along the floor to wall corners and from floor to about 3 or 4 feet up. The triangles are about 10" by 10" by whatever the hypotenuse (~14"). I always thought that those would be somewhat effective bass traps but since they were not wrapped in fabric, I did not like them because they 'shed' fiberglass a lot. I have since removed them from the room and I am now wondering about wrapping them in fabric. Since the Linacoustic has very little stiffness, I imagine it that this would require a triangular frame on each end (thin plywood or even fur 1"x2" in a triangle) and some type of straight piece to attach the fabric to. Long story short, would it be more effective to double or even quadruple the 1" Linacoustic in a frame to straddle corner? I've seen that most people like to use the OC 700 Series for this because of the stiffness. I have looked at bobgolds.com to check the coefficients for the materials, just wondering about doubling them up and their effectiveness in bass trapping (the Linacoustic that is).

Is your question: "Should I go with a 10" x 10" x ~14" super chunk vs. a 4" thick standard size absorber straddling the corner" ?

I'm not too sure honestly, I've never used a superchunk that sized before but it is quite small. I would think you will get similar results. If you already have the pieces cut into triangles, it seems the path of least resistance. Perhaps you can put the triangles back in, and build a standard 4" thick absorber, and just cover the triangles unwrapped with the standard panels? Just an idea.

The first absorber I ever built myself was made from four 1" thick sheets of JM to make a 4" thick 24x48" absorber. They worked good enough. I ripped the dark side (the "RC") off the panels when I quadrupled them up so the GFR wouldn't be changing every inch back and fourth. Not sure how they would perform otherwise (but I don't suspect them to be insanely different either way).
post #9348 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

Is your question: "Should I go with a 10" x 10" x ~14" super chunk vs. a 4" thick standard size absorber straddling the corner" ?

That's exactly what I am asking and it looks like you answered below. Thanks again.
Quote:
I'm not too sure honestly, I've never used a superchunk that sized before but it is quite small. I would think you will get similar results. If you already have the pieces cut into triangles, it seems the path of least resistance. Perhaps you can put the triangles back in, and build a standard 4" thick absorber, and just cover the triangles unwrapped with the standard panels? Just an idea.

That's a good idea. It seems like there are a lot of directions I could go and utilizing the triangles I already have cut covered with a larger panel absorber might just be the ticket.
Quote:
The first absorber I ever built myself was made from four 1" thick sheets of JM to make a 4" thick 24x48" absorber. They worked good enough. I ripped the dark side (the "RC") off the panels when I quadrupled them up so the GFR wouldn't be changing every inch back and fourth. Not sure how they would perform otherwise (but I don't suspect them to be insanely different either way).

Wow, you read my mind about the RC. I was wondering about removing the reinforced coating when doubling (or quadrupling) things up. Since I just doubled up, I ended up putting the RC on the outsides of the doubled up sandwich. I have always heard that the RC should be put towards the room side when placed on a wall so I thought having it on the outside was appropriate. If I go quadruple, I guess I'll take it off.

And speaking of building one's first panel. . . I finished mine and hung it. It’s 4’ by 4’ by 2” thick (doubled the linacoustic) and has a little over an inch gap between it and the ceiling. Thanks to your suggestion, I put in a couple cross braces to remove the sag in the fabric due to the weight of the Linacoustic and it worked like a charm. Mounted it so it’s rotated 45 degrees from the outside walls (askew) to cover more of the reflective area as determined by the mirror method, and because the kids said it would look cool. It’s big and I love the look.

A few pics:







Thank you again for your help.

Now that I'm getting the hang of this fabric stretching, it's time to look for some fire rated material for my walls.
post #9349 of 10165
Kudos - great work!
post #9350 of 10165
Thanks.
post #9351 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

Yes! Depth of the diffusor will determine how low in frequency it diffuses to (but this also requires being farther away from it to gain the benefits). Likewise, the width of the wells will determine the high frequency cut-off of the diffusor.
I don't work for Auralex, but I'm quite sure I can confidently say yes - filling the cavity behind the T-Fusors with fiberglass will result in some low-mid to mid frequency absorption. It won't necessarily enhance the performance of the diffusors though (as in, it won't change the working frequencies of them)
The only product Auralex makes (that I'm aware of) labelled as a diffusor at a thin depth is the MetroFusor. It is slim at 2" of depth. While the product does work (I don't want to say that the product is a sham, as it isn't) it is VERY limited by the size. As I've stated above, depth of the diffusor determines how low the diffusor works. Diffusors 2" or thinner will not give you any considerable diffusion for anything other than very high frequencies. Building your own or purchasing MUCH thicker diffusors would be much more beneficial IMO.
Could you find a link to a similar product? I've never seen something like this sold in stores. Concave and convex shapes such as these are typically bad though, as they focus sound and typically don't offer great spacial diffusion.
Different depths are more beneficial in different places. To be general, you can be closer to a diffusor that only diffuses high frequencies than you can to a diffusor that diffuses mid and hi-mid frequencies. You usually don't want to be within a few feet of a wide performing diffusor.

I really appreciate the in depth response and it certainly helps. I also watched all of the video's on your site regarding diffusion and placement. My room design started with similar ideals to what you have on your site so the start is good. Front corners are floor to ceiling 2" OC703 chunk traps. Entire front wall is 1" OC 703 with an air gap, equipment rack in the back corner has a removable back panel that is 3' x 5' and that is a panel based bass trap to work on the upper bass frequencies (airgap is between the resonant panel and the 2" OC 703).

Plan right now is to use the remaining 2" OC703 I have to treat the first reflection points for all listening positions and then use diffusion on the rest. My back wall is roughly 2.5' from the rear row listening position. The original plan was to use an array of the mini fusors there but I am not sure if I will do that at this stage.

I am certainly not afraid to construct my own diffusors and I have a radius based design stuffed with OC703 that I am considering. I will post pics. as I make progress in my treatment fabrication.
post #9352 of 10165
Sounds like you're definitely on the right path. I would look into diffusors roughly twice as deep as the MetroFusors (around 3-4" deep). You can use these on your back wall but also the rear side walls, and even the rear ceiling as well.
post #9353 of 10165
Quote:
Originally Posted by GIK Acoustics View Post

Sounds like you're definitely on the right path. I would look into diffusors roughly twice as deep as the MetroFusors (around 3-4" deep). You can use these on your back wall but also the rear side walls, and even the rear ceiling as well.

Thanks for the advice. I just measured the mini fusors and they are 5" deep. I currently have about 15 of them and can at least try them out stuffed with OC and see how they work.
post #9354 of 10165
Quote:
Originally Posted by HaroldKumar View Post

I thought I'd share my some build pictures of my N31+6 panel. Built with 3/16" gatorboard and hot glue. The cavities will be filled with OC703. Should be finished and installed tonight on the back wall! Hopefully will turn my little room into a concert hall. smile.gif



Did you buy 4x8 sheets... If so how many did you get and where?
post #9355 of 10165
I bought all the pieces pre-cut (1/16 tolerance) from 8x4' at www.artsupply.com. Just email Mira and tell her what you need. It's $71 per 8x4 sheet cut how you want. Since I had mine cut into 32" high pieces shipping charges were only $30 for 3 boards.
post #9356 of 10165
Harold, how did you fix the well depth, i.e. the location that the "bottom" piece would be glued?
post #9357 of 10165
Pepar, I had a carpenter build it, he's a former architectural model maker and has been gluing foam for 30 years. so he's got skills.

I watched him put some pieces on. He basically glued a well and a fin together on the table, then placed the piece into the frame, and hot glued it from the back. The skill is he uses just the right amount of glue to seal everything, but without any oozing or bubbles or trailers.

I can tell you my wife commented on how beautiful it is. If anyone's interested PM me, he is out of work, so maybe he can build some more.

I'll post some pics of it on the wall tomorrow.

OK, on the important part....... This thing sounds amazing, it really does make the room feel bigger, a lot bigger quite frankly. If sometimes you feel like Stan Getz is 10 feet tall and blowing his horn 3 feet away from you, try a QRD diffuser, he'll get back on stage.
post #9358 of 10165
Quote:
Originally Posted by HaroldKumar View Post


OK, on the important part....... This thing sounds amazing, it really does make the room feel bigger, a lot bigger quite frankly. If sometimes you feel like Stan Getz is 10 feet tall and blowing his horn 3 feet away from you, try a QRD diffuser, he'll get back on stage.

smile.gif

identify any other boundaries incident of later-arriving sparse energies and continue to place RPGs there!
post #9359 of 10165
I have 10 RPG skyline diffusors that I got a great deal on. I've been experimenting with them, but they don't seem as effective as the QRD. That could be because my custom QRD is huge around 2100 sq inches. One place I liked the RPGs was on floor like a mat at first reflection point. A studio friend says put the RPGs on ceiling directly above seating position. I'm only using two right now on the front wall between speakers. I could put a bunch on front wall and/or ceiling. Another possible location is sidewalls up high.

Can you have too much diffusion?
post #9360 of 10165
Quote:
Originally Posted by HaroldKumar View Post

I have 10 RPG skyline diffusors that I got a great deal on. I've been experimenting with them, but they don't seem as effective as the QRD. That could be because my custom QRD is huge around 2100 sq inches. One place I liked the RPGs was on floor like a mat at first reflection point. A studio friend says put the RPGs on ceiling directly above seating position. I'm only using two right now on the front wall between speakers. I could put a bunch on front wall and/or ceiling. Another possible location is sidewalls up high.

Can you have too much diffusion?

The QRDs you are building and the "Cityscapes" are different tools. I got a good deal on some of the latter as well, but I am thinking what I should use are QRDs....
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