Materials to use?

[Davemcc]

I find my room too bright sounding and want to tone down the highs a bit. I understand that panels can be used on the walls to prevent high frequency reflections. I'm wondering what materials to use to make such panels.

I have a bunch of foam underlay, like what's used under laminate floors. Would this work alright if mounted on a board and covered in cloth to prevent reflections? What are the best materials for this purpose?

 

[jaxvon]

I find my room too bright sounding and want to tone down the highs a bit. I understand that panels can be used on the walls to prevent high frequency reflections. I'm wondering what materials to use to make such panels.

I have a bunch of foam underlay, like what's used under laminate floors. Would this work alright if mounted on a board and covered in cloth to prevent reflections? What are the best materials for this purpose?

Dave,

The best materials depend on what frequencies you're trying to absorb. That type of foam would probably not be the best. High-grade acoustical foam, such as that found in Echobusters branded panels is insanely expensive. The best choices for sound absorbing panels are rigid fiberglass and mineral wool. Both of these products are fairly inexpensive and come in nice, large, rectangular shapes, often 2'x4', and in thickness ranging from 1"-6" generally. If you choose to go with mineral wool, you might think about adding an extra layer of cloth or perhaps some thin speaker fill fluff that comes on a roll to act as a filter. The fibers from mineral wool are really, really bad for your lungs and you don't want to end up inhaling them. I do not know if a single layer of cloth would suffice, as most acoustically transparent cloth is fairly coarse in weave. Bear in mind that it is important that you use such material instead of any old fabric, as cloth that is not designed for acoustical purposes can actually reflect high frequencies! If you decide to go wild with building treatments, you might also choose to build some large bass traps, such as the Tri-Traps made by GIK. Again, high-density mineral wool is an excellent choice here.

 

[Scott R. Foster]

There are a couple of tested DIY porous absorber designs here:

http://forum.studiotips.com/viewforum.php?f=8

If you truly could only benefit from High frequency absorption [hard to believe] then 1 or 2 inch upholstered mineral fiber panels should do the trick.

Good Luck!

 

[Davemcc]

Thanks,
I've managed to tame the sub somewhat using the parametric eq down to a 6db gain at 40hz. At my normal listening levels, I can live with that for a while. But when I do turn it up, the highs really punish first and I've already got -4db on the treble. I probably will do bass treatments in the near term, but for now, I've got to tame the higher frequencies.

 

[Scott R. Foster]

Dave:

Buy or build broadband absorbers... and you'll spend less, and work less, because there will be no "later chores". You'll also get better results.

It makes no sense to treat half the problem when you can treat the whole problem for a tiny increase in time/cost... given all the trouble/expense of buying/building and mounting porous absorber treatments, adding a couple of inches to the thickness to yeild units that work on lows as well as mids and highs is trivial.

That's my $0.02 anyway - Good Luck!

 

[Glenn Kuras]

Thanks,
I've managed to tame the sub somewhat using the parametric eq down to a 6db gain at 40hz. At my normal listening levels, I can live with that for a while. But when I do turn it up, the highs really punish first and I've already got -4db on the treble. I probably will do bass treatments in the near term, but for now, I've got to tame the higher frequencies.

For higher frequencies you can get away with using 2" OC703 or 4 pound mineral wool, but as Scott pointed out you may want to really think about bass control. For bass control it is best to use no less then a 4" panel and should really be straddling the corners of the room. Placing a 4" panel directly on the wall (or spaced off the wall 4") will help, but straddling is going to be the key. If you would like take a look at your test data to see the difference between panels on the wall vs straddling.

Good luck on your room,

Glenn

 

[Davemcc]

I've gone through both your Ready Acoustics and GIK websites and followed some links that make me remember something. Six or seven years ago, my wife worked at a building supply company that is an Owens Corning dealer. During that time, we had a contractor do some work on our furnace room walls. I remember we talked about using accoustic insulation around the furnace room, but since my wife worked at the supplier, I let them work out the details.

What I have down there is a dense yellow fiberglass padding four inches thick, four feet tall and 16" wide (cut by the contractor to fit the wall studs, I presume). I pulled a bat and stood it up in the corner by my sub and retested with Avia. It seems to have cut my 40hz spike by 2dB. So I grabbed another and stood it up in the opposite front corner and retested. I got slightly different results, so I did it again with another bat standing in a third corner. (There is no fourth corner - hallway.) The third test shows a slightly different graph, maybe even within the margin of error of trying to record a static point on an LFE sweep, but the final graph does look slightly smoother. I tried some music that I'm familiar with and the bass seems tighter and the highs less bright, but that's pretty subjective and I have no way to put any numbers on tighter bass or high frequency changes.

Is anybody familiar with an Owens Corning fiberglass product that is yellow and 4" thick? Is it worth the time and expense to make some proper 8' tall corner baffles out of this stuff? I hope so because my basement is full of it, but I don't know exactly what it is.

 

[Glenn Kuras]

I've gone through both your Ready Acoustics and GIK websites and followed some links that make me remember something. Six or seven years ago, my wife worked at a building supply company that is an Owens Corning dealer. During that time, we had a contractor do some work on our furnace room walls. I remember we talked about using accoustic insulation around the furnace room, but since my wife worked at the supplier, I let them work out the details.

What I have down there is a dense yellow fiberglass padding four inches thick, four feet tall and 16" wide (cut by the contractor to fit the wall studs, I presume). I pulled a bat and stood it up in the corner by my sub and retested with Avia. It seems to have cut my 40hz spike by 2dB. So I grabbed another and stood it up in the opposite front corner and retested. I got slightly different results, so I did it again with another bat standing in a third corner. (There is no fourth corner - hallway.) The third test shows a slightly different graph, maybe even within the margin of error of trying to record a static point on an LFE sweep, but the final graph does look slightly smoother. I tried some music that I'm familiar with and the bass seems tighter and the highs less bright, but that's pretty subjective and I have no way to put any numbers on tighter bass or high frequency changes.

Is anybody familiar with an Owens Corning fiberglass product that is yellow and 4" thick? Is it worth the time and expense to make some proper 8' tall corner baffles out of this stuff? I hope so because my basement is full of it, but I don't know exactly what it is.

Sir you are sitting on a TRESURE CHEST!!!!!!!! OC 703 or OC 705 is used all the time and that is what I bet you have. If you have a butt load of it, cut it into triangles (17x17x24 inches) and stack them floor to ceiling in as many corners as you can. You will be amazed by the sound quality. If you are making just panels it really is best to have a 24 inch spanning a corner if you can.

That stuff can also be used for the reflections in the room.


Glenn

 

[Davemcc]

I had a few minutes to speak with my wife last night and she thinks the product is not OC, but is from Roxul. I did a little check and sure enough, not only is Roxul an actual insulation company, but I have what appears to be their mineral wool insulation. Jeez, I've got to have about 40 bundles of this stuff downstairs in the walls and ceiling, some of which I can easily grab. No wonder I couldn't hear what my teenagers were doing down there.

So you think it would be OK to make up some frames, lay in the Roxul and cover it with some speaker cloth? Then I could make some corner frames, lay in the triangles and cover that with speaker cloth as well?

Thank you for your input. I've already started to see the dramatic difference even the simplest room treatment makes. This morning I just stood two bats up behind against the wall behind my main speakers and the difference is remarkable.

 

[Glenn Kuras]

I had a few minutes to speak with my wife last night and she thinks the product is not OC, but is from Roxul. I did a little check and sure enough, not only is Roxul an actual insulation company, but I have what appears to be their mineral wool insulation. Jeez, I've got to have about 40 bundles of this stuff downstairs in the walls and ceiling, some of which I can easily grab. No wonder I couldn't hear what my teenagers were doing down there.

So you think it would be OK to make up some frames, lay in the Roxul and cover it with some speaker cloth? Then I could make some corner frames, lay in the triangles and cover that with speaker cloth as well?

Thank you for your input. I've already started to see the dramatic difference even the simplest room treatment makes. This morning I just stood two bats up behind against the wall behind my main speakers and the difference is remarkable.

If it is between 4 pound and 8 pound you should be fine. The only thing is you are going to have to frame it due to mineral wool not being able to hold its shape over time.

Glenn

 

[Scott R. Foster]

Dave:

Sounds like you got stuff that will work [BTW here is a pic of OC 700 series board].

Look at these pages to try and identify the product and verify its acoustic performamnce.

http://www.owenscorning.com/comminsul/products.asp?product=1&system=83

http://www.roxul.com/sw10392.asp

http://www.bobgolds.com/AbsorptionCoefficients.htm

Use at least 4" of material, and upholster with breathable fabric.

The below graphic is from a case study on adding a dozen such panels to a small room. It has 13 frames, the first is a low frequency time/energy plot of measured reverberation resonances of an empty room, measured from the proposed listening position. An additional frame was made each time one of the 12 panels was added [RT424 4" thick broadband panels were used for this case study - but panels made from a similar rockwool material will perform likewise if unit thickness is sufficient - 4" or more].

Note how the modal resonances smooth out as panels are added. This applies not just to corner panels, but also the first reflection panels - it is a cumulative affect and illustrative of how you can benefit from using all broadband treatments as opposed to resorting to thin panels in a small room.

You can do the same thing using the material you have on hand.

Good Luck!

http://www.readyacoustics.com/index.php?go=acoustics-advice.case-study

 

[Davemcc]

There's no way to create a perfect acoustical environment in this room. It's an 11 x 14 living room (small by most standards) that has the front door, kitchen door and hallway entrance and a closet door, plus a couch and 2 chairs. With one wall dedicated to the TV and stereo, there are few options for treatment.

I've decided to build the 17" x17" x 24" x 8' towers for the only two corners that such a thing can be placed into. I'll have a 6" x 18" panel and a 6' x 24" panel in the closest I can consider opposite corners, one being the hallway and the other the front door. I'll have a 48" x 18" panel behind each speaker (each side of the TV). Plus, I'll have a 36" x 24" panel on the side wall above one chair. The other wall is a curtained picture window. That's about as much as I can fit into the room and maintain any aesthetics, given that this is the main living area.

I'm constructing (slowly) the frames now. I'll let you know how it turns out.

 

[ehurnie]

Has anyone heard of a product called UltraTouch Natural Cotton Fiber insulation. I am thinking of using this to make panels and cut into triangles and stuff in the corner to make bass traps. Here is a link with some of the properties.
http://www.acousticalsurfaces.com/wall_insulation/ultratouch.htm?d=28
Let me know what you think.

 

[Scott R. Foster]

The reports I have received from several DIY bassrtrap builders is that the cotton batts work well, but you may well get good or better results using either a semi-rigid fiberglass or rockwool product for lower costs. Check out your local commercial insulation supply houses and compare cost to stuff like 3 lbs. density fiberglass or +/- 60 kg/m3 rockwool.

It pays to shop

 

[Glenn Kuras]

Has anyone heard of a product called UltraTouch Natural Cotton Fiber insulation. I am thinking of using this to make panels and cut into triangles and stuff in the corner to make bass traps. Here is a link with some of the properties.
http://www.acousticalsurfaces.com/wall_insulation/ultratouch.htm?d=28
Let me know what you think.

If you are looking for something to use that will not make you itch then the cotton is pretty nice (see baby on website helping dad put it up ). But the cost is pretty.

Glenn