[rajacat]

I suppose this topic is similar to the previous one but instead of adding various devices, I plan to build a second insulated studded wall on the inside of the existing one both for heat insulation and sound absorption qualities.
Would this be too much of a good thing? Is it possible to make the room too dead? What kind of insulation would be best? I'd rather not go with fiberglass or mineral wool boards both for expense and lack of local availability. How about cotton? I like that it's clean and non toxic. OTOH just standard fiberglass batts would be the path of least resistance at the price of less absorption.
I've also toyed with the idea of integrating diffusion into the wall if I could find some inexpensive ones that are 3-1/2" or less in depth.

I'd like to cover the wall with Parts Express speaker cloth, corner to corner.

My current speakers are Omega Hemp Bipoles which have dual opposing drivers that, of course, fire to the front and the rear equally. In the near future I'll be building some waveguide type speakers, similar to Econowaves, that are conceptually totally different from the Omegas.

Any comments will be appreciated.

-Roy

[mikeeastman]

I used a product called Ultra-Touch which is made out of recycled blue jeans, it is denser than fiberglass so is supposed to be more absorbent in the mids. I got it from local supplier but was told it can be ordered from Homedepot , they also make one with a foil face thats used as a hot water heater blanket, which might help with heat insulation.

[jimbop]

How does "Ultra Touch" compare price-wise to fiberglass?

[Tyson]

I'm in the middle of building a couple of acoustic panels myself - I'm doing mine 4" thick.  The back half will be 2 inch compressed fiberglass, and the front half will be 2 inch thick UltraTouch cotton insulation.  I figure the combo of the 2 will give me a good, broad spectrum of absorption.

[Russell Dawkins]

I suppose this topic is similar to the previous one but instead of adding various devices, I plan to build a second insulated studded wall on the inside of the existing one both for heat insulation and sound absorption qualities.
Would this be too much of a good thing? Is it possible to make the room too dead? What kind of insulation would be best? I'd rather not go with fiberglass or mineral wool boards both for expense and lack of local availability. How about cotton? I like that it's clean and non toxic. OTOH just standard fiberglass batts would be the path of least resistance at the price of less absorption.
I've also toyed with the idea of integrating diffusion into the wall if I could find some inexpensive ones that are 3-1/2" or less in depth.

I'd like to cover the wall with Parts Express speaker cloth, corner to corner.

Any comments will be appreciated.

-Roy

I did the equivalent 17 years ago when I built my small mastering room in the basement. The wall you see is about 10" in front of the original exterior wall, which is still in place. It uses 2X6 studs and was dry walled as you can see, and an area around 4 1/2' by 12' was left open. Two layers of fiberglass batts were hung between the studs with a space between the rear one and the wall, and a space between the rear and the front batt, so they can both vibrate freely, the better to absorb bass. The top plate has openings cut into it so the space can vent into the space between the ceiling and the floor above to further extend lowest frequency absorbed. That's the thinking - I don't really know how effective hat part is.

In treating a small room it is easy to absorb treble and not so easy to absorb bass. As a result, many rooms are both "dead" and boomy.

I think you should start with some sort of wideband absorption, as you intend to do, then fine tune by selectively using HF absorption for specific purposes, like absorbing the first bounces off the ceiling, side walls and floor (that's a hard one).

I have had most success with absorptive front walls and symmetrical front halves of rooms coupled with irregularity and diffusion, or at least diffusion, in the rear half. In my studio, I had curved walls built left and right to distribute lateral modes and also to create a symmetry that otherwise wasn't there. The room sounds very good in the bass. The picture shows it nearly empty - we are in the process of moving.

For the record, in the new mastering room the first thing I did was built a wideband absorber 5' high and 9 1/2 ' wide with a 2X6 frame. Within it are hung three pieces of thick wall to wall carpet with about a 1" space between each and a similar distance to the wall behind (the front wall). This is covered with an ornamental Armenian carpet. The room already sounds nice.

Here's my original studio, as described above:

[bpape]

The Ultra Touch and the other cotton based products that I've dealt with, on a same thickness, same density basis, will outperform their fiberglass counterparts in the lower frequencies.  The drawback is the cost.

Bryan

[rajacat]

I think I'll give cotton batts a try. I also may build in some low freq. absorption into the corners by cutting the cotton into triangles, stacking them in both corners behind a frame covered with either speaker cloth or some other open weave cloth. I have to deal with a very low ceiling (7'-8").  I already have some 2" panels screwed to the ceiling joists. I also have some 6" panels that I can move here and there but too thick for ceiling use. The room is 35' x 15' x 7'-8"; long, relatively wide but low. It's a somewhat cluttered great room with an open arrangement encompassing the kitchen and dining area too.

Russel, It's interesting that you hung the batts or carpet so that they could vibrate for better bass control . BTW nice studio! That wouldn't work for me though because this is an exterior wall and I want some heat insulation. I can see that you've had to contend with a low ceiling too. I'm hoping the my upcoming waveguide speakers will help with the ceiling issue. I'm hoping that rectangular design will direct the highs away from the ceiling.  BTW here's the waveguide.

[poseidonsvoice]

Nice  I'll look forward to your project. Please post it in the lab. I've always admired Wayne Parnham's work as well as the late Zilch. There is so much to read between the both of them, that you could spend a pleasant weekend doing it (what I'm doing this weekend!).

Best of luck,

Anand.

[Russell Dawkins]

Russel, It's interesting that you hung the batts or carpet so that they could vibrate for better bass control . BTW nice studio! That wouldn't work for me though because this is an exterior wall and I want some heat insulation. I can see that you've had to contend with a low ceiling too.

Note that the wall in the picture is an outside wall, and with 2X6s for studs, you could use all the insulation you wanted behind the gyproc (dry wall) and the fiberglass I used for sound absorption in thee open section also insulates like crazy! One of the standard ways to absorb bass is a hung heavy, flexible, lossy membrane - could be a heavy curtain, an industrial conveyor belt. That's why the carpet I am now using in my latest absorber works so well in the deep bass - it's heavy!

[fishinbob]

As for your room becoming too dead that probably won't be the case. Adding a second wall is primarily done for sound transmission or like in your situation adding furring to install additional thermal insulation. I don't feel the type of in-wall insulation will make that much difference to your acoustics as it will be covered with wallboard. Go fiberglass if money is a concern.  If sound transmssion is an issue (neighbors?), adding two layers or one layer with a layer of sound board to your one sided wall would be preferable.
I'm currently doing my space with 703 mini and superchunks in the corners and have enough left for several 4" panels when I find out where I need them or more to the point, where I can get away with them.