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DIY Covid19 @ home limp mass vinyl bass trap build
Old 13th April 2020
Here for the gear

DIY Covid19 @ home limp mass vinyl bass trap build

Howdy all,

Long time reader, first time poster. I am trying to use this time spent at home due to Covid-19 to improve the acoustics of my control/mix room. This is for a home based project mix room, so no double walled construction, no floating floors, etc. I'm not expecting perfection, but improvement to the best of my ability and budget. My room is pretty large with a high ceiling which has a slanted 5 degree pitch, with the high wall on the back side (behind mix position) and the low wall in front behind the speakers. Here are the stats:

L = 16' 5"
W = 14' 4"
H (low wall) = 9' 6"
H (high wall) = 10' 6"

This room is about 235sq/ft

There is also an adjacent closet/storage area space to this room, currently with an open door frame and no door. It's dimensions are roughly as follows:

L = 11' 5"
W = 3' 11"

For all of the above, see the attached 2D overhead image for a more detailed account of the measurements, as there are some variations in the size of the spaces, such as a cutout area within the closet, and a non-movable built-in bookshelf in the main mix room.

I currently have no sound absorbing material in the room other than book shelves with a number of books in them (including EVERY issue of TapeOp!). What I have at my disposal from a previous studio that I was part owner of, are around ten or twelve 4' x 8' x 1.5" thick professionally made broadband (mostly HF, I believe treating down to about 1KHz) sound insulation boards that use what looks like OwensCorning 703 hardpressed fiberglass material, aluminum frames, fabric covering. I have been doing some reading on limp mass vinyl (also known as Loaded Mass Vinyl, or LMV) bass traps which seem to be the way to go for both "bang for the buck" and space saving reasons. In reading around various websites, there are a number of different ways to construct them. All of them similar, but all having slight variations in size and materials used. A few professional companies sell resonator bass traps such as this, and they measure 2' x 4' x 8" or 10" thick design, consisting of a fabric face, 2" of 703, an airgap of I'm guessing 1", then the suspended limp mass vinyl, then the remaining 7" is empty air space within the enclosure (an example of this can be found here; . This type of design is supposed to treat low end frequencies down to 100Hz. I've read that is design can treat as low as 40Hz, depending on the density of the LMV and the thickness used of the 703 in the front of the design.

What I would like to do is try to use my 4' x 8' x 1.5" thick 703 boards to build two large front corner bass traps. Given what is being sold on the market, and what I've read others are building, it seems like building two large bass traps using the method below would provide great full frequency absorption down to at least 100Hz, if not lower given the volume and size of the design I am proposing. Here is what I was thinking:

*A large 4' wide x 8' tall x 10" deep box constructed of 3/4" plywood sides and back.
*The front of the box has 2 of my existing 4'x 8'x 1.5" deep boards sandwiched together, totaling 3" thick, held in place by 1x1 trim boards.
*Air gap of 1"
*Suspended sound deadening MLV 1.5 LB (29 STC) measuring 4' x 8' held in place with 2x2 boards (sandwiched between and stapled and sealed with silicone or green glue).
*Empty air space in the rear totaling roughly 5" to 6" (I have also read that some people have used R13 insulation in the back of these designs, so long as it does not come into contact with the MLV and prevent it from freely resonating).

I know that the above plan would make a difference, but I don't have any math to prove it as of yet, nor measurements. I have used the amroc room mode calculation website ( to roughly determine the modes of my room, however, I am averaging the room height as 10' given that the site does not allow for a slanted ceiling calculation, and it does not take into account the adjacent room. I am not too concerned with this, as I could frame up a solid core door between the rooms in a weekend to mostly eliminate that open space.

Is the above undertaking a worthwhile project to help with the overall sound of my mix room? I'd like to spend my money on acoustic treatment as wisely as could be, which is why precise measurements and calculations would certainly help. Before going to town, should I use REW to get a sweep of the room first? And if so, should I empty the room out first of all furniture, gear, equipment, etc? The two best rooms that I have ever mixed were both acoustically treated using about 30% calculations and 70% a combination of ears, time, and fixing as you go and get used to the environment. I am used to this approach, and think that the above would be a start in the right direction to really help deal with the low end issues, then I could start to hit the room with a combination of using the remainder of my 4' x 8' 703 boards as clouds above the mix position, and then build some quadratic diffusors for the side walls and center front wall.

I welcome all feedback and look forward to reading any and all comments.


Old 13th April 2020
Lives for gear
avare's Avatar

+1 to shooting the room. what is of interest is decay rate and waterfall plots.
Old 13th April 2020
Here for the gear

@ avare , any recommendations as to software? REW? FuzzMeasure? Also, should I take out any of the furniture that I plan on taking out of the room? Thank you for the quick response!

Old 13th April 2020
Lives for gear
avare's Avatar

Originally Posted by silvertone77 View Post
@ avare , any recommendations as to software? REW? FuzzMeasure? Also, should I take out any of the furniture that I plan on taking out of the room? Thank you for the quick response!

You already mentioned REW. Use it. Leave the furniture as you intend to place them. You are welcome.
Old 8th August 2020
Here for the gear
Hey Tim did you end up building these?? I’m in the same exact boat and was hoping someone would chime in with some more details. Like you I want some real big broad band bass traps Like what you’re talking about
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