Starting a Large DIY Project for Acoustic Absorbers/BASS Traps. Please advice.

[rimmi2002]

Hi I have a 30'W x 15'L x 10'H HT / dual use bonus room and I need to treat it for better sound (Room Schematic Below). My bass was way too boomy. I just tested by placing 9 layers of 3” x 16” x 48” Roxul Safe’n’Sound mats wrapped in breathable cotton fabric (just for trial), and it’s made a huge difference in my room acoustics already. Bass already sounds much better and it shows with a much fast decay time for lower frequency on REW measurements

I’m planning a DIY acoustic panel project (starting with many thick corner Bass traps) using Roxul Safe’n’Sound as the core absorptive material but with a strong emphasis on safety since it contains fiberglass, which ideally should be fully contained to prevent fibers leaking into the room. My goal is to optimize acoustic performance while ensuring no fiberglass escapes into the environment.

My proposed layering setup is below. Thickness will vary based on location of trap, but I am going to hit corners first to get my bass under control first as its the main culprit. AFter this is done I'll see if I'll need anything for higher frequencies and address that appropriately.

1. First layer: Wrap Roxul Safe’n’Sound batts in some simple acoustically transparent (AT) fabric. This layer is primarily for fiber containment and safety rather than acoustics. (just needs to not interfere with sound making it to Roxul Pads and do something to contain fibers from getting out)
2. Second layer: Enclose this fabric-wrapped insulation with a foam layer (I’m currently considering 1/2” thick Neoprene High Quality single-sheet foam). This layer is also for safety fiber containment—to prevent any fiberglass escape—without compromising on AT of the setup.
3. Third (outer) layer:
   1. Option 1: Cover the foam with an aesthetically pleasing and acoustically transparent (AT) fabric that will not interfere with sound absorption.
   2. Option 2: Make diffusion plates as the final outward face of the trap if my upper frequencies start decaying out of proportion to lower frequencies.
      

Specific questions I have for experienced DIYers and acoustics experts:

• How thick should I make these corner Traps. The Roxul is 16" wide so 16" x 16" is easy, but if there is benefit in going higher I can. Is there a calculator that can show a abroption profile based on material / type of trap and thickness?
• Does placing Roxul Safe’n’Sound inside a foam layer (like 3/8” to 1/2” neoprene foam) reduce or interfere with its sound absorption performance, especially at bass frequencies?
• What is the minimum foam thickness that can effectively contain fiberglass fibers, provide durability, and still maintain the panel’s acoustic efficiency? Would 1/2” neoprene be overkill? Could a thinner foam layer work just as well?
• Are there any safety or off-gassing concerns with using neoprene foam in this layered configuration inside a room?
• For the outer facing fabric, what are the best materials that combine good aesthetics, durability, and acoustic transparency (allowing sound waves to reach the Roxul core without attenuation)? I’ve heard burlap and certain synthetic fabrics are common but want recommendations on options that are both safe and visually appealing.
• From a construction standpoint, does compressing or tightly wrapping Roxul Safe’n’Sound inside these layers degrade absorption?

I also found an interesting post that mentioned for traps thicker than 8", lower density materials like R-30 (~5000 Rayls impedance) might outperform high-density alternatives (like OC 703 at ~30,000 Rayls) in bass absorption:
https://www.avsforum.com/threads/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs.1449924/

Any practical experience using Roxul Safe’n’Sound in thicker panels or bass traps under these principles?

 

[TLS Guy]

Hi I have a 30'W x 15'L x 10'H HT / dual use bonus room and I need to treat it for better sound. My bass was way too boomy. I just tested by placing 9 layers of 3” x 16” x 48” Roxul Safe’n’Sound mats wrapped in breathable cotton fabric (just for trial), and it’s made a huge difference in my room acoustics already. Bass already sounds much better and it shows with a much fast decay time for lower frequency on REW measurements

I’m planning a DIY acoustic panel project (starting with many thick corner Bass traps) using Roxul Safe’n’Sound as the core absorptive material but with a strong emphasis on safety since it contains fiberglass, which ideally should be fully contained to prevent fibers leaking into the room. My goal is to optimize acoustic performance while ensuring no fiberglass escapes into the environment.

My proposed layering setup is below. Thickness will vary based on location of trap, but I am going to hit corners first to get my bass under control first as its the main culprit. AFter this is done I'll see if I'll need anything for higher frequencies and address that appropriately.

1. First layer: Wrap Roxul Safe’n’Sound batts in some simple acoustically transparent (AT) fabric. This layer is primarily for fiber containment and safety rather than acoustics. (just needs to not interfere with sound making it to Roxul Pads and do something to contain fibers from getting out)
2. Second layer: Enclose this fabric-wrapped insulation with a foam layer (I’m currently considering 1/2” thick Neoprene High Quality single-sheet foam). This layer is also for safety fiber containment—to prevent any fiberglass escape—without compromising on AT of the setup.
3. Third (outer) layer:
   1. Option 1: Cover the foam with an aesthetically pleasing and acoustically transparent (AT) fabric that will not interfere with sound absorption.
   2. Option 2: Make diffusion plates as the final outward face of the trap if my upper frequencies start decaying out of proportion to lower frequencies.
      

Specific questions I have for experienced DIYers and acoustics experts:

• How thick should I make these corner Traps. The Roxul is 16" wide so 16" x 16" is easy, but if there is benefit in going higher I can. Is there a calculator that can show a abroption profile based on material / type of trap and thickness?
• Does placing Roxul Safe’n’Sound inside a foam layer (like 3/8” to 1/2” neoprene foam) reduce or interfere with its sound absorption performance, especially at bass frequencies?
• What is the minimum foam thickness that can effectively contain fiberglass fibers, provide durability, and still maintain the panel’s acoustic efficiency? Would 1/2” neoprene be overkill? Could a thinner foam layer work just as well?
• Are there any safety or off-gassing concerns with using neoprene foam in this layered configuration inside a room?
• For the outer facing fabric, what are the best materials that combine good aesthetics, durability, and acoustic transparency (allowing sound waves to reach the Roxul core without attenuation)? I’ve heard burlap and certain synthetic fabrics are common but want recommendations on options that are both safe and visually appealing.
• From a construction standpoint, does compressing or tightly wrapping Roxul Safe’n’Sound inside these layers degrade absorption?

I also found an interesting post that mentioned for traps thicker than 8", lower density materials like R-30 (~5000 Rayls impedance) might outperform high-density alternatives (like OC 703 at ~30,000 Rayls) in bass absorption:
https://www.avsforum.com/threads/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs.1449924/

Any practical experience using Roxul Safe’n’Sound in thicker panels or bass traps under these principles?

Those room ratios are very close to ideal. I highly doubt the room is requiring savage acoustic treatment.

I suspect the usual culprit the speakers. What are your speakers and subs?

I have a similar sized room, and I have not had to plaster anything all over the walls.

 

[lovinthehd]

What sort of REW measurements are you working with, what changed with your experiment?

 

[rimmi2002]

Those room ratios are very close to ideal. I highly doubt the room is requiring savage acoustic treatment.

I suspect the usual culprit the speakers. What are your speakers and subs?

I have a similar sized room, and I have not had to plaster anything all over the walls.

My Setup:
1. AVR: Onkyo NR7100 receiver + minidsp 2x4HD for subs. Benq Q HT4550 Projector with 150" Screen.
2. Speakers: Ascend Acoustics Sierra 2's (Front 3) with 2x In wall speakers for rear
3. Subs: 2x Rythmik FV18


Nice to hear that the room size is ideal. Definitely doesn't sound like that for bass. I think my use of it is not ideal. (schematic added the first post now) Its a dual purpose room and I have limited flexibility in where I can move the seats/ speaker. The mid room subwoofer can be moved to other corner opposite the current corner sub ~28 feet away.

So I decided to expirement by placing 9 layers of 3” x 16” x 48” Roxul Safe’n’Sound mats wrapped in breathable cotton fabric (just for trial), and it’s made a huge difference in my room acoustics already. The Bats are in the Bottom right area of the schematic (where it say flex/empty space) Bass already sounds much better and it shows with a much faster decay time for lower frequency on REW measurements.

What sort of REW measurements are you working with, what changed with your experiment?

I am using REW RT60 calculate plots. I listened to 2 of my friend's setup who had much more inferior equipment (1x SVSSB-12) and (1x Paradiam XR13) but there bass was way more punchy and better than mine. My SPL graph looked better than their but my decay time, both in RT60 and waterfall were horrible.

All 4 are graphed Below:

Red - Mine Rt60 with no Treatment
Purple - Mine RT60 with first batch of treatment

Cyan --> Paradigm XR13 setup
Blue --> SVS SB12 setup

 

[TLS Guy]

My Setup:
1. AVR: Onkyo NR7100 receiver + minidsp 2x4HD for subs. Benq Q HT4550 Projector with 150" Screen.
2. Speakers: Ascend Acoustics Sierra 2's (Front 3) with 2x In wall speakers for rear
3. Subs: 2x Rythmik FV18


Nice to hear that the room size is ideal. Definitely doesn't sound like that for bass. I think my use of it is not ideal. (schematic added the first post now) Its a dual purpose room and I have limited flexibility in where I can move the seats/ speaker. The mid room subwoofer can be moved to other corner opposite the current corner sub ~28 feet away.

So I decided to expirement by placing 9 layers of 3” x 16” x 48” Roxul Safe’n’Sound mats wrapped in breathable cotton fabric (just for trial), and it’s made a huge difference in my room acoustics already. The Bats are in the Bottom right area of the schematic (where it say flex/empty space) Bass already sounds much better and it shows with a much faster decay time for lower frequency on REW measurements.



I am using REW RT60 calculate plots. I listened to 2 of my friend's setup who had much more inferior equipment (1x SVSSB-12) and (1x Paradiam XR13) but there bass was way more punchy and better than mine. My SPL graph looked better than their but my decay time, both in RT60 and waterfall were horrible.

All 4 are graphed Below:

Red - Mine Rt60 with no Treatment
Purple - Mine RT60 with first batch of treatment

Cyan --> Paradigm XR13 setup
Blue --> SVS SB12 setup



View attachment 74203

There are three problems.

The system is set up to fire down the short axis of the room, and NOT the long axis. This is always bad.

Clearly your subs are turned up way, way too high.

You can't fill a space like that with bookshelf speakers. No way!

People think that subs can make up for the bass deficiency of small speakers, and they absolutely can not.

The reason is that most of what is perceived as bass, is well above sub range. You can see from your graphs that the bass output of your front three speakers is inadequate.

You have fallen into a common error and trap. You won't solve that with room treatments, but only a significant system redesign.

The first thing you need to do is turn your subs way, way down. The punch of bass NEVER comes from subs. The punch factor is way above sound range.

If a system does not sound reasonably well balanced with the subs off, then no amount of subwooferage will fix it.

 

[lovinthehd]

So what speakers do your friends use in what size rooms? How about general response graphs? Having tried using my Sierras (with 170s and 200s for surrounds/rear surrounds) in a slightly longer and wider room than yours (but only 8 ft ceilings), I found them a bit lacking, as TLS said, only so much smaller speakers can do let alone providing punch. Why are your surrounds in the rear wall? What are they?

I moved my Ascends to my bedroom where they are much better in the much smaller room, altho went to just the Sierras and 170s for a 5.2 setup. I also use and prefer the long axis of a room whenever possible. More info about your basic sub integration might be helpful, but having two larger subs than your friends doesn't particularly mean better otoh. Why are they placed where they are in your diagram, especially one in a corner?

 

[rimmi2002]

So what speakers do your friends use in what size rooms? How about general response graphs? Having tried using my Sierras (with 170s and 200s for surrounds/rear surrounds) in a slightly longer and wider room than yours (but only 8 ft ceilings), I found them a bit lacking, as TLS said, only so much smaller speakers can do let alone providing punch. Why are your surrounds in the rear wall? What are they?

I moved my Ascends to my bedroom where they are much better in the much smaller room, altho went to just the Sierras and 170s for a 5.2 setup. I also use and prefer the long axis of a room whenever possible. More info about your basic sub integration might be helpful, but having two larger subs than your friends doesn't particularly mean better otoh. Why are they placed where they are in your diagram, especially one in a corner?

Thanks, this is a multi-purpose room, not a dedicated HT room, so I am limited on placements. No doubt some of the bass issues might be due to small bookshelf speakers, but the muddiness / lack of clarity is likely due to the real high T60M time in low frequency for me. As I wrote, just throwing 9 mats of Roxul Safe and Sound in the bottom right area of the schematic has already made the bass much more punchy / tight. So my plan is to treat the room first and then experiment with further modifications with speakers if needed.


Setups for my friends are listed below:

1. Cyan Setup (Very high end 2.1 setup; best sound / bass I have heard bar none): 2x Focal Sopra with 1x Paradigm Sub 15 (previous version of XR13): Xover 80
2. Blue Setup (5.1; 5x Monoprice Satellite Speakers + SVS 12-NSD) Bass is much better than mine. My speakers sound better. Xover 100.
3. Red (No Traps); Purple (With experimental Traps): 5.2; Surrounds are in the ceiling above the couch. Xover is 150Hz, sound best for bass with high Xover and it might be because the bookshelves are not enough to fill the room so I need to push the subs to higher frequencies.

Below are SPL and RT60M graphs for all 4 systems:

RT60M Measurements for 4 systems:

My theory for the biggest difference in my bass sounding muddy and others' clear sound is that the real high reverb time created by my room. So I am planning on working to fix it, early experiments tend to support that theory.

 

[lovinthehd]

Thanks, more information is always good. Is this room already furnished? With what? Limited placement options are possibly not helping. How big are your friends' rooms or why do you think yours is showing so much more decay in the xt60 measure?