stacking insulation rolls as corner bass trap?

eyeballing

New member
Oh I was just talking in general in acoustics. Yes I will follow advice and think twice.

I am in US and I did see that date sheet somewhere else, just that on that forum there was someone saying JM representative gave him a different numbers... and no one knew for sure.

I will try to make some use out of the John Brandt page. So much to learn and it's so far so interesting, and painful.
I'm not so sure why it has to be try and fail. My dad used to say, "measure twice, cut once". This thinking applies. Spend more time planning than constructing is about the best advice you can get. No point is trying to prove that 4+4=10.
 

witzendoz

Senior Member
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1. it wasn't just you I was commenting on. 2. you are almost on the right track. 3. leave if you want but what would you learn?

I got to go on a service call for a client. I'm hoping it doesn't take too long and will get back to the office early. This will take a bit of time to lay it all out with graphs that will compare materials and how effective they are at low frequencies and when they cease to be absorptive and become reflective. Really, stick around. No one says your voice isn't welcome.
Well, nothing I read that you posted contradicts anything that I posted previous. My answers were trying to explain to the OP what you can achieve with what he was asking about. I was trying to put the case that dense material was more efficient that the light fluffy stuff, which is what the charts say.

I don’t know quote; “A whole lot of experts in acoustics and building studios. Your statement takes a few principles and mashes them up into something incoherent. Frankly there is more acoustic misinformation in this one thread than I have seen in a long time. Thanks for adding to the pile, I got a good chuckle out of this.” Why this was pointed at me. I have in fact carried out a lot of acoustic studies, extensively read acoustics design articles, and been involved in building 4 studios, learning more each time, as you would expect.

I found this comment offensive: “leave if you want but what would you learn?” I am one to say that you learn everyday, but that comment was very patronising.

It’s no point baffling the OP with science when the start of this thread was a very simple question “I heard some people bought those rolled insulation and stack them as is, without unwrapping it or doing anything do it, and that makes something similar to superchunk bass trap but thicker, hence awesome bass absorption.” Which I was trying to answer in a simple manner.

Cheers
Alan
 

Folkcafe

Active member
Oh I was just talking in general in acoustics. Yes I will follow advice and think twice.

I am in US and I did see that date sheet somewhere else, just that on that forum there was someone saying JM representative gave him a different numbers... and no one knew for sure.

I will try to make some use out of the John Brandt page. So much to learn and it's so far so interesting, and painful.
Learning curve on this stuff is huge. My first copy of the Master Handbook of Acoustics was 3rd edition. 7th edition comes out this Sept. I first built my current studio 20 years ago. In remodeling it, all the changes in knowledge and best practices had changed so much it was like learning a whole new subject.

Adding a couple bass traps will help. Will it ultimately be enough? Depends on your goals. I was looking for somewhere less than +/- 3db room. Except for one troublesome floor bounce that gets me just outside of that, I am at +/- 2db for bass response at listening position. Took way more treatment than I originally planned on. End result is really detailed bass response. I even ditched my 15inch Tannoy Sub. It is kind of like listening to really good headphones without the discomfort.

Good luck with your project.
 

Folkcafe

Active member
\

Well, nothing I read that you posted contradicts anything that I posted previous. My answers were trying to explain to the OP what you can achieve with what he was asking about. I was trying to put the case that dense material was more efficient that the light fluffy stuff, which is what the charts say.

I don’t know quote; “A whole lot of experts in acoustics and building studios. Your statement takes a few principles and mashes them up into something incoherent. Frankly there is more acoustic misinformation in this one thread than I have seen in a long time. Thanks for adding to the pile, I got a good chuckle out of this.” Why this was pointed at me. I have in fact carried out a lot of acoustic studies, extensively read acoustics design articles, and been involved in building 4 studios, learning more each time, as you would expect.

I found this comment offensive: “leave if you want but what would you learn?” I am one to say that you learn everyday, but that comment was very patronising.

It’s no point baffling the OP with science when the start of this thread was a very simple question “I heard some people bought those rolled insulation and stack them as is, without unwrapping it or doing anything do it, and that makes something similar to superchunk bass trap but thicker, hence awesome bass absorption.” Which I was trying to answer in a simple manner.

Cheers
Alan
I said it was incoherent.. It implied that denser materials and mass is needed for building bass traps and the opposite is in fact true. There was a ton of misinformation in this thread that is clearly wrong. With you, I simply stated you inarticulately tried to make a point that clearly either didn't come out as intended or is just factually wrong. Take your pick. I stand by my post.
 

Folkcafe

Active member
\
I was trying to put the case that dense material was more efficient that the light fluffy stuff, which is what the charts say.
Um, no. In context of bass, the opposite is true. Denser materials become reflective at low bass frequencies at much shallower depths than lower density materials. I posted one comparison. I could compare any material you pick in these calculators and the same would be true.

Here is Owens Corning EcoTouch R38 vs Owns Corning 705 6lb density rigid fiberglass. Same material, different density. Blue is low density. Tell me which one goes lower?
Screen Shot 05-03-21 at 09.32 PM.JPG
 

witzendoz

Senior Member
But it depends on the trap design, he was originally talking tube traps and a simple rolled up insulation. If you use high density insulation of say 4" and leave an air gap behind that works in a different way to filling the whole corner completely. I think we are on the same page but its more the explanation than the information.
 

Folkcafe

Active member
But it depends on the trap design, he was originally talking tube traps and a simple rolled up insulation. If you use high density insulation of say 4" and leave an air gap behind that works in a different way to filling the whole corner completely. I think we are on the same page but its more the explanation than the information.
The devil is in the details and 4 inch of anything regardless of gap isn't going to get you low bass reduction. Based on his room dimensions, he has two fundamental modes that will take more than 4 inches of high density insulation. To say that 4 inches of high density outperforms 4 inches of low density is misleading as neither gets you much in the way of bass treatment. It is the case of being a distinction without any practical difference as a bass trap. At 6 inches low density begins to be about even but still not that effective below 100Hz. Here you are more at broadband absorber than any sort of bass trap. If our fundamental disagreement is nomenclature around what is a bass trap and what isn't, I can accept that. If that is what you mean by on the same page. As to the OP, he seems far more informed later in this thread than initially. I wouldn't completely write him off.
 

eyeballing

New member
Learning curve on this stuff is huge. My first copy of the Master Handbook of Acoustics was 3rd edition. 7th edition comes out this Sept. I first built my current studio 20 years ago. In remodeling it, all the changes in knowledge and best practices had changed so much it was like learning a whole new subject.

Adding a couple bass traps will help. Will it ultimately be enough? Depends on your goals. I was looking for somewhere less than +/- 3db room. Except for one troublesome floor bounce that gets me just outside of that, I am at +/- 2db for bass response at listening position. Took way more treatment than I originally planned on. End result is really detailed bass response. I even ditched my 15inch Tannoy Sub. It is kind of like listening to really good headphones without the discomfort.

Good luck with your project.
Thank you. Just one more question if you don't mind:

I'm right now looking at the room mode calculator from John Brandt, and while I am not entirely sure how to read all this chart, there is a part says "CONTROL ROOM BROADBAND TRAPPING" and shows some frequency with trap depth MINIMUM, also says "REAR WALL" or other spaces. Is this like a suggestion of the trap size and the location for it?
 

rob aylestone

Well-known member
The trouble with doing all these calculations is that from my own practical experience is that the results always suggest more is needed. In my last two studio builds it meant people getting a few bargains when I sold piles of excess product. The snag for me is that I quite like walls, and the data means covering more and more of your studio with product of some type. I stuck in the obvious and had a listen. An improvement. Add another, and maybe experiment with moving or angling it? At some point the sound starts to change less. I stop when the next addition I cannot hear, not see on a screen. The little hump still visible at 8.5k? Leave it, because the big hump at 325Hz I got rid of. That made a difference.

if you have a small room, getting rid of the big issues is really worthwhile, but you need perspective. It’s always going to be small, and the people in it will change the acoustics. One person to three will be a visible change if you check, so at this point, what is the purpose of more treatment? Perspective is required. Get rid of big problems, then the law of diminishing returns kicks in. If you need to remove a huge bass honk, sort it, but gentle peaks and troughs in a home studio can be sorted by EQ on your monitors. Of course, this just attempts to repair the extra emphasis on certain ranges, but in a big studio the latitude for perfection spreads over a good left/right backwards/forwards area, but in a small room, moving your head a foot left changes the sound anyway.
 

Folkcafe

Active member
Thank you. Just one more question if you don't mind:

I'm right now looking at the room mode calculator from John Brandt, and while I am not entirely sure how to read all this chart, there is a part says "CONTROL ROOM BROADBAND TRAPPING" and shows some frequency with trap depth MINIMUM, also says "REAR WALL" or other spaces. Is this like a suggestion of the trap size and the location for it?
John spreadsheet generates such a wealth of information that it takes a bit to sort through it all. The depth to be effective is for the fundamental modes based on room dimensions. That is only a portion of the equation. As Rob alludes to, how much in addition to how deep is another part of the equation. The spreadsheet also generates a treatment quantity based on a ratio of room volume and hence surface area. Ultimately it is a matter of deciding how much you wish to improve the acoustics and yes, small rooms are next to impossible to get right. Again, all room design is compromise. Biggest bang for the buck in treatment is effective bass traps. Absent you taking your own room mode measurements before you start and listening position measurements, your only option is to go by the model which often varies somewhat. Treat to the lowest mode or settle for monitoring above the lowest troublesome mode. What you'll note is the mathematical relationship between these axial mode in your model. The first 3 are one octave lower than the the next 3 and so forth. Fix the lowest modes and many of the higher ones are taken care of with them.

As to how much. The spreadsheet gives a space taken for treatment as16.65% and depths for treatment for back, front, ceiling and sides. This is just under 160 cu ft. One pack of R38 2ftx4ft is 64 cu ft. and a roll of R30 15 inch x 25ft is 31 cu ft. So it is not that much insulation to hit that number.
 
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