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Post by mahdes on Feb 4, 2020 22:17:22 GMT
Hi! I made my own rockwool bass traps (tons of it). I covered them ALL with unbreathable plastic fabric (ReflectionFreeZone as well) (1st picture) and then add nice looking textile on the top of it. (2nd picture)In the corners I have small triangles from floor to ceiling - all covered with the same unbreathable plastic fabric and also I have normal bass traps in front of those triangles - all covered in fabric and textile. (3rd and 4th picture). On Gearslutz there are tons of posts about how unbreathable plastic fabric can reduce effect of absorption - reflect highs and mids especially but also affect low end absorption. Is it even possible? Questions: 1. Will it make any REAL difference in sound if I cover it ONLY with breathable textil? 2. Is it really safe? I sleep in that room aswell ! 3. Is thick carpet on the wooden floor in the small room good or bad thing? (5th picture) On Gearslutz many people claims its a nightmare for acoustic but I have slightly better results in REW with it, but maybe REW is not showing everything. Thank you so much and sorry for noob questions. There are tons of opinions online - sometimes its very difficult to pick something from all of that. PHOTOS HERE drive.google.com/open?id=1Jjzf3f7-Y54t458z37q5jPcdmVFMEIye
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Post by Hexspa on Feb 4, 2020 23:01:40 GMT
Yes, it's possible. Plastic reflects frequencies above around 1kHz and helps low-end performance; probably due to a dampened membrane effect. It's insane with the membrane. Insulation is an irritant and not a carcinogen, as far as I know, so it's relatively safe as compared to, say, asbestos or lead.
Carpet will act on higher frequencies, mostly. This could be good or bad depending on your SPL and decay. Usually, you want more decay above around 4kHz, I think; I forget the exact cutoff. So, like all things acoustic, it's a balance that you have to figure out with measurements and analysis - look for decay in higher frequencies.
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Post by mahdes on Feb 4, 2020 23:32:10 GMT
Yes, it's possible. Plastic reflects frequencies above around 1kHz and helps low-end performance; probably due to a dampened membrane effect. It's insane with the membrane. Insulation is an irritant and not a carcinogen, as far as I know, so it's relatively safe as compared to, say, asbestos or lead. Carpet will act on higher frequencies, mostly. This could be good or bad depending on your SPL and decay. Usually, you want more decay above around 4kHz, I think; I forget the exact cutoff. So, like all things acoustic, it's a balance that you have to figure out with measurements and analysis - look for decay in higher frequencies. "and helps low-end performance" I'm not sure I get this. So plastic fabric makes basstraps more effective in the low end? So theoretically everything under 1K is uneffected - plastic/no plastic, Carpet/no carpet right? If I will keep plastic there, maybe putting FOAM on the front of my basstraps will help? Only in the reflection free zone for example. Thanks
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Post by Hexspa on Feb 5, 2020 5:38:57 GMT
So, there are two types of absorbers - broadly speaking: resonant and frictional. Helmholz and diaphragmatic absorbers are resonant whereas foam and fiberglass are frictional. By placing a membrane directly on a frictional absorber, you get a hybrid. In this case, it helps with low-end performance. There is no doubt about this - just look at the performance of insulation with FRK on any coefficient chart.
Not sure what you mean about "everything under 1K is uneffected [sic]". FRK reflects above 1kHz but helps the absorber below maybe 200Hz - not sure of the exact cutoff - see the charts I mentioned.
Sandwiching, as we call it here, your plastic between foam and another absorber is not what we recommend. While it'll probably do something, it's complicating the basic practice of either having a reflective membrane or not.
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Post by mahdes on Feb 5, 2020 7:08:37 GMT
So, there are two types of absorbers - broadly speaking: resonant and frictional. Helmholz and diaphragmatic absorbers are resonant whereas foam and fiberglass are frictional. By placing a membrane directly on a frictional absorber, you get a hybrid. In this case, it helps with low-end performance. There is no doubt about this - just look at the performance of insulation with FRK on any coefficient chart. Not sure what you mean about "everything under 1K is uneffected [sic]". FRK reflects above 1kHz but helps the absorber below maybe 200Hz - not sure of the exact cutoff - see the charts I mentioned. Sandwiching, as we call it here, your plastic between foam and another absorber is not what we recommend. While it'll probably do something, it's complicating the basic practice of either having a reflective membrane or not. Thank you so much for this! So if putting Foam on fabric is not recommended. What is to best way to kill hi mids/hi end refrections from the fabric in the RFZ? Because I think in the RFZ you have to tame those hi mids and highs as well. Maybe in the corner its ok.
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Post by rock on Feb 5, 2020 14:11:11 GMT
I'll chime in here and try to simplify:
1.) For RFZ build panels without plastic membrane, cover with breathable cloth for aesthetics and fiber containment. Spacing from the wall or ceiling is recommended to extend LF performance.
2.) For bass traps in corners and out of places that will reflect to the listening position, build panels with membrane (plastic, paper or foil) on the outside only (facing the room). Cover with breathable cloth for aesthetics and fiber containment.
Hexspa has given you much more detail but on a fundamental level, you should find the above is in agreement.
If you have not yet read the "Stickies" at the top of this list, please do so and follow all the links the the various subjects.
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Post by Hexspa on Feb 6, 2020 0:57:34 GMT
Rock is right, as usual.
You can put foam on fabric but we don't recommend foam over FRK/membrane.
If you put foam on fabric with no membrane you're just adding more thickness. Exactly how that will play out, only your measurements can reveal.
If you put foam over FRK/membrane you end up with a sandwiched panel. This is not what I see anyone recommending. Why? I don't know but why not do what people have proven to work and just put the membrane on the front of a sufficiently thick absorber?
You can experiment but it's time consuming and requires a strong reference point, in my opinion. To put it another way, I say that everyone should first practice the fundamentals and get a good result before trying out fringe options. Really, this is a principle of education and learning to treat your room falls under that umbrella.
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Post by mahdes on Feb 6, 2020 7:43:05 GMT
I'll chime in here and try to simplify: 1.) For RFZ build panels without plastic membrane, cover with breathable cloth for aesthetics and fiber containment. Spacing from the wall or ceiling is recommended to extend LF performance. 2.) For bass traps in corners and out of places that will reflect to the listening position, build panels with membrane (plastic, paper or foil) on the outside only (facing the room). Cover with breathable cloth for aesthetics and fiber containment. Hexspa has given you much more detail but on a fundamental level, you should find the above is in agreement. If you have not yet read the "Stickies" at the top of this list, please do so and follow all the links the the various subjects. Thanks Rock! " build panels with membrane (plastic, paper or foil) on the outside only (facing the room)." Why on the outside only? Sorry for noob questions. I just want to know
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Post by mahdes on Feb 6, 2020 7:51:03 GMT
Rock is right, as usual. You can put foam on fabric but we don't recommend foam over FRK/membrane. If you put foam on fabric with no membrane you're just adding more thickness. Exactly how that will play out, only your measurements can reveal. If you put foam over FRK/membrane you end up with a sandwiched panel. This is not what I see anyone recommending. Why? I don't know but why not do what people have proven to work and just put the membrane on the front of a sufficiently thick absorber? You can experiment but it's time consuming and requires a strong reference point, in my opinion. To put it another way, I say that everyone should first practice the fundamentals and get a good result before trying out fringe options. Really, this is a principle of education and learning to treat your room falls under that umbrella. Thanks Rock! If I have rockwool panel covered with plastic (all sides) in front of another rockwool panel - covered with plastic aswell (all sides). Is it sandwiching as well? Because there is plastic between panels? Thank you"!!!!!
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Post by rock on Feb 6, 2020 13:58:08 GMT
Yes, it is "sandwiching as well.
I don't know if or what testing and acoustic measurements have been done with such panels, but it is my understanding that for best broadband absorption, all sides (mainly front and back but sides help a little too) should be only covered with breathable fabric.
For bass traps cover only the ONE side facing INTO the room with plastic, paper or foil. If you want thicker panels, it's OK to build up the thickness with 2 or more panels but the additional panels should be uncovered both front and back (sides too).
You asked: Why on the outside only? To my understanding, firstly, the plastic membrane allows LF to pass into the absorber while reflecting MF & HF (please keep in mind that the rolloff between LF & MF is gradual). Secondly, the thickness of the panel (and space) behind the membrane acts a one unit with a total thickness to absorb LF. If you "sandwich" more layers of membrane in between each extra layer of mineral wool or fiberglass, you no longer have ONE THICK absorber but several THINNER absorbers "sandwiched" together and you reduce the maximum LF you can get with just one thick absorber and the air space behind it.
I believe I have seen that Ethan has done some tests with FRK (foil membrane) VS non-FRK and the results can be found by going to the Stickies to please check them out. I can't remember exactly where this info is but I'll try to find it or maybe someone else can help you find it if you can't.
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Post by mahdes on Feb 6, 2020 14:35:50 GMT
Thank you sooo much Rock for this! btw "you no longer have ONE THICK absorber but several THINNER absorbers "sandwiched" together and you reduce the maximum LF you can get with just one thick absorber and the air space behind it." Is it big difference or very very tiny? Before I will start redoing everything here I wanna know because its tons of work. But I think I will do it anyway haha
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Post by rock on Feb 6, 2020 21:31:48 GMT
"Is it big difference or very very tiny?" I really don't know Maybe someone else here can help? I have to admit that some of what I have learned is from doing and reading but most of what I know (or think I know) is from what I've learned from Ethan and discussions on this site. If you do un-wrap your traps, if you take before and after acoustic measurements with REW (or the like) you'll know and I would very much like to know for my own learning.
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Post by Hexspa on Feb 7, 2020 4:57:30 GMT
Just unwrap your RFZ panels - those are the only ones that work better with no 'wrap'.
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Post by mahdes on Feb 9, 2020 13:44:33 GMT
"Is it big difference or very very tiny?" I really don't know Maybe someone else here can help? I have to admit that some of what I have learned is from doing and reading but most of what I know (or think I know) is from what I've learned from Ethan and discussions on this site. If you do un-wrap your traps, if you take before and after acoustic measurements with REW (or the like) you'll know and I would very much like to know for my own learning. Thanks! I will test it when I will have more time. btw I just noticed that in REW - when I measure both speakers I have ugly deep between 5k-10k, but when I measure each speaker separately - its Ok.
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Post by Hexspa on Feb 10, 2020 3:33:22 GMT
Ethan says it's from each of the stereo signals arriving at a slightly different time - phase cancellation, basically. For this reason, we use smoothed full-spectrum SPL and unsmoothed below 300Hz. Feel free to post a screenshot - keep it a reasonable size - if you want us to take a look.
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