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Post by adamforemusic on Jul 23, 2016 22:09:39 GMT
I have used plastic garbage bags on my corner traps to reflect some of the mid and high frequencies at one end of my room. The plastic is stapled across the rockwool but it's not touching it or tight to it, it may be 1cm away. How will this affect the corner traps?
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Post by Hexspa on Jul 24, 2016 3:34:45 GMT
The only way to know is to A/B test.
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Post by adamforemusic on Jul 24, 2016 8:00:36 GMT
Thanks for your reply hexspa, how would you test it? I've seen Ethan has commented on GS before saying the facing has to be tightly pressed against the fibreglass, I'm just wondering if he could shed any light on what the result of it not being tightly pressed against the fibreglass would be.
How will it affect the effectiveness of the corner trap?
Am I right to assume it will still reflect mid and high frequencies the same as it would if pressed tightly against the fiberglass?
Is gluing the plastic garbage bag material directly onto the Rockwool a good idea? I was hesitant to do it as I thought it might change the absorption properties of the Rockwool - make it less effective?
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Post by rock on Jul 24, 2016 16:32:02 GMT
It was my understanding that the membrane, (paper, plastic or foil) is glued (spray glue) to the rockwool or fiberglass to make it MORE effective at low frequencies. I don't understand the science of how it works but Ethan's test data with OC FRK panels show that it does absorb more LF at the expense of reflecting Mid and high freq (which is not necessarily a bad thing if the absorber is not in the reflection zone).
I don't have the link handy but if you look for it you should be able to find Ethan's test. The way the test was done was with software like REW (Room EQ Wizard, it's free). First measure an empty room as your basis. Next, place absorbers without membranes in the corners, cover as many corners as you can or you can make incremental tests. Next, do the same thing with absorbers with membrane. In your case, if you want to test a spaced membrane VS glued, obviously, you want to test the spaced before you glue on the membrane and then test again with the glued on membrane. Hopefully, your results will prove the glued on membrane works best since if not, you'll have to remove the membrane (which should not really be too bad as I believe you only need a fairly light application of spray glue to hold it in place)
Whew, That's a lot of work but I think that's one way to know for sure. If you do all that testing please share the results with us. On the other hand, from everything Ethan has taught and showed us, I think you can be confident to just glue the membrane on your absorbers. But don't use membrane glued on absorbers at reflection zones (on the sides and ceiling between listening position and speakers).
Cheers,
Rock
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Post by adamforemusic on Jul 24, 2016 21:51:04 GMT
Thanks rock, appreciate your help. I have a good understanding of when and where to use and not to use Rockwool with a facing. My question is specifically 'what is the effect of the membrane being stapled to the wood holding the Rockwool in place rather than attached to the Rockwool itself?'
Unfortunately quite a bit of the treatment is in place and I'm working to a deadline so I have no time to empty the room and make measurements etc.. I did make some before I started the treatment to see why I was working with but I knew the first thing was to trap all corners with 4 inch thick Rockwool and so I'm in the process of completing that. I currently have 30 slabs of Rockwool sitting in the middle of the room which cant be stored anywhere else and I'm assuming will have a profound effect on the data.
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Post by adamforemusic on Jul 24, 2016 21:54:38 GMT
I think I'll just glue it on instead like you're suggesting. It will look neater and hopefully have the same if not a better outcome acoustically. Thanks
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Post by Ethan Winer on Jul 25, 2016 20:34:50 GMT
I believe if the plastic is not bonded to the fiberglass it won't increase bass absorption as much. It should reflect higher frequencies the same. You can test it yourself if you make 2-4 bass traps each way, and do what I did here: Density ReportIf you do this, please post your results here. But be sure not to move the microphone even a tiny bit between tests. --Ethan |
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