Plastic Over Insulation-Still Effective Hi Freq. Absorption?

hills · Post by **hills** » Wed Oct 01, 2003 12:29 am

I noticed in the pictures of the "Silva Productions" studio (http://johnlsayers.com/Studio/Mainpage/ ... ctions.htm) that "a thin layer of plastic" was used to cover the insulation in the control room ceiling. This seems desirable from an air quality / health point of view, but will this plastic layer make the insulation ineffective as a high frequency absorber?

Thanks,
Scott

knightfly · Post by **knightfly** » Wed Oct 01, 2003 2:05 am

It will slightly reduce high frequency absorption, but that's usually a GOOD thing - a lot of times there is too much absorption and the room loses its "shimmer", causing you to make incorrect decisions in mixing.

The type of plastic that works best for this is really thin, which minimises the restriction on absorption - something like the so-called "painter's drop cloths", for example... Steve

hills · Post by **hills** » Wed Oct 01, 2003 6:34 am

Thanks Steve.
I understand the concern about too much high freq absorption, but for that reason I would only place bare fiberglass insulation in locations where I WANTED high freq absorption. (For absorption in lower freq ranges I would use slat-resonators, panel-resonators, or "hangers").

So I still wonder about how effective the high freq absorption would be with that thin plastic over the insulation, because I'd like to cover the insulation like that for air quality reasons but don't want to loose the benefit of the high freq absorption. What I think I'm hearing you say is the plastic reduces the effectivenss somewhat, but not enough to make you decide not to use the plastic. Is this a correct understanding? Would (or did) you use the plastic in your studio? Has anyone out there evaluated the absorption difference with & without the plastic?

Thanks again,
Scott

knightfly · Post by **knightfly** » Wed Oct 01, 2003 8:23 am

Scott, so far I'm still scheming on a REAL studio, just working in a bedroom since I started tearing down the old studio to make room for a work shop. The new facility will hopefully "break ground" in a couple of years, meanwhile I'm stuck in a bedroom and making what I can of it. (Hate it when those song ideas squirt out your ear and run down your neck for lack of a way to record them...)

My gut feel for this is that the really thin (painter dropcloth stuff) plastic is so thin it's lucky to hold the fibers that shed, much less much else. In a few months I plan to have software/hardware for my new laptop that can tell me EXACTLY what difference such changes make, without having to build serious structure to find out (at least for some things) - meantime, with me it's more instinct based on 20 years study... However, John's the guy that's DONE most things and knows firsthand what happens.

Another thing that contributes to my own feeling on this - I'd much rather have a room slightly "bright" and have to turn the highs DOWN a bit, than the other way around. Even well-designed digital EQ's work better in "cut" mode than in "boost" mode.

Add that to the health concern, and I'll be getting a supply of "drop cloths" when the time comes for fiberglas... Steve

Post by **John Sayers** » Wed Oct 01, 2003 9:42 am

Scott - I first tried it in the ceilings in Left Bank - these rooms sound really nice. You can record flat without EQ and it sounds great. There is still life in the rooms - I recommend it highly.

cheers
john

hills · Post by **hills** » Wed Oct 01, 2003 11:57 pm

Great!
Steve & John - thanks for your help.

Scott