[tmaslar]

I am planning to build bass traps out of 2'X4' 6 pound Johns Manville compressed fiberglass. I am going to buy 2" thick material and double it up to make 4".

I can get it with the FSK face or plain face. I am a bit confused....I have read that it is best to install bass traps with some sort of facing toward the room to prevent absorbing too mid and high frequency information from the room. After surveying several different manufacturers websites it appears to me that many do not use any sort of facing on their bass traps. One exception being the Realtraps.

Is it better to use FSK facing which is fairly thick? I have also read that using a thin poly like shrink wrap glued to the face works better than FSK. Or no backing at all?

For making high frequency absorbers for first reflection points Is is best to build the panels with no backing or  to just have the backing towards the back of the panel.

What will work best?

[bpape]

For reflection control, you can use faced and just turn it toward the wall.  You'll pay a lot more for faced though.

For the other, FSK will work fine.  What you use will determine at what frequency you start to absorb less AND at what lower frequency you'll get a hump in absorption.  It also matters whether you bond the facing to the absorption or whether it's stretched tight and undamped.

BTW, we also restrict upper mid and high frequency absorption in our bass control products.

Bryan

[tmaslar]

Bryan,

Thanks for the reply.

Are there any guidelines for how the the facing material will affect the frequency at which the bass trap will begin to work?

 How much different will attached FSK be from placing a sheet of poly or gluing a sheet of poly verses a thin sheet of shrink wrap for example.

Tom

[bpape]

You can get a good idea on FSK by looking at OC's own test results.  Notice that the upper end doesn't change much as thickness changes but where the hump  in the bottom is does change a lot.

It's impossible to say exactly how any one thing will react without testing it.  There are just too many variables.

Bryan