I've seen enough variations on Ethan's simple fibreglass panel corner traps now to make my head spin!

I've noticed some designs do not span the entire distance from the floor-to-ceiling. Some finish maybe a few inches, others more than a foot, below the ceiling. Also, some traps are not sealed against the walls and sit roughly an inch off the wall on either side. This is due to that strip of wood running along the join between wall-floor and wall-ceiling (crap... can't think of the name!) getting in the way of a trap being right against the wall surface.

My questions are:

How crucial is it that the traps are flush and sealed with all surfaces to create an "air-tight" mass of air behind the trap?

How much difference is there in the results by making it air tight or not?

IF the ceiling can't be reached with a corner trap, and an air seal is important, should the top of the trap be sealed with a panel of wood, or more fibreglass?

These questions seem daft and obvious... but I have seriously looked and searched forums and received conflicting opinions. Grrr. And the search engines in forums generally suck hairy ones

1- It depend of the kind of trap your building. There is not any importances for most of trap, only pannel trap need air tight deseign. But those trap should be used for the fine tuning of the room, not the general acoustical control.

2- Air tight is important when the pannel witch is exposed is used as a membrane witch will vibrate under sound and disperse energy through his mass. When the pannel trap is airtight, the air inside is used as a buffer to keep vibration under control and accurate.

3- yes

4- no question is daft and obvious when it come to acoustic.

You are just building a fiberglass only bass trap. Therefore you dont care about how airtight it is. Just take 2ftx4ft panels of rigid fiberglass and put cloth on them. Then hang them across the corners. Try to make them at least 4" thick and try to cover as many corners are possible.

Thanks, both of you! That's all I needed to know.

The fibreglass is on order. Once I've got everything togethether I'll make sure to post some pix of how it all went.

rock on