"Airtight" bass traps why?

[jingleheimer]

Why exactly is it that sealing bass traps "airtight" is so important? Is it to stop sound spill or something else? Thanks for any help you can give me! -Jingleheimer-

[A Reel Person]

the fibers of which you don't want free floating in the air, as they may be harmful if you breathe them in.

[Ford Van]

The enclosure of the bass trap (mechanical) has to be sealed for it to work right.

[pandamonk]

Originally Posted by A Reel Person

the fibers of which you don't want free floating in the air, as they may be harmful if you breathe them in.

Surely you could just cover both sides with fabric?

[pandamonk]

I was under the impression you could just use a thick broadband style absorber around 4-6" across the corner.

[Farview]

Originally Posted by pandamonk

I was under the impression you could just use a thick broadband style absorber around 4-6" across the corner.

You can, but the absorber is a sealed unit.

[A Reel Person]

as one "bass trap" would be mostly home made fiber "panels", and the ones needing to be "airtight" would be mechanical and/or manufactured specialty items.

[Ziller]

I edited my above post for clarity, and it refers to the mechanical type (pressure absorber) vs the fiber panels accross corners (velocity absorber). In the latter case, you wound not want it to be airtight, as the sound must pass into it to be absorbed.

[Ziller]

If it is sealed, when the plywood face vibrates, it forces the air inside the trap to move into and out of the fiberglass panel inside, which dampens the vibrating plywood and soaks up the energy. If it was not airtight, the air would just move in and out the holes, and the plywood would not be dampened, so would just vibrate until it stopped on it's own (sending all that energy back into the room until it did).

[A Reel Person]

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