Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[jimmyjazz]

Hi Fran . . . any thoughts on the utility of hanging a 4" mineral wool panel at the "entrance" of a dormer to make an ad hoc bass trap?  It wouldn't seal off the space behind it, which in this case is about 4' W x 5' D x 8' H (at the peak of the vault).

I don't want to permanently enclose the space, but I'd like to balance the absorption I'm putting on the opposing wall to maintain symmetry.  Of course, the mineral wool panel will do just fine down into the low mids, regardless of whether it's hanging in space or attached to a wall.  I'm just curious to see if the dead space of the dormer itself behind the panel might augment the panel's natural low-frequency absorption.

[franman]

yes.. good idea, BUT definitely dampen the space behind the surface insulation... Hang some more batt in there or something.. otherwise you can create a bit of a comb filter in your absorption, caused by the space behind the insulation... if it's just a few inches, it basically increases the lf bandwidth but when you're talking about a couple of feet, then you are much better to dampen the "trapped" space... (pun intended)...

[jimmyjazz]

Yeah, I thought about hanging rows of the mineral wool panels.  Do you think the fact that the "trap" isn't sealed off is a problem?

Ethan, what's your take?  Have you tested "free-hanging" absorptive panels that don't seal off a large cavity?  Anyone else?

I'm not really sure how to analyze it!

[franman]

When you say "not sealed off"  you mean that there are windows behind the absoption??? These types of traps are never sealed on the "front".. Am I reading you right?

[Ethan Winer]

Jimmy,

> Ethan, what's your take? <

Can you post a drawing that shows what you mean?

--Ethan

[jimmyjazz]

All I'm saying is that a single hanging 2' W x 4' H panel wouldn't come anywhere near filling the opening of the dormer, which is probably 4' W x 8' H.

[jimmyjazz]

The second photo isn't EXACTLY like the dormer I'm dealing with, but it's close.  The photo shows a "pony wall"; i.e., a short wall maybe 3' tall.  The space I'm dealing with has a deeper dormer which intersects a wall that's more like 7' tall.  Still, you can see how the dormer creates a "closet-like" space without a door.  I want to use it to trap some low end.

[franman]

Why not Frame out around the dormer opening, and cover the whole opening with Rigid Fiberglass and Fabric?? That's what I though you were proposing originally....

[jimmyjazz]

I'd rather it be more of a temporary solution, so that the dormer space remains available for other things like storage, amp nooks, etc.  It's not a permanent studio space.  

I'm planning to use ReadyTraps DIY bags to trim out the 4" mineral wool, and then hang them from the ceiling by hooks & fishing line.  I've even considered putting multiple pairs of hooks in the ceiling at various locations around the room to allow me to create artificial "dead spots", in a similar manner to how one might move gobos around a room.

I'm just curious whether anyone else has PARTIALLY fronted a space like that and gotten any bass trapping action at all.  My gut tells me it will work -- if you consider the wavelengths involved and the space around the panels, you can imagine the frequency above which signficant loss of trapping might occur -- but if the front panel has to truly seal off the cavity, then of course, my idea won't work.

It certainly isn't going to cost me much to try it out.  I'll probably just shoot the room with and without the dormers "trapped" and see what happens.

[Ethan Winer]

Jimmy,

> The second photo isn't EXACTLY like the dormer I'm dealing with, but it's close. <

Stuffing that with fiberglass could only help. But a better place for absorption is the room corners.

--Ethan

[jimmyjazz]

Ethan, I agree, but in this case, only 1 of the 4 corners is "accessible" for trapping, because of proximity to doorways, windows, etc.  (I guess the tri-corners where each corner meets the ceiling are all possibilities, and good spots for absorption, too.)

[franman]

Yes the most active corners are where three boundaries come together.. This is a prime location for some broadband trapping.