Bass traps question

[octatonic]

I posted this in geekslutz but I think it might be the wrong forum....

Hi all,

looking for some feedback from people who know what is what regarding DIY basstrap construction.

I've built 4 traps.
All are 1200mm x 600mm.
2 are 200mm deep
2 are 125mm deep

All of them have 80mm of steinwolle (rockwool in english) which is 2 x 40mm units.
I've covered them in a stretchy fabric which is on a frame that sits inside the main box.

My main questions are - do I need to have a large air gap behind the rockwool?
The traps that are 125mm deep only have about 15mm of air.
The 200mm traps are quite bulky and now I need to make more.

Can I get away with having them 125mm deep with 80mm of rockwool?
Is there anything crucial I am missing here?

Pic enclosed

[Ethan Winer]

James,

I'm not sure what you're asking, but with DIY rockwool panels you want the mineral wool to operate as a single piece. If you have to double up two more more panels to get the desired thickness, there should not be an air gap between the layers. Then put them straddling the room corners.

--Ethan

[octatonic]

Originally Posted by Ethan Winer

James,

I'm not sure what you're asking, but with DIY rockwool panels you want the mineral wool to operate as a single piece. If you have to double up two more more panels to get the desired thickness, there should not be an air gap between the layers. Then put them straddling the room corners.

--Ethan

Ethan,

Thanks for the response- I do have the layers pushed up against each other and glued in place.
I guess my question was regarding the air gap in the 125mm panels vs the 200mm panels.
I would like them to be as thin as possible.
How much of a gap between the mineralwool and the edge of the box is needed?

How should I fit them? Suspended on a wire or fixed flat against the wall?

Many thanks..

JR

[tomdarude]

simple.......the thicker the rockwool is.....AND the more you space it off the wall, the lower (frequency-wise) goes your absorbtion!!

so, I´d suggest to add another layer of 40mm rockwool (-> total 120mm) and still space the frames a bit from the wall....so you get at least a 100mm airgap behind the rockwool.
you could use the smaller frames (125mm) to straddle the corners (also add another rockwool layer....or two!!), so they also have a huge airgap behind them.


cheers tom

[bpape]

How dense is the wool?

200mm is nice and thick already. Spacing it off the wall will help some but if you're tight for space, they'll already be pretty effective down pretty low.

As for the 125mm absorbers, what are you using them for and where will they be positioned in the room? That will help to determine what the best course of action will be.

Another thing to consider (don't know if you did the first time or not) is to slot or drill holes in the sides of the frames to expose more material - especially on the thicker ones. Think about the thickness you'll be getting to waves exposed to the sides - and on a 200mm panel, it's not an insignificant amount of surface area.

Bryan

[octatonic]

Thanks for the responses guys- this is uncharted territory for me.

The 125mm traps I am going to install in the corners behind the monitors.
I have more space at the back of the room and will put the 200mm traps in the back corners.
I have some wood left over to make 2 x 70mm traps which will fit 1 x 40mm slab each.
These I might mount on the side walls (where I don't have much space as the room I am currently in is roughly 2.2 times the width).

All this will change in 6 weeks time as I am moving everything back to the US and have no idea what space I will be in.

I have a couple of foam corner traps also- haven't installed them yet but will put them in the the side ceiling/wall join unless someone else can suggest a good position.
Trail and error... trial and error... etc

JR