Open back Bass traps?

5

5stringer

New member
Should bass traps have an open back?

Here's my situation - I made (12) panels for my basement band practice / recording space.
The panels are 2" x 24" x 48" OC 703 mounted to 1/4" particle board, wrapped and stapled
(no wood on the sides - cloth is basically holding the fiberglass to the wood.) The basement
is 23' x 19' x 8' tall with carpet, drop-ceiling, and paneling. I was trying to tame the reverberation
and "brightness" but with these panels the bass problem became accentuated - the room became
very boomy and dark. My plan was to re-do these and make them 4" thick (doubling the OC703)
and mounting them across the corners behind the band and along the ceiling corners. My hope is
that this will help tame the bass and liven up the room. Should I make these to have an "open back"
or is the 1/4" particle board thin enough that it really won't make much of a difference either way.

Here is a pic of the space.

attachment.webp

Thanks for your input.
 
Yes, four inches thick is much better than only two inches, and you should absolutely remove the solid backing. Since you have a drop ceiling, I'll add that packing thick fluffy fiberglass above the ceiling tiles will give you even more bass trapping. If you can't do the entire ceiling, at least do the area around the perimeter.

--Ethan
 
Thank You Ethan! I was wondering about the space above the tiles as well. Should this be acoustic batting material or will R30 fiberglass insulation work?

Also, the black "curtain" hanging all the way around the band is a heavy, thick velour material that is doubled up atleast half-way up the wall (curtains are 12' long in an 8' space). As soon as we hung this, the room became less bright - probably due to some sort of high frequency absorbtion going on? Would I still need 4" thick panels on the walls with these heavy curtains if I treat the corners and above the drop ceiling?

Thanks again for your input!
 
Insulation above a drop ceiling should be as thick as possible. How thick you can manage depends on the available space, what else is up there (lights, plumbing), and your budget. If you can fit 12-inch thick R38 that's ideal. If you can't afford to do the entire ceiling, at least do the perimeter to handle the wall-ceiling corners.

A very thick curtain absorbs well down to about 1 KHz, or maybe even 500 Hz. So putting additional thick absorbers on the wall behind is still useful.

--Ethan
 
Hey Ethan...on the subject of the solid bass trap backing....how is it different from a solid membrane in a bass trap?
Would it work if the solid backing was only connected at two ends, and allowed to vibarate (is that how the membranes work)...?
 
A "solid backing" to me is 1/8-inch or thicker plywood or MDF. You can make a "vibrating" bass trap from plywood, but it's a special sealed design with specific dimensions etc. A slab of rigid fiberglass is best by itself, or with a very thin paper or plastic membrane bonded to the front surface.

--Ethan
 
miroslav said:
Hey Ethan...on the subject of the solid bass trap backing....how is it different from a solid membrane in a bass trap?
Would it work if the solid backing was only connected at two ends, and allowed to vibarate (is that how the membranes work)...?
Click to expand...

It isn't too different, the largest difference is simply that its too thick to really give any useful membrane action. And especially in the corners, you don't get the benefit of the large air gap while mounting a wooden board. For the sake of ease of DIY, remove the wood, you're good to go. If you want to do a membrane absorber I would recommend reading around and experimenting with additional pieces after the basic treatments in the room have been covered (corners, first reflection points, etc)

To the OP, I think your new plan is good. Too many 2" thick panels just overdeadens the room, so using half of the traps but twice as thick will restore the high end while giving much better bass absorption.
 
GIK Acoustics said:
It isn't too different, the largest difference is simply that its too thick to really give any useful membrane action. And especially in the corners, you don't get the benefit of the large air gap while mounting a wooden board. For the sake of ease of DIY, remove the wood, you're good to go. If you want to do a membrane absorber I would recommend reading around and experimenting with additional pieces after the basic treatments in the room have been covered (corners, first reflection points, etc)

To the OP, I think your new plan is good. Too many 2" thick panels just overdeadens the room, so using half of the traps but twice as thick will restore the high end while giving much better bass absorption.
Click to expand...


Thanks for your input GIK - the 2" panels are hung every other stud all the way around the band and behind where I was standing when I took the pic. If I double them and remove much of the wood back (was thinking about cutting a large rectangle out of the middle of the wood backing so there is some wood to staple the cloth to and hang hooks from) this would give me (6) 4" bass traps. I was thinking about putting 1 in each verticle corner behind the band (all the way up against the ceiling), 2 panels stradling the ceiling corner behind the drums, and 1 panel on each side wall / ceiling corner. Is this the the arrangement that will give me the most coverage and "bang for my buck"?
 
5stringer said:
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Thanks for your input GIK - the 2" panels are hung every other stud all the way around the band and behind where I was standing when I took the pic. If I double them and remove much of the wood back (was thinking about cutting a large rectangle out of the middle of the wood backing so there is some wood to staple the cloth to and hang hooks from) this would give me (6) 4" bass traps. I was thinking about putting 1 in each verticle corner behind the band (all the way up against the ceiling), 2 panels stradling the ceiling corner behind the drums, and 1 panel on each side wall / ceiling corner. Is this the the arrangement that will give me the most coverage and "bang for my buck"?
Click to expand...

Yes, you can cut the wood to open up the back and keep it on the sides as a frame. Note that this isn't necessary for panels mounted directly on the wall.
I actually wouldn't worry too much about the ceiling wall corners for now. If you have 6 panels, then you would have enough to do one in each wall/wall corner now and two by the drumset. If you added more absorption, I would do it so that they go floor to ceiling in the corners.

Another idea is to use slats in front of the absorption to reintroduce life back into the room. This is something I suggest for a lot of tracking rooms as you can get scattering, diffusion, and absorption all in one package (though obviously a much more involved build). Something like this: GIK Acoustics Scatter Plate
 
GIK Acoustics said:
Yes, you can cut the wood to open up the back and keep it on the sides as a frame. Note that this isn't necessary for panels mounted directly on the wall.
I actually wouldn't worry too much about the ceiling wall corners for now. If you have 6 panels, then you would have enough to do one in each wall/wall corner now and two by the drumset. If you added more absorption, I would do it so that they go floor to ceiling in the corners.

Another idea is to use slats in front of the absorption to reintroduce life back into the room. This is something I suggest for a lot of tracking rooms as you can get scattering, diffusion, and absorption all in one package (though obviously a much more involved build). Something like this: GIK Acoustics Scatter Plate
Click to expand...

Thanks GIK - Is this the best arrangement or should the 2 panels behind the drumset straddle the wall/ceiling corner? (Please see the rudimentary photoshop "sketch" LOL)
The opposite wall (from the band - looking outward) is somewhat open so there really isn't much I can do about panels there. Do you see a bass trapping issue there? (see next post for a pic)

View attachment 79133
 
Last edited:
That is exactly what I was suggesting. No need to hang them from the wall/ceiling corner by the drumset, the wall reflections is what will make the biggest difference to your recordings.
If your ceiling is insulated, then it already acts as a pretty good bass trap in the first place. So when you get the insulation in there you might not want to hang much treatment on the ceiling corners as you'll get more bang for your buck in other corners.
Above the drums you could always build some simple empty frames and cover with fabric to replace the drop ceiling tiles too so the sound gets absorbed by the insulation above. Should give you much better recordings from your overheads.
BTW, my name is Alexander. :)
 
GIK Acoustics said:
That is exactly what I was suggesting. No need to hang them from the wall/ceiling corner by the drumset, the wall reflections is what will make the biggest difference to your recordings.
If your ceiling is insulated, then it already acts as a pretty good bass trap in the first place. So when you get the insulation in there you might not want to hang much treatment on the ceiling corners as you'll get more bang for your buck in other corners.
Above the drums you could always build some simple empty frames and cover with fabric to replace the drop ceiling tiles too so the sound gets absorbed by the insulation above. Should give you much better recordings from your overheads.
BTW, my name is Alexander. :)
Click to expand...

Thank You Alexander!

Do you think I will need anything on the other side of the room? The opening in the wall and the doorway make it pretty hard to add any 4" bass traps.
Also, would you recommend any particular insulation for above the drop ceiling...or just the pink, home insulation? I'm not aware of any "batts" for acoustic
treatment.

Thanks for all your help!
 
I don't think it's necessary for now. Maybe if you find yourself recording other instruments closer to there often you might consider it (could always consider panels on stands as well for recording use).
For above the drop ceiling, use standard pink fluffy / building insulation. OC EcoTouch or whatever is available in your area. Use the thickest pink fluffy insulation you can fit. Don't pack it tight - but get the correct amount. If there's 6" of space, get 6" thick fluffy. The "r" value when comparing the same product is just a different thickness BTW. Though some also have foil attached for an added price, and that's unnecessary for you so don't worry about any facing.
 
GIK Acoustics said:
I don't think it's necessary for now. Maybe if you find yourself recording other instruments closer to there often you might consider it (could always consider panels on stands as well for recording use).
For above the drop ceiling, use standard pink fluffy / building insulation. OC EcoTouch or whatever is available in your area. Use the thickest pink fluffy insulation you can fit. Don't pack it tight - but get the correct amount. If there's 6" of space, get 6" thick fluffy. The "r" value when comparing the same product is just a different thickness BTW. Though some also have foil attached for an added price, and that's unnecessary for you so don't worry about any facing.
Click to expand...

I have alot of plumbing / electrical fixtures and wires above the drop ceiling making it a little difficult to put insulation there. Would I get a similar result from dropping
in some 3" thick ceiling tiles made for absorbtion....leaving the space above un-treated?
 
mjbphotos said:
3" thick ceiling tiles? never heard of them. they're probably heavy as hell!
Click to expand...

Actually, they are made for this application. Cut a little smaller so you can drop them right in without any trouble.
If they are OC703 - they won't be heavy at all. Just wondering if the result (bass trapping) will be similar to insulating
the floor joists above the ceiling.
 
Ethan Winer said:
RealTraps sells ceiling tiles 1-1/2 and 3 inches thick. They're heavy, but not too heavy for a normal ceiling grid. See the bottom of this page:

RealTraps Ceiling Tiles

--Ethan
Click to expand...

Thanks Ethan.

Will the RealTraps ceiling tiles work better than insulating above standard ceiling tiles? How effective is insulating above my current drop ceiling?
I thought the sound would just reflect off the ceiling and not even get to the insulation behind it.
 
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