Space Between Bass Traps and Wall or Not?

[Jens Eklund]

Originally Posted by npatro22

Most pro studios have the bass traps hanging like paintings on the wall, ...

I have never seen what you’re describing in a "pro" studio. Broadband absorbers maybe but not bass absorbers.

[Glenn Kuras]

Originally Posted by npatro22

Most pro studios have the bass traps hanging like paintings on the wall, isn't it better to have space in between the wall and the bass trap or will there be a huge difference?

Basically yes, when spaced off the wall it will absorb more low end. But when using broad band panels it is best to straddle the corner to get the best bang out of them. Not that they actually go "bang" but.......

[johndykstra]

Oh Jens....

OP,

It's definately a good idea to get air behind the trap.... space from the wall. 'Free depth' some call it. It makes the trap more efficient at lower frequencies without having to purchase more fiber.

Keep in mind, that just because you see the trap frame touching the wall, does not necessarily mean that the fiber is full frame depth... there may be space in there.

Jens is implying that most "pro" joints don't really hang traps, rather they are built into the wall structure.

[npatro22]

thanks glen

[Jens Eklund]

This might interest you npatro22:

Air gap: maximum size?
first reflection panels density and thickness
PAROC WAS 50 sound absorption?
http://www.gearslutz.com/board/bass-...ml#post6280707
this type of rock wool could work?
bass traps done, what next?
Velocity based vs. pressure based absorbers

[JoRillo]

Originally Posted by Jens Eklund

This might interest you npatro22:

Air gap: maximum size?
first reflection panels density and thickness
PAROC WAS 50 sound absorption?
http://www.gearslutz.com/board/bass-...ml#post6280707
this type of rock wool could work?
bass traps done, what next?
Velocity based vs. pressure based absorbers

Thank you for actually helping the man with location links rather then just saying "Try Search." There needs to be more of you. lol

[Einstein]

Originally Posted by JoRillo

Thank you for actually helping the man with location links rather then just saying "Try Search." There needs to be more of you. lol

Man, Jens has a machine gun loaded with good links. I swear he has a program where every thread on this forum is organized into common topics. This way when someone asks a question he can just hit the button that applies to the topic and off they fire.

[Glenn Kuras]

Originally Posted by npatro22

thanks glen

No problem.

[avare]

Originally Posted by npatro22

Most pro studios have the bass traps hanging like paintings on the wall, isn't it better to have space in between the wall and the bass trap or will there be a huge difference?

The query does not make sense by itself. Bass traps can be solid backed or open backed with porous fronts or solid fronts.

It all depends on the specifics.

No insult intended to great GS friends who have tried answer your question without asking for necesary details and then working on their assumptions.

Andre

[Glenn Kuras]

Originally Posted by avare

The query does not make sense by itself. Bass traps can be solid backed or open backed with porous fronts or solid fronts.

It all depends on the specifics.

No insult intended to great GS friends who have tried answer your question without asking for necesary details and then working on their assumptions.

Andre

Good point, my answer was based on open fronts and backs. Maybe I should not think that is a given anymore.

[localhost127]

Originally Posted by Einstein

Man, Jens has a machine gun loaded with good links. I swear he has a program where every thread on this forum is organized into common topics. This way when someone asks a question he can just hit the button that applies to the topic and off they fire.

i did the same thing with my bookmarks last weekend, lol (4hours well spent)... for my own reference of some of the gems within this sub-forum, and also for quick links when someone else is in need of explanation.

[DannyMac]

When using rockwool, spacing them from the wall will give a better result,
Using proper solid membrane then efficiency will be highest close to the wall

[avare]

Originally Posted by DannyMac

When using rockwool, spacing them from the wall will give a better result,

Correction. When using rockwool or moderal wool, the gas flow resistivity of the material should selected to give optimum absorption with the depth of the material AND the depth of the space behind the material being siginificant factors.

There is no cut and dry for all depths.


Andre

[Craigster]

Originally Posted by avare

Correction. When using rockwool or mineral wool, the gas flow resistivity of the material should selected to give optimum absorption with the depth of the material AND the depth of the space behind the material being significant factors.

There is no cut and dry for all depths.

Andre -- could you add a little detail to this, or confirm/edit my understanding?

- If you are using LOWER density material (i.e. Safe N Sound, 4-6 lb Roxul rockboard, OC703) for bass trapping purposes, then you can pack the corners -- as air is able to move through the lower density.

- If you are using HIGHER density material (i.e. 8 lb rockboard, OC705) for bass trapping purposes, then you are better off leaving an air chamber behind - so that air is not stopped, but can continue to move through.

- With broadband panels, you can greatly increase the effectiveness (including lower frequencies) by leaving an airgap up to equal the panel thickness (i.e. a 4" gap for 4" panels).

Please confirm or edit.

Craig

[BriHar]

If we're speaking about absorber panels as opposed to actual tuned traps, then keep in mind that the absorbers work on the velocity component of the wave which is virtualy zero at the surface of the wall, so spacing away from the wall will afford greater efficiency. Theoretically 1/4 wavelength of the primary frequency being addressed would be the optimum distance (including the thickness of the panel), in practice however this is usually impractical.

[Michael E]

Maybe a stupid question, but...
What is the best option for wall Rockwoll panels?

• 5 cm depth & 5 cm distance from the wall
  or
• 10 cm depth & NO distance from the wall

[avare]

Originally Posted by Michael E

Maybe a stupid question, but...
What is the best option for wall Rockwoll panels?

• 5 cm depth & 5 cm distance from the wall
  or
• 10 cm depth & NO distance from the wall

It depends on the material. For 64 kg/m3 material, full is best. For denser material have the gap.

Andre

[JLiRD808]

Slightly related, hopefully Im contributing and not thread jacking.

What if I have plenty of 705 (or other porous absorber) and want to build a corner trap. Does the air gap help (straddle style) or can I go ahead and build a big FAT PILLAR in the corner with no air gap?

THANKS!!

[kasmira]

Originally Posted by JLiRD808

Slightly related, hopefully Im contributing and not thread jacking.

What if I have plenty of 705 (or other porous absorber) and want to build a corner trap. Does the air gap help (straddle style) or can I go ahead and build a big FAT PILLAR in the corner with no air gap?

THANKS!!

The air gap helps but usually fully filled is better. Do you actually have 705 on hand? If not, I wouldn't suggest buying it - it is quite expensive and you would get better results with large square traps in the corners made of light, simple, cheap attic insulation.

[JLiRD808]

Yeah I have a great deal on 705...and access to pretty much an unlimited supply.

[Glenn Kuras]

Originally Posted by JLiRD808

Yeah I have a great deal on 705...and access to pretty much an unlimited supply.

Since you are using 705, I would make the panel around 8" thick (2' face) and straddle the corner vs doing a pillar design. BTW if you do a pillar design you want to make it no less then 17" on the sides.

[JLiRD808]

Originally Posted by Glenn Kuras

Since you are using 705, I would make the panel around 8" thick (2' face) and straddle the corner vs doing a pillar design. BTW if you do a pillar design you want to make it no less then 17" on the sides.

Thanks Glenn...another issue thats come up in another thread is that I have a superchunk in the opposing corner. This 705 trap would be behind my right monitor, I have an R30 chunk from ceiling to floor behind the left monitor.

U see any issues with this?

Also...I heard the size of the straddle trap and air gap helps with particular freqs whereas the pillar would be more broadband...agree?

[JLiRD808]

Also Glenn....the pillar was gonna be 12"x24"x8'....u say at least 17" so I would need to do 17"x24"x8'?

THANKS!!

[kasmira]

Originally Posted by JLiRD808

Also Glenn....the pillar was gonna be 12"x24"x8'....u say at least 17" so I would need to do 17"x24"x8'?

THANKS!!

JLiRD,

A 17" square has double the amount of insulation than a 12" square. Does a 8" absorber work better than a 4" absorber? Yes.

You don't 'need' to make it any size, but if you want effectiveness and great low end absorption, bigger is better. 24" would be even better than that...assuming you could spare the space and material. (Of course, anything this large would be much more effective if built with very porous stuff - attic insulation - not 705 or the like).

I really think the OP should get some measurements up in here. All of our suggestions are based on speculation of what is typical in a room...if we knew what was going on in there currently from an actual tested acoustic standpoint...I think we'd all be able to help more.

Sent from my SCH-I535 using Tapatalk

[Glenn Kuras]

the pillar was gonna be 12"x24"x8'.

I have never tried that size flat in the corner so no idea how well it would do. I would think pretty well over all.

[JLiRD808]

Picked up my stack of 705 yesterday....just gotta cut n wrap, probly this weekend.

Im thinking of just going as FAT as I can which would be pillar style...no air gap. 12"x24"x8'. If symmetry flies out the window I can just move it and do a superchunk.

I guess I can do that or a straddle strap...24" face and basically up to about 9" thick before it juts out too far and hits a nearby small bookcase. Again...back to air-gap vs pillar LOL.

[kasmira]

If you could find a GFR number for the 705 you could use absorption calculators to match the absorption as close as possible between the two traps. Just a thought.

Sent from my SCH-I535 using Tapatalk

[avare]

Originally Posted by kasmira

If you could find a GFR number for the 705 you could use absorption calculators to match the absorption as close as possible between the two traps. Just a thought.

30,000 Rayls. Ask and you shall receive!

With good resistance,
Andre

[JLiRD808]

Hmmm...how do I do this? Where is the absorption calculator?

THANKS!