Jus another Bass traps question

[Gerax]

Hi everybody

I was checking out some topics about bass trapping here on the site and even though I've found several intersting and usefull infos I'd like to explain my situation and see if I can get some answers specifically related to it.

My project studio is laid down like the pic I attached, where the speakers are hung over the DAW desk, the red dot is my working position.
At the moment I have taken care (successfully) of the high end reflection with some absorptive panels on side and front wall and ceiling. The floor is parquet and I have a carpet down at the DAW to create an effective RFZ. The rest of the studio walls is wood panels, which gives the acoustic a nice environment, diffuse but not too mutch. The black rectangle in the back is a 2 seat leather couch. Ceiling height is a bit low, about 8'.

My Problem is that I'm having an annoting (you guessed it) resonance and bass buildup at about 60-to 120 Hz, a thing that I marginally reduced with the two corner traps I built (the two green triangles in the corners): those two are a sandwich of plywood sheets that go from floor to ceiling about 2" thick and the resulting cavity formed by that and the two walls is filled with slabs of cut rockwool (703 fiberglass is not easy to find here, so I went with rockwool, as I red somewhere that is a good substitute). Back in my previous studio the two panels worked quite well, but having expanded to this situation recently I'm experiencing this problem.

Based on this what do you think I should do to improve the bass response(I'm monitoring on Genelec 1030A and Tannoy Nearfields) which seems inaccurate and suffers from this annoying resonance: I work a lot with a producer who's a double bass player and double bass is always featured in his records, so I really NEED the low end to be right and accurate (every time the bass hits some particular notes which go around those frequencies I've pointed out the room shakes quite a bit...), plus I'm considering a future expansion to 5.1 for video projects, so I have to have to room tuned.

Thank you very much for your help.

L.G.

[Ethan Winer]

LG,

> what do you think I should do to improve the bass response <

Remove the plywood because it's preventing the rock wool from absorbing as much as it could.

> I really NEED the low end to be right and accurate <

You need to add more bass trapping in the form of rock wool straddling the corners. Treat all of the corners, including the corners at the tops of the walls where they meet the ceiling. If you have room, do the same at the bottom of the front wall too. The more bass trapping you add, the flatter and tighter the low end will become. It's as simple as that.

--Ethan

[Gerax]

Ethan

Thank you for your reply.

If it really is that imple I'll try as soon as possible.

If you say that rockwool is similar in acoustic properties to fiberglass I have a pack laying in the storage room that may be worth using. A few questions: do I have to put it in as intact (big sheets) as possible or can I cut it to fit shape? And being that rockwool is toxic can I wrap it in some fabric to avoid it loosing powder, yet still keeping its absorptive property? Does the thickness of the rockwool has an influence on the absorption, I mean if I put several sheets together to form a 10" thick sandwich is it going to have more absorption, right?

Thank you again for your expertise and help.

L.G.

[Ethan Winer]

LG,

> can I cut it to fit shape? <

Acoustic treatment is all about coverage. The larger the surface you treat, the more absorption you get overall.

> Does the thickness of the rockwool has an influence on the absorption <

Yes. For the complete story see the Acoustics FAQ, second in the list on my Articles page:

www.ethanwiner.com/articles.html

--Ethan