Help me with my low mid hump - Please!

[Dayo]

First of all, thanks so much for looking at this, and thanks in advance for your thought and insights.

It's my voice-over booth.

Well first of all, it's not a linear hump that you could cook out with EQ. It's more of a resonance, or ring. Can't pinpoint it exactly, but a fellow gearslut has indicated that it'll be in the 300 to 500 Hz region.

And secondly it's not so much a booth, more of a screened off area that includes a small walk in closet.

I'll try and describe;

Imagine a typical small bedroom. 12 foot by 8 or thereabouts.

At one end is a small walk in closet, 4 foot 6 wide and 2 foot deep. Stand just inside the closet and face back into the room and that's where the mic stands. 3 or 4 feet in front of you is a free standing acoustic screen, like a 6 foot by 6 foot tall office divider. This screens off the booth area from the rest of the room. It's got a 2 inch layer of rockwool covered with fabric. On top of that is are a couple of Auralex panels, 2 inches deep, making a total of 4 inches. On the reverse of all that is a hardboard panel.

Above you, on the bedroom side of the closet is a large panel hanging from chains from the ceiling. It's got 2 inches of rockwool, covered in fabric and hangs about 18 or 20 inches off the ceiling. Total area about 5 feet by 5.

Nearly there! The closet (behind you, remember?) is like a giant bass trap. There's a large limp membrane bass trap, 4 foot by 6 foot. In the corners a couple of LNRD Auralex things and pair of home made low mid rockwool bass traps. Above you in the closet is another large haning panel, stuffed to the gunnels with all the spare rockwool I could find. NB - it's the high density RW 45 stuff.

The rest of the room - outside of the booth area is pretty much untreated.
But a sofa acts as an aborber of sorts.

So, my feeling is that the low bass is quite well tamed. The booth area is reasonably dead, but far from anechoic. It breathes. So what's causing this low mid resonance?

And most importantly, how can I fix it, cheaply and quickly?

Would it be helpful if I drew a plan?

Is the resonance perhaps coming from the larger part of the room that is untreated? Our work is voiceover, and when I'm in the booth area, not too much voice escapes into the room, so I find it hard to believe it's exciting any room modes. So, I'm at a bit of a loss, since I've got so much absorbtion going on and in places it's quite deep. The limp membrane trap is obviously working well too.

As we say in the UK, I'm flummoxed!

Help, please....

Big thanks

Dayo

[Ethan Winer]

If you can post a photo that will help a lot. From the sound of it, you basically need corner bass traps and possibly other absorbers elsewhere.

--Ethan

[Dayo]

Pic attached Ethan.

Hard to photograph I'm afraid. The bass traps are repeated on the corner of the closet that you can't see in the pic.

Thanks!

[jhbrandt]

Dayo,

Yes, you do have modal resonance problems. From the pic it looks as though you have the mid-range taken care of, but you need proper bass traps to address the particular problem frequencies.

Can you give exact dimensions of your rooms? H X W X D of both rooms. I will calculate your modes for you and can then suggest what kind of trap you will need to build or buy.. or Ethan will.

Cheers

[Dayo]

Ethan and John

Thanks again for your help. I've never drawn anything on my computer before, so the attached pics are painfully amateur I'm afraid and certainly not to scale.

Hope they help. I've done a floor plan of the whole room and a vertical detail of the closet/booth area.

In case it's not clear the carpet felt/barrier mat/rockwool at the back of the booth are the components of my limp membrane bass trap.

I can't believe that there is enough voice escaping from the performace area to excite the room modes in the main part of the room. Bear in mind it's just teh boot area that concerns me and what I'm recording. Playback/monitoring is not the priority at the moment.

Thank you so much again.

[Ethan Winer]

Originally Posted by Dayo

I can't believe that there is enough voice escaping from the performace area to excite the room modes in the main part of the room.

I assume the main resonance problems are due to the parallel walls of the booth itself. As John said, the booth itself needs bass traps. 2-inch thick foam or insulation are not thick enough, especially when mounted flat on the walls and ceiling.

--Ethan

[Dayo]

Originally Posted by Ethan Winer

I assume the main resonance problems are due to the parallel walls of the booth itself. As John said, the booth itself needs bass traps. 2-inch thick foam or insulation are not thick enough, especially when mounted flat on the walls and ceiling.

--Ethan

Assume from that Ethan that you're not a fan of the limp membrane design that's currently in there?

[Ethan Winer]

Originally Posted by Dayo

Assume from that Ethan that you're not a fan of the limp membrane design that's currently in there?

Without knowing the details of their construction it's impossible for me to comment.

--Ethan