thinking of treating walls in order to get rid of Low-mid up

Hi all, I've got a studio in Brooklyn that has pretty decent sound, but our recordings always need to have freq's in the area of 200-500 cut out. There are also ceramic brick and drywall walls, which lead to some crappy sounding reflections. We're trying to find ways of getting the HF reflections to be a little nicer, yet get all the woofiness out of the room. We're thinking maybe suspend some helmholz-type traps off the walls.-- Horizontal slats of wood with some space in between the slats, with a couple inches of insulation behind them. As I'm sure everybody knows, experimenting in this area of expertise ain't cheap, so we're trying to get it right the first time. Details: We don't have to worry about noisy neighbors or anything like that. It's a commercial loft in Brooklyn. The floor is carpet which sits on some sort of epoxy coating sprayed onto brick. Ceilings are drywall, about 11.5 feet high (I included a sketchup for details). There is a vocal booth installed in one corner of the room, and two of the walls were built so that they wouldn't be parallel with their counterparts on the other side of the room. We have resonator traps (a la Ethan Winer) up on the walls and corner traps up in the ceiling corners, which have helped a lot. But the main question, again, is how do we smooth out the reflections from the brick, yet kill the mud? Any thoughts? -Hild

A couple of points: From your description, I guess we are talking about a live room (tracking room), not a control room, correct? It isn't surprising that you have serious issue with that room: it is square! You say the height is 11'5", and the width is also 11'5". Your modal distribution diagram is lit up with red flags all over the place! The Bonello diagram has several kinks in it, too. Your solution should probably start with changing the position of either one of the walls, or of the ceiling, or both. Have you measured the room response? If not, then please do so and post the result here, to see where / what your room is really doing. But theory predicts serious issues around roughly 30 Hz, 49 Hz, 60 Hz, 75 Hz, and around 100 Hz, plus of course the harmonics of those. How much bass trapping do you have in there, and what type?

We're thinking maybe suspend some helmholz-type traps off the walls.-- Horizontal slats of wood with some space in between the slats, with a couple inches of insulation behind them.

Slot walls. Quite possibly that would be part of the solution, but first it would be useful to see the room response graphs, and some photos of the room, too.

As I'm sure everybody knows, experimenting in this area of expertise ain't cheap, so we're trying to get it right the first time.

A broadband slot wall combined with proper bass trapping shouldn't be too expensive, and shouldn't need any experimentation.

the floor is carpet which sits on some sort of epoxy coating sprayed onto brick.

It wouldn't surprise me that the carpet is part of the problem, too... What kind of instruments are you tracking in there? Anyway, the results of the room response analysis and a few photos would help to get a better idea of what is going on in there. - Stuart -

Soundman, much obliged for your insight. Yes, you are right, we are using the room for tracking. Drums and guitar amps, mostly, but sometimes we squeeze a group in there, if possible, we have some decent separation via gobos. The bass traps on the walls are resonator type traps. The design came from Ethan Winer's site. It's basically a box designed to soak up resonance at mid/low-mid frequencies. When we put them in, there was an improvement, thought not too much. We stuck a big corner trap up in one ceiling corner--4" of rigid insulation spanning the corner. This made a big difference. Then we installed traps on an adjacent corner of the ceiling which was loaded with even more insulation (more=better, right? :/ ) and that helped even more. But we decided if we kept going that route, we'd run out of corners. Thus my questions here... I'll get on it with the pics and the room response and post back soonly. Again, thank you for your help! -Hild

Drums and guitar amps,

Let me guess: the room itself sort of hums along with the guitars on some chords, right? But slightly off-key? :) And the toms don't sound right?

The bass traps on the walls are resonator type traps. The design came from Ethan Winer's site.

Resonators traps are (by definition) tuned to specific frequencies. The ones you build may or may not have been tuned to one or two of your problematic frequencies, but even if that's the case, then they would only be treating those specific frequencies: however, you have more than a dozen problematic frequencies below 100 Hz alone, and nearly one hundred problematic frequencies below 200 Hz! So at best your tuned traps will be dealing with a tiny fraction of your problems, whereas your corner-straddling bass traps are broadband by nature, and are dealing with large bunches, all at once. That's the way to go initially, and only adding tuned traps later, if you are still left with a couple of stubborn frequencies.

But we decided if we kept going that route, we'd run out of corners.

Well, a room has twelve corners.... treating them all with bass traps would probably help greatly! By the time you get to treating 6 or 8 of them, I bet you'll find that things improve considerably. But you might end up making the room too "dead" like that, since you'd be sucking out mids and highs too, not just lows. So you could consider putting something thin and flexible across the front of your bass traps, such as plastic, to help keep the highs in the room while still dealing with the lows.

We stuck a big corner trap up in one ceiling corner--4" of rigid insulation spanning the corner.

Have you considered putting superchunks in the vertical corners? Big, wide, deep ones... But you might still need treatment for the mids, though, so I'm thinking "slot wall" for that... But let's see your photos and room response first. - Stuart -