question about absorption in a small drum room


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So, I got this small room made out of thick concrete walls where I record my drums. It's 3.35m x 3.35m x 2.15m, doesn't have windows and just a small metal box where air gets "indirectly" through (airwaves hit metal) - it's a bunker. I sit asymmetrically close to a corner for now. The goal is to have it pretty much dry, especially behind the kit, over the kit, corners (3 can't really be treated, 2x ceiling :( ), some in front of the kit and then i experiment with the sides; much of which will be accomplished with mobile absorption walls (t.akustik mobile wall) - for which i have a side question: I have 3 setup in front of the kit, 2 or more to the sides and 4 behind me. Is it better to get them close to the kit like a "room" in a room or as close to the walls as possible? Maybe even use the foam directly on the wall - although I would have more absorption panels for that-? I sure will experiment, but putting panels up isn't easily reversible..

Alright, the main question is about the ceiling treatment. Oh and btw, one corner has a AVAA C20 in it (will get another), which is really helpful for all the boom in that room and tuning of the drum, dynamics and dampening can only do so much.. I have yet to decide how I'll treat that... 2 ceiling corners have big bass traps and the rest has to be installed. I have this ceiling cloud made out of PET (t.akustik_pet_ceiling_absorber_120_wh), which I also could use elsewhere, and lots of thicker basotec panels. I never saw somebody using a ceiling cloud to record drums and never experienced them.

I also have quite some thicker HOFA absorbers for the lowmids, where would be good places to put them besides the mid points of the walls? Also, am I correct in assuming, that diffusion won't help much in my situation (I don't plan on using a room mic yet, for the AEA R88A in a M/S configuration in front of the kit seems to sound best as of yet, the rest, close mic'd)?

please excuse my french.

addendum: the floor just has a thick rug under the kit.
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I'm not sure if this forum sends link to this user I posted above. John Brandt would be the one to ask these questions. Try sending him a message.

Google him and you can find his resource page with a shit ton of info.

I'm not sure if this forum sends link to this user I posted above. John Brandt would be the one to ask these questions. Try sending him a message.

Google him and you can find his resource page with a shit ton of info.
Thanks for the reply and the info!

I am reading into one thread from him about treatment in small rooms. Good stuff, some explanation baffled me - and still does.

The main thing about which I can't find an answer yet, is the placement of the mobile walls and the usefulness of a ceiling cloud over foam panels.
What I know basically comes from Mr Brandts writings and lots of Skype conversations with him. So any advice I give is 2nd hand from what I have read and what I have applied in my studio. I have paid him for a full control room design with CAD drawings and plans for everything, but have not yet found the time to build it...
Now, there is quite a large difference between how one would treat a live room and a control room. In a live room, you typically don't necessarily want it to be completely dead, but that just depends on the room itself as well as what you are recording.

Looks like you have invested quite a bit in products already. Man those AVAA's aren't cheap huh?

So, looks like you have a bunch of foam products and some made of other materials that I'm not sure about. Keep in mind the foam ones and the 2" ceiling PET's are only really dealing with high end reflections. Even the 4" HOFA's are really only effective down to about 450hz and drop off quickly below. And keep in mind that is only effective in the area it covers. The untreated areas are reflecting everything back. Not always an issue in a live room though. Room modes are killing you in that space, but then you are not necessarily looking for a flat response in there... You can see what I mean by entering your dimensions in Johns 'Room Mode Calculator'. Not much you can do about that in such a limited space, but it may help you to understand what is happening in your room. Hey, what are the ceiling corner bass traps? I'm hoping not foam...

So, start with what you can do in your space. A basic starting point for a live room is to leave 3 non paralel walls untreated. Typically in a drum room you want the floor to be a reflective/hard surface. The thick rug is probably ok. I use a thin piece of 8x10" commercial carpet in my drum room which is concrete floor and 3 walls (basement). Also in my drum room if a fully treated ceiling, 6 4" rockwool panels staggered on opposing front and back walls with some office divider panels hanging at an angle on the side walls.

What is your ceiling construction? Can you open up the ceiling? Are there floor joists above? I ask because I have great results in my 27' x 13' x 8'3" drum room with the ceiling filled with rockwool insulation that is covered with polyester cloth. That will soon be replaced with a combination of 4" 'limp bag' absorbers and a 4" layer of pink fluffy stuff. Seems you will be getting crammed in there dropping a cloud with only 7' in height to deal with. For a drum room you want as much space as possible above the kit as you can squeeze. That is where you will get the most reflections from cymbals that makes them sound like shit. I was amazed at the difference filling the ceiling helped with that. Also on a side note, get some boom stand ceiling mounts for your overhead mics. Saves you a bunch of space and gets you tight to the ceiling. Also easier to experiment with mic positioning.

And yeah, I'm not sure any diffusion will do you any benefit in that room and its purpose. Use your money elsewhere.
The question I have is a simple one. What does it sound like?

Before you do anything, that's top of my list. Loads of people work to formulas, or pictures on the net, but if it is a concrete bunker, then it probabloy doesn't have anything capable of resonating, like panels, so your potential treatment is simpler - sound in and out is controlled already, so it's reflections and those nasty sum and difference frequencies that exhibit as peaks and nulls in the response. Play some pink noise and tone sweeps and see where the room needs taming, and just a vitally, where it doesn't. Then you can make sensible purchases or build stuff.