Live rehearsal space and concrete surfaces...

i008580
New Member

Posts: 3

Live rehearsal space and concrete surfaces... May 26, 2016 16:44:51 GMT

Quote

Post by i008580 on May 26, 2016 16:44:51 GMT

Greetings! I have a rehearsal space that sounds horrible. My goal is sound absorption; minimize reflection/bounce, especially at low end. The room is very rumbly. As you might imagine after reading about the details of the room, no one can hear what is going on. Only concerned about the general live sound of the room; there is no central listener spot to tune; not a recording studio. Willing and ready to put the effort and money into improving the situation, but suffer from being at the beginning of an acoustics learning curve!

About the room (it's a garage)
- Room is 26x24, ~8' ceiling

- Front wall (back of speakers to this wall) is Concrete.

- Back wall (speakers facing) is interior 2x4 wall with 1/2" drywall

- Side walls - one side is two garage doors (Sometimes open, sometimes closed... obviously bounce is less when these are open, but not anywhere near acceptable.) Other side wall is hollow 2x4 partition wall with 1/2" drywall, not insulated, concrete wall ~3' behind the partition wall.

- Floor is concrete

- Ceiling is 1/2" drywall

Concerns about the front wall
Drums, bass guitar speaker and two main speakers (vocals+keys) are on stands ~16" from the front concrete wall (top of speakers is ~36" from ceiling).

I've been worrying and reading about whether/how I should treat the front wall behind the speakers. Most of what I read says that effectiveness of covering the wall with absorbing panels or foam is minimal with regard to addressing low frequency issues. These usually focus on the limited sound coming out the back and sides of speakers. But as I have a live drummer sitting with his back to the wall, there is a lot of sound heading in that direction...

Back wall (is 20'+ from where the drummer is sitting)
The back wall seems pretty straightforward... - absorption panels or 2" foam, and bass traps for the corners. I've read the great article by Ethan that talks about either rigid fiberglass panels in the corners with a large air gap, or simply stacking bales of fiberglass insulation. Which would be best for my situation? I am happy to do either, but as the air gap is praised as a virtue of the 1st technique, I don't know whether the bale stacks is as good an option, or whether the bulk is actually better than having the airgap...?

For the ceiling, I assume foam would make the most sense, and maybe traps for the corners where ceiling meets vertical walls.

Finally, I am planning to make use of large, thick (85g weight fabric) moving blankets wherever they give the best effect.
If this sounds like a good idea, I will buy as many 72x80 blankets as it takes to enclose a space around the band... ?

This is what I have gotten from my few hours of reading... but I would be so grateful for any suggestions. Specifically:

? - Best treatment for the front wall as described... implications of a live drum kit against a concrete wall is something I haven't seen addressed...

? - Best route to go for corner traps in my situation - stack bales of insulation, or rigid fiberglass panels with a significant air gap behind...

? - Thoughts on the use of the moving blankets described above...

Finally just to summarize on goals -

- I'm mostly concerned about controlling the muddy low end situation

- As it's not a recording space, it's about overall general clarity of sound in the room. Minimizing the reverb/bounce effect. Not about soundproofing, not about creating a "true" mix in a specific sitting location.

- Based on where I am now, I would say the "deader" I can make the sound, the better. I read a lot of controversy about that; but given the size and materials in this room, I can't imagine I'll get to to point where it sounds "too dead".

Any and all advice would help! Thanks!

Kevin

Last Edit: May 26, 2016 16:53:33 GMT by i008580

Rock
Guest

Live rehearsal space and concrete surfaces... May 26, 2016 17:59:03 GMT

Quote

Post by Rock on May 26, 2016 17:59:03 GMT

What it sounds like you need is absorption at all frequencies everywhere. You mention bales or rolls and that will be a the easiest for bass traps; all you need to do is stack them in the corners to the ceiling. If your set up is temporary, you could sell the insulation for construction or whatever on CL in the future. If you want to build corner traps, that's more work but it all depends. For the walls, you can hang absorbers or if you want more coverage, build an open frame, floor to ceiling and fill the cavities with insulation. If you leave a space behind the insulation (8" + 8" un-faced fluffy insulation) you walls will be wideband absorbers. You can do one at a time and see how it sounds as you go. I like a dead rehearsal space, I think it makes it easier to hear everything. Diffusors are great in front of the absorption but that gets expensive, time consuming or both ... but it you want, you can add them later.

Cheers,
Rock

Ethan Winer
Administrator

Posts: 790

Live rehearsal space and concrete surfaces... May 26, 2016 17:59:23 GMT

Quote

Post by Ethan Winer on May 26, 2016 17:59:23 GMT

For a rehearsal room that's not a studio, the main goal is to spread the absorption more or less evenly around the room. So put some on each wall where you can, and some on the ceiling. I'd use rigid insulation four inches thick everywhere. They mostly go on the walls, but I'd also straddle the corners to increase absorption at low frequencies.

--Ethan

Ethan's Audio Book
The Acoustic Treatment Experts

i008580
New Member

Posts: 3

Live rehearsal space and concrete surfaces... May 26, 2016 18:06:23 GMT

Quote

Post by i008580 on May 26, 2016 18:06:23 GMT

Thank you Ethan and Rock! One follow up based on reading the FAQ... (GREAT article, BTW). It is described that low frequencies are not well absorbed when attaching the traps directly on vertical walls... something about the long wavelength of low frequencies, and them needing absorption when they are moving toward and away from a hard surface.

So, seeing that I have the space, would be be ideal to build large floor to ceiling freestanding panels (roll aways) and pull them 2-3ft away from the walls when in use? Or did I misunderstand that part?

Thanks again!!

Rock
Guest

Live rehearsal space and concrete surfaces... May 26, 2016 22:06:53 GMT

Quote

Post by Rock on May 26, 2016 22:06:53 GMT

The idea of spacing panels away from the wall allows a given thickness more effectiveness at lower frequencies "for free"as opposed to using twice the thickness right up against the wall, which would actually be better...but more expensive too. Typically the space equals the thickness but it can be more or less. It does work for lower frequencies farther than equal the thickness but if you take take that idea to extremes, you'll be in the middle of the room and the bass tends to "pile up" in the corners and boundaries so I don't know how much you'll gain farther than equal the thickness but if the panels are portable, you can experiment.

I suggested building a frame floor to ceiling because hanging stuff on a concrete wall can be a pain and spacing it away from the wall is easy if you're "stick building", but on your stud and drywall, it's not as much of a problem to hang panels but you still have to build them and figure out a way to space them from the wall.

Like Ethan said, spread it around, and to help kill flutter echoes, alternate panels on opposite walls.

Cheers,
Rock

i008580
New Member

Posts: 3

Live rehearsal space and concrete surfaces... May 26, 2016 22:19:03 GMT

Quote

Post by i008580 on May 26, 2016 22:19:03 GMT

Thanks guys for the great explanations and advice! As Rock indicates there should be nothing materially wrong with building rollaway rigid fiberglass panels, I'm going to try that out. It has the added benefit of being able to roll them away when not in use and freely positioning them at whatever distance from the back wall works best. I'll let you know how I make out!

Hexspa
Global Moderator

Am I A Musician Or?

Posts: 2,176

Live rehearsal space and concrete surfaces... May 27, 2016 3:34:12 GMT

Quote

Post by Hexspa on May 27, 2016 3:34:12 GMT

This sounds like an inverse of the classic mixing mistake about too little bass. Essentially you might think there's too much rumble when in fact, the 4" panels will probably solve your problem since they're effective at "mud" frequencies of 250-500Hz, NOT 40-80Hz and definitely not 20-40Hz or less (where actual rumble is).

Don't worry about bass right now, just do 4" with 4" air gap evenly distributed as suggested with (all if possible) your corners having straddled 4" panels.

Or, if as you say it' can't be "too dead", do 24" thick fluffy with a 24" air gap everywhere but the floor. Heck, do the floor too and walk on mesh.

It might not be a "recording studio" but sound is sound, ears are ears and, more or less, we're all striving toward similar goals.

-m

Last Edit: May 27, 2016 3:38:06 GMT by Hexspa

Words and music.