Maximizing sound panels in a rehearsal space

[Chris Fitzgerald]

At my university, we are converting an unusual shaped office into a rehearsal space for jazz combos. Walls are drywall, drop ceilings are about 10’, and the floor is carpet squares over concrete. Outside walls have large banks of windows about 4’ off the floor. See picture below:

The space is kind of weird, but it’s what we have. The groups will usually be rhythm sections (pno, gtr, bass, drums) plus a couple of horns. The 7’ grand piano is tentatively scheduled to go in the narrow end of the office with the lid opening into the room. Bass in the crook facing in, drums on the other side of the bass, guitar on the other side of the drums. Horns along the diagonal wall space pointing in toward the rhythm section.

The school has budget for 11 1.5” panels. Current thinking is 9 4x4’ panels and 2 2x4’ panels. The panels are to help tame the sound as much as the budget will allow. It’s not ideal, but again, it’s what we have.

One desired outcome is to insulate the office next door from too much bleed, but we understand that anything we do will be stopgap. Main goal is just to tame things a bit. I was thinking of stacking the 2x4 panels across the lower right corner, which is the only true corner in the room, as a makeshift bass trap.

The question is where to place the remaining panels for greatest effect? The powers that be are thinking 4 on the wall between the two rooms, and the other 5 somewhere along the long diagonal wall. What panel placement would help out the most? All advice welcome, but would especially love to hear from the studio guys like @silky smoove and folks who have dealt with sound treatment like this.

Thanks in advance!

 

[silky smoove]

The school has budget for 11 1.5” panels.

Are they commercially built panels, or a DIY product? Is the insulating medium OC 703, Knaff Ecose, or something comparable? Are the panels paper or foil backed?

Current thinking is 9 4x4’ panels and 2 2x4’ panels.

Same question as above. I'm guessing DIY since a 4'x4' panel is a pretty odd size for what most manufacturers are offering these days.

One desired outcome is to insulate the office next door from too much bleed,

Keep in mind that sound isolation only works as well as the weakest link in the chain. If you isolate the door but do nothing to the walls, ceiling, floor, or any other possible path for sound conveyance, then the time, effort and money spent on the door probably won't do much. Sound isolation is quite expensive and complicated if you want to see appreciable results in most cases, so unless you want to get into a whole thing on that front I would recommend spending those funds elsewhere. I've seen too many projects where the thought was to do "a little" sound isolation, only for the team to later realize that the little they did was pointless.

I was thinking of stacking the 2x4 panels across the lower right corner, which is the only true corner in the room, as a makeshift bass trap.

Panels on each side of a corner can make an effective bass trap without eating up too much floor space, albeit by using twice the material compared to straddling a corner. Pros and cons either way.

What panel placement would help out the most?

I'll give you my standard "here's what I would do if I've never been in the space, have not taken any measurements, and have to work entirely on assumptions" advice that I give folks when they're looking at treatment:

• Have realistic expectations.
• Use a broadband sound treatment medium such as OC703 or Knaff Ecose.
• Don't expect your treatments to be super effective below the upper end of the bass range, or MAYBE down to the midbass if you're lucky.
• Place treatments in as many vertical corners as you can manage.
• Place treatments at the first reflection point of any obnoxiously loud sound sources if you can.
• Don't waste money on excessive treatments. If you get it to a point where you like the sound, then stop there and spend your money elsewhere.
• Throw all of this out if you can do proper room measurements done by someone who will know how to translate the results into useful product recommendations and placements.

 

[Chris Fitzgerald]

@silky smoove They are commercial, but I don't know the brand. I am working with our facilities coordinator, who is doing the ordering. They are wood frames with dense insulation that feels like rock wool to me covered by fabric. They feel and "sound" like my rock wool panels in my home studio, which is to say when you clap or yell right in front of them they pretty much eat it.

Thanks for the listing at the end of your post. The part about the reflection points is helpful. Drums are obviously going to be the loudest thing happening, but these are jazz combos, so the amount of high energy rock/funk wailing will be minimal.

Two followups:
- Lets assume that we had four 4x4 panels on each of the long walls, and a McGyvered bass trap in the one true corner. How high up on the wall should the panels be? We have to have physical plant install them for bureaucracy reasons, so I realize that we may need to guess.

- Is there any benefit to putting a panel behind the drums, or better to go with just across from them?

Thanks!

 

[silky smoove]

They are wood frames with dense insulation that feels like rock wool to me covered by fabric. They feel and "sound" like my rock wool panels in my home studio, which is to say when you clap or yell right in front of them they pretty much eat it.

Sounds like a typical DIY-style broadband absorption panel. Assuming they're Rockwool, they'll perform a less effectively, or at least differently than OC703/Knaff which is the typical go-to material for this application. At only 1.5" thick you won't see much in the way of low frequency absorption. You can increase that performance by spacing the panels off the wall, but that will in turn reduce usable floor space, so it all becomes a trade-off of sonic performance and room functionality. It might be sacrilegious, but I'd rather have a well-functioning room than a good-sounding one at the expense of floor space. There's obviously a sweet spot that you'll want to try and hit.

The part about the reflection points is helpful. Drums are obviously going to be the loudest thing happening, but these are jazz combos

Never underestimate the intensity and directionality of a trumpet player in a jazz combo.

How high up on the wall should the panels be?

The more absorption in a corner, typically the better the low frequency performance will be, but it's obviously all a trade-off between cost and performance. Many would advocate for floor-to-ceiling. My studio misses that mark by 4" from the floor and 18" from the ceiling and the performance is excellent, but full disclosure, mine are fully filled 45-degree corners so that is almost certainly more of a factor than the total vertical spread.

Is there any benefit to putting a panel behind the drums, or better to go with just across from them?

In a room that small you'll be dealing with reflections from all angles. If you fly some panels behind the drums and they improve the sound of the room then go for it. It probably wouldn't be where I'd start, but it's definitely worth a shot. Keep in mind that drummers have a tendency to lean back on their thrones and rest on the wall behind them when not playing, so keeping that space obstruction-free might have a functional benefit that's interrupted by a treatment.

You mentioned the installation, bureaucracy, etc. Will you have an opportunity to install these, try it out, and move them if needed, or is it a one time opportunity to have them installed?

 

[Chris Fitzgerald]

Sounds like a typical DIY-style broadband absorption panel. Assuming they're Rockwool, they'll perform a less effectively, or at least differently than OC703/Knaff which is the typical go-to material for this application. At only 1.5" thick you won't see much in the way of low frequency absorption. You can increase that performance by spacing the panels off the wall, but that will in turn reduce usable floor space, so it all becomes a trade-off of sonic performance and room functionality. It might be sacrilegious, but I'd rather have a well-functioning room than a good-sounding one at the expense of floor space. There's obviously a sweet spot that you'll want to try and hit.

Understand and agree with all of this. They will definitely be mounted to the walls.

Never underestimate the intensity and directionality of a trumpet player in a jazz combo.

No worries there! I am not above asking trumpet players point blank “could you please aim that elsewhere?”

The more absorption in a corner, typically the better the low frequency performance will be, but it's obviously all a trade-off between cost and performance. Many would advocate for floor-to-ceiling. My studio misses that mark by 4" from the floor and 18" from the ceiling and the performance is excellent, but full disclosure, mine are fully filled 45-degree corners so that is almost certainly more of a factor than the total vertical spread.

Understand. The ones in my music room are also a few inches short of floor to ceiling and in every corner, although they are only 2’ wide and diagonally placed.

This room has only one true corner, the southwest-most one in the picture I posted above. The other corners in the narrow space in the south east part of the pic have columns protruding from them and a bank of windows between them, so I’m not sure if this affects the “corner-ness” of them acoustically. I had been wondering whether it might be wise to put a 4x4 panel on the floor across each of those corners, but except for the sound coming off the piano soundboard underneath, there will be no sound sources there.

In a room that small you'll be dealing with reflections from all angles. If you fly some panels behind the drums and they improve the sound of the room then go for it. It probably wouldn't be where I'd start, but it's definitely worth a shot. Keep in mind that drummers have a tendency to lean back on their thrones and rest on the wall behind them when not playing, so keeping that space obstruction-free might have a functional benefit that's interrupted by a treatment.

You mentioned the installation, bureaucracy, etc. Will you have an opportunity to install these, try it out, and move them if needed, or is it a one time opportunity to have them installed?

Unfortunately, we will only get one shot at this because of bureaucracy, but the good news is that when this room was an office, I rehearsed in there for over 20 years and it doesn’t sound bad even when there was only carpet and furniture in it. Whatever we do with these panels certainly will not hurt anything, will likely improve things somewhat, and will make admin feel like they’ve done something. So we have no way to go but up!

 

[silky smoove]

so I’m not sure if this affects the “corner-ness” of them acoustically.

It certainly will, but to what degree will be impossible to say without knowing all the details. It's likely inconsequential in the big picture and they'll still function as corners.

Unfortunately, we will only get one shot at this because of bureaucracy, but the good news is that when this room was an office, I rehearsed in there for over 20 years and it doesn’t sound bad even when there was only carpet and furniture in it.

That's a bummer about the bureaucracy of it all, but at least you're starting with a good sounding room. Hopefully it works well!