John Sayers' Recording Studio Design Forum

I love this forum, and have been “lurking” for some time, trying to learn all I can. Some great information, especially when reading about projects like mine. I’ve posted a couple of times with no response, but admittedly, the posts were about my project that, in retrospect were not well thought out. I think this time we have our act together, so to speak, so we’ll try again.
We’ve cleared out the 3rd car portion of our garage and are getting ready to build. Attached are pictures of the space from all 4 corners, plus a picture of the concrete footing on the outside walls, and also a picture of the sloping roof. I’ve spend tons of time on Sketchup and just can’t figure out how to draw our plan properly, so will insert what I could figure out and do my best to describe instead.

Project Objectives
What we’re looking to do is use the 3rd car space as the outer leaf. It will be sealed, and we’ll put in fiberglass insulation in the existing studs of the outside wall and roof, all to help isolate the outer leaf to the extent possible. The idea will be to build a stand-alone space, completely detached from the outer leaf, with the exception of the floor, which is concrete. 2 of the walls adjacent to the outer leaf will be approx. 4” inside, and the roof will be approx. 6” below a small portion of the floor of a room on the 2nd story. The wall adjacent to the outside rollup door (which will remain) will have approximately 3 feet (.91m) of separation. Room will be used as a drum practice room for my son and I, as well as practice space for a full band. We’ll do a bit of scratch recording as well. We have a proper studio nearby which we use for “real” recording, so our recording needs are secondary to the isolation needed for the drums. I’ve measured drums at about 115db, and we’re hoping to cut 45 – 50 db. Not sure if important to note, but the remaining band will be routed through a mixing board, to a headphone amp, so we won’t really have amps going. So really just the drums to worry about.

Dimensions
The space we have to work with (outer leaf) is 19 feet long, 11 feet wide and the sloping roof runs 8.5 ft. up to 12.5 ft.
Here are the planned dimensions for the practice space / studio:

Feet / Meters
16 / 4.88
10 / 3.05
8 / 2.44

Using the Bob Golds online calculator our mode comes out to 1 : 1.25 : 2
The comparison to the Louden model is : “M. M. Louden: 1971: 2nd best ratio" 1 : 1.3 : 1.9

Construction
• The entire structure will be one frame of 2 x 4 wood studs.
• Floor studs will be bolted down to the existing concrete garage floor.
• Will staple material to outside of structure on the short wall facing the outside rollup garage door.
• Rock wool insulation throughout walls and ceiling
• Will install horizontal stringers (at 2 ft / .61m intervals) for mounting drywall
• 2 layers of 5/8” drywall, with Green Glue in between.
• Structure will be finished with paint on the drywall, and most likely laminate wood flooring. After install, the gap between the drywall and floor will be sealed.

Electrical
• One conduit will be run into the structure, surrounded by Quiet Putty
• Will surface mount a sub panel with 2 circuit breakers (probably 25 amps each)
• All outlets will be mounted on the inside of the drywall, as well as the circuits themselves (in conduit)

Doors
The outside door in the pictures will be replaced with a solid core door, swinging outward. We plan to have a 2nd solid core door align with it as part of the space, this one swinging inward. This provides 30” of straight-through access for any load in / load out. There will be another door on the long wall facing the remaining portion of the garage. It will be solid core as well.

Ventilation
Probably the weak spot in the design at this point. As it doesn’t get very hot, or very cold where we live, a split system seems like overkill. Was thinking of building a “cooling closet” in the space between the room and the outside rollup garage door. Space would be approximately 2ft x 2ft. and 6 ft. tall. Would install a portable AC unit (probably 12K BTU), and pump the air in via flexible ducting attached to a bathroom type fan. The AC units I’ve looked at also have heat, and run about $500 USD.

Questions
• Do the walls need to be splayed? I don’t really have a good sense for this, after a bunch of research. I know it messes with the mode a bit, but can be corrected with treatment. I have heard that it is important to have one of the long walls at a 3 degree differential to the other one.
• Is the height of the space too low? I could potentially slope the roofline, and pick up volume. However, when I type a larger average height (to account for the slope) into the mode calculator, the results get pretty ugly. 8 feet seems low for drums, but not sure the trade off for more average height is worth it, in terms of the effect on the room mode.
• Does the overall design make sense? I’ve gone at this several times, and I’m sure I’m missing something (probably a lot of things). Any help would be most appreciated.

Sorry! Looks like I missed the questions in this post.

Splaying is an option that you might want to use for several reasons. One reason is flutter echo. If you have two hard parallel surfaces, then you will probably get some type of repetitive echo between them. One way of controlling that is by splaying the walls. According to the BBC, you should splay them at least 5° on each side (total of 10°), but John recommends at least 6° on each side (total of 12°).

Another reason is to create an RFZ design, in which case the splay angle will need to be much larger, and will depend on many factors.

That's fine. 8 feet is OK, anything more is a bonus. 12.5 feet is heaven!

You could try playing around with the length and width, to see if you can improve that. at 4.9 and 3 m, you so have a bit to play with. Also, don't forget that sound waves don't care which way is "up": they aren't affected by gravity, so it makes no difference to them if you want to think of the room as turned on its side, from the point of view of the mode calculators. In other words, you can swap the "height" with the "width", and see if you can come up with something better like that.

For drums, I'd always look for more height if possible, then see what can be done with the other two, to compensate.

Sounds like a reasonable goal, and very do-able.

Not quite sure what you mean by that. What "material"? For what purpose?

That's good, but you also need to be sealing continuously, as you go. For example, as you lay the bottom plates for the walls, you should seal underneath those, with 3 beads of caulk run lengthways: one down the middle and one on each side of that, about an inch out. You should also seal under each layer of drywall as it goes up. You need multiple seals, especially for isolating drums!

Apart from that, it looks good to me!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

No worries. Everyone is busy these days. Any time you put in on my question(s) I consider a gift !



Good to know, thanks. Will definitely give this direction to my contractor.




Thanks. Good to know I can make 8 ft. work. Keeps the construction material costs down, and keeps me further from an upstairs bedroom.




Should have mentioned in my original post that drums are played primarily through mics, a mixer, headphone amp and headphones. Does this make a difference?


Whew! So glad !


Since I planned to leave the outside of the walls open, and this is the only portion visible, I wanted to "hide" the insulation for visual purposes. Was planning to look into material similar to that used on office cubicles. Just the material, not anything underneath (besides the rock wool, of course). So from the inside out, 2 layers of drywall, 2 x 4 studs, filled with rock wool, then the material, again for visual purposes..

Good advise. So, if I understand you, I'd seal the drywall gaps before taping them, right?

[/quote]Great, thanks. I'm really excited to get this done. By kids are off school soon and are dying to have the "jam room" done. I'm just looking forward to getting my drums set up again! Thanks for all your input!

You are talking about a full acoustic drum kit, right? (Not electronic drums) And you are also talking about recording those drums for later mixing, right? If the answer to both is "yes", then it dos make a difference: the mics on the drum kit will pic up some of the room sound: that's inevitable, and can be a good thing of the room sounds good. But the biggest problem with a low ceiling, is the overhead mics. If the ceiling is low, the mics are close to the ceiling, so the pick up ceiling reflections as well as phasing issues, comb filtering, and other artifacts. Not nice. Depending on what micing technique you use, it could be a biggie or not such a biggie, but it will always be there to some extent.

I think I'm still not understanding: I don't see where your second leaf is there! I see only a single leaf with 2 layers of drywall, which is not going to give you much isolation at all. And since you seem to be talking about the "outside" of that wall (not the side facing into your studio, but the other side), then who is going to be looking at it? What is there? Is that facing your kitchen, dining room, living room, or something like that?

Maybe you could do a diagram of what you have in mind. But from what you say, if there really is no second leaf in that plan, then you don't have isolation at all. 2 sheets of drywall together gives you about 24 kg /m2 surface density. According to mass law, that will get you maybe 25-28 dB of isolation. Your drums will be LOUDLY audible on the other side, close to 90 dB.

Maybe I'm misunderstanding you, and there really is a second leaf, but I'm not seeing it in your description! If that cloth cover is facing people that aren't inside the studio, and there's only two sheets of drywall together on one side of a stud frame, then there is no second leaf between the studio and the people, and therefore there is no isolation.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Let's see if this explains it better. The yellow space is the existing portion of the garage. The blue space is the proposed "jam room" / studio. The red space is the HVAC exchange room. The jam room is to be built completely isolated from the existing garage space. I've numbered the walls of the existing garage: 1 is just inside a rollup garage door, which I plan to build with 2x4 studs, 2 layers of drywall on the outside, and open (with insulation) on the inside. I would staple fabric to the inside to "hide" the insulation. Wall 2 is 2x4 framing, with 2 layers of drywall on the side facing AWAY from the studio, and insulation facing the studio. I was not planning on finishing the inside of this wall. Wall 3 and wall 4 are existing exterior walls. These walls are 2x4 framing, with stucco on the outside. Wall 3 is finished with 1 layer of drywall and wall 4 is open studs. My plan was to pack wall 4 with insulation, but leave it unfinished on the inside.
The studio space is per dimensions. I believe the shape maximizes the total space, keeps pretty faithful to the mode calculation, and provides 12 degrees of splay. I may be wrong about this, but was assuming the splay is mathematical (so, 3 degrees of splay, in 4 sections). Studio construction to be 2 x 4 studs, 2 layers of drywall on the inside, with green glue, with outside unfinished, but packed with insulation. The sections of the studio facing walls 2, 3 and 4 would be completely isolated by about 4 inches, all filled with insulation. So, from the inside out, I would have Mass (2 layers of dry wall), Spring (insulation) and Mass (outer layers of drywall on 2 walls, stucco on the other 2). Does this make any sense?

The diagram makes it clearer, for sure, and now we have an easy way to talk about the walls, as they have names! Good! I just made a couple of models in SketchUp, to try to make it even more clear.

OK, so walls 1, 2, 3 and 4 will all basically end up as studs-and-insulation facing towards the jam room, and will all have their drywall on the other side of those studs (facing away from the jam room) like this:



I'm not showing your cloth or the acoustic treatment: just the walls.

Is that what you have in mind? (In your case, wall 3 has drywall on the studio side, which will have to come off to look like the above).



Because if that's the case, then all I see there is a single leaf: There is no inner leaf, just an outer leaf. If you build it like that, your isolation will be very practically non-existent. But I don't think that is what you are talking about. I think you are talking about 2-leaf.

Adding the inner leaf, it would look like one of the following two possibilities:





The first one is using "conventional" construction, where the drywall faces the room, and the second one uses "inside-out" construction, where the drywall faces the cavity.

(Once again, you will have to take off the drywall from wall #3 to make that work.)

Both of those are 2-leaf leaf MSM construction, which is what you need for good isolation. Both will work: Both will give you the same amount of isolation if you use the same amount of drywall and the same size gap between the leaves.

So are you talking about one of those arrangements?

If there are any walls with extra leaves of drywall (such as wall #3), then that MUST come off. take off anything that does not look like one of the above options. If you leave it on, then you have a 3-leaf wall, which is a bad idea for low frequency isolation.


I think what you are talking about is conventional 2-leaf construction (the second option, above). Is that correct?

If so, then I don't see where the cloth goes! That's what isn't make any sense to me. Since the cavity between the walls is totally sealed, and nobody every goes in there, then I don't see any place you would need cloth.

Just to complete the design more correctly, here is a version that also includes the garage door and HVAC space:



And here's a close-up of the HVAC section:


The only place I can see where it would make sense to put cloth is in that HVAC section, and yes, you sure could do that if you want. In fact, you could even finish those walls in the HVAC section with drywall, if you really wanted to: they are not part of your isolation system, so it doesn't matter. Yes, from one point of view that would create a 3-leaf system, but the air gap is so large there that the 2 resonant frequencies would be tuned very low, so it would not be an issue.

So your studio needs to end up looking like one of the two options above: either "conventional" or "inside-out", and of course with the HVAC area built correctly too, and that section can be finished with cloth, or drywall, or left unfinished, whatever you prefer.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Stuart, the latter drawings are exactly what I have in mind. Thanks a million for the Sketchup designs! I'm a pro at all sorts of software, but for some reason just can't figure that one out! The cloth would indeed go on the inside of the AC room. Sorry that wasn't clear. The only thing(s) missing are the doors. Was planning on having 1 door to the AC Room, 2 to the outside (one for each leaf) and 2 to the remainder of the garage (wall 2 ... also one per leaf). Doors to be solid core, following the guidelines laid out in Rod Gervais' book. Thanks for your guidance and advise. Definitely filled in a few knowledge gaps for me!