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Vaulted Ceiling AND Angled Walls??!?
Old 3 weeks ago
  #1
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Vaulted Ceiling AND Angled Walls??!?

I'm planning out yet another studio build. This one will be a mix/production room with new, foundation-up construction. The plan is a single room "cabin studio" with maybe a small booth and a machine room/storage closet.

Vaulted ceilings seem like a really cool design element and the extra room volume is a bonus. At the same time, angled interior walls are nice. But building both sounds like a framing and finishing headache.

Since I'll be building it myself, I want to keep things realistic from a construction perspective.

Proposed size right now is 16'X20' the vaulted ceiling would be 8' on the outside to 12' in the center. I could also just forget the vault idea and do a flat 8' or 10' ceiling, focusing on making angled walls.

Anyone want to weigh in?
Old 3 weeks ago
  #2
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avare's Avatar
 

Why are you angling the walls?
Old 3 weeks ago
  #3
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Quote:
Originally Posted by avare View Post
Why are you angling the walls?
The thought was to alleviate flutter and potentially create an RFZ if I angle them correctly. I can also use the space created behind the angles to insulate for bass trapping.

But I'm not dead set on angling.
Old 3 weeks ago
  #4
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Quote:
Originally Posted by EMMST View Post
The thought was to alleviate flutter and potentially create an RFZ if I angle them correctly. I can also use the space created behind the angles to insulate for bass trapping.

But I'm not dead set on angling.
Huh? The space is where? You are angling your walls? Why flutter in a properly treated room?

Andre
Old 3 weeks ago
  #5
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Quote:
Originally Posted by avare View Post
Huh? The space is where? You are angling your walls? Why flutter in a properly treated room?

Andre
The outside walls of the building will be straight. So, more walls would be built inside the structure, leaving a cavity that can act as a bass trap.

Obviously I'm going to treat the room. The angled walls would contribute to treatment and affect how I treat it. I know from previous builds that if the walls aren't angled, the flutter needs to be treated with a lot of broadband absorption, and overall that would lead to a lower high frequency RT60. Which is fine, but since the primary use of the room is mixing I want a relatively even RT60 across all bands.

Since low end is harder to control, it makes sense to me that dealing with high frequencies by angling walls would give me a better starting place for treatment, while also trapping bass that looses energy as it goes into the cavities.
Old 3 weeks ago
  #6
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Quote:
Originally Posted by EMMST View Post
The outside walls of the building will be straight. So, more walls would be built inside the structure, leaving a cavity that can act as a bass trap.

Obviously I'm going to treat the room. The angled walls would contribute to treatment and affect how I treat it. I know from previous builds that if the walls aren't angled, the flutter needs to be treated with a lot of broadband absorption, and overall that would lead to a lower high frequency RT60. Which is fine, but since the primary use of the room is mixing I want a relatively even RT60 across all bands.
If the absorbers have a high enough absorption coefficient above the Schroeder frequency, they will affect all those frequencies the equally. If you are experiencing shorter HF decay times it probably has more to do with speaker directivity, as the treble has a narrower pattern than mids and low mids and then whatever is still reflective in the room (floor etc) is reflecting that where little treble reaches. My understanding is this is why in a 'classic' NE room you would need the constant directivity speakers. All of that then doesn't require angling.

For RFZ/LEDE, then you would angle with the purpose of reflective side walls (no absorbers here) aiming the reflections into rear wall diffusers.

What's is your design criteria/paradigm?

-edit-

Last edited by RyanC; 3 weeks ago at 02:21 PM..
Old 2 weeks ago
  #7
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Quote:
The outside walls of the building will be straight. So, more walls would be built inside the structure, leaving a cavity that can act as a bass trap.
Actually, the purpose of the cavity in the "room-in-a-room" construction that you are describing, is not to act as a bass trap, but rather to act as the isolation system for the room. It's an MSM resonant system, and it should be tuned at least an octave lower than the lowest frequency you need to isolate, ... much lower than your bass! So it won't be doing any bass trapping. Bass traps go inside the room, not inside the walls. In other words, the final surface that you see around you as you stand in side the room right after the inner-leaf is completed: that surface marks the acoustic boundaries of the room. That's what you use for all your modal calculations... and therefore that's what you take into account for your bass trapping.

Quote:
The angled walls would contribute to treatment and affect how I treat it.
Actually that isn't true. The only thing that angled walls help with is flutter echo: but to do that, the walls need to be angled in excess of about 10° to 15° total (eg, each wall angled 7°)... and that eats up a lot of space! Flutter echo can be treated much more effectively with the exact same treatment that you would need anyway. So there's no point in angling your walls... and that's what Andre was getting at! Angling them complicates things, wastes space, and isn't necessary.

Quote:
the flutter needs to be treated with a lot of broadband absorption, and overall that would lead to a lower high frequency RT60.
Flutter doesn't need that much absorption if it is placed correctly and dimensioned correctly. This is a control room we are talking about, so for a typically sized home-studio control room, the exact same treatment that you would have on your first reflection points anyway, would already be sufficient, or nearly sufficient, to do the job.

Yes, the combination of the very deep bass traps you will need, plus the first reflection point treatment, can indeed "suck out" the highs... but there are very simple methods for dealing with that, to keep the highs in the room.

Quote:
Which is fine, but since the primary use of the room is mixing I want a relatively even RT60 across all bands.
Right! And that should be in the region of maybe 180 ms to maybe 350 ms, depending on room size, with no more than +/-50ms difference between adjacent 1/3 octave bands. Take a look at ITU BS.1116-3 (chapters 7 and 8) or EBU Tech.3276 for the full set of specs that are commonly used for control rooms. You mentioned a size of 16x20, with maybe 10' ceilings, which is a very decent floor area and room volume (but no so good on the ratio...) I would shoot for decay times of around 250 ms - 300 ms in that room.

One minor point on semantics: you mentioned RT60, but it's a small room so RT60 is not a valid concept here. "Decay times" is more correct. For the layman, it looks like the same thing, but for the acoustician or studio designer, those are two different things. Probably no important really, but semantics is important... So decay times is more correct.

Quote:
Since low end is harder to control, it makes sense to me that dealing with high frequencies by angling walls would give me a better starting place for treatment, while also trapping bass that looses energy as it goes into the cavities
Well, no, that's not true either. The angled walls have practically no effect on the modal spread. When you consider that you could angle your walls by a few inches, maybe a foot or two max, but that you are dealing with waves that are many dozens of feet long, it becomes clear that angling a wall here or there won't actually have any real effect on the modes. It might move a mode up or down to a slightly different frequency, but that's all. But what angling your walls DOES do, is make it very, very hard to accurately predict the modal response of your room! The typical modal calculators, or "room ratio calculators" that you can find on-line, only work for rectangular rooms. If you angle the walls, the results they give won't be valid. Or rather, they wont be accurate. For example, if you only angle your two side walls (leaving the front and back parallel, and also the ceiling and floor parallel), then your axial modal response in two of the three prime directions will be correctly predicted, but not for the room width. In addition, all tangential mode predictions that involve the side walls will be wrong, and so will ALL of the oblique mode predictions. Now, as long as you are aware of that, and know what to do about it, then that's fine! But for most people it's not so easy. It's far better to just keep the room rectangular, then the results will be correct for all modes.

Another thing: bass does not "lose energy as it goes into the cavities". All sound waves are reflected by the walls (assuming that your room is well isolated), so practically no energy is lost for any given reflection, regardless pf whether it is into a "cavity" or not. The energy in a sound wave can only be lost by changing it into some other form of energy, which is pretty much always heat in studio treatment. The energy in the bass can be absorbed and converted to heat in several different ways, but the geometry of the room corners is not one of them. Bass traps usually take the form of deep low-density porous absorption (velocity based traps), or sealed membranes, or Helmholtz resonators, (pressure based traps). Corners are neither of those, and don't remove any bass energy. There is no acoustic mechanism is a room corner that could convert sound into heat. So... angling your walls won't do anything to trap bass either!

Which gets us back to the point Andre was making: don't angle your walls! It wastes space, complicates the construction, makes it more expensive, makes it impossible to predict the modal response with simple tools, and serves no real purpose. Rather, make your room rectangular, then treat it in the normal way.

As Ryan mentioned, for some room design concepts, the walls do appear to be angled, but in reality even RFZ rooms are usually still built as rectangles, then the appropriate surfaces are built at the appropriate angles within that rectangle. It's simpler, faster, easier, and cheaper to do it that way, and also easier to predict the acoustic response with a good degree of confidence. That's the way we normally do it.

- Stuart -
Old 1 week ago
  #8
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Quote:
Originally Posted by Soundman2020 View Post

As Ryan mentioned, for some room design concepts, the walls do appear to be angled, but in reality even RFZ rooms are usually still built as rectangles, then the appropriate surfaces are built at the appropriate angles within that rectangle. It's simpler, faster, easier, and cheaper to do it that way, and also easier to predict the acoustic response with a good degree of confidence. That's the way we normally do it.
Thanks for the comprehensive response. I suppose my comments this far have been poorly communicated.

I'm definitely planning on building the room as a rectangle, my initial question was really more aimed at construction technique with adding splayed treatment, not really "walls" but inner treatment (probably pegboard faced) sloping up a cathedral ceiling.

However, at this point I'm reconsidering both the cathedral ceiling AND the splay. I would rather have a small attic for storage.

The outside dimensions are pretty much set on 16'Wx20'L for a variety of reasons, not the least of which is that I'll be building this on my own and the time savings of using dimensional lumber, avoiding a lot of cuts. Of course in a perfect world, I could spend more time on the construction, but time is of the essence here.

So the question now falls on ratio. The ID would be 15.25' X 19.25' I need to figure out a ceiling height that works with what I can do. 9' or 10' look to bring the ratio into the Bolt-area with the amroc calc.
Why would the ratio be bad and what can I do to dial it in within my limits?
Old 1 week ago
  #9
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Kyle P. Gushue's Avatar
If you use a cathedral ceiling you can make it a large bass trap.
Old 6 days ago
  #10
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Quote:
Originally Posted by EMMST View Post
The outside dimensions are pretty much set on 16'Wx20'L for a variety of reasons, not the least of which is that I'll be building this on my own and the time savings of using dimensional lumber, avoiding a lot of cuts. Of course in a perfect world, I could spend more time on the construction, but time is of the essence here.
I think cutting lumber on my project might have amounted to .05% of the project time, I doubt that would be a big part of the labor of this unless I'm really missing something. This would be on a concrete pad?

In any case, you can get engineered I-joists in any length up to 40'. People commonly call them TJI's. And/or if you are going to do a gabled roof with an attic space (or vaulted) you can get prebuilt trusses. But a 16" wide roof with a 4/12 gabled roof isn't going to have much of an attic with a 32" high peak.

Quote:
Originally Posted by EMMST View Post
So the question now falls on ratio. The ID would be 15.25' X 19.25' I need to figure out a ceiling height that works with what I can do. 9' or 10' look to bring the ratio into the Bolt-area with the amroc calc.
Why would the ratio be bad and what can I do to dial it in within my limits?
Andre has posted (many times) on here that Bolt is obsolete, and/or really applies to rooms that are 5000 cubic ft or more. I've also seen some graphs showing that one issue with Bolt is that the middle section is actually not very good, so ideally it should be to the left or the right. On amroc if you check the bonello the distribution is better when the x isn't in the center...

Also just more volume is always good. If you are looking to save time on cuts, I would use 12' 2x6". With a double top plate, and sill plate that would put you at 12' 4 1/2" to the ceiling framing. This is still in the left side of bolt, has good modal distribution and will leave you more room for treatment.

One thing you might look into if you are looking to save time would be a pre-engineered SIP building to make your outer leaf. Being all OSB panels with ridged insulation you could attach clips and channel directly to the inside.
Old 6 days ago
  #11
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Kyle P. Gushue's Avatar
You could also go with a flat ceiling, and just use fabric and wooden slats, a perforated plywood panel, or just fabric, to finish it off instead of drywall. It depends on how much isolation you need. Essentially making the ceiling/attic one large bass trap.

This keeps things more simple to build and calculate, but takes advantage acoustically of maximizing the cubic footage of the room. It can help maximize floor space within the studio too, since a lot of bass trapping is being done overhead, and bass traps consume the most space.
Old 1 day ago
  #12
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Quote:
Originally Posted by Kyle P. Gushue View Post
You could also go with a flat ceiling, and just use fabric and wooden slats, a perforated plywood panel, or just fabric, to finish it off instead of drywall. It depends on how much isolation you need. Essentially making the ceiling/attic one large bass trap.

This keeps things more simple to build and calculate, but takes advantage acoustically of maximizing the cubic footage of the room. It can help maximize floor space within the studio too, since a lot of bass trapping is being done overhead, and bass traps consume the most space.
This is actually a great idea. Keeps things simple and there is a lot of benefit to a bass trap that large.
Old 1 day ago
  #13
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Originally Posted by RyanC View Post
I think cutting lumber on my project might have amounted to .05% of the project time, I doubt that would be a big part of the labor of this unless I'm really missing something.
I've built a lot of stuff; 3 full studio buildouts, multiple house renos, ect...

One of the top time eaters IME is measuring and cutting. Sure, running the saw itself only takes a couple of seconds, but measuring twice, marking, moving the lumber to a cutting surface and so on adds up. It doesn't seem like a lot, but it really is, especially if I have to cut 75 2x4's for the walls and rip a bunch of OSB. (Maybe I'm jaded from doing so much retrofit construction, but I just want to haul butt on this.)

If I can sheathe the entire building and only make cuts for the doors and windows, it's going to make the project a lot easier. Basically like putting together a shed kit.

Thanks for the info on the Bolt-area! I'll look into that more.
Old 1 day ago
  #14
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by EMMST View Post
I've built a lot of stuff; 3 full studio buildouts, multiple house renos, ect...

One of the top time eaters IME is measuring and cutting. Sure, running the saw itself only takes a couple of seconds, but measuring twice, marking, moving the lumber to a cutting surface and so on adds up. It doesn't seem like a lot, but it really is, especially if I have to cut 75 2x4's for the walls and rip a bunch of OSB. (Maybe I'm jaded from doing so much retrofit construction, but I just want to haul butt on this.)

If I can sheathe the entire building and only make cuts for the doors and windows, it's going to make the project a lot easier. Basically like putting together a shed kit.

Thanks for the info on the Bolt-area! I'll look into that more.
I got a makita 12" sliding compound miter saw, and i can cut like 8x 2x4s at once. Together with the saw stand with adjustable lenght guide, it saves a ton of time, and eliminates a bunch of measuring. Set the lenght, cut 8x at a time until its done. It will shave hours off the build. If only they had that for drywall!!
Old 3 hours ago
  #15
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That would be nice. I just have a little 7 1/4 sliding miter with a good stand, but I do a lot of cutting with my worm drive saw.

Like I said, I'm probably just jaded from all the old retrofit stuff, on my 100+ YO farmhouse, I had to measure and cut every single stud and joist individually because everything is so crooked.


Quote:
Originally Posted by Kyle P. Gushue View Post
If only they had that for drywall!!
Indeed. Drywall is the worst. Dremel tool for electrical boxes is the best trick I've learned.
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