Gable vs Gambrel ceiling - no drop

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Jeremy Garber
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Gable vs Gambrel ceiling - no drop

Post by Jeremy Garber » Tue Jun 19, 2012 8:54 am

Hi all. I'm finally at a point (and need) to construct a detached room behind my house. It will serve as my office and music room. I'm wondering how these two types of ceilings will affect the acoustics of the room. The inside space will be 24x16' with 8' walls. I was initially planning a gambrel style roof with a rise of 4 or 6' to allow storage loft space over a porch. After working on some truss designs, I may just stick to a gable style roof to keep it simple.

Any ideas of how either will affect the sound of the room? I eventually plan on building my own absorption and diffusion panels if needed.


Thanks,

Jeremy

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Post by Snarl 12/8 » Tue Jun 19, 2012 2:14 pm

Aren't you going to have nodes and nulls like a mofo if you go 8x16x24?
Carl Keil

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Jeremy Garber
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Post by Jeremy Garber » Tue Jun 19, 2012 5:46 pm

No idea. :/ Just trying to make it easy to build.

Actual ceiling height will be 12 or 14' at the peak.

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Seamonster
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Post by Seamonster » Tue Jun 19, 2012 11:35 pm

I'll get to your question in a sec, but first...

The simpler the ratios among dimensions (H,W,L), the greater the standing-wave resonances, and the further your room will be from displaying a smooth, balanced frequency response. Ideally, you want the dimensions not to share common multiples. For instance, one commonly suggested set of ratios is 1(H) : 1.963(W) : 2.593(L). Another would be if each were a prime number. Try Googling "room modes" in conjunction with other terms (e.g., acoustics, nodes, standing waves, etc.)

Given the ocean of theory and practice out there, your proposed 16 X 24 is not good. To get a less rational ratio with a 16 X 24 space, I'd be considering putting in an iso booth, storage closet, reverb chamber or *something* to alter the room dimensions. Or just build it to different dimensions in the first place.

As for comparing roof styles, I don't know for sure, but here's a few considerations and leads. If you go with the gambrel, you'll have a surface parallel to the floor. If that's what you say would be 12 or 14 feet high, then you'd be better with it at something like 11, 13, or 15, to get away from the common multiples 2 and 4 in both 16 and 24.

On the other hand, a gambrel might get you more volume overall (than a gable), which is desirable.

You don't say, but it sounds like you'd be tracking and mixing all in one room? Note that the ideal control room and tracking room have different characteristics, e.g., with regard to symmetry, a control room should be symmetrical with respect to the L/R listening axis, whereas a tracking room can actually benefit by having some asymmetry, where there's some complexity to the reflections.

You might consider pitching your ideas (in somewhat more formalized form; check the FAQ's) at this website:
http://www.johnlsayers.com/phpBB2/index.php
Someone there should have a comment on gable vs. gambrel.

Also, play with a room mode calculator, of which there are at least a few on the web as Java apps. Here's a good one:
http://www.bobgolds.com/Mode/RoomModes.htm

See also, "Acceptable Room Ratios (an overview)":
http://forum.studiotips.com/viewtopic.php?t=684

Check out Gervais' book too (mentioned all over TOMB). If I recall, he gets into some theory before addressing practical details.

There's a lot to consider, and much of it will make a huge difference one way or the other. If you're ready to build something this involved, hopefully you're ready to do more studying first, to avoid making some of the most easily-avoidable mistakes. I say this as one who did the research, built my space, and now I frequently see horror stories on studio-build websites where someone has done something wrong that I did right... and I get to sigh with relief and some satisfaction (not schadenfreude!). It's worth doing it right.

HTH,
K Hill
www.seamonstersounds.com
"May my silences become more accurate." -Theodore Roethke, poet

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Jeremy Garber
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Post by Jeremy Garber » Wed Jun 20, 2012 5:47 am

Thanks for the references. I did a little reading last night, including playing with a room mode calculator linked from GS. Out of curiosity I also searched for studios with a 16x24 tracking room, and surprisingly found quite a few. The gambrel roof doesn't have any parallel surfaces to the floor- it's four sides with a peak at the top.

It probably wouldn't be that hard to shave a little off in each direction to remove the common multiples. We were just designing to keep material waste in mind. I didn't want to invest a huge amount into making the perfect room here, but, if there are some simple things like this I can consider I think it is worth it.

I'm not sure if it helps, but those are outside dimensions, so the actual interior dimensions are about a foot less or so due to wall thickness. Also, on one wall I plan to install/build cabinets and shelving which will take up ~2' of interior space.

I will search for Gervais' book as well. Thanks again!

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Post by Seamonster » Wed Jun 20, 2012 12:25 pm

Lots of 16 X 24 tracking rooms? I would wonder what proportion of all rooms they comprise ? there are lots of studios in the world ? and how many of 'em actually sound good.

Reducing by a foot to account for the walls would certainly be better. How much, I dunno. A foot is pretty thick for a single wall, unless you're talking about having staggered studs and more than two layers of drywall on the inside. And room experts advise against coming within 5% of common multiples. But then, by the time you factor in cabinets, etc. you might be pretty good. Do check into what experts say about the ideal ratios, while you have the luxury of designing from scratch.

It looks like we both were a bit confused on roof terminology. What you've described as a gambrel is commonly known as a "hip roof." A gambrel is typically symmetrical along one axis (like a gable), the sides each having two slopes: a lower steep slope and a higher, flatter slope. (I was thinking a gambrel was like a gable with the top shaved off flat.) Here's a few pics:
http://en.wikipedia.org/wiki/Gambrel
http://en.wikipedia.org/wiki/Hip_roof

Anyway, you'd get more volume with a gabled than a hip roof, all else being equal, because you wouldn't be losing the volumes at each end ? only two slopes, vs. four slopes.

But don't listen to me *too much*; when it comes to building design, I'm precisely halfway between an idiot and a genius.

- K
www.seamonstersounds.com
"May my silences become more accurate." -Theodore Roethke, poet

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Jeremy Garber
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Post by Jeremy Garber » Wed Jun 20, 2012 11:18 pm

No idea how other people's 16x24 rooms sound. It wasn't a purely scientific survey- just a Google search. It certainly looked like they knew what they were doing. Hah! For years I've been working with a 10'x10'x8' spare bedroom, so I figured 16x24 would be a dream.

Yes, the barn style roof! That's what it's official name should really be. I didn't describe it well. I appreciate the input. I know very little about this type of stuff. I'm just happy to be moving into a bigger space.

Most of that room ratio link blew up my brain. I did play with some of the numbers though. They are pretty specific, but some are not that far off from my proposed room with different ceiling heights taken into account (also imagining for ceiling slope here). The closest fit ratios however were still a bit shorter than my longest dimension. I'm wondering if some home made gobos would do the trick when/where needed.

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Post by Seamonster » Thu Jun 21, 2012 1:10 am

PM sent.

Anyway, I should let others chip in here....

- K
www.seamonstersounds.com
"May my silences become more accurate." -Theodore Roethke, poet

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