Tracking Room Dimensions

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Tracking Room Dimensions

Postby Predrag Trpkov » Mon Mar 08, 2004 10:32 pm

Hi everybody,

I've been following this newsgroup for several years now and preparing to build a proper studio for even longer. Although the money's still not there, I've decided to take a plunge and build from scratch.

I'll probably have more questions in the near future (with restraint), but right now I'm concerned with dimensions of the tracking room. This is Croatia, so no excesses are necessary (or possible). There aren't any world-class studios here and, as far as I know, not a single good (read: reasonably live and acoustically pleasing) tracking room in a commercial facility. It's an afterthought, as a rule. So I don't have to compete with anybody and am interested in investing as little as possible. I need a room that can accomodate a regular rock/jazz band or a small string ensemble, both in terms of available elbow space and natural ambience. What do you consider to be minimal dimensions for such a room?

Thanks in advance,

Predrag Trpkov
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Tracking Room Dimensions

Postby Jas » Tue Mar 09, 2004 1:35 am

Hi there,
Don't really know enough about your situation to give you more useful info, but about 5000 cubic feet will do the job.
Cheers
Jas
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Tracking Room Dimensions

Postby Predrag Trpkov » Tue Mar 09, 2004 10:04 am

Thanks Jas. Yes, 5000 cubic feet is the figure stated in the FAQ as the minimum for a full fledged reverberant field. I was actually hoping someone would help me translate it into a set of dimensions proven in practice. Also, I'm not chasing an absolute minimum. Apart from a reverberant field, I need enough floor space to accomodate a smaller group of musicians, up to 5-6. You know, a rock/jazz setup - drums, bass player with an amp, one or two guitar players with amps, a keyboard player... Nothing fancy, but they should feel comfortable in there.
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Tracking Room Dimensions

Postby Predrag Trpkov » Tue Mar 09, 2004 12:12 pm

More to the point, I was considering building the room used as an example for good modal distribution in the Alton Everest's book. It's dimensions are 19,5 x 25 x 30 ft (14625 cubic feet) or 5,9 x 7,6 x 9,1 m (414 cubic metres). However, it seems too big and too expensive for my needs. I was hoping to find info on a smaller room, between 5000 and 10000 cubic feet, that would still have an adequate modal distribution and be spacious enough to accomodate a rock/jazz band.
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Postby Bob » Tue Mar 09, 2004 1:38 pm

In this thread
http://www.recording.org/ubb/ultimatebb ... 01388.html
Jeff D. Szymanski wrote
I would reiterate (I've said it elsewhere - don't know if it was here) that the "ideal" ratios listed in the acoustics texts are a very small sampling of what actually can work. What must be kept in perspective is that the folks (Bolt, Louden, Sepmeyer, etc.) who listed these ratios were providing them as examples of ratios that met the criteria they developed. We have the capability now (others - and myself - are doing work in this little "niche" of small room acoustics) to use the criteria more extensively; as opposed to just looking at a few examples that were computed from - at the latest - 1970s computer technology. (I.e., there were lots of "short-cuts" taken to reduce the computing time back then. "Short-cuts" that are totally unnecessary nowadays.)
Regards
Bob Golds
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Postby Scott R. Foster » Wed Mar 10, 2004 3:42 pm

7,000
SRF
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Tracking Room Dimensions

Postby Jas » Thu Mar 11, 2004 3:30 am

I don't know the exact dimensions of a good sounding room that I have worked in with the approximate volume you gave. Someone who does might post? If you have read Everest's Master Handbook, you probably know this stuff already but......You can work on dimensions that are roughly right for you? and then modify them by testing the dimensions to get good modal spacing. (Use the spread sheet from the file area here to save time from doing it manualy) I don't know of an easier way to work this stuff out. (Scott or Eric might?) Also check the 'Bolt' area plot in Master handbook. I think the point is that whatever room dimention you decide on (as long as you get this roughly right) The room is going to need at least some treatment (unless you want it to sound exactly like an untreated room which I'll asume you don't!?) no matter what dimensions you decide on or how good the dimensions are. Unless you're a super whiz designer, use rectangular dimensions to start with so you can predict room modes with relative accuracy yourself then correct any problems with suitable treatment eg. traps, absorption, diffusion. This is proven to work! If you slightly angle a wall you can still approximate modal spacing by using the average. I'm sure you would also have some ideas of your own as to how to design the interior to give you the sound you're after. In my own humble experience in a room approaching 10000ft3, (with reasonable mode spacing -something inside the bolt area), the internal design will have a much greater effect on the sound than the dimensions. Smaller rooms are much harder to treat.
If you wan't to have live rock bands in there - you WILL need to save some money for treatment and maybe an Isolation booth for vocals would be well worth the money.

Given the potential cost of a room this size, (can get expensive to have a roof span more than 6m without any internal Load bearing walls) It's always better to consult with an Acoustician or at least use an architect with acoustic design experience.

Cheers,
Jas
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Postby Dan Nelson » Thu Mar 11, 2004 4:37 am

What size can you afford to build? I'v recorded albums in bands homes with 14x11x8 (in feet) rooms and it worked very well, a pretty small room for a 4 piece band. You can get a 1500cf room to sound pretty good with the acoustical options we have to us now. I like to have at least 10-12 ft high ceilings in tracking rooms and enough room to spread people out. With a high ceiling you hit 5000 cubic feet pretty fast.

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Tracking Room Dimensions

Postby Predrag Trpkov » Thu Mar 11, 2004 11:19 pm

14000 cf would be an excess, but 7000 is within reach.

Would a slanted ceiling, if high enough (say 12-13 feet average) be a problem?

Predrag
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Tracking Room Dimensions

Postby Jas » Fri Mar 12, 2004 6:02 am

The good news with slanting the ceiling is that you can avoid flutter echo between it and the floor.- I think it needs to be more than about 10 degrees to really work though. Someone else might be able to clarify that angle. Obviously, you also increase your volume as compared to a flat ceiling made from trussing with the same roof. I like the general idea of an angled ceiling in a tracking room, which ever way its done.
12 - 13ft is a nice height. At that height and 7000ft3, where does this put your walls?

jas
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Postby knightfly » Fri Mar 12, 2004 10:47 am

Using ratios of 1:1.6:2.33 (Sepmeyer I think) and 13' ceilings, a room that's 20.7 x 30.3 feet (3.96m x 6.34m x 9.24m) gives a volume of 8153 cubic feet - according to Jeff's mode calc, Bonello distribution is good almost down to 20 hZ.

You could go down to 12.5 foot ceilings with those same ratios and get just over 7000 cu ft. - 5 or 6 degrees splay seems to be minimum (from reported results I've seen) for flutter control - you can use the average dimensions of the room for modal calculations to keep ratios right, you would probably need less treatment in a slightly splayed room by not having to control flutter with so much absorption... Steve
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Tracking Room Dimensions

Postby Predrag Trpkov » Fri Mar 12, 2004 11:04 pm

13 x 20.7 x 30.3 feet or 8153 cubic feet - that sounds good. Thanks.

My ceiling, actually the roof of the building, would be at 20-25 degrees angle. That should prevent flutter between the floor and ceiling. What's the cheapest way of preventing flutter between the side walls? Splaying them seems to be both expensive and a waste of space.

Predrag
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Tracking Room Dimensions

Postby Jas » Sat Mar 13, 2004 12:33 am

Two options left - diffuse or absorb.
To absorb if you can afford the top end loss - 4' of rigid glasswool board, 4' out from the wall as stated in the faq. - I have tried this in few (smaller) rooms, one very recently using Fibertex 350, (65kg rockwool board with material over the top) and it sounds great with predictable results. I have previously used 32kg glasswool with similar results. Although didn't get down quite as low. Doesn't just suck the top end out of the room. If you need more highs you can use a similar design but turn it into a slat resinator and angle it out from the wall more than 6 degrees. That'l kill the flutter, absorb broad range mid and lows without loosing too much top end.
Alternatively, could diffuse with poly's.
Both ways are pretty cheap and work well. Slat absorber is little critical, more work and expense.

Cheers
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Tracking Room Dimensions

Postby Predrag Trpkov » Sat Mar 13, 2004 8:43 pm

Thanks Jas.

What about both absorption with rock(glass)wool panels and diffusion with polys?

Predrag
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Tracking Room Dimensions

Postby Jas » Sun Mar 14, 2004 1:05 pm

Might be cool to look at going more live one end with polys and maybe corner traps, then more dead down the other with more broad band absorbsion. I guess this would give you more options with different instruments etc.

jas
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