Ideal ratios: Is 2 out of 3 still useful?

I'm planning my backyard studio, and considering the "ideal" acoustic ratios I've seen bandied about here and elsewhere: 1.00 - 1.14 - 1.39 1.00 - 1.28 - 1.54 1.00 - 1.60 - 2.33 (H x W x L) The first two are both possibilities for fitting into and making best use of the space I have, at about 4m wide by 4.8m long (internal dimensions). The only problem is that both of these result in extremely high ceilings, which I'm worried would be very imposing and ugly, and possibly piss off the neighbours. The third one gives a lower ceiling but ends up too long. So what I'm wondering is, if I work out the width x length according to one of the first two formulae, would this still be advantageous even though I disregard the height and make the ceiling substantially lower? Alternatively, if I work out the width x height according to the last formula, would this still be advantageous given that the length will be reduced? I know whatever I come up with won't be AS good as keeping all three dimensions as stated, but will it still help? Or would I be better off just forgetting about them? Another way of phrasing the question might be: given maximum possible dimensions of say 4.2m wide x 5m long x 2.5m high (internal) - what would be the best shaped room to (a) fit this space, using as much of it as possible, and (b) sound good? Thanks in advance.

What a mouthfull to address shortly! :) In general terms, if you have choice between bigger (volume) and closer to ideal ratios, go with the bigger. This lowers the fundamental frequencies of the room modes, which is more beneficial in the range of home facilities. If you read the NARAS 5.1 document stickied at the top, you will find formulas for acceptable ratios relating back to BBC studies and AES/EBU/CCITT etc recomendations. Andre

Thanks Andre. Which document are you referring to? I couldn't find it just from your description.

I think he means this one http://www.grammy.com/pe_wing/5_1_Rec.pdf

Thanks. OK next question: I finally found a way of fitting the space that conforms to one of the idea ratios perfectly: 7'2' high x 11.52' wide x 16.78' long (= 1 x 1.6 x 2.33) The problem with this of course is the very low ceiling. I will have some restrictions on ceiling height, since I need to keep the building within 55 cubic metres (visible) to avoid regulatory hassle, and I want to maximise floor space for use as a rehearsal room. But it's not like it's a basement where I'm completely hemmed in. We're looking at sinking the building a foot into the ground to get these dimensions. Question is: if I can sink it further, would it be better to get a higher ceiling? ie, would the same dimensions but with say an 8'2" ceiling be better, even though I've lost one part of the ratio? My instinct is that it would be, as 7'2" is really quite low. But then I wonder whether 8'2" is getting dangerously close to half of 16'78'', the length. How close is too close in this respect, or do problems like that only occur when dimensions are exactly half or double each other? Many thanks.

The greater height is better. MOre volume and room for ceiling acoustic treatment. Don't get too hung up on a few recommended ratios read BBC RD 1993-08 for an indepth discussion of ratios and their effects. Andre