mixing room from scratch - ratios/size etc

Hello, this is my first post and I am bowled over by this resource! I have been reading the posts for a while but get confused if I try and apply all the useful knowledge to my situation. Here’s the story: I occupy a large factory space (6m by 12.5m and 2.81m high (19.6’ by 41’ and 9’ high). as seen in the attached diagram called plan.gif. It has concrete floors and ceilings and breeze block walls. At one end I have an open plan living area and the other a large MDF platform (for storing amps/gear/junk etc). I have been rehearsing and recording in this space for a while and despite its roominess I have worked with that ‘garage sound’ and its been fine for what I want so far… But…I am doing more and more mixing and I would like to build a mixing/control room – a place to focus rather than as a totally 100% sound proofed room – what really matters to me is to build the ‘right room’ acoustically so mixing is pleasant and accurate. As you can see from the diagram I have a certain amount of available space I can build in (the whole white area on the top diagram in plan.gif) and I have the advantage that I can build from scratch so the can be any shape or height that is optimum. The downside is I need to leave space for playing (guitars/drums/amps usual rock set up) so the approximate area I can fill is not going to be huge – I figure about 3m by 3.6m (or 118” by 141”). I can set the height too – I have up to 9 feet to play with… I can go bigger but want to be able to leave enough room to perform in. At the moment I am thinking of the yellow area marked in the second diagram of plan.gif. Here are my key questions: 1) is it worth building a mixing room within a space this size? It’s would be a big enough room for comfort but is it big enough to get decent acoustics? 2) If it is worth doing what ratio is best at this size? I’ve seen the various ratios quoted here and on other sites but cant figure out if they are redundant after a certain size. Whats the optimum sort of design for this size – is it non-parallel walls and sloping ceiling? 3) Is stud walling with insulation the way to go? 4) I am happy to build bass traps etc – if I get the room ratio right how much more acoustic treatment is needed? 5) I’m using Yamaha MSP10s – as it is a small room and I can build anything I want is it best to build soffits? Will that become horribly expensive?? Anyway – Apologies for the length but it seems like people get more annoyed by vague questions than involved inquiries…. If there is anything newcomers like me can contribute to the list beyond a donation (i.e. report back on how it all went etc) to help the more experienced members then please tell me! David

And so, what have u done about your plans?