Hi there Paul. Welcome! Please read the
forum rules for posting (click here). You seem to be missing a couple of things!
About the best I can manage in that garden is a large rectangular shoe-box of a building measuring approx 40ft x 22ft.
At nearly 900 square feet, that's an excellent sized space for a studio! The majority of home studios have to squeeze into much smaller spaces. So you are one lucky man, from that point of view! Are there any restrictions on height? Any idea how high you'll be allowed to go?
The control room should end up about 25ft long by 19ft across before treatment
That's also a good size. Pretty much spot in the middle of the recommended range from places like the EBU, ITU, AES and others. It could be smaller and still be good, if you wanted to designate more space for your live room or other rooms in the facility.
I was planning on a 20ft x 28ft live room in there, with 12ft ceiling and no parallel walls :
). Sadly a 19 x 13 rectangle is about the best I can do at this location.
Hang on a sec: You say you have a total area of around 40 x 22, so you should be able to fit in something bigger than 19 x 13 and still have space for a good control room. And don't get too hung up on the "non-parallel walls" thing: it really is not as big a deal as many people think. The only real issue with parallel walls is the increased possibility of flutter-echo, but that's plenty easy enough to deal with in other ways, and the angle you need to eliminate flutter echo is rather larger than most rooms can afford anyway...
I would prefer it to have some life rather than be a dead padded cell of a room,
Not a problem. It's big enough that it certainly doesn't have to be dead.
but on the other hand I guess there are likely to be modal issues to deal with, and I don't want to end up with a live space that has any obvious "rehearsal room" honk or ringing.
ALL rooms have modes. Modes are a simple consequence of having walls at the edges of the space. The only way to have no modes, is to have no walls! It's also a myth that having non-parallel walls somehow gets rid of all our modes: it does not. The modes are still there, just of different types. Having non-parallel walls might reduce axial modes, if the angles are large enough, but in that case there would be more tangential modes and oblique modes to deal with, so you don't really gain much. So modes are a fact of life. Studio designers aren't afraid of modes: we design to control them, not eliminate them, since eliminating modes is impossible, but controlling them is very possible, and very effective.
But, generally speaking, what kind of treatments would you use in a room that size?
The simple answer here is a question: "For what purpose?"
The more reasonable answer is even less helpful: "It depends...." That sounds a bit like a cop-out, so let me explain:
Deciding how a control room should sound is dead easy: it should not. Control rooms, by definition, have to be as neutral as possible. It should have no sound of its own at all, neither adding to nor taking away from the pure, clean sound coming out of the speakers. That's what the engineer needs to hear, without any coloration at all, and that is the goal of pretty much all current control room specs, in their various guises.
But that's not what you are asking about: you are asking about the LIVE room, not the control room, and that's an entirely different matter. Live rooms should sound exactly like the owner wants it to sound, and exactly the way it needs to sound for any specific session. Hopefully, those two agree with each other! So it all depends on what you plan to record in there. If we are talking about recording soft classical guitar solos and quiet female acapella ballads, then that's one type of acoustics. If we are talking about a jazz quartet, that's another. If we are talking about a typical contemporary pop band, that's yet another. And if it turns out that we are talking about the Grateful Dead renting your place to record their final album, then that's yet another. Different genres have different needs. If you plan to record a lot of live drums, then you'd probably be looking for a brighter, liver sound, slightly diffuse, but not enough to kill the attack of the cymbals or mute the slap of the snare. Electric guitar, on the other hand, often sounds better with more damping up close and not too much room, while other instruments might need really dead acoustics, or really live acoustics, as the case may be.
So that's the best non-answer that anyone can give you about how to treat a live room, and is also the reason why there just isn't much information out there on how to go about it! There simply is no one "correct" way to treat a live room, since all live rooms are different, and are designed for different purposes. In general, if the owner isn't certain about what types of music will be going on in his space, then I try to design rooms that either have variable acoustics (things that can be opened, closed, slid, rotated or otherwise moved to modify the acoustic response of the room), or I design the room with two or more different "zones": one area that is very much deader, while another area is more live, and yet another part might be more diffuse. That allows the musicians themselves to move around the room and find the spot that sounds best for their instrument, style and song. So if you don't know what type of music might turn up in your room and beg to be recorded, I'd suggest either a "zoned" room or variable acoustic devices. Take care of the major issues with minimal basic treatment, then do the rest with fixed or variable treatment.
Unfortunately, there's not a of of info out there on how to do that either! It seems like room designers are a bit jealous of their designs for acoustic treatment, and don't like to give away all their ideas openly...
Obviously I need to be mindful of how much room volume I lose to various treatments,
In general, the larger the room is, then less overall percentage of the total you'll lose to treatment. Small rooms need proportionally more treatment, just to get them in the ball park, and really small rooms need mountains of treatment. Often, small rooms need so much treatment just to make them sound acceptable, that there isn't enough space left for the treatment needed to make them sound good! So I'd urge you to make your live room as big as you possibly can afford, even if it means sacrificing a bit of size in the control room. You can still get a fairly decent control room into 250 square feet, and John has built successful control rooms even smaller than that (inside a shipping container, for example!). So making your CR a bit smaller would be worthwhile thinking about.
There's another reason why a smaller CR is a good idea: you need to be able to hear the reverb "tails" of the live room, when you are listening to your mics inside the control room. If both rooms are similar sizes, then that become impossible: the reverb tail of the CR overpower the tail from the LR, masking it. You can only here the tails from the LR if the tails from the CR are sufficiently short. In other words, the natural decay time of the CR needs to be sufficiently short such that the much longer decay times of the LR can be heard without being masked. How can you track and mix a sound that you can't even hear?
Then ideal situation is that the volume of the LR should be 3 to 5 times the volume of the CR for that to happen nicely. If the LR and CR are similar volumes, then the subtle sounds of the LR will not be audible in the CR. I would shoot to get at least twice the volume in the LR, if possible.
and perhaps I can make the room a more irregular shape,
Irregular live rooms look nice, and they can have slight acoustic advantage, but it really isn't necessary as any time you angle a wall, you waste space. In general, a simple large rectangle is a good basic shape for the overall room, and the TREATMENT can be angled, tilted, twisted, or even curved to provide the desired look and also the desired acoustics.
Budget for the studio build is about £60,000, with a lot of the carpentry done myself.
For 900 ft2, that works out to around £67 per square foot, which is reasonable if you are doing a lot of the work yourself. That's roughly £700 per square meter, which fits in well with other studios my clients have built in the UK. (I'm assuming you are in the UK, since you did put the budget in pounds, and you did mention London!)
Overall, I'd say you have an excellent sized space, a realistic budget, and a good basic idea of what your priorities are, so your next step should be to take figure out how much isolation you need (that's the key to determining what building materials and techniques you will need), then to start sketching out a few different layouts to see what makes the most sense, and post them here for comment!
I, for one, am looking forward to seeing this happen!
- Stuart -
. Rather easier.