it looks like it will be impossible to achieve a true RFZ given the small dimensions of the control room...the back two walls are too close to the mix position and there is no way to provide the necessary angles for deflection.
To me, it looks like you have your mix position and intersect point too far back in the room. I think I would try to bring the mix position further forwards, and toe-in the speakers a bit more. That should help with your angles and times.
However, there is no way to keep them from arriving within 20ms from the direct signal so it would not be a true RFZ (I hope I've got this concept right and didn't just sound like a fool
). I realize that shooting for 15ms and sometimes even 10ms is the best one can do but I really want to do this right since we are pretty much starting from scratch.
What times are you seeing in your calculations? It's hard to get 20 ms unless you have a fairly large room. In other words, how long are your rays (from speaker to ear) for the earliest bounces off the rear wall?
Also, it isn't just time; it is level as well. You need to get the level down by 20 dB. And getting both 20 ms and 20 db is really hard. 15/15 is easier, and probably do-able in your room.
But looking at your ray-trace diagram, it seems that you are reflecting the rays at the front face of what I assume is a large superchunk on the side/rear wall: Why did you do that? Are you planning to wrap your bass traps with something reflective, like thin plastic, in order to keep highs in the room? Or is that a mistake?
You said something along the lines of, "the live room should be at least 50% larger than the control room otherwise the engineer would not be able to hear the reverb tails of the live room considering that the control room's reverb tails would 'mask' those of the live room"...this makes since to me however does this "volume/reverb" issue apply to the outer shell of the control room or the inner shell that is controlling the RFZ?
Pretty much everything is referenced to the inner-leaf surfaces: what you see when standing in the finished room, before any acoustic treatment is installed.
And as with most "rules" in acoustics, then 50% figure is just a guideline: so don't go jump off a cliff if you can only get 40%, or whatever!! It is what it is. As long as there is a reasonable difference in size, you'll be fine.
However, I cannot draw the same angles on the left side because I have the sliding doors...this is where my question lies: is there any way I could keep the sliding glass doors and provide proper angles for an RFZ or is this one of those "compromises" where it's either sliding doors or RFZ?
I'm not sure I understand: the left and right side walls seem to be symmetrical to me. So what works for the right wall must also work for the left wall, regardless of whether we are talking about glass or drywall: there isn't much difference in reflectivity.
Also, you might be taking your ray-tracing to unnecessarily high angles. It is mainly mids and highs that you should be concerned about, not lows. Lows are not directional, and act more like expanding hemispheres, while highs are very directional and act more like rays. Your speaker manual should show you what the dispersion angles are for each frequency band, so take a look at those polar patterns to see what type of angles you should be worried about. There is practically no high-frequency energy going out at angles of 60° or 70° off-axis: Most of it is going out in a cone within about 30° or so of the axis. So you might want to ray-trace out to, say 55°, just to be sure, but there's no need to go out to 80°, for example.
-What type of inner shell materials would provide reflections for a large enough range of frequencies? I've read many different opinions about RFZ and what range of frequencies need to be controlled...one opinion was that if you can achieve an RFZ down to 1k, then that would pretty much take care of any stereo imaging problems etc...what are your opinions on this issue?
1 kHz sounds about right, which is kind of what I was talking about above. You only need to worry about the top half of the spectrum (1k to 20k). The bottom half is not so important, and the lower you go, the less directional it is anyway.
Your inner-leaf materials should not be frequency-based: the inner leaf is there for isolation, not treatment, so they should reflect all frequencies as well as possible. That's why you need heavy, massive, rigid materials, such as concrete, glass, drywall, brick, etc. Different parts of the spectrum are governed by different physical characteristics.
-Then depending on how low I would need to go (still talking about frequencies here lol) to achieve the best possible RFZ, would there be a limit regarding mass just because of a potential 3-leaf effect with the outer shell?
Not really: you seem to be confusing isolation and treatment. They are two different and opposite things. Isolation does one thing: it stops sound leaving the room. That's all it does. And obviously, if it is stopping sound form leaving the room, then it must be keeping the sound
inside the room, where it bounces around all over the place, making the room sound bad. That's what treatment is for: to fix the problems created by the "bouncing around", which was in turn caused by the isolation. If you did not have any isolation at all, then you would also not need any treatment at all: Your studio would have to be in the middle of an empty field, with no walls or roof at all. With zero isolation, no sound ever comes back, so no treatment is needed. But since that is a bit impractical, you have to have a room around you, so that's where the problems start. Any type of room at all implies some amount of isolation, which in turn implies some level of "bouncing around", therefore needing some form of treatment. The better the isolation, the WORSE the room sounds, so more isolation is needed.
So try to think of your build as being two entirely different things: Isolation to keep the sound in which makes your room sound bad, and treatment to make it sound good again.
I'm just a little confused on what materials would be used for this inner shell and how they would not create the dreadful 3-leaf effect
...
I don't think I understand: There should be only 2 leaves: the outer one (the building wall itself, probably) and the inner one, which is what gives the room its shape. If you stand inside the room after you finish building it, but before you put any treatment at all in it, then what you see around you is the inner leaf. Everything you add
after that is treatment, and that will be mostly absorption, perhaps some diffusion, and perhaps some form of resonant device. So building your inner leaf should not ever create a three-leaf system, unless you built the outer leaf wrong, with two leaves.
About the only except I can think of is a panel trap (membrane trap), which could theoretically create a 3-leaf system, but in that case it is only a small part of the total wall area that would be 3-leaf, and since that trap would most likely be tuned to a much higher frequency that the MSM resonance of the wall itself, it shouldn't be an issue.
also I'm assuming that whatever frequencies are allowed to pass through the mass, would then enter the cavity which could be designed to act as a trap (between the inner RFZ shell and inner drywall)?? am i crazy?
Now you are really confusing me! The only "cavity" is the one between the inner leaf and outer leaf! What cavity are you talking about? The "RFZ shell"
is the inner-drywall! So how can there be an cavity between that drywall and itself, when it is the same thing?
You lost me there...
-Oh... and I guess it goes without saying but we are sort of pushing the budget to the side for a while until we achieve exactly what we want out of the design...then we will scale down as need...but there's quite a bit of wiggle room in the budget if it means the difference between an average studio and a phenomenal studio. All in all we want the money to be well spent!
Ahhh! Yes, about budget. The correct way to estimate the budget for a studio build, is to come up with the largest possible amount of money that you could ever image spending on it, multiply that by a randomly chosen number between 2 and 10, add the cost of an outrageously expensive luxury car, then add a couple of zeros on the end...
- Stuart -
.
) (still talking about frequencies here lol) to achieve the best possible RFZ, would there be a limit regarding mass just because of a potential 3-leaf effect with the outer shell? I'm just a little confused on what materials would be used for this inner shell and how they would not create the dreadful 3-leaf effect 
