This process is exhausting!
Welcome to the world of studio design! It is, indeed, a tough job, and not easy to do. People think it's just a matter of "copy/pasting" a few standard bits into a rough outline, and you are done.... Nothing could be further from the truth. Good design takes time: Months, usually, from an empty page to a workable final design with good acoustics built in, along with good functionality and good aesthetics. It ain't easy!
My listening position apex is about 6' from the wall (38%) of the room, and my ears are about 18" in front of that.
You seem to have things a bit backwards! The theoretical 38% spot is where your EARS go, not where the triangle apex goes. The reason for that is because the 38% spot supposedly has the least-terrible modal response. If you figure out all the major modal issues for modes related to the front-back direction (including axial, tangential, and oblique modes associated with that dierection), superimpose them all on one another, then 38% is where the ugliness is least ugly. So that's where you want your ears: where the modal response is minimally bad.
In practice, it's just a starting point. In real-life there are many other things that can affect the "best" spot, which is why I recommend using the "walking mic" process to help find that spot. The "walking mic" test, using REW
... and to help avoid unpleasant spots.
It is often the case that the "best" spot (or more correctly, the "least bad" spot) is a few inches in front of the 38% theoretical ideal... but not always. The most important point about the 38% rule, is that it is not a rule at all! It is a guideline, or a starting point.
Following all the best design guidelines 25-35 degree sofit angles, 38% of room length for listening, and position the speaker neither on the 45 degree line from the corner of the room, nor at 25% of the room width,
Those, too, are guidelines, not carved in stone. When I wrote that, I was of two minds of publishing it, or not, for the same reason Wes later regretted publishing his 38% rule: People see that, and think that they absolutely must follow the "rules" exactly, in order to get a perfect layout in the room. In reality, there is no "perfect" layout: Just a bunch of really bad ones, a few not-so-bad ones, and maybe one or two "acceptable" ones. That's part of what studio design is about: identifying the most acceptable spot in any given room, based on that room and that set of speakers, not necessarily a set of "rules" that might not be totally accurate for the room in question, or for the speakers actually used.
I'd encourage you to do the walking mic test, identify the good and bad spots, then do some critical listening in the room to confirm if that really is the case, then choose your listening position based on that.
If you want to get extra fancy, then once you have your listening position decided, then do the same thing with the speakers. I've been meaning to add a "walking speakers" test procedure to the forum, similar to "walking mic", as that can also help avoid trouble spots for speaker placement.
And if you really want to go "extreme overkill" on this, then, with the speakers in their new "optimal" position, repeat the walking mic test, to see if there might be an even better spot. Rinse. Repeat.
Of course, you have an empty room right now, so doing the above isn't easy to start with, and the conditions will change once there is treatment in the room, but this process can usually get you to a pretty decent arrangement of speaker locatio and mix position. Then you can adapt the speaker position to the soffit design, trying to keep a similar position and relationship.
Ive only done the first few ray traces and Im already seeing issues.....it is discouraging.
Your soffits have no "wings" on the outboard front faces. Right now, you have a sort of "reverse wing" that is just perpendicular to the wall, but proper wings can be adjusted to help with reflections.
Also, your window seems to extend too far forward, as it is catching the first reflections and preventing you from adding the soffit wing. I would move the window backwards a bit.
Another issue:; If you do insist on splaying the side walls of the room, then splay them at a greater angle and don't extend the splayed part so far back into the room. Your splayed wall end very far back in the room, and are not accomplishing anything useful like that. I'd still suggest just building the room as a rectangle, and adding soffit wings to accomplish the same purpose as splayed walls would, far more simply, cheaply, and with a greater chance of being able to predict modal response correctly.
but I am now getting some reflection from the rear wall that will be problematic.
Then your rear wall is badly designed!
as Starlight and Gareth mentioned, your rear wall acoustic treatment needs very careful design to deal with those issues you are encountering, as well as with a whole series of other issues. The real wall of any control room is always the one that needs the most treatment, by far, and that treatment needs to be deep, wide, high, and properly tuned to deal with the problems. Rear walls should not be reflective at all, or if there are reflective surfaces back there, then the necessary precautions should be taken to minimize the problems, and absolutely to ensure that there are no specular reflections back to any listening position in the room.
One of the key design concepts for RFZ style rooms, is the "20-20" issue (hence, my screen name...). Your goal should be to ensure that there are no reflections at all arriving back at your ears within 20 ms of the direct sound, and the ones that do arrive should be -20 dB down in intensity. That 20 ms "initial time delay gap" followed by a smooth, even diffuse decay across the entire spectrum, and the overall decay time should then meet the criteria for critical listening rooms: you don't want it decaying too fast for the size of room, or the room will sound "dull" and "dead", and you don't want it decaying too slowly for the size of the room, or the room will sound "harsh", "live", "reverberant". The decay time is chose in accordance with the room size: there's an equation for doing that, but in most typical home studios, a decay time of around 200 ms is about right. To avoid yet another "carved in stone rule", let's rather make that a target range of somewhere between 180 ms and 250 ms.
Achieving the 20-20 criteria and a smooth, even decay across the board, of about 200 ms, is the "holy grail" of control room design. If you can do that, then chances are, your room will be pretty good. This is NOT easy to do, however! If it was, people like Glenn, Andre, and myself would be out of a job! Designing the room up front with these goals in mid, is a tall order.
I guess I could build another bass trap in the middle and that might catch those rays?
At the most basic, the entire rear wall should be one huge bass trap. But it should also NOT trap too much of the mids and highs, and has to create that diffuse, smooth, even decay that arrives back at your ears after at least 20 ms, and it also needs to attenuate the levels such that the above "smooth, even etc." arrives at a level that is 20 dB down, then decays over a period of 200 ms. A single bass trap "wedge" in the middle of the rear wall is not going to do that. It might help with the bass a little, and also with deflecting some of the mids, but it simply isn't big enough to do the job.
I need to do the real math on the depth and density I'd need. Can I do that without actually testing the room fully stood up?
You can do the standard REW measurements in the empty room ( How to calibrate and use REW to test and tune your room acoustics
), and the data you get from that will help you understand what the rear-wall issues are, and thus guide you in what you need to design to get the treatment to achieve what you want it to achieve.
though I still feel like I could free up floor space for the live room
I agree! I still think there.s probably a better overall layout that would trade off some of the CR space for a better LR, without losing the "lobby", bathroom, or booth/storage.
- Stuart -