RScott's Mix Room Design thread

Location: Atlanta, GA USA Purpose: Home studio, one room. Primary professional purpose will be to serve as a Mix room for post-production sound for film, TV, etc. Secondary purpose will be as a home theater. Some foley (and much folly!), voice and instrument recording will happen in this room, with headphones. Budget: I'd like to spend $3500 to 5000 to get this made, but as with all starting budgets, who knows. I will be completing most of the design and construction, but will certainly require outside professionals for electrical and HVAC. I will also be seeking outside professional advice regarding code compliance and to make sure that everything is legal and also safe. My budget goals are to keep costs down as low as possible, but I'd rather spend $8000 to get it right than $5000 to get it wrong. Outer leaf diminsions (inside edges): 26.5' L x 16' W x 10' H Inner leaf diminsions (inside edges): 22'10" x 14'3" x 8'10" (around 2900 cubic ft) Ratio: 2.588 : 1.618 : 1 Isolation Design goals: Two-leaf design in an unfinished basement. Three walls of the outer leaf are the outside walls (Vinyl siding over OSB on 2x6 frame) of my house. One wall is at ground level and opens with two windows and a door to face a pond with no nearby neighbor. The two other walls are partially underground (cement walls come up 3.75 feet from the basement floor) with no windows or doors. Each of those walls faces a neighbor, one at roughly 20' and one at roughly 35-40'. The fourth wall will face the rest of my unfinished basement. Flooring is cement foundation. Above, joists hold the floor (Laminate, underlay pad, plywood) of my house's entry level. One floor above the studio is my living room, kitchen, and dining room. Two floors up are the bedrooms. Inner leaf walls will sit on the concrete floor and will be fully detached from the outer leaf walls and floor joists above. Walls will have a 9" air gap. Ceiling will have around 10" air gap. Isolation goal will be to lower roughly 100dB peak levels (theater playback peaks) to 35dB or lower at the inside of the neighbor's house. Once I order my sound meter I will have more specific information about the TL I will need. Room Design goals: The room will be designed for 5.1 using soffits for the 5 main speakers. The front face of the room will use a RFZ design on the walls, with an angled ceiling treatment or cloud with reflective face to deal with ceiling reflections. L, C, R Speakers will be mounted at ear height. Surrounds will be mounted higher and angled downward (preferably under 12 degrees.) Primary listening position will be forward in the room around the 38% point from the front wall. Seating will be placed behind the mix position for theater and producer use. Design progress: I am currently designing the room so that I can get an idea of materials costs and have a solid idea of what will be impacted when I talk to contractors about Electrical, HVAC and construction requirements. For now, the only things that are for sure are the dimensions of my existing house. My knowledge: As with almost all project studios, my education began with "I want to build a studio." At this point I've read Everest's Master Handbook and am reading through Rod's book (smart planning to release a new edition in a few months.. I think this guy will be selling me two books by the time it's all said and done!) I'll do my best to avoid asking questions that will paint the word "Idiot" all over my forehead, but it's fair to say up front that this is the first time I will be doing anything like this. Attached is a Sketchup file of my design thus far. It is the illustration for my questions. First question: My room is oriented with two exterior windows and a door along the right side of the room. To keep the room as symmetrical as possible, design considerations for the right side will be mirrored more or less on the left side. For instance, a splayed window on one side will be mirrored with similarly splayed gypsum on the other wall. The front-most window on the right-hand wall of the room will be incorporated into the RFZ design in order to keep it as a usable light source into the room. It also looks out to a pond and I'd love to keep that view in my work environment. By angling the inner leaf window at 24 degrees, I can shoot first reflections behind the mix position. Due to the outer window's forward position in the room, I must deal with it being in front of the Right speaker soffit wall. To do this, I've angled the space between the exterior window and the inner leaf window so that the inner window is now not as forward into the space and meets the right soffit wall. This significantly changes the geometry of my inner leaf, because I must bring the leaf in to meet the soffit wall, and then it follows the window back out to where it meets the side wall. The window is not the entire height of the wall, so I have two ideas in my head that I am considering and I would love feedback on these or any other options I may not be thinking of. First idea -- use thick walls all around the window to connect it to the rest of the inner leaf wall. Essentially the inner leaf starts as a normal rectangular room shape but has a big indention at the window space. Keep the cavities above and below the window as part of the room and stuff those spaces with fiberglass to trap bass and reduce the resonance of the cavity. Second idea -- extend the window plane upward and downward from floor to ceiling, cutting that entire area out of the room. From above, the room would no longer have a rectangular shape at any point. I'm leaning toward the first idea because it maintains some of the room's area and also maintains the room's rectangular shape above and below the window. The cost is a slightly more complex construction, but I've spent quite a bit of time working on this design and am fairly confident that it can be done properly (as far as the construction goes). What I don't have a firm grasp on is the acoustic implications of this design. I am assuming that modal issues will be complicated significantly. I'm not sure what to expect from the small concave zone forward in the room from the window, located behind the soffits. I understand that the parallel walls to the sides of the listening position will need to be addressed, but I'll do that after sorting out if this window design is really what I want to commit to. I'm using a recommended ratio at the moment as a starting point. Is that even worthwhile with this window design element, or should I just toss that recommended ratio out the window? Any ideas regarding the window specifically would be greatly appreciated. Sealing off the window completely is something I'd prefer to avoid if possible. Please take a look at the Sketchup if you haven't. I'm sure that this will make no sense whatsoever without that as an illustration. Second question: The door at the rear of the room on the right side is located quite near the rear wall. With my recommended ratio suggesting a shorter room length, I've moved the entire inner leaf rear-ward to keep the inner door opening lined up with the outer. I have not decided yet if I want to use a single door as mentioned in Rod's book or two doors, but either way, the entryway would need to line up. When using mass-air-mass two leaf construction, what is the effect of varying air gaps from one wall to the next? I understand the effects of changing the air gap on a single wall, but what about affecting adjacent gaps? For instance if I have 10" gaps on all sides of a room and scoot the room 2" rear-ward... the front wall now has 12" gap and the rear has an 8" gap. Will each wall function with properties that mostly relate to its own air gap, or will flanking cause the wall system to respond relative to the weakest link, even if that link is a smaller air gap on the opposite wall? I must give so much thanks for the existence of this discussion forum! It's such a huge resource. Thank you in advance for time spent pondering the things that keep me up at night. -Scott