From what I can tell everyone here prefers Sketchup drawings? I don’t know if there is a way to export files through the free version.
Don't use SketchUp Free! It is a really lousy attempt to create a web-based version of the actual program. You can still down-load the REAL thing, which is called SkecthUp Make 2017. It is actually usable, and you can export files from it. SketchUp Free is a bad joke. Don't waste your time. As you noticed, they make you jump through hoops top export a file...
How snug would the top of the box need to fit the curved profile of the top of my speakers?
It would need to follow the curve within a couple of mm (maybe about 1/16"). You need a fairly tight fit (small gap), and the gap should really be sealed. Some people just caulk the gap, others put soft rubber strips in there, but not foam: the typical "foam in a can" that you buy in hardware stores is very light weight: no mass at all, and dries hard and brittle. You need something soft and flexible for that gap.
How “permanent” is a soffit design? Is it something I could salvage and move 2 years down the road if I want to move to a new room?
You can if you build it that way! It could be designed as a group of several parts that are bolted together, and could then be taken apart and carried away.
This is a 2 year long commercial lease and I may or may not want to move at the end of the lease.
Realistically, it will take you many, many months to design and build your place.... I would be surprised if it is finished inside two years, so you might want to get an extension on that lease right now! Realistically, it takes about 3 to 6 months for the average first-time studio builder to learn the basics of acoustics well enough that he can design his own place, then another three to six months to actually design it, then another six months to a year to build it. Those are very typical timings from forum members. If you wanted it built faster than that, you'd need to hire a studio designer to design it for you, then a contractor to build it for you, and even then it likely would not be done in less than six months.
If I do not end up going for a flush mounted system, what alternatives do I have for a good RFZ CR?
If you don't soffit-mount your speakers, then it isn't an RFZ design!
The actual RFZ spec has the speakers flush-mounted as part of the design concept. Having said that, you could build a room with angled front wall sections that mimic the shape of an RFZ room, then just mount your speakers on stands directly in front of those angled sections, but it would not be RFZ, since you would still have all of the artifacts that flush-mounting eliminates. It would work, but with caveats... it would not be as good as an RFZ style room.
I’ve heard the Shape 65’s perform well directly in front of walls due to the passive radiators on the sides.
I've heard NS10's "perform well" on meter bridges!
But I would never use that setup as my main monitoring.
What flush mounting gets you is this:
1) It eliminates the power imbalance problem (or "baffle step response" issue)
2) It eliminates the major SBIR artifact caused by the front wall
3) It eliminates the edge diffraction problem
4) It eliminates several other reflection and comb filtering problems
5) It extends the low-end response of your speakers
6) It tightens the bass very much
7) It looks cool!
... and a few others too. If you don't flush mount your speakers, then you WILL have all of those issues still, simply because the speaker is in the room! Just having the speaker in the room causes all of those. By flush-mounting the speaker, you have effectively removed it from the room: it is no longer "in" the room, so it is physically impossible for it to cause any of those artifacts associated with the speaker being in the room.
I’ll post some of my plans tomorrow when I have some free time.
Cool! Looking forward to seeing that!
- Stuart -