. All these projects had isolation a key factor - they needed to keep sound in, and keep outside sound out.
While I have considered that requirement, and in this new build originally planned for it...I also realized that it wasn't an absolute necessity for my situation.
If I was building in an urban, noisy environment with critical neighbors, etc,...then it's needed, but I don't have that situation.
Oh for sure...if my neighbor is out there running a lawnmower, I'm going to hear it as a faint sound inside the studio...but not enough to where it ends up in any recordings. Likewise, if I have a drummer banging away, I could stand outside and hear it...it's muffled, but not 100% contained...but it is enough so that it isn't annoying anyone.
Commercial studios have a much more critical need for 100% soundproofing...but like you discovered, you have to have the room-in-room or some other involved build design in order to get to 100% soundproofing...and it adds a lot to the build in effort, materials and cost....and then...you STILL have to treat the inside for acoustic audio quality and/or build it in with the overall construction while also building for 100% soundproofing.
It's not a relatively simple task..as I'm sure you know!
I mentioned in another post here or maybe one of the other ongoing threads...that I notice in the home recording world, the majority of guys seem to be focused on soundproofing when they ask for advice on how to build or what materials to use in an existing space to get soundproofing, which is often difficult to do, since most typical houses/building are not focused on 100% soundproofing...so no matter how much you "throw" at the problem, you still can't get there...and often it's solved best with a ground-up build.
I don't deny that some of the home rec people have a need to soundproof...but I can't help but notice that not many are concerned about sound quality in their spaces....mostly how to keep sound in.
With my own studio build...I seriously considered the room-in-room. I knew that would get me close to optimal soundproofing, but then as we got to that stage,. I gave it some more thought and decided that doing the second room inside the room would both reduce my overall room size and add a nice chunk of cost in the process. So I opted to not go that route because I realized that in the 20 years I've been here with my old studio setup where there was no formal soundproofing and the walls had even less "beef" to them than codes currently require...I never had a problem with sound going out or coming in.
Like now...I have 4 large windows in the new studio...where I originally wanted to avoid them, but then I knew how much I enjoyed the view and the daylight coming into the studio...so I'm glad we put them in, but yes, they don't improve the sound control...but I will be able to deal with that if needed.
So like I already mentioned...I'm more about the audio quality in the room...and certainly the "vibe"...attention to aesthetics and visual details, etc.
I think that stuff for me, goes a long way to creating a studio space that is comfortable and pleasing to be in...with a good sound. This new studio was all about having a large open room...which is why I didn't bother with control rooms or iso-booths...and I can certainly work around not having those things...but in return, I hope to have a dynamite tracking/mixing space.
Short anecdote...
I was at a somewhat local studio a few months back to buy up some equipment because the guy was closing it down permanently. I was quite impressed with the build quality...inside it was all rough-cut wood on the walls, but in-between that layer and the drywall/outside, he had lined the walls with lead sheets!!!
He said it was a real job to do that, and he had acquired the lead sheets somewhere, I forget...but the result was a pretty near 100% soundproof room.
I told him about my build, and he looked at me and said not to waste my time going that crazy...because he understood that I didn't have a need to be 100% soundproof....and he even said looking back, he now realized it was way overkill...since he also didn't have that need, but kinda just followed the typical commercial studio build.
His live room was not huge, but decent size, tall ceiling...yet his control room was actually small and the back wall you could almost lean onto from the mix position...and right away he said if had to do it over, he would push the control room wall back at least another 10'...which was my thought too. He also had a bunch of small iso booths, but only used them occasionally.
So while you can follow a typical commercial studio design approach...it's not always the best way to go for every situation...which is why I constantly tell home rec builders to rethink their plans to do a small control room and small live room, and just open it up...but people get stuck in that mindset. It has to be soundproof and with all these smaller individual rooms...which has a legit purpose...but is not always necessary, and often uncomfortable if you work solo a lot.
The idea of constantly walking from a control room to the live room when working alone...would be tedious. With the open room, I can just move freely...but that's my approach.