This is an interesting discussion and something that has been very close to my heart for more than 57yrs (yep I am a VERY old fart !!!!!!) when I designed and built my first studio --- only small but did some great recordings --- especially one that became very famous world wide.
Having worked in many studios of greatly differing sizes and quality over the years, one thing that has been proven to me is that it is not easy to build a studio that will cater "PERFECTLY" for every type of musical genre. A classical studio requires a reasonable reverb time whereas a rock studio requires a much tighter reverb time, and so on.
NOW, so that some will not pick me up on what I am about to say, let me emphasize that the three studios that I have owned/built have ALL been "professional" studios and NOT "home " studios where the best is not always possible and compromises often have to be made, but the principles are still valid.
After my first studio, I decided that I really needed a bigger studio and closer to the client base I was looking for (at that time the advertising industry and larger orchestras) so I built the studio with mid range RT-60 --- from memory I think that it was about 1.5sec, with acoustic absorbing baffle units that I could place around instruments if I wanted/needed a tighter reverb time.
But rather than an RT-60 time, I was more interested in having the minimum number of standing waves. After quite some researching I discovered that the best investigation into this situation had been undertaken by the BBC in London some years earlier and that their findings were generally accepted as being fairly accurate. What they discovered was that the best room size dimensions were 1:1.78:2.33 and for the room to then be acoustically treated to give the RT-60 required for the room's usage. This I did and had a great sounding and popular studio for the intended purpose.
A few years later my direction had changed (had opened a record label and was releasing mainly "rock" type music) and the current studio was simply not giving me the results that I wanted ---too alive even with baffling.
I started to think that the best recording space for a "rock" recording would be in the middle of a 1000 acre cow paddock (ignoring the crows, cows mooing, etc), because there would be no standing waves and no reverb/echo to contend with and any effects required could be post added and added exactly as required.
So, I thought that if I could build a studio that effectively had no walls I would achieve the ultimate "rock" studio, BUT how to go about this !!!!!
Firstly I had to find the correct building (I didn't particularly want to have to purchase property and build from scratch), thankfully I found a building in the center of the CBD that had been constructed more than 100yrs previously and was constructed of 2ft thick solid sandstone walls, a 1.5ft concrete floor and a solid concrete ceiling (not sure how thick) and no windows. In other words the room was soundproofed and amazingly very close to the required dimension ratio. With the building of a solid double brick wall at one end, I was able to get the required 1:1.78:2.33 ratio, with the room measuring (in round figures) 15x28x36ft.
Thankfully at the time I had a relative that worked as the PA to the biggest insulation manufacturing company in the country and through her I was able to get the company to design me a very dense standard type 3" fiberglass system that came in a roll 15ft long by 4ft wide with a chicken wire type mesh internally embedded/woven into it length wise through the middle (to hold it all together) and then covered on both sides with a glued on fabric (to stop fiberglass particles escaping).
To achieve the required "no wall" effect I was after, firstly I had glued to all of the walls and the ceiling a product that is now unfortunately no longer available --- 4" Type-B Building Bat (it was so dense that if you stood on a bat you would not compress it), Its sound absorption properties (not sound proofing but reverb killing) were amazing (can't recall the actual figures).
I then had bolted to the ceiling and about 1ft out from each of the walls, a 4"x3" timber batten, and then had each roll of the especially manufactured fiberglass, nailed to this batten so that the individual rolls hung so that the bottom of the roll was about 2" above the floor (which was carpeted in a fairly dense carpet with a double thickness underlay), with each drop being tied to the one next to it so as not to have any gap between the drops. I then had another 4"x3" batten secured to the ceiling about 6" in front of the hanging fiberglass and from this I hung theatre type heavy duty curtains that just touched the carpet flooring.
The only gap in all of this soundproofing was for a 5ft air gaped door entrance that had two center opening doors with these doors being fully sound insulated and sound absorbing type panels on the walls between the inner and outer doors and a 5ft x 2ft triple glass window into the Control Room --- each sheet of glass being a different thickness with the two outer sheets being at a slight angle and each sheet being mounted in a u-channel rubber section to minimize vibration leak through. The gap between the door frames and the windows frame and the solid wall that they were secured to, being packed with "filla foam" to reduce leak through.
When finished, the principle of operation was that (say) a bass guitar when played (with the speakers being about 2ft from the curtain and facing into the wall) would have the sound from the speakers hit the hanging wall (and if we consider that the sound was actually hundreds of single point sounds) each point source because of its sound pressure, would effectively cause the hanging wall to swing backwards (thus reducing its intensity) but also being broken up in to many smaller point sources as it passed through the 3" hanging fiberglass, so that as each sub point source came out of the back of the hanging fiberglass, it would have very low intensity.
This point source would then travel across the 1ft air space and enter the very dense Type-B Bat that was glued to the wall, where it would again be greatly reduced in intensity and also broken up into much smaller sub points, before hitting the solid stone wall and being reflected back towards the room, where all of the just detailed sound reductions would again occur as it traveled back towards the studio.
The end result being that there was measurably zero sound bounced back into the room and therefor virtually zero signal returning to the room and therefore zero reverberation time or standing waves.
After 8yrs of owning the studio I could not enter the studio and close the doors unless I had some form of noise going (possibly the almost silent air con system) because otherwise I could virtually hear the blood flowing through my body --- a really strange and off putting feeling/experience !!!
BUT, as a rock studio, it very soon achieved the reputation of being one of the best rock studios ever constructed and even today, about twenty years after the building was sold and demolished to build a multi storied office block, it still has the reputation as being one of the best if not the best rock studios by those who recorded their music there. Even many of the orchestral type session musicians that recorded there (we placed highly reflective baffles for them) say it was a great studio.
So, even in a home studio situation, if you can possibly build your studio with the correct dimension ratio and then decide exactly what type of music you want to record and acoustically treat it for that type of music, it is possible to have a studio that can obtain excellent results, provided of course that you also have very good recording equipment (whatever type that might be) and you have the correct ear for the type of music you are recording and the musicians who can play the music (!!!!!).
I hope all of the above gives you (singular and plural !!!) something to think about and work towards to get excellent results and most importantly many years of enjoyment and satisfaction within this great industry.
David