Seamus, this will likely answer all your questions.
http://www.ebu.ch/en/technical/trev/trev_274-hoeg.pdf
The BBC R & D archives are brilliant also.
There can be no definitive answer. Acoustically small might for instance mean incapable of supporting a diffuse field down to a specific frequency. The Everest and oher guidelines are from experience. The EBU reckons no less than 30 square metres floor area for a decent control room, 40 for a critical listening room. As you can see that's most EU rooms gone right away. Take a look at the EBU requirement to eliminate very early reflections. You will quickly see why us small room users end up almost anechoic.
Lupo, when I read that thread I find string instead of a mirror. I find an absorptive panel being inserted block a path to identify it's source. I also see distance measurements and calculations. It's all in reverse. ETC is used at the end of all this to view what we already know is there.
Quote:
|
Is it possible then, to combine the information given by an ETC reading, and transpose that time based information with frequency waterfall plot and determine from the given reflection points that the spectrum arriving at the listening position is bad (absorption) or needs augmenting (diffusion)?
|
That haircut is absolutely no help in answering this question, as evidenced by the silence. There is no post anywhere illustrating how an ETC can be of primary use in this very common endeavour. It can only confirm that one has succeeded.
I firmly believe that in a small room:-
Destructive refective surfaces are blatantly obvious to the eye.
A mirror can refine this.
Audibly troublesome reflections can be distinguished from beneficial ones by ear, eye, or even measuring tape!
This is very simple well covered stuff. I suggest a healthy interest would veer towards Ethan, Russ Berger, Jeff Syzmanski, and others, who attempt the seemingly impossible, i.e. make the small room sound big.
DD