Which elements of room design are subjective and which are objective?

That is because "design" by it's very nature is really an effort of making the best compromises. Each designer will approach every decision based on their experiences and comforts and this will lead to different approaches. As for what is objective and what is subjective. How a room sounds is subjective. Measurement data on isolation, noise, & spkr to room interaction is objective. But, no measurement can tell you what a room sounds like...similar to how no medical test can tell you how you feel.

One of the main reasons Nyal and I published the paper linked below is to address this very question..."bridge the objective and subjective".

http://www.hdacoustics.net/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf

...just because each of the 100 rooms in the hypothetical are different doesn't by itself equate to anything wrong...it should speak to the exciting potential of human creativity and understanding.

Thanks Jeff.... very much enjoyed reading Nyal and your paper. In essence, the 2-channel "listening room" can also be a professional mastering room.

You're welcome Bruce and I'm really pleased you read the paper and enjoyed. I'm a big fan of your work, your facility and maybe mostly how you've created a facility to serve your business model. I've used you as an example in conversations with clients to that point...BRAVO.

On the point of the possible similarity of a dedicated 2-Channel room and a pro mastering room, "you got me" . I personally think of them as having similar needs. Of course I come from a pro background so there's no conflict in my mind...just the same, I wouldn't want the correlation to be "off-putting" to someone without the same background.

Hmmm... While recognizing I am way out of my league, my listening room is close to most mastering rooms I have work3ed in, and it is much deader than most audiophiles prefer. recording studio, maybe, but mastering room, not sure...

I downloaded but have not read the paper yet -- it looks awesome!

When I was helping acoustic designers, the hard part was realizing the client's goals, which sometimes differed quite a bit from what we would have done (particularly in terms of frequency response and reverberation). We had plenty of objective data, but ultimately it came down to how the listener(s) wanted the space to sound, and that was always the biggest subjective factor.

FWIWFM - Don