Okay...I visited the JBL showroom in Phoenix on Sunday with another friend (Thatguy). The folks at the place were very courteous and cooperative. They patiently played all our songs as we kept moving around the listening area like cats on a hot tin roof.
The audition was severly hampered by the setup. It is a super-small space with Glass/open space on one side. The speakers were kept too close to the back wall causing the bass to get too boomy and muddy. We moved them up a bit and toed them in, this brought in some control to the low end but left us with just around 4-5 feet of listening distance. We continued with our session nonetheless.
One thing I observed was clear mids. The vocals were dead center and mid-bass were very well articulated. The highs were not sharp. The shimmers felt very gentle and decayed beautifully.
The sound stage was pretty narrow and not very deep. The lower end of bass was still a bit overwhelming and lingered a bit longer. Though moving them up did help but they were still muddy and some frequencies were all but lost. I would not attribute this to the speakers at all but to the room entirely. Remember, the F12s go down really low (around 28Hz IIRC).
We also heard a tall JBL (Studio 590) for a little while. What really stood out was the vocal clarity and projection, they were so spot on that I had to double check if the centers were actually not operational (initially they were). The overall sound, especailly the bass was a bit recessed. The soundstage seemed a bit too deep in the center. The mids were crisp but bass had very little articulation. This again must be due to the room.
I would want to hear the F12s one more time in a more conducive setup. The nice folks at the showroom offered to bring them out of the small demo area and play them in the main display area. This may help a bit though not sure how much considering there'd be glass at the back and the front. There used to be a JBL dealer on Lavelle Road, I don't have the contact, need to google more vigorously. If nothing, might make a trip to Decibel in Chennai.