Found this in another thread:
I suggest you use this answer to Eric’s question, and maybe push him a little towards the K712Pro J
“Often it’s the attention to details and extras that make an already good product even better. It’s not a secret that the K712Pro is based on our successful model the K702. Construction and acoustics of the K702 have been the base of operations. Notwithstanding we managed to launch a slightly improved capsule with the K712Pro. The driver is boasting even less tolerances and in combination with improved acoustic materials a better low end performance than the K702 is achieved. The K702 anniversary was acoustically already a step in this direction. But this was an anniversary product only available in a strictly limited quantity, with only few products left in the market.”
Sales Assistant, PRO Division
AKG Acoustics GmbH"