Been testing the FSP for a few days and wanted to share my humble inpressions, really nice and refined closed cans I have to say. Only a few hours of burn in though.
I will also make a few comparisons with other closed studio headphones like the DT150 and AKGK271s
FSP offer tight bass, less bloated lo-mids than DT150´s for example (300hz +/-) and with a bit more pronounced lo end/slam than the K271s with velour pads.
Better driven with my Heed Canamp than with my Xonar D2´s stereo output. The Canamp controls FSP with authority (it´s gain output can be a bit high perhaps if you ask me). This amp is an outstanding match the K271s and results a bit too dark with the DT150.
I´ve found the FSP not so solid for studio use, construction seems a bit weak (DT150 wins by a large margin), quality is fair but not the best, tight headband and -hot- small pads doesn´t make you forget you have them on either.
Isolation is very good, perhaps a bit better than the K271s witch I find sonically overall more refined, with better soundstage (a bit more laid back too) and with realistic rich mids and sparkle. Also more coherent over the entire spectrum and no so upfront like the FSP.
Presentation on the Focal is engaging, fast, very flat and balanced, gutsy at the lows, a tiny bit nasal at mids with good detail at hi freqs. Bass drums sound punchy witch is great, electric guitars have lots of body, also bottom end of snares sound pretty good too (sparkle and ¨crunch¨ doesn´t match K271s IMHO).
Noticed that the coiled cable seems to sound a bit fuller tan the other short one.
Mod-wise, 3.5mm jack opens a door for recabling (but finding a similar -slim- quality connector (Switchcraft, Neutrik...) can be hard though)
These cans perform really good but confort and design could be improved, a versión with roomier pads and softer headband clamp would be a winner