F6S is heavily upgraded from F-6, it has bigger and double magnetizing system with adjusted coil, and also PC basket which is more robust than tinplate. The sound is more present, with better detail and imaging. If you are a F-6 user, we won't hesitate to recommend this one to be drop-in upgrade as improvement is remarkable. Technical Data: Power——20W – 40W Nominal impedance Z——8 Ohm Frequency response——-fu – 20kHz Mean sound pressure level——95.7 dB(2,83V/1m) Resonance frequency fs——40Hz Qes——0.713 Qms——3.343 Qts——0.587 Vas——21.62 litre Weight (a pair): 2.4KG