There is an excellent review in the April-June 2011 issue of HIFICRITIC which has impedance curves, frequency responses, energy decay patterns etc. If I was at all interested in the speaker I would purchase that issue, or the review if it is sold separately. It was in the main positive but with reservations. It required some tweaking for best results and even then they felt it was so balanced for digital that they did not recommend it for a system that used vinyl to any degree, having a too laid back and too rich sound on LP. Of course this may just suit your taste or room conditions. It was a worse than average load with a 2.6 ohm minimum. That is also the minimum for my Gamut L5s and they are quite hard to drive but the phase angle may be different on the SF, it is suppose to be mild. They say " Only larger SS amps or more powerful 4 ohm rated tube ones will drive it really well". Hope this helps.
