I think it's the compendium of all those factors. Sony designed and produced a very good transducer, quite sensitive, fast, not too low impedance, and with good tone in the midrange, so they went as far as they could to design the "perfect" housing to let the driver come to life.
By tuning the enclosure choosing carefully the wood, the shape, the inner chamber, the driver's placement/angle, the way to decouple the driver-housing unit from the headband and chassis, and also making the whole thing very comfortable, they came out with a very special headphone.
Perfect? Probably not, I don't think so nevertheless, but there are very few pieces of audio gear which can draw you into the music with the R10's intensity.