Test between Sony MDR-F1, Sony PFR-V1 and modified Grado PS500.
In this test, I have listened to a range of very good acoustic recordings (mostly classical music). I hope you find this test useful.
Comfort: Sony MDR-F1
Despite no clamping force and less weight than the MDR-F1, the bass ducts of PFR-V1 lead to discomfort. For that reason, MDR-F1 wins. Compared to the successor MDR-MA900, the MDR-F1 is softer and more gentle, both on the skull and around the ears, and I believe I do not exaggerate when I state that MDR-F1 is regarded as one of the most comfortable headphones ever made. In this test, I used a rather heavily modified version of PS500 - first a replacement of the L-cush to G-cush (larger), then on top of this Beyer DT-770 velour pads. Yes, really. They are huge now, and slightly heavier, but also more comfortable since the ear lobes do not touch anything inside and nothing is itching.
Soundstage: Sony PFR-V1
When listening to acoustic recordings, soundstage is of great importance. What makes the PFR-V1 top-notch when it comes to soundstage is that the membranes are not placed around, onto or into the ears. The sound is projected towards the ears, similar to loudspeakers. Only AKG K1000, and in some degree Stax Sigma, are using a similar approach. The result is a sort of holographic sound where you can sense the presence of the instruments in the room. The MDR-F1 and PS500 provide a pretty impressive soundstage as well but their design puts them one step behind.
Audio quality: Grado PS500
Despite the addition of both G-cush and Beyer velour pads, the audio quality of PS500 is fantastic thanks to the superb detail and treble. An equalizer can somewhat correct the remaining frequency distortion. Beware of bad recordings though - PS500 will not treat them gently. To my surprise, I found that PFR-V1 brings a more natural treble than what MDR-F1 does. The latter being a bit tame and more diffuse. However, there are advantages and disadvantages of both these models and it can be difficult to decide which one of the two that is the better sounding.