Hey Roasty,
Turns out the squeaking/creaking was the pads rubbing against my glasses frames (thanks to
@lator for alerting me to that, above). I installed Dekoni FSS pads on my Susvara around the time they came out, and haven't looked back. The leather is smooth and cool, and doesn't squeak against my frames. The Dekonis are also a bit thicker than the stock pads, and I'm not bothered by any minimal contact with my ears. The scratchiness of the Soli P pads would actually be a deal-breaker for me. I also find the clamping force of the Soli P to be a bit light, which causes a couple of pressure spots on either side of the crown of my head over time. I've ordered a knit headband cover, which should arrive tomorrow and may help with the overall feel of the headband. I'll report back on that.
Thanks for the suggestion about cabling. I probably won't have the headphones long enough to warrant ordering adapters. If I can't get the feel of the pads sorted, any other mods would be academic, anyway.
Thanks also for the music selection. Truth be told, while it (the first track) sounds very nice on the Soli P, I clearly prefer the presentation on the Susvara. The bass is certainly more enveloping and present on the Soli P, but vocals reign supreme on the Susvara, as does the layering of the soundstage. In general, acoustic guitars and cymbals often seem a bit unconvincing (as the real thing) on the Soli P. It's really in its element on something like
Mezzanine by Massive Attack, in my opinion. Throbbing rock and roll is also great on the Soli P. In a nutshell, I feel like the Soli P is a headphone that speaks a bit more to the right brain than the Susvara does.
If I take off my reviewer's hat and just listen, there's no denying the Soli P does a ton of stuff well, offers a coherent presentation, and is a highly enjoyable listen, even spectacular in certain contexts. It's firmly on the warm side of neutral, but if a headphone is going to lean either way, that's the direction I'd prefer!