A bit of cross-posting from another thread:
Sourcing foam tips: I did not find, in a cursory search, any inventory of Phonak-labeled tips. But I checked the Comply stores in a comple of countries. I found at complyfoam.com that Phonak was listed (though not on the PDF, only on the web interface), and that PFE 232 was one of those listed (probably most PFEs use the same tips). Price is better than at the defunct Audeoworld; you can order 3 or 5 pairs, light or black in color.
PS: the reason I thought that the Phonaks might not use a standard size is because the folks at Audeoworld told me so. They might have been wrong though.
T-130 - Comply™ Foam Tips
I had seen, IIRC, someone mention T-150 here, but can't find any mention of that anywhere in the interwebs including Comply's site.
Regarding sibilance, I've done some tests in the last day. I was able to tame the emphasis in the sibilance region and just above by two things:
One is using Comply tips, the smallest size that still provides a seal, so that insertion is as deep as possible. This seems to reduce a resonance both by damping material and by pushing it up in frequency (perhaps into a dip where it isn't a negative).
The other is selection of amplifier (and source: my old Nano was splashy out of the box). I switched from the E7 and E17 to the Arrow 4G (in all cases, using the interal DACs of my iPhone 4s and iPad 3).
The settings of the Arrow are very good at minimizing the v-shaped response to where it is a virtue (outside the head image) not a vice: I set all EQ flat, crossfade off... and set the gain at the "|" or middle setting. This last bit is ultra-important. This all-analog amp seems to use the amount of negative feedback as a way of setting gain, as many analog amps do. On the lowest gain setting, the feedback is high; this causes some artifacts: a bit of overshoot in the treble that makes it feel hard and emphasizes if not creates sibilance. It also makes the tonal balance flatter, meaning relatively cold, tilting in the direction of analytical (but not so in absolute terms). The medium gain/feedback does not induce an overshoot or emphasis in the treble, and also allows the midrange to bloom a bit, compensating for the 232's v-shape. And, the highest gain just doesn't provide enough negative feedback to tame a different splash/brightness in the treble.
So only the middle gain setting makes for natural treble and for natural midrange. Some (but probably not all) of this characterization applies to my high-impedance HD650 as well as the low-impedance (47ohm) PFE. This would perhaps be due to changes in output impedance of the Arrow with changes in gain, i.e. negative feedback.
Edited by Stoney - 4/6/13 at 4:51pm