After another week going back and forth between the M-90s and B-90s, I can confirm that my B-90s have a fuller, richer sound signature at louder volumes (e.g. the B90s sound better when listening to music through my car speakers). The difference might be due to my fittings, or it might be inherent in the sound signatures of the devices (or some combination of the two factors). I plan to analyze my fittings with my audi the next time I see him. [EDIT: we adjusted the fitting for the M90 and it is now much fuller and richer. So it wasn’t an inherent difference, just the fitting]
I wonder if the difference is due to the larger receivers in the B-90s. I read that smaller receivers typically are limited to lower Max Power Output (MPO), which correlates with compressed sound at louder volumes. I posted a separate discussion of that here:
On my fittings, the B shows higher MPO for the mid-low frequencies (e.g. at 850: B=119, M=110). Perhaps my M’s MPO is being capped lower by my fitting, or perhaps that is the max MPO the little receiver is capable of producing. I’ll ask my audi. But if the B90 does indeed have higher MPO, perhaps that explains why the Bs sound better in some situations, capable of producing richer, more detailed sound like an audiophile stereo system with a strong amp and big speakers. Does anybody else have experience with this? [EDIT: in my thread linked above, a number of people replied to say that the opposite is true: the SMALLER receivers have better sound.]
My audi suggested that maybe I should try the M-90s P receiver, which is larger than the M. He chose the Ms for me because my hearing loss is not profound (60-70 dB across all frequencies) and I don’t need that much power to achieve a sufficient volume. But maybe it’s worth trying the P to see if it sounds “better”. Does anyone here have experience with the different receiver sizes? Does the P provide richer, fuller sound than the M, and if so, what are the drawbacks of the P? Too big for some ears? More feeling of occlusion? Lower battery life? Increased feedback? All of the above? Phonak offers 4 different receivers (S, M, P, UP) for different levels of hearing loss, so there must be some advantages to getting a lower power one if you don’t need the higher power… [EDIT: people are saying that SMALLER receivers have better sound. See other thread linked above].
–rex