In having more than one Piezo in the review queue at the moment. I am noticing a couple things hold true on all of them.
1.) They are more power hungry than the specs would suggest. All show low impedance and high sensitivity specs, and yet still consume at least 25% more power to really open up than others with the same ratings.
2.) Without that additional power coherency suffers to some degree on all of them and worse on some than others. The **** likes the Opus#1s on high gain while the N3 really prefers it paired to the xCan to really do its best work, (Which is still nothing special as others have already noted).