Lets start with the good: non-linear distortion is decent and these tweeters do indeed work very low. A steep 900 or 1000 Hz crossover would be fine.
Now for the bad news: everthing else about these tweeters was horrible. The response curve borders on unusable and the build quality is low. One tweeter arrived with a cracked faceplate, even though they seemed well packed. The damage was cosmetic only, however when the faceplate came off, a bunch of paint chips came with it, some of which got into the pleats. I was unsure of how that might affect the testing, so I only tested the other one. The other sample seemed fine. I inspected the pleats and there was no damage. The faceplate was loose however so I securely taped it down to prevent rattling before testing. The faceplate is just a 1/16" thick painted piece of plastic glued onto the stamped steel front. It looked like a cheap afterthought. The tweeter was tested on a proper countersunk baffle, open back. I did not test with an enclosure on the rear of the baffle, but of course you'll need one in a box system to prevent woofer pressure from affecting the tweeter membrane. I would expect that experimentation and lot of measurements would be needed to see what the optimal enclosure size would be.
Honkey low ends are a trademark of most AMT based drivers. I've seen response curves of a few, like the Eton version for example. I could hear the 500 Hz resonance of this tweeter just by lightly blowing on the pleats. My guess is that the tweeter filter's transfer function had better be at least 30 or 40 dB down at 500Hz. If this isn't done, there will be audible issues right in the vocal range. Simple first or second order filters won't work well with this driver.
Could this tweeter sound good in a system? Yes, if you could manage to hammer the response curve into a workable shape. I see it as not worth the effort however, unless you happen to have a DEQX box around to do the hammering for you in the active digital domain. Or at least, an HT receiver with DSP EQ that does not suck. But even with active EQ, the low build quality could still be an issue.
