https://page.auctions.yahoo.co.jp/jp/auction/d467238563 found it on the japanese auction site, unfortunately it's only a single driver. I never heard the HP-1 myself, just the HP-50 and that was quite decent, definitely could have used some modding.
The biggest issue with all AMT's is the lack of bass. That's pretty much the main complaint against the ESS mark 1 and the Precide Ergo AMT. Some designs combined it with a dynamic driver to make up for it though others such as TakeT H2+ or the HEDDphones managed to solve the issue. Not sure how HEDDphones did it but TakeT managed to do it by changing the whole driving principle to a piezoelectric one. Funny enough the TakeT is probably the best bass headphones I ever heard and I'm still trying to get a pair. Anyway, it seems the driver from aliexpress is no exception. With just a frequency response of only 3k-40k, you might get a good mid-range and for sure fantastic highs but bass will be pretty much non-existent. Still it's always worth a try. You might need to play around with getting their resistance up a bit and use a decent amp to power them since their sensitivity is low as a headphone driver. Maybe a closed back enclosure could help with the bass issue. Soundstage might be an issue as well due to the enclosure design. I've thought of trying it myself but the prices were too prohibitive though going through some of the other listings, it might be cheap enough to give it a go.
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