I havent heard the new stuff , but the older Alchemy's were very accurate and great sounding . They are NOT an SPL sub company so if your looking for alot of boom I'd look elsewhere .
You obviously have a horrible ear or your friend has a horrible install.
Alumapro Alchemy's (I run the MX versions) have been competing and WINNING SQ competitions since they were released back in the early 90's. Alumapro was the FIRST company to produce a subwoofer with an all aluminum cone.
I haven't heard the BP versions, but something to remember, before a bunch of people come in hear bringing down the Bandpass box.. The woofer and the box it is in is all designed to work together to provide the best aural experience possible. The BP from Alumapro is desiged to sound good in that box. If you put another woofer in it, it'll probably sound like ***.
Does Ken still own Alumapro? We use to sell there stuff and the BP enclosures were a great seller, they sound good and pound. What else was nice about them is they dont need very much power to get loud