Having reviewed the Alumapro Alchemy 12DVC in January 1999, I was rather interested to see what changes had been made to the current versions almost two years later. The woofer we looked at this month is the latest single voice coil model, the Alchemy 12, and if you missed the review on the dual voice coil version, some background is in order.
Alumapro is a pretty interesting company. Unlike most loudspeaker companies, where the only business is audio, Alumapro is actually a division of Syntronic Instruments, Inc., a leading manufacturer of precision magnetic devices and a long-time contractor for the U.S. military.
This 51-year-old company has supplied the government with a number of magnetic type devices, including a specialized CRT deflection yoke for computers. In fact, the founder of Syntronic developed a high tech deflection yoke that made the first earth-to-the-moon communication possible. Needless to say, the company's ability to produce high-tech magnetic equipment goes way beyond the engineering expertise normally found in the loudspeaker business.
What prompted Syntronic to go in the audio direction was the end of the cold war and the lucrative military contracts that had come with it. The company had to find new ways to apply its experience. Fortunately, one of the Syntronic's engineers also happened to be a bass guitar player with a lot of loudspeaker experience. His knowledge and enthusiasm for music influenced the company's decision to develop an aluminum cone bass guitar speaker. After developing a driver that could take the abuse of an electric bass guitar on stage, the company turned its attention to other markets that could take advantage of their high power handling technology. It was a no-brainer that car audio subwoofers would be the next logical step.
Alumapro's Alchemy 12 has all the same high performance features that I noted in the 12DVC, which includes a very well designed cast frame. Not only cosmetically good looking, the Alchemy frame has several important features: a full 1-inch of depth between the spider and the front plate to allow long rear excursion strokes, and air vents beneath the spider mounting shelf built into the sides of the frame (called "aeroport" venting by Alumapro) for more efficient voice coil cooling.
The Alchemy motor system uses a T-yoke (single piece front plate and pole piece) with a 3mm extended pole to linearize the magnetic circuit in the forward direction and includes a 7/8-inch pole vent. Both the T-yoke and front plate have a black coating to increase heat dissipation (the black body radiation effect). Since the driver also uses magnetic fluid in the gap for cooling, it has four 1/8-inch peripheral gap area vents to provide the appropriate air relief that prevents the magnetic fluid front squirting into the spider on long excursions. The 12 Tesla Meters of BL required to push around the 12-inch spun aluminum cone is produced by two stacked 140mm x 15mm magnets, covered by the an injection molded rubber "boot."