The voice coil itself is two layers of copper wire wound on a very high "Q" (well damped) fiberglass former. The voice coil assembly is connected to the base of the V-Cone with a special coupler that bonds the two of them together. The large 8" spider is mounted to an elevating ring that's vented around its base to improve linearity by minimizing any air pressure differential from behind the spider.
Just looking at the ML3000 you can see how the engineers at Hertz tried to improve the breed. As I wrote earlier, this is an impressive subwoofer to look upon, but all of this technology doesn't come cheap. The ML3000 has a retail of $900, but you get an awful lot for the price, including a three-year warranty if you purchase it and have it installed by an authorized Hertz dealer. If you do your own enclosure and installation, then Hertz will stand behind the ML3000 for one year. If you buy any Hertz products online, or mail order, forget about the warranty alltogether. Hertz strongly believes, and I think rightfully, that their products sound and perform better when properly installed by their knowledgeable authorized dealer base.
Installation
Time to figure out the enclosure. I broke open the owner's manual to see what Hertz states as their recommended enclosure sizes for sound quality. This manual is chock-full of good information about the special features, power handling, wiring configurations and even enclosure sizes. Of course, this being a European product, the enclosure recommendations are all in metric sizes, and frankly, my head hurt that day and I didn't want to perform the math conversion, so I called Larry Penn, Elettromedia's American Grand Pooh-Bah. It just so happened Penn was speaking to the head office in Italy when I called, so he was able to get Rome's blessing on a sealed enclosure of 1.2ft3. Making sure I didn't foul this up, I asked Larry if that was gross volume or net. Larry informed me that this recommendation was gross and that the ML3000 displaced 0.1ft3, leaving a net volume of 1.1ft3 for the sealed enclosure. As massive as this subwoofer is, 1.2ft3 is impressively small.
Master installer Patrick Holdaway, of Speaker Works fame, ground out our test enclosure. He liked how the ML3000 fit into a standard 12" subwoofer cutout and how Hertz supplies it with a large, molded (to fit the frame) rubber gasket to ensure the best seal possible. However, he wasn't satisfied with the cosmetic beauty ring that hides the screw heads once the ML3000 is mounted. While we both liked how it ties the overall style of the front and the rear of the subwoofer together, he could see having trouble with the little plastic clips if you have to take the subwoofer in and out of the enclosure a couple of times.
Once the ML3000 was installed in the enclosure, it was off to my daily driver where I hooked it up to power and broke it in for the recommended six hours. For power, I installed two Crossfire VR1000d amplifiers and strapped their outputs together. Running into the 4-ohm load of the ML3000, the Crossfire duo easily produce over 1,000 watts of RMS power.
Once broken in, I dialed in the sub to pair up with the front half of my Reference speaker system that consists of a pair of USD Audio B-72pro WaveGuide separates and an Alpine center channel speaker. I bypassed the built-in crossovers and subsonic filters of the amplifiers, set the levels and divided the frequency range to all of the speakers using an Alpine PXA-H701 processor.