About 23 years ago, two Italian men, Emidio Vagnoni and Pietro Pantaleone, were working for the famed Von Tempi Company that invented the accordion. This was their day job. At night they designed and built amplifiers in their garage while their wives packaged them and shipped them out to car audio dealers in Italy and Europe during the day. This was the meager beginnings of Audison (1984) with the introduction of their first amplifier, the HP 110. The Audison amps were successful enough that Vagnoni and Pantaleone incorporated their fledgling company under the name Elettromedia in 1987.
In 1998, Elettromedia created the Hertz brand of car audio to, as explained on their website, "give voice to its amplifiers." With their amplifiers setting high standards for audio reproduction, the engineering staff was challenged to build better speaker systems than any other available on the market today - a pretty bold challenge for sure, and one that Hertz has faced with impressive results.
This month we looked at the fruits of this labor in the Hertz Mille ML3000 12" subwoofer. The Mille designation marks the top of the line for Hertz, so I was predicting a high-end performance based on Elettromedia's goals. Even without the name designation, the high build quality of this subwoofer gives one a sense of performance to expect. Its frame looks completely original and is powdercoated in a black-crinkle finish. Hertz invested in a number of cosmetic flourishes on each spoke of the basket and a unique trim ring that hides the mounting screws regardless of whether you install the ML3000 with the magnet in or out of the enclosure. They even added a magnet cover that makes the frame look like it completely encapsulates the motor structure.
The ML3000's cone gives it one of its most distinguishing features. Hertz eliminated the dustcap that you see on most other woofers by designing the cone in one solid piece, without the "normal" hole in the center to mount the voice coil. Hertz calls this cone design the "V-Cone." The cone is made from a talc and mineral dust impregnated polypropylene that's injection-molded into an exponentially curved cone. This shape adds rigidity and allows for a lighter mass. The surround attaches to the V-Cone at an angle. Hertz claims that the angle and shape of the surround improves its linearity through the full stroke of the cone. I haven't seen this applied to any other speaker, and it's easy to see how the surround stays full and doesn't flatten out even at high excursion. Hertz is definitely onto something with this design.
The motor structure is magnificent. Too bad nobody can look inside the magnet to see all the amazing design work that has gone into focusing and shaping the magnetic field for optimal performance and how airflow is managed within the structure. When I look at the cutaway drawings of the Hertz ML3000, JL Audio's W7 and Alpine X-Type subwoofers, where these technologies are being really refined and explored, I'm enamored at the beauty of human invention. Hertz placed an aluminum ring inside the motor assembly and shaped the top edges of the pole piece to improve the symmetry of the magnetic field, yielding a very linear impedance curve. They have further shaped the inside diameter of the pole piece to provide clearance for the V-Cone and to also create a more effective air pump to move air through the pole-piece vent as well as the magnet gap vents in the bottom plate of the motor structure. Considerable time was taken to design the airflow through the motor structure to gain a large advantage in power handling (about 30 percent improvement) and minimize the dreaded power compression distortion as a speaker's voice coil heats up.