To say the KFC-XW1300DVC looks like a spectacular piece of work is putting it mildly. Kenwood has obviously invested a substantial amount of engineering time and money to develop a product like this. The overall motor configuration of the KFC-XW1300DVC is not your conventional single voice coil single gap, but has a dual voice coil and dual gap layout, something Kenwood calls a "multi-bias magnetic circuit." Since this is a DVC (Dual Voice Coil) woofer, each terminal is connected to one of the upper and one of the lower voice coils. While this is not a patented magnetic circuit, there have been a number of dual gap dual coil patents over the years similar to this, some coming from pro sound companies. Kenwood engineers claim that the dual gap configuration will have more linear forward and backward movement which in return should reduce distortion compared to a conventional design. Beyond this, the other important advantage is probably the enhanced heat dissipation that is split between two coils. In terms of excursion, operation is similar to a standard single gap, single coil motor.
While on the subject of the KFC-XW1300DVC's motor system, readers will be interested to know that Dr. Wolfgang Klippel has graciously loaned a Klippel analyzer for use in CA&E reviews. This amazing machine allows engineers (quite a number of car woofer manufacturers now use the Klippel analyzer) to get a better look at large signal (high SPL) performance in a woofer. Pat Turmire, CA&E reviewer and CEO of Red Rock Acoustics, performed the Klippel analysis on the Kenwood KFC-XW1300DVC woofer, including the Bl curves. The Bl curve shows the motor strength of the woofer as it moves in both directions from center. The other recorded curve is a sort of displacement curve. Ideally, the Bl curve would be centered on the 0mm point (where the cone is positioned when there is no signal). When a woofer shows an offset, it means that the mechanical system has not been completely optimized and it will run out of out the gap faster in one direction than the other, and this means more distortion at high operating levels than if it were operating perfectly symmetrically. This type of offset is pretty common. While it doesn't mean the woofer is not working sufficiently well to be seriously impressive, it does mean that it could be further optimized and enhanced. As you can see, there is an offset in the KFC-XW1300DVC and its Bl is biased about 2mm to the rear, according to the Klippel machine. Not a fatal flaw, but this does indicate that you could probably exact some additional performance out of this already high performance woofer.
At first glance the KFC-XW1300DVC is visually impressive. The woofer is built on a proprietary two-piece die-cast frame with the front half containing the cone assembly and front mounted spider, and the back half the motor assembly, rear mounted spider plus pole piece and pole vent. The frame has 12 spokes; six to support the mounting flange and six to support the front spider mounting shelf. This is fully vented for cooling. Additional cooling comes from the vents and fins on the bottom half of the frame. Since there is no backplate, air flows on both the front and back of the voice coil in both directions-very cool, literally! The mounting lip has a thick front rubber gasket with metal Kenwood logo inlays and mounts with eight screws or bolts to your enclosure.
The motor assembly for the KFC-XW1300DVC is also unique. Rather than the conventional frontplate and backplate arrangement, the KFC-XW1300DVC motor instead has two frontplates, perhaps better described as front and rear gap plates. Since there is no backplate for a pole piece to be attached to, the pole piece is attached to the back half of the frame assembly that also has the venturi-type exhaust for the pole vent. The pole vent is 1.25 inches in diameter through the pole and expands to a 2.5-inch exhaust port at the back of the rear half of the two-piece frame. Since there is no backplate, the pole is extended 13mm in both directions. And, like most of the larger companies in the business, Kenwood engineers used computer FEA (Finite Element Analysis) software to optimize the motor parts.