UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil

Key Specs:

• Nominal Diameter: 18"
• Power Handling (RMS): 1,200W
• Power Handling (MAX): 2,400W
• Impedance: 2Ω + 2Ω (Dual voice coils)
• Frequency Response: 20 - 500Hz
• Sensitivity: 90.7 dB 2.83V/1m
• Voice Coil Diameter: 3"
• Maximum Linear Excursion: ±28 mm

With a remarkably high strength to weight ratio, Dayton Audio chose a single layer woven carbon fiber cone for the Ultimax II. This rigid diaphragm resists deformation from the stress of high displacement to ensure pistonic movement and extreme durability. Thanks to the low mass, this driver can reproduce every detail with accuracy and control. More than just a cosmetic touch, the cone is indexed for a smooth transition between the cone and surround adding extra rigidity on the edge to minimize unwanted resonances. Supporting the diaphragm is a high roll butyl rubber surround that has been optimized to allow extreme excursion without sacrificing cone area.

In order to reliably handle up to 1,200 watts RMS, the UMII18-22 is driven by a 3" diameter, 4-layer, flat wound voice coil on a vented aluminum former. The flat ribbon wire has significantly more surface and contact area than round wire resulting in improved heat transfer and dissipation. The 4 layers put more windings in the magnetic gap while keeping the gap as tight as possible, improving motor strength and overall control. Additionally, the thick aluminum former plays a crucial role by efficiently drawing heat away from the voice coil, the first step to keeping the motor cool.

In order to ensure optimal performance and minimize distortion, the voice coil is driven by a FEA optimized magnet assembly. This assembly creates a powerful and symmetric magnetic field in the center of the voice coil allowing for identical forward and backward movement of the cone, even at maximum displacement. The top and back plates have been precisely machined with sculpted edges to effectively contain and transfer the magnetic force. To prevent overheating, the motor assembly and frame feature extensive venting, allowing heat to escape from the voice coil and former. This venting is achieved through various paths, including the voice coil former, sub-cone, under the spider, through the pole piece, and voice coil gap, ensuring efficient cooling and preventing power compression, even during long listening sessions.

To keep distortion at a minimum, the UMII18-22 incorporates an aluminum shorting sleeve and a thick aluminum pole piece cap. These elements play a crucial role in maintaining stability and consistency in the motor's magnetic field as the voice coil moves within the magnetic gap. In addition, they ensure that the inductance remains linear throughout the entire stroke of the voice coil. This consistent motor force is instrumental in minimizing non-linearities and intermodulation distortion. Moreover, the shorting rings contribute to a reduction in the overall inductance of the voice coil, thereby enhancing the output capability in the mid-bass and upper bass frequencies.

Achieving truly linear movement in high excursion drivers is of utmost importance. Even the tiniest rocking motion can be greatly magnified as the cone travels further away from its resting position. In order to avoid this issue, the UMII18-22 driver incorporates a dual spider system. The spiders are intentionally spaced as far apart as possible to ensure that the cone and voice coil move reliably in a pistonic manner. Furthermore, in order to prevent fatigue and breakage the tinsel leads have been meticulously stitched onto the top spider. This not only enhances the overall durability but also eliminates any possibility of contact between the leads and the cone or spider.