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Dayton Audio's UMII18-22 Ultimax II is a Ø46cm subwoofer driver with a carbon fibre cone and 1200W of power. It is part of the new version of the Ultimax range and benefits from improved excursion capacity, lower distortion, greater sensitivity and increased power output compared with its predecessor.
With a remarkably high strength-to-weight ratio, Dayton Audio has chosen a single-layer woven carbon fibre cone for its Ultimax II range. This rigid diaphragm resists the deformation caused by the stress of large displacement, allowing it to take on pistonic movement while displaying extreme durability. The diaphragm is supported by a butyl rubber surround that has been optimised to allow very high excursion without sacrificing cone surface area.
To reliably handle up to 1200 watts RMS, the UMII18-22 is driven by a 76.2mm diameter, 4-layer, flat-wound voice coil on a ventilated aluminium support. The flat winding offers the advantage of a much larger contact area than a round wire winding, drastically improving heat transfer and dissipation.
To ensure optimum performance and minimise distortion, the voice coil is driven by an assembly of magnets optimised by FEA. This assembly creates a strong, symmetrical magnetic field at the centre of the voice coil, allowing identical forward and backward movement of the cone, even at maximum displacement. The top and rear plates have been precisely machined with sculpted edges to effectively contain and transfer the magnetic force.
To keep distortion to a minimum, the UMII18-22 incorporates an aluminium shorting ring. These elements play a crucial role in maintaining the stability and coherence of the motor's magnetic field as the voice coil moves through the magnetic air gap. In addition, it ensures that the inductance remains linear throughout the travel of the voice coil. Finally, a shorting ring helps to reduce the overall inductance of the voice coil, improving output capability in the mid-low and high-low frequencies.
It is extremely important to achieve truly linear movement in high excursion drivers. The slightest tilting movement can be considerably amplified as the cone moves away from its rest position. To avoid this problem, 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 and pistonically. In addition, to avoid stress and breakage, tinsel threads have been meticulously sewn onto the upper spider. This not only improves overall durability, but also eliminates any possibility of contact between the threads and the cone or spider.
Technical characteristics
Specifications | |
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Speaker driver type | Subwoofer |
Nominal diameter | Ø46cm (18") |
Power handling | RMS : 1200W Max : 2400W |
Impedance | 2Ω + 2Ω (dual voice coil) |
Frequency response | 20 - 500Hz |
Voice coil diameter | 76.2mm |
Sensitivity | 90.7dB |
Thiele-Small Parameters | |
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Max linear excursion (Xmax) | ±28 mm |
Resistance DC (Re) | 4.2Ω |
Inductance coil (Le) | 1.15 mH @1kHz |
Resonance frequency (Fs) | 22 Hz |
Mechanical quality coefficient (Qms) | 2.53 |
Electrical quality coefficient (Qes) | 0.67 |
Total quality coefficient (Qts) | 0.53 |
Moving mass + air charge (Mms) | 420g |
Suspension compliance (Cms) | 0.124 mm/N |
Emissive surface of the membrane (Sd) | 1184 cm² |
Maximum volume of air moved (Vd) | 3315 cm³ |
Multiplying the magnetic field strength in the coil air gap by the length of the coil wire. (Bl) | 19.2 Tm |
Equivalent Compliance volume (Vas) | 248.2 liters |
General | |
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Weight | 17.4kg |
Package | 1x DAYTON AUDIO UMII18-22 ULTIMAX II DVC |
Speaker Power (W RMS) | 1200 |
Speaker Type | Subwoofer |
Impedance (Ω) | 2 |
Loudspeaker diameter (mm) | 460.0 |
Diaphragm type | Carbon fiber |
Efficiency / Sensitivity (dB) | 90.7 |
Max Linear Excursion (Xmax) (mm) | 28 |
Lowest frequency (Hz) | 20 |
Highest frequency (Hz) | 500 |