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Sundown Audio

Sundown Audio - U v.2 18 U Series 18" Subwoofer Dual 4 Ohm (Open Box)

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Sundown Audio - U-18 Standard Suspension U Series 18" Subwoofer D2/D4 The Sundown U Series is our premier “standard suspension” woofer ser…

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Sundown Audio - U-18 Standard Suspension U Series 18" Subwoofer D2/D4

The Sundown U Series is our premier “standard suspension” woofer series. It is the most direct replacement for the world famous Z v.3 woofer line which we produced from 2011 to 2016 before launching the “new platform” Z v.4 series. Due to numerous advancements in our design process the U Series is able to deliver performance on-par with the Z v.3 series but at a much lower cost.

We start with a double-stacked / 8.66” wide Y35 grade ferrite magnet system coupled to a one-piece, bumped T-Yoke and a 0.6” thick top-plate. Just as with the Z v.3 before it and our other high-end subwoofers we also add a very thick (5mm thickness) aluminum shorting ring inside the magnets to reduce static inductance and level out inductance over stroke. The U series motor also features a 0.6” long pole-extension to keep the coil under control at high levels of excursion.

The voice coil is a 2.36” long / 3” diameter 4-layer aluminum winding / aluminum former unit – which is the same coil we use in our X v.2 series and, thus, the U series has the same 1500-watt RMS ratings. The coil temperature is kept in check by a heavily smoothed / high-velocity pole-vent and a series of ten direct air-gap vents in the back plate. The U series also features newly tooled cast aluminum vent rings in between the frame and top plate to effectively exchange air at a high velocity over the voice coil beneath the spider landing.

The U series features an all-new cast aluminum frame series to the Sundown line which allows for taller cones than the older frames used on the Z v.3 series. The taller cones provide enhanced coil stability and increased mechanical excursion capability. We also tooled matching cast-aluminum surround clamps for the U series to ensure durability in the most demanding situations. The surrounds and cone bodies have been fully custom tooled especially for the U series and are stronger / support more excursion than the Z v.3 series cones and surrounds. The new cone bodies also feature an indentation for the same wide-flange, ultra-strong dust caps as our new platform subwoofers.

If you are looking for a woofer that sounds similar to the SA series but handles significantly more power… the U series is exactly what you need. It has been designed to live up to the reputation earned by our Z v.3 series both in terms of every-day music enjoyment and SPL competition.

  • Features

    • Black Aluminum 3” voice coil former for superior heat dissipation
    • High Temperature Round-Wire CCAW voice coil with high-temp black adhesive
    • Double stitched surround
    • Heavy duty cast basket
    • Spring loaded terminals accept up to 8 gauge
    • Stitched-on double-XL tinsel leads
    • Rear vented pole piece
    • Rear drilled gap-venting
    • Innovative high-velocity cast aluminum vented frame spacer ring
    • Magnet ID shorting ring
    • Top-Plate Cooling Channels
    • Cast Aluminum surround bolt-on rings
    • Optimized for small ported or bandpass enclosures


    U 18"

    T/S SPECSU 18" D2U 18" D4
    RE (Ohms) 3.8 6.1
    FS (Hz) 31.3 31.4
    VAS (L) 135.4 135.4
    Qes 0.37 0.42
    Qms 3.41 3.55
    Qts 0.33 0.38
    Le (mH) 2.62 3.97
    BL (NA) 29.9 35.3
    Mms (Grams) 444.1 441.3
    Cms (uM/N) 0.06 0.06
    Sens (dB @ 1w/1m) 92.3db 91.8db

    Enclosure Specifications

    U 18"

    Sealed Enclosure 3.0 cu ft
    Ported Enclosure 4.0 cu ft
    Recommended Tuning 35Hz
    Recommended Port Area 64 sq in
    Displacement 0.26 cu ft
    Depth 10.11″
    Outside Diameter 18.66″
    Cut-Out 16.69″
    Physical Dimensions Download

    Enclosure Designs

Warranty Information
Open Box Item / no warranty by the manufacturer

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