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  • U-SERIES V1 6.5" U-65SW 400W SUBWOOFER
  • U-SERIES V1 6.5" U-65SW 400W SUBWOOFER
  • U-SERIES V1 6.5" U-65SW 400W SUBWOOFER


The Sundown U Series is our premier “standard suspension” woofer series. The all-new U v.2 improves on the already incredible performance of its predecessor.

We start with a double-stacked / 9.44” wide Y35 grade ferrite magnet system (3/4” wider than the v.1) coupled to a one-piece, bumped T-Yoke and a 0.6” thick top-plate. Just as with 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 v.2 adds a pole-cap aluminum shorting ring which doubles as a heat-sink and airflow guide. The U v.2 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 design from the U v.1 – but the new version is built with a stronger aluminum former. The coil temperature is kept in check via a high-velocity solid pole / machined pole channels arrangement and a series of 16 direct air-gap vents in the back plate. The U v.2 series also features custom 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 v.2 series features an all-new, custom tooled, cast aluminum frame designed specifically for this line. The cosmetics are very similar to the original v.1 frames but every size frame is substantially thicker and even features stiffening / heat dissipation ribs around the bottom part of the frame. The new frame design allows for significantly taller cones and wider spiders on the 10s and 12s compared to the v.1 which greatly enhance mechanical clearances. Moving on to the 15 the spider is also wider than the originals. The 18 uses the same spider and cone height as the originals but the frame is, of course, much stronger.

Given the stronger motor (15% more powerful), stronger coil construction, superior motor air-flow characteristics, and enhanced mechanical capacity we boosted the power rating to 1750-watts RMS from the 1500-watt rating of the previous version.

If you are looking for a woofer that sounds similar to the SA series but handles significantly more power… the U v.2 series is exactly what you need. It has been designed to live up to the reputation earned by our U v.1 series both in terms of every-day music enjoyment and SPL competition.

Physical Dimensions


  • RMS: 400W
  • Black Aluminum 3” voice coil former for superior heat dissipation
  • High Temperature Round-Wire ALU voice coil with high-temp black adhesive
  • Double stitched surround
  • Heavy duty cast baskets – all new, custom-tooled
  • Spring loaded terminals accept up to 8 gauge
  • Stitched-on double-XL tinsel leads
  • Solid pole with vent channels and aluminum shorting ring cap
  • 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


T/S SPECS U-6.5SW" D2 U-6.5SW" D4
RE (Ohms) 4.0586 6.6274
FS (Hz) 41.9533 38.6925
VAS (L) 2.9053 3.7701
Qes 0.5238 0.5005
Qms 8.5834 7.2470
Qts 0.4937 0.4681
Le (mH) 4.0112 5.5892
BL (NA) 16.7428 20.0082
Mms (Grams) 137.2546 124.3518
Cms (uM/N) 104.8528 136.0613
Sens (dB @ 1w/1m) 77.8706 78.1460


  • Ported Enclosure
    • Size: .25-.35 cuft net
    • Port Area: 4-5 sqin
    • Port Tuning: 35hz -40hz
  • Sealed Enclosure
    • Size: 0.125-0.2 cuft net
    • Displacement:  .04 cu. ft. 
  • Depth:  5.71"
  • Outside Diameter: 7.17"
  • Cutout: 5.94"
  • Physical Dimensions
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