Sundown Audio

SUNDOWN AUDIO U-65 6.5" Subwoofer D4 | 400W RMS - 4 OHM

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  • Sundown Audio SUNDOWN AUDIO U-65  6.5" Subwoofer D4 | 400W RMS - 4 OHM
  • Sundown Audio SUNDOWN AUDIO U-65  6.5" Subwoofer D4 | 400W RMS - 4 OHM
  • Sundown Audio SUNDOWN AUDIO U-65  6.5" Subwoofer D4 | 400W RMS - 4 OHM
  • Sundown Audio SUNDOWN AUDIO U-65  6.5" Subwoofer D4 | 400W RMS - 4 OHM
MSRP: $191.99
— You save $22.00


Are you ready to elevate your audio experience to new heights? Look no further than the Sundown Audio U-6.5 Subwoofers. Engineered with precision and cutting-edge technology, these subwoofers deliver outstanding performance and unrivaled power.

Featuring a robust 400W RMS (Root Mean Square) driver, the U-6.5 Subwoofers pack a punch that will leave you breathless. Whether you're craving deep, booming bass or crystal-clear lows, these subwoofers are designed to exceed your expectations.

With the U-6.5 Subwoofers, you have the option to choose between two voice coil impedances: D2 (Dual 2-ohm) and D4 (Dual 4-ohm). This flexibility allows you to customize your setup and optimize your audio system for the perfect sound.

One of the standout features of the U-6.5 Subwoofers is the "W" surround, inspired by the successful SD-4 model. This surround is meticulously engineered using Finite Element Analysis (FEA) to push the limits of mechanical performance. Its stiffer construction near the limits ensures maximum durability and helps prevent damage, even when the subwoofers are pushed to their extremes.

To further enhance performance, Sundown Audio is developing a specially designed spider that works in harmony with the surround, catering specifically to the U-6.5SW model. This synergy between components ensures optimal performance and delivers a listening experience like no other.

When it comes to excursion capabilities, the U-6.5 Subwoofers boast an impressive 19mm one-way linear X-max, reaching a remarkable 70% BL. This extraordinary excursion is backed by a substantial amount of motor force, providing you with the ultimate sonic experience.

Unlike previous models that had depth limitations, the U-6.5 Subwoofers are designed without constraints. Sundown Audio has pulled out all the stops to create a subwoofer that excels in performance, without compromising on size or form factor.

Experience the future of bass with the Sundown Audio U-6.5 Subwoofers. Elevate your sound system, make a statement, and feel the music like never before. Get ready to unleash the power!


RMS: 400W
Black Aluminum 1.753” voice coil former for superior heat dissipation
High Temperature Round-Wire Copper voice coil
Double stitched surround
Heavy duty cast basket
Spring loaded terminals accept up to 8 gauge
Stitched-on heavy-duty tinsel leads
Solid pole with vent channels and aluminum shorting ring cap
Rear drilled gap-venting
Magnet ID shorting ring
Top-Plate Cooling Channels
Optimized for small ported enclosures

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.

Physical Dimensions

Depth: 5.71"

Outside Diameter: 7.17"
Cutout: 5.94"

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Warranty Information

Warranty Information

Sundown Audio requires us to send customers with equipment problems directly to them for all warranty and non-warranty claims. Please follow their proceedures..


Sundown Audio RMA form:

Sundown Audio Product Warranty Information:


Sundown Audio - Hours of Operation

Monday 9am - 5pm EST
Tuesday 9am - 5pm EST
Wednesday 9am - 5pm EST
Thursday 9am - 5pm EST
Friday 9am - 5pm EST
Saturday Closed
Sunday Closed
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1 Review

  • 5

    Sundown u6.5sw

    Posted by Andres Lozano on Dec 18, 2023

    Alright listen here this is an amazing subwoofer not to mention it's small size. Best sub I've had it bangs and good sql...

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