About: Sundown Audio U-6.5 U-Series 6.5" 400W RMS Car Subwoofer
Perfect for high-power underseat enclosures and designed to be at home in the competition lanes or playing your favorite tunes, the U Series is the premier “standard suspension” woofer in the Sundown lineup. A double-stacked 9” wide ferrite magnet system is coupled to a thick top plate. A thick set of shorting rings are also used inside the magnets and on the pole cap, smoothing out frequency response while doubling as a heat sink and airflow guide. An all-new, substantially thicker custom aluminum frame was designed specifically for the U Series, and equipped with heat-dissipation ribs. The v.2 motor also features an extended pole piece to keep the coil controlled under high stress!
Specifications:
Enclosure Specifications:
| Thiele-Small Parameters | U-6.5SW" D2 | U-6.5SW" D4 |
|---|---|---|
| Dc Resistance (Re) | 4.0586 Ohms | 6.6274 Ohms |
| Resonance Frequency (Fs) | 41.9533 Hz | 38.6925 Hz |
| Equivalent Volume (Vas) | 2.9053 L | 3.7701 L |
| Electrical Factor (Qes) | 0.5238 | 0.5005 |
| Mechanical Factor (Qms) | 8.5834 | 7.2470 |
| Total Factor (Qts) | 0.4937 | 0.4681 |
| Inductance (Le) | 4.0112 mH | 5.5892 mH |
| Bl Factor (BL) | 16.7428 | 20.0082 |
| Mechanical Mass (Mms) | 137.2546 g | 124.3518 g |
| Mechanical Compliance (Cms) | 104.8528 uM/N | 136.0613 uM/N |
| Sens (dB @ 1w/1m) | 77.8706 | 78.1460 |

Most products include a
limited one year manufacturer’s warranty covering defects in materials and workmanship under normal use.
Warranty coverage does not apply to improper installation, misuse, or damage caused by operation outside
manufacturer specifications.
For complete warranty terms, exclusions, and claim procedures, please visit our full
Warranty Policy page.
Most products include a
limited one year manufacturer’s warranty covering defects in materials and workmanship under normal use.
Warranty coverage does not apply to improper installation, misuse, or damage caused by operation outside
manufacturer specifications.
For complete warranty terms, exclusions, and claim procedures, please visit our full
Warranty Policy page.
Fast shipping across Canada from our Toronto warehouse. Most orders ship within 1–2 business days. Shipping costs and delivery estimates are calculated at checkout. Returns are accepted on eligible items that are unused and in original packaging within our return period. For full details, please view our Shipping Policy and Returns & Exchanges Policy.
Please note that final sale, clearance, open-box, and refurbished items are not eligible for returns or refunds. These items may only be covered under their respective warranty or exchange terms where applicable. For full details regarding open-box items, please review our Open Box Policy.
Sundown Audio
Sundown Audio
Sundown Audio
Sundown Audio
Sundown Audio
On orders over $200*
Competitive pricing you can trust
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