Car Subwoofers


8-inch single voice coil 4 Ohm subwoofer

8" woofer
20.32cm woofer



Available Finishes:
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Incredible Sound, Affordable Price

It’s all here. All the Polk goodness and technology that makes our subwoofers a kickin’ addition to any vehicle’s audio system, as only Polk can deliver.

db840 Features:

“Dished” polypropylene cone supported by a vented cone/coil coupler stiffens the cone for greater mechanical stability and lower distortion.

Marine Certified Polk db Series speakers are built tough to withstand the toughest environments so they are perfect for use in boats of all types. That’s why Correct Craft offers Polk speakers in their award-winning Nautiques ski and wakeboarding boats.

Santoprene surround is impervious to extremes in temperature, humidity and exposure to sunlight for excellent long term reliability.

Fire-retardant flat NOMEX® spider allows extended linear motion while providing highly reliable mechanical and thermal stability.

Triple venting of the 4-layer Kapton voice coil former, cone/coil coupler and pole piece contribute to the high power handling and reliability of the db Series subs.

As with all Polk subwoofers, the voice coil alignment, motor and suspension were optimized using a state-of-the-art Klippel laser analyzer. The result is superior cone travel linearity for flatter response and lower distortion.

Dual voice coil version also available - db840DVC

Optional db8G grille is available.

All Polk products are made using the best materials and the most advanced manufacturing techniques. They pass the industry’s most exhaustive quality tests, including drop testing, extreme signal response and UV & salt exposure testing. Polk loudspeakers are built to perform for a lifetime.

Driver Complement

Diameter8" (20.32cm) 
TypeDynamic Balance woofer polymer composite cone 


Total Frequency Response30-200 Hz 
Nominal Impedance4 ohms
Efficiency85 dB
Power Handling
Continuous180 watts
Peak360 watts
Voice Coil
Driver Diameter1 1/2" (3.81cm) 

Thiele / Small Parameters

Resonant Frequency49 Hz
Xmax Linear.51 inch/13 mm (peak to peak) 
BL10.3 Tesla Meters 
CMS157.6 Micro Meters 
Recommended EnclosureSealed/Ported/Bandpass 
SD35.65 sq inch/ 230 sq cm 
VAS.42 cubic feet/11.9 L 


Cut-Out Diameter7 1/8" (18.10cm) 
Driver Mounting Depth
Top Mount4 1/16" (10.32cm) 
Bottom Mount4 1/2" (11.43cm) 


Unit of Measureeach 


Speaker Warranty1 year parts and labor (original purchaser) 

Specifications, dimensions and features subject to change without notice. For more information call us at 1-800-377-7655 (USA and Canada). Outside of North America call +1 (410) 358-3600.

db840 Media

db840 Accessories