No one’s music is really all there without a dedicated subwoofer to add the thump that gives a performance its raw, in-your-face feeling. If you’re serious about your music, you want to take a serious look at our subwoofers for filling out the low notes. And Polk subwoofers are styled to make an install a real contender on the show circuit. All at a price that’s hard to beat.

db840 8” Subwoofer

8-inch single voice coil 4 Ohm subwoofer

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.

RRP $129.00 AUD

Product Manual

“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

Diameter 8" (20.32cm) 
Type Dynamic Balance woofer polymer composite cone 


Total Frequency Response 30-200 Hz 
Nominal Impedance 4 ohms
Efficiency 85 dB
Power Handling
Continuous 180 watts
Peak 360 watts
Voice Coil
Driver Diameter 1 1/2" (3.81cm) 


Unit of Measure each 


Diameter 7 1/8" (18.10cm) 
Driver Mounting Depth
Top Mount 4 1/16" (10.32cm) 
Bottom Mount 4 1/2" (11.43cm) 

Thiele / Small Parameters

Resonant Frequency 49 Hz
Xmax Linear .51 inch/13 mm (peak to peak) 
MMS 67g 
BL 10.3 Tesla Meters 
CMS 157.6 Micro Meters 
Recommended Enclosure Sealed/Ported/Bandpass 
SD 35.65 sq inch/ 230 sq cm 
VAS .42 cubic feet/11.9 L 
QTS .6 
QES .6 
QMS 14.1 


Speaker Warranty 1 year parts and labor (original purchaser)