Car Subwoofers


8-inch single voice coil subwoofer

8" woofer
20.32cm woofer



Available Finishes:
Additional Images

Designed to Perform

The MM840 high performance 8-inch subwoofer maybe compact for a subwoofer but it cranks out waves of bass. As a result of 3 years of Polk research and development, every woofer and driver in the MM Series has been designed to offer unparalleled sound quality with exceptional fit to meet virtually any application. Borrowing technology from our flagship SR Series, the MM Series offers outstanding performance for your mobile audio dollar. With 250 Watts continuous/500 Watts peak power handling, the MM840 is recommended for small sealed (.35 cubic foot) enclosures.

MM840 Features:

New polymer woofer cones and butyl rubber surrounds will not break down over time and will survive the rigors of harsh automotive environments.

High temperature copper voice coil (51mm) and polyamide former withstands the most rigorous use while maintaining extremely low distortion for bass punch and output.

Heavy duty input terminals accommodate speaker wire up to 8 AWG or twisted pairs of 12 AWG.

Advanced carbon composite basket based on the spokes of a wheel is lightweight, will not flex during peaks and looks great! Don’t be afraid to show off the back of your woofer.

Klippel optimized components using a state-of-the-art Klippel distortion analyzer, Polk engineers were able to optimize the woofer’s motor structure, voice coil alignment and suspension for the best possible performance, even at extreme listening levels.

Available matching grille complement the wheel spoke design.

Dual voice coil configuration (MM840DVC) also 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 poly composite woofer 


Minimum Impedance3.3 
Total Frequency Response26-200Hz 
Nominal Impedance4 ohms
Efficiency90 dB
Power Handling
Continuous250 watts
Peak500 watts
Voice Coil
Driver Diameter1 1/2" (3.81cm) 

Thiele / Small Parameters

Resonant Frequency35 Hz
Xmax Linear.75 
LE2.3 mH
SD35.65 sq in/230 sq cm 
VAS.54 cu ft/15.4L 


Cut-Out Diameter7 1/8" (18.10cm) 
Driver Mounting Depth
Top Mount4 1/8" (10.48cm) 
Bottom Mount4 11/16" (11.91cm) 


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.

MM840 Media

MM840 Accessories