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Polk Audio MM521

5-1/4" 2-way Mobile Monitor Series Coaxial Speakers (Marine Certified)

4.7

(11 reviews)

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MM Series Superior Performance

The Mobile Monitor Series by Polk Audio is the result of 3 years of research and development. The series uses high quality materials and the newest loudspeaker technology to bring the listener an unforgettable experience. The best part about the MM Series is the affordable price.

  • 5-1/4" 2-way MM Series Marine Certified Coaxial Speakers
  • Power Handling:
    • Peak: 400 watts per pair / 200 watts each
    • RMS: 180 watts per pair / 90 watts each
  • Woven glass composite cone woofer
  • Butyl rubber surround for a smoother response
  • 1" Silk/Polymer composite swivel tweeter
  • Klippel optimized components for distortion-free sound
  • 2.7 ohms impedance
  • 25mm Large diameter voice coil increase reliability
  • Carbon composite basket
  • Neodymium magnet structure for more power
  • Top-mount depth: 2-1/2"
  • 1-year SonicElectronix.com warranty

Priced Per Pair

Note: Polk Audio specifies the nominal impedance of these speakers to be 2.7 ohms. The product box states the impedance to be 4 ohms and the speaker magnet shows 2 ohms, this has been confirmed by Polk Audio to be an incorrect specification. The product manual is correct in stating the nominal impedance of the MM series of speakers to be 2.7 ohms.

Speaker Specifications
Speaker Size5-1/4"
Design2-way
Tweeter DesignDome
Tweeter CompositionSilk-Polymer Composite
Woofer CompositionWoven Glass Fiber
Woofer SurroundButyl Rubber
Peak Power Handling200 watts
RMS Power Handling90 watts
Sensitivity92 dB
Frequency Response50 - 25000 Hz
Impedance (Per Voice Coil)2.7
Shallow Mount InstallationN/A
Top-Mount Depth2-1/2"
Bottom-Mount DepthN/A
Cutout Dimensions4-11/16
Speaker GrillesYes
Warranty and Return Policy
Return Policy Standard Return Policy
Parts Warranty Duration1 year
Labor Warranty Duration1 year
Warranty ProviderSonic Electronix
Customer Review Summary for Polk Audio MM521
Average Customer Rating is 4.7 out of 5 stars:
4.7
based on 11 Reviews
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Rating Distribution:
5 star:
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73%
4 star:
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27%
3 star:
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0%
2 star:
.
0%
1 star:
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0%
what's this?
Average Attributes Rating:
Durability
4.7
Value
4.6
Features
4.8
Design
4.9
Usability
4.9
what's this?
Most Helpful Customer Reviews:
January 21, 2012 Great sound and lightweight!
Review by
Ryan from Reynoldsburg, OH
Overall
Durability
Value
Features
Design
Usability
I purchased two pairs of these speakers and the sound is phenomenal. I bought them for a 2 seat roadster with a very loud cabin and they have done very well on only head unit power. As a plus, they're very lightweight but sturdy. I'd highly recommend them.
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January 20, 2012 Polk is it
Review by
Paul from Edison, NJ
Overall
Durability
Value
Features
Design
Usability
Awesome speakers for my topless Jeep, got rained on several times and NO problem.
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December 23, 2011 boat
Review by
dennis from gardner, KS
Overall
Durability
Value
Features
Design
Usability
The speakers sound awesome and just have them running off of the head unit highs and mid have great sound getting ready to add more speaker to the boat this winter going to amp these speakers and see what they can do.
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September 6, 2011 Great speakers
Review by
Mark from The Colony, TX
Overall
Durability
Value
Features
Design
Usability
Polk makes a great marine speaker. I won't use anything else.
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April 28, 2011 Polk Audio MM521
Review by
WKahler from San Jose, CA
Overall
Durability
Value
Features
Design
Usability
Works Great, I have had these installed for more than 6 months. Even though they have the correct size for a Plymouth Voyager, they are a little too tall. I got them mounted, but not recommended for this minivan...they sound spectacular though!
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View All 11 Reviews for Polk Audio MM521
Speaker Wire
Upgrade your factory speaker wire to aftermarket speaker wire and hear the difference! Using thicker gauges, newer technology, and higher quality materials, aftermarket speaker wire is key to upgrading the sound in your car.
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20 ft. of 16 AWG KICKER X-Series Speaker Wire20 ft. of 16 AWG KICKER X-Series Speaker Wire
Get high quality sound from Kicker's twisted-pair, true to gauge speaker wire.
$19.99
50 ft. of 14 AWG StreetWires Speaker Cable50 ft. of 14 AWG StreetWires Speaker Cable
Streetwires Super Cable provides a zero-grip insulation for a smooth install as well as true gauge twisted wire construction.
$29.99
50 ft. of 16 Gauge Monster XLN Series Speaker Cable50 ft. of 16 Gauge Monster XLN Series Speaker Cable
Upgrade to clean and clear sound with Monster Cable's Xtra Low Noise (XLN) construction.
$35.00
Sound Dampening Material
Get optimal sound from your new speakers with some high quality sound dampening material. It will keep the road noise out and the music inside the car.
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Dynamat Xtreme Speaker KitDynamat Xtreme Speaker Kit
Eliminates speaker panel distortion and reduces vibration, rattles, and squeaks!
$21.99
Dynamat Dynaxorb Speaker PakDynamat Dynaxorb Speaker Pak
Revolutionary damping material designed to prevent distortion caused by the back wave of a speaker interfering with the front wave.
$19.99
Dynamat Rubber RollerDynamat Rubber Roller
Install your Dynamat with ease! This heavy duty rubber roller is designed specifically to install your Dynamat products!
$18.99
Ballistic Speaker KitBallistic Speaker Kit
Eliminate speaker distortion, road noise, and rattles with this sound dampening material from Ballistic.
$15.99
Speaker Baffles, Spacers, and Depth Extenders
Mount your speakers in the location that you need with these speaker spacers, extenders, and adapters.
 ProductPriceAdd?
Speaker Baffles for your SpeakersSpeaker Baffles for your Speakers
Enhance the sound of your speakers with these easy to install speaker baffles.
$9.99
3/4" Depth Extender for 5-1/4" Speakers3/4" Depth Extender for 5-1/4" Speakers
Add 3/4" of extra space when installing your speakers.
$8.99
Installation, Tools & Accessories
Get all of the tools and accessories to install your new speakers like a professional, or take your car to an expert and have them installed by redeeming professional installation cards.
 ProductPriceAdd?
Door Panel & Upholstery Remover ToolDoor Panel & Upholstery Remover Tool
The ideal tool for removing your car's door panels to replace you speakers!
$11.99
Universal Window Handle Remover ToolUniversal Window Handle Remover Tool
Designed to easily remove the manual window handles without breaking any interior pieces.
$4.99
Universal Wire Puller & GrabberUniversal Wire Puller & Grabber
Running wires has never been easier! This wire puller allows you to run wires through those hard to reach places!
$6.99
16-14 AWG Butt Connectors16-14 AWG Butt Connectors
These blue butt connectors are ideal when connecting thicker speaker wire your new aftermarket speakers!
$4.99
Tone Generators and Sound Testing Equipment
Optimize your new system's sound quality by testing and calibrating all of your components with these items.
 ProductPriceAdd?
AutoSound 2000 CD-101AutoSound 2000 CD-101
Low frequency test CD
$12.99
AutoSound 2000 CD-102AutoSound 2000 CD-102
High frequency test CD specifically designed for the set-up and evaluation of sound system imaging and placement.
$12.99
AutoSound 2000 CD-103AutoSound 2000 CD-103
Audiophile reference series test disc for evaluation of all audio components.
$12.99
Main Product
 ProductPriceAdd?
Polk Audio MM521Polk Audio MM521$99.99

Product Summary

Manufacturer: Polk Audio
Model number: MM521
UPC: 747192114497
Weight: 4.00 lbs
Internal SKU: mm521
Internal product ID: 17948

Price Information

$189.95

–$89.96

$99.99

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Customer Testimonial

I ordered 4 items from Sonic Electronix. Delivery was right on time and everything appeared to be in good condition. No issues as of this point, but I need to install and see how everything works.

- Rich from Schaumburg, IL

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