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Polk Audio MM521

5.25" 2-way Mobile Monitor Series Coaxial Speakers (Marine Certified)

In Stock. Only 2 Left!
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List price $229.95

$139.95

with warranty

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Arrives by Monday, Sept. 29 to zip 07095

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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

Series
This is the manufacturer product line of speakers.
MM / Mobile Monitor (Polk)
Priced Per
Car Speakers are typically sold in pairs so you will receive 2 speakers for each speaker purchase on speakers marked "Priced Per Pair". If a speaker is marked "Priced Per Each" then the speaker is sold individually and each purchase you make will result in 1 speaker. High-powered tweeters, midrange and full-range pro audio for car speakers are typically sold per each speaker.
Pair
Speaker Size
Refers to the size of the speaker measured in inches. Every vehicle has standard application sizes. Please use our vehicle fitment guide for your vehicle's specific speaker sizes if you do not know them.
5-1/4"
Design
The number of individual drivers in a car speaker. Speakers with 2 drivers are known as a 2-way, and 3 drivers are known as a 3-way. Component systems are often referred to as "separates" because the tweeter is not attached to the midwoofer (main speaker driver) and mounts separately in a location such as a door post. Component systems typically come with an external crossover so you can easily adjust the high and low frequencies sent to both the midwoofer and the tweeter. Center channel speakers are great for those looking to have surround sound in their vehicle.
2-way
Tweeter Design
Designs such as cone, dome, semi-dome, balanced dome, and whizzer are most popular. Cone tweeters are simple, efficient and typically are the most reasonably priced. Dome tweeters are used in most home speakers, and provide a smoother and more accurate sound. Semi-dome design is one with a dome placed inside a cone. A Balanced dome driver is a semi-dome with equal reproduction area given the cone and dome portions of the driver. A whizzer tweeter is a separate tweeter cone driven by the voice coil of the woofer.
Dome
Tweeter Composition
Materials such as polypropylene, silk, cloth, and paper are the most common, where as many more recent tweeters are now manufactured with composites such as Aluminum, Titanium, Mylar, and other materials.

PEI is an acronym for "Polyetherimide" which is an amorphous, amber transparent, high-performance thermoplastic.

Silk-Polymer Composite
Woofer Composition
Lightweight woofer cone materials are essential for efficient operation. Poly cones produce exceptional sound and are sturdy against various changes in temperature. Paper cones are very efficient, and when treated for moisture resistance, will perform at a high level. Poly refers to polypropylene, which is thermoplastic or fibers that are polymers of propylene. IMPP refers to injection molded polypropylene, a commonly used process and material in speakers.
Woven Glass Fiber
Woofer Surround
A speakers surround is part of the suspension system. The surround protects the cone and prevents it from being displaced as it flexes out from the basket. It is usually made of a durable material like treated foam or rubber in order to withstand the strenuous job of producing bass frequencies.
Butyl Rubber
Peak Power Handling
Peak power handling refers to the amount of power a speaker can handle during a brief musical burst. The RMS power range figure is a much more reliable rating for determining the speaker's power requirements. The Peak power handling specification is typically rated per speaker unless otherwise noted.
200 watts
RMS Power Handling
The RMS power is the amount of power the speaker requires to operate safely and properly. RMS Power Handling refers to the amount of power a speaker can handle on a continuous basis. We recommend powering your speakers or subwoofer with 80%-120% of its recommended RMS rating. The RMS power handling specification is typically rated per speaker unless otherwise noted.
90 watts
Sensitivity
An efficiency or sensitivity rating tells you how effectively a speaker converts power into sound. The higher the number, the more efficient the speaker and the louder it will play with the same input power. An efficient speaker helps you maximize your available power. Most sensitivity ratings measure the speaker's output with 1 watt of input, 1 meter from the speaker. Some speakers' sensitivity is measured with 2.83 volts of input, instead of 1 watt.
 
Efficiency (1w/1m) is not an accurate indicator of a subwoofer's output capability and should not be used as a comparison to other speakers or subwoofers to determine which one is "louder".
92 dB
Frequency Response
The range of frequencies the speaker will reproduce (lowest frequency to the highest). Bigger is better, meaning the wider the range, the better. The optimal range is 20 - 20,000 Hz (which is the range of human hearing).
50 - 25000 Hz
Impedance (Per Voice Coil)
The load value (in ohms) that the speakers present to the amplifier per voice coil - the amount of resistance to the current flow. This is a key specification as subs wired in parallel or low impedances can create problems with your amplifier and potentially void all warranties. We encourage you to ask our support department prior to purchase if you do not understand which impedance level will suit your application best.
2.7
Top-Mount Depth
The depth when installed on top of the mounting surface. Measured from the bottom of the speaker's magnet to the bottom of the mounting holes on the rim of the speaker.
2-1/2"
Cutout Dimensions
Refers to the dimensions of the hole, measured in inches or millimeters, required to contain the speaker.
4-11/16 x 4-11/16 
Speaker Grilles
A grating or screen of metal or plastic bars or wires, mounted in front of a speaker as protection. If yes, the speakers will include matching speaker grilles. If no, there are no grilles included.
Yes

Warranty and Return Policy

Parts Warranty Duration
1 year
Labor Warranty Duration
1 year
Warranty Provider
Sonic Electronix

Summary of Customer Ratings & Reviews

Rating Distribution

5 Star
77%
4 Star
23%
3 Star
0%
2 Star
0%
1 Star
0%

Average Attribution Rating

Durability
4.8
Value
4.6
Features
4.8
Design
4.9
Usability
4.8
j

san mateo, ca.

Overall
Durability
Value
Features
Design
Usability
quality 5 1/4 in. speaker

August 25, 2014

to me, these mm521 speakers sound great. have quite a collection of 5 1/4 in. and 4 in. 2 way speakers I didn't like. using these for front dash speakers on a early jeep tj wrangler with pioneer 100 rms watt x 4 ch. amp. setting front filter on amp. to cut some base for higher higher volumes. they will make the dash vibrate. my front speaker quest is over. a little over priced but recommend these speakers.

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UniqueCarts

Urbanna, VA

Overall
Durability
Value
Features
Design
Usability
Polk Audio MM521 Speakers

May 30, 2014

I have used many brand marine stereo speakers and these are by far the best sounding speakers that I have used. Have installed about 300 stereos in golf carts and now this is the only speaker that I use.

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Ryan

Reynoldsburg, OH

Overall
Durability
Value
Features
Design
Usability
Great sound and lightweight!

January 21, 2012

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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Paul

Edison, NJ

Overall
Durability
Value
Features
Design
Usability
Polk is it

January 20, 2012

Awesome speakers for my topless Jeep, got rained on several times and NO problem.

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dennis

gardner, KS

Overall
Durability
Value
Features
Design
Usability
boat

December 23, 2011

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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Mark

The Colony, TX

Overall
Durability
Value
Features
Design
Usability
Great speakers

September 6, 2011

Polk makes a great marine speaker. I won't use anything else.

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WKahler

San Jose, CA

Overall
Durability
Value
Features
Design
Usability
Polk Audio MM521

April 28, 2011

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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RJW

McAdenville, NC

Overall
Durability
Value
Features
Design
Usability
Polk MM521

November 17, 2010

I put these in my 2006 Harley Davidson Electra Glide Classic running the stock radio w/o an amp. They are a huge improvement over stock, and have amazing clarity and bass. They do get louder with use. I had to ziptie the crossovers to the fairing supports, which was no problem. I had to remove the little speaker covers, but the speakers look cool. I've washed the bike and they've been wet several times with no issues. I may try a small amp with them for more sound and clarity at speed! Highly recommend!

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brlanha

Chicago, IL

Overall
Durability
Value
Features
Design
Usability
Polk MM521

October 27, 2010

I have these in my boat wired to a 2 channel 120watt amp and they sound awesome..Def recommend them

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nunyo

Anchorage,AK

Overall
Durability
Value
Features
Design
Usability
MM521 = Great speakers.

August 9, 2010

I have these speakers in the fairing on my motorcycle. I have not heard better sounding 5-1/4" or smaller speakers. They play loud and clear, with great highs, and surprisingly good bass. They far surpass the stock speakers. Plus, they are waterproof.

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Matt K

Richmond, VA

Overall
Durability
Value
Features
Design
Usability
Buy these

June 14, 2010

Best speakers for the value by far. its honestly not even close. Ive owned so many different pairs of speakers and I can tell you with no bias, that these speakers are in a class of their own. For the price you will not find better i promise you. they sound amazing, crystal clear with no noise. do yourself a favor and order them as soon as possible, so they get to your door quicker. there is honestly no need to look around any more

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sanjaystuart

Australia

Overall
Durability
Value
Features
Design
Usability
pretty damm goof

May 21, 2009

Very tight sound, awsome looking speaker as well. Good bass level from such a small speaker.

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michael

Bismarck, ND

Overall
Durability
Value
Features
Design
Usability
Great sounding speaker

April 21, 2009

Overall this speaker has a nice warm sound that gets better and better. I have only had these for a week and they get better bass extension, although it isnt completely needed because I have a sub. I purchased these the 6.5 components, and the 6x9 polks as well they sound great together. I have a 12 inch kicker L7 solobaric and these speakers keep up the bass doesnt over power them. Pros Great customer service and quick shipping clean sound, with crisp not overall bright highs perfect sounding. Cons: none really they sound great

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Accessory Tools and Products

Accessories added

NVX 25 ft. of True Spec 12 Gauge Speaker Wire

100% OFC wire with EnvyFlex metallic jacket insulates and protects against damage from extreme conditions.

Your Price $39.99

Streetwires 25 ft. of True Spec 12 Gauge Speaker Wire

You need speaker wire to connect your speakers!

Your Price $44.95

Belva 23 ft. of True Spec 12 Gauge Speaker Wire

100% Copper Clad Aluminum, high strand count with ultra-flexible PVC blended jacket for easy installation

Your Price $14.99

12-10 AWG Yellow T-Tap Adapters

Allows for fast and easy splicing of wires by easily tapping into the cable.

Your Price $4.49

12-10 AWG Quick Disconnect Connectors

These yellow quick disconnect connectors make it easy to connect and disconnect speaker wire your to your new aftermarket speakers!

Your Price $6.99

NVX SDDK12 Door Kit

Eliminates speaker panel distortion and reduces door vibration, rattles and squeaks!

Your Price $49.99

Dynamat Xtreme Door Kit 10435

Enough sound dampening to cover most doors!

Your Price $69.95

Stinger Roadkill Door Kit

Use this to eliminate rattle from your doors!

Your Price $46.99

Car Stereo and Speaker Installation Tool Kit

Includes Test Light, Crimp/Splice Tool, Multi-bit Screwdriver and more.

Your Price $12.99

Universal Wire Puller & Grabber

Running wires has never been easier! This wire puller allows you to run wires through those hard to reach places!

Your Price $6.99

Xscorpion 9-Piece Nylon Plastic Pry and Chisel Tool Set

Easily removes dash/trims, door clips, panels and pins, rubber grommets and vehicle emblems.

Your Price $14.99

3 in 1 Wire Quick Splice T-Tap and Butt Connector Crimper + Wire Cutter

Used for cutting copper and aluminum wires up to 8 gauge.

Your Price $21.99

NVX SDRLR1 Sound Dampening Rubber Roller

Install your Sound Dampening with ease! This heavy duty rubber roller is designed specifically to install your NVX products!

Your Price $7.99

Speaker Baffles for your Speakers

Enhance the sound of your speakers with these easy to install speaker baffles.

Your Price $9.99

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• Peak Power: 200W
• RMS Power: 90W
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• 1" Silk/Polymer composite swivel tweeter
• Klippel optimized components for distortion-free sound

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• Peak Power: 160W
• RMS Power: 80W
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Browse 1 question and 2 answers
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Why did you choose this?
Sonic Electronix Store
This completes the 1st phase of my upgrade of my soundsystem. Now I will have audiophile quality sound at a reasonable price.
Nelson H on Aug 25, 2014
Marine certified speakers are great for jeeps.
Matthew H on Aug 7, 2014

Product Summary

Manufacturer

Model Number

MM521

UPC

747192114497

Weight

4.00lbs

Internal SKU

mm521

Internal Product ID

17948

Sonic Electronix Wiring Guide

Wiring Diagram Legend

Warning: The image depicted shows the resistance change when wiring multiple subwoofer terminals. Please refer to your subwoofer's owner's manual for the proper wiring of its terminals. Sonic Electronix, Inc. is not responsible for damage caused to your audio system or vehicle due to improper installation. Please call tech support at 1-877-289-7664 if you require additional assistance.

Product Name: Polk Audio MM521