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Polk Audio continues its tradition of making brilliant-sounding speakers in stylishly designed packages — their Mobile Monitor (MM) Series Ultra Marine speakers look great and sound even better. Each speaker utilizes an extra-strong, extra-small neodymium magnet that saves space and weight, while still delivering a full sound with lots of kick. Their lightweight carbon composite frames provide strong, flex-free support for the speakers' motor assemblies.

The Polk MM6501UM 6-3/4" marine component system features 6-3/4" woofers with honeycomb-textured woven glass fiber composite cones that resist and suppress unwanted resonances yet respond very quickly for a crisp and powerful sound. Large voice coils — over an inch in diameter — give the speaker high-power handling capability and extended reliability.

Separate 1" soft dome tweeters add a sweet high end that blends perfectly with the low notes. The crossovers, sealed behind the woofer magnets, direct the signal flow so all your music stays in perfect harmonic balance, from the electric bass all the way up to the cymbals. Stainless steel terminal posts will not corrode or rust, keeping your speaker wires reliably connected.

Note: Polk describes this model as a 6-1/2" speaker. Most manufacturers designate this same frame size as a 6-3/4" speaker. For simplicity's sake, we list it as a 6-3/4" speaker.

Product Highlights:

  • marine component speaker system includes two 6-3/4" woofers and two 1" tweeters
  • woven honeycomb glass fiber composite woofer cone with butyl rubber surround
  • 1" soft dome tweeter
  • 2-way crossover attached to the woofer basket
  • designed and certified for marine use
  • 4-ohm impedance
  • power range: 25-125 watts RMS (250 watts peak power)
  • frequency response: 40-25,000 Hz
  • sensitivity: 92 dB
  • top-mount depth: 2-5/8"
  • warranty: 1 year
  • Our 60-day money-back guarantee

Polk Audio MM6501UM Reviews

Average Customer Review:

2 Reviews

Great Speakers

Written by: soccerson114 from Greenville, SC on March 25, 2013

Great middles. Great high notes. Good Lower end. Very Tight Sound. My subs spoiled me on the low end.

Pros: Tight Sound. Can handle loud sound. Can get wet and not be ruined.

Cons: Tweeter intall instructions could be better. Lower end could be better, but am unsure how they compare to others b/c subwoofers make me base heavy biased.


Written by: Jesse T from Raleigh, NC on October 20, 2012

These are some great marine speakers. Picked these up, along with their sister model the MM651UM, and they are great in my boat. Big sound upgrade over the stock speakers. Can't go wrong with Polk.

Pros: Splitting the tweets is fantastic in my boat setup!

Cons: A bit pricey

Hands-on research

What's in the box?

Download owner's manual

  • Two 6.75" marine woofers with built-on grilles
  • 2 Tweeters
  • 2 Tweeter flush-mount cups with metal clamps attached
  • Two 40" Speaker wires
  • 8 Speed clips
  • Eight 1" Self-tapping hex-head screws (3mm)
  • Owner's Manual (English/ Spanish/ French/ German/ Italian/ Portuguese)
  • Online registration sheet

Features and Specs

Speaker Size 6 3/4
Design 2-way
Tweeter Design 1" Soft dome
Tweeter Composition Silk/Polymer composite
Woofer Composition Glass Fiber Composite
Woofer Surround Butyl Rubber
Parts Warranty 1 Year
Labor Warranty 1 Year
Sensitivity 92 dB at 1 watt
Frequency Response 40 - 25k Hz
RMS Power Range (Watts) 25-125
Peak Power Handling (Watts) 250
Impedance (Ohms) 4
Top-mount Depth (Inches) 2 5/8
Bottom-mount Depth (Inches) N/A
Cutout Diameter or Length (inches) 5

Product Research


Marine Certified: This Polk MM Series speaker is built to withstand exposure to moisture, salt water, high humidity, UV rays, and a wide temperature range so they work well in a marine environment, such as a boat. The speaker has passed rigorous hours of salt fog and UV testing. The speaker also features a completely sealed front design to prevent water intrusion. In addition, they include stainless mounting hardware for corrosion and rust resistance.

Woofer Cones: Woven glass composite cones feature tremendous stiffness-to-mass ratio. Lower mass means faster transients and finer detail.

Butyl Rubber Surrounds: For a smoother response and improved durability, the woofers use butyl rubber surrounds. The airtight rubber surrounds stand up to moisture, sunlight and extreme temperatures while allowing long excursion linear motion and years of reliable use.

Separate Tweeters: The 1" silk/polymer composite tweeters provide clear, detailed highs. The attached 19" wire is connected to the tweeter terminals on the back of the woofer. Mounting dimensions:

  Flush Mount
Mounting Height 0.325"
Depth 0.98"
Frame Diameter 2.29"
Cutout Diameter 1.944"

Neodymium Magnets: The woofer's neodymium magnets offer exceptional strength to performance ratio and are extremely lightweight.

Large Diameter Voice Coils: Large diameter, 30mm voice coils increase the woofer's reliability and power handling capacity.

Carbon Composite Basket: The woofer's carbon composite basket is lightweight and will not flex during music audio peaks.

Built-In Crossovers: A sealed crossover assembly is built onto the back of each woofer; no need to find room to hide an external box.

Built-On Grilles: The woofer's grilles are not removable.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.