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Polk Audio MM651

6-3/4" 2-way speakers

66 Reviews | 10 questions - 30 answers

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Overview

Our take on the Polk Audio MM651

Polk Audio continues its tradition of making brilliant-sounding speakers in stylishly designed packages — their Mobile Monitor (MM) Series speakers look great and sound even better. Each speaker utilizes an extra-strong, extra-small neodymium magnet that saves space and weight, allowing these speakers to fit into more places in more vehicles 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.

Polk Audio continues its tradition of making brilliant-sounding speakers in stylishly designed packages — their Mobile Monitor (MM) Series speakers look great and sound even better. Each speaker utilizes an extra-strong, extra-small neodymium magnet that saves space and weight, allowing these speakers to fit into more places in more vehicles 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 MM651 6-3/4" speakers feature honeycomb-textured woven glass fiber composite woofer cones that respond very quickly for a clean, crisp, and powerful sound. Large voice coils — over an inch in diameter — give the speaker high power handling capability and extended reliability.

1" silk dome tweeters add a sweet high end that blends perfectly with the low notes so your music stays in harmonic balance, from the electric bass all the way on up to the cymbals. Swivel mounts on the tweeters allow you to aim the high notes to produce a superior sound stage in your car.

Important Note: These Polk speakers use a low-impedance design to pull more power safely from your car stereo or amplifier. This design is compatible with all factory and aftermarket stereos.

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.

Priced per pair

Excellent speakers with everything to install.

Michael, Michigan

What's in the Box:

  • Two 2-way 6.75" speakers
  • 2 Grilles
  • 2 Passive crossovers (with wire attached)
  • 2 Mounting ring adapters (includes GM/Chrysler 6-3/4G)
  • 8 Hex-head screws
  • 4 Phillips-head screws
  • 8 Speed clips
  • Owner's manual
  • Product registration information sheet

Product Highlights:

  • 6-3/4" 2-way speakers (pair)
  • woven honeycomb glass fiber composite woofer cone with butyl rubber surround
  • 1" silk composite dome tweeter with swivel mount
  • includes two external crossovers (speaker wire not included)
  • certified for marine use
  • 2.7-ohm impedance for extra power (compatible with all factory or aftermarket car stereos)
  • power range: 15-100 watts RMS (200 watts peak power)
  • frequency response: 40-25,000 Hz
  • sensitivity: 94 dB @ 1 watt
  • top-mount depth: 2-5/8"
  • warranty: 1 year
  • Our 60-day money-back guarantee
Reviews

Polk Audio MM651 Reviews

Average Customer Review(s):

(66 Reviews)
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Details

Hands-on research

Features and Specs

General
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
Specifications
Sensitivity (1W at 1 meter) 94
Sensitivity at 2.83 volts N/A
Frequency Response 40 - 25k Hz
Minimum RMS Wattage 15
Maximum RMS Wattage 100
Peak Power Handling (Watts) 200
Impedance (Ohms) 3
Top-mount Depth (Inches) 2 5/8
Bottom-mount Depth (Inches) N/A
Cutout Diameter or Length (inches) 5

Product Research

Features

Dynamic Balance: Dynamic Balance is a proprietary Polk Audio technology using laser imaging to determine what combination of speaker materials create the least amount of resonance. Eliminating resonance in speakers results in a wide, smooth response and low distortion.

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.

Silk/Polymer Composite Swivel Tweeters: The 1" liquid-cooled, silk/polymer composite tweeters provide clear, detailed highs. The 15-degree swivel tweeter housings deliver direct, detailed imaging; instantly adjustable through the grille.

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

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

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

Crossover: The speaker comes with two separate 2-way crossovers; one for each speaker. Each crossover's input and output wires are attached. The 38" input lead is terminated with tinned wire and the two 20" output leads (one for the woofer and one for the tweeter) are terminated with female quick-slides. The positive woofer lead has a 0.250" female quick-slide and the negative woofer lead has a 0.187" female quick-slide. The positive tweeter lead has a 0.187" female quick-slide and the negative tweeter lead has a 0.110" female quick-slide. These quick-slides connect directly to the woofer and tweeter terminals on each speaker. The 2-way crossover networks send the appropriate frequencies to each driver for cleaner sound and better imaging.

Crossover Dimensions:

  • Width: 3.5" (3.875" including wire)
  • Height: 1.02"
  • Depth: 2.645"

Mounting: The speaker itself has 4 mounting holes for a standard 6-3/4" application. The supplied mounting rings have multiple mounting holes for non-standard 6-3/4" and many 6-1/2" applications, allowing the speaker to fit more vehicles.

Grilles: Strong ABS plastic grilles are included. These computer optimized grilles feature a spoke-wheel design.

Marine Certified Woofer: Polk MM Series speakers are built to withstand exposure to moisture and UV rays, so they work well in boats and cars. They also include stainless mounting hardware for corrosion and rust resistance.

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.

Accessories
Q & A

Customer Q&A

10 questions already asked

Yes as long as your amp or receiver can handle 2 separate pairs of speakers. The JL speakers are 4 ohm and the polks are basically 3 ohm. Most quality amps are 2 ohm stable and shouldn't have an issue. [ Robert  Apr 20, 2017 ]
I was going to do the same thing in conjunction with a JL audio amp and my crutchfield tech told me not to mix did ohm speakers. [ James  Apr 18, 2017 ]
Sure. You can mix and match any speakers. As long as your amp can handle the ohm load that you wire your speakers.(Parrallel or series) What you will lose, is timbre matching. In a car, I would keep the same brand and line for mids and highs. In a boat, it might not matter as much. You might not notice if you place the speakers outdoors. [ MOSES  Apr 18, 2017 ]
I have no idea about the ohms, sorry. I do think they sound real nice...... only running 40watts per channel though. [ Kevin  Feb 13, 2017 ]
For additional details on fit or installation please contact an Advisor by phone (1-800-324-9695) or online chat. They will be able to pull up your vehicle and give you the details on if this will fit and what you will need for an installation in your vehicle. [ Kenny  Feb 10, 2017 ]  Staff
Yes, they fit great, you will need 5.25x6.5 adapter rings if used on pre-14. They handle a lot of power and perform great, however, i have went through two sets of these. And I'm now running Hertz, because the tweeter posts sag and then the driver starts rubbing the post and makes the speakers pop. they don't last if you run them hard. [ Richard  Feb 03, 2017 ]
Yes in a 2014 inside the speaker pods [ Stephanie  Jan 30, 2017 ]
I put them in my 2010 Street Glide. They are not bad speakers, but at highway speeds you loose some of the volume. I ended up putting my Hog Tunes speakers back in, They are designed for bikes and sound 100% better at highway speeds. I have tried the Polk, Kenwood, Rockford Fosgate, Alpine, and I always ended up putting the Hog Tunes back in. Learned the expensive way. [ FRED D  Jan 30, 2017 ]
No, but if the hole is the correct size these speakers are pretty standard in size. I have a pair of these and do not like them at all. They do not have good midbass. I would recommend a pair of kicker marine speakers, I had way better luck with those. In addition on a motorcycle space is a concern just like it is on my boat, the crossovers on the polk speakers might be an issue and if you don't mount them may vibrate on the bike. [ GARRETT  Jan 30, 2017 ]
I do not think the crossovers are waterproof. I have them mounted in a batwing fairing on a Harley, so they stay dry. The speakers themselves have been wet many times and no problems with them so far. [ Southside  Sep 07, 2016 ]
I do not know. I was actually wondering the same myself. [ Kevin  Sep 06, 2016 ]
I wouldn't call anything "waterproof". They are marine rated so they can handle some moisture, but I wouldn't install in a known wet space or where they will get constant water contact. Outside of speaker is sealed well enough if the mounting surround is tight and flush. Crossover looks sealed, but again I wouldn't put it in a spot to get ruined. [ Mikael J.  Sep 06, 2016 ]
speaker assembly is waterproof crossover I don't think so but mine is in a console so are covered but I would hope to be water resistant since they are on a boat [ SPENCER  Sep 06, 2016 ]
The MM651 are marine certified, not waterproof. When you open the crossovers to mount them they do appear to have a significant amount of some type of coating on the circuitry to protect them, but they also have an open woofer with a stalk mounted tweeter where water can intrude. I would consider them more splash-proof or water resistant. For most situations they will be fine. The MM651UM version however has a completely sealed front and speaker mounted crossover with additional protection like you may be after. They are not available at Crutchfield however. [ Jerry  Sep 06, 2016 ]
The speaker is specified as 2.7 ohm but is 4 ohm compatible. To get the best sound you will need an amp. I am running four of these off a ppi phantom 900.4 and the sound amazing. [ William  Aug 17, 2016 ]
Sorry for fhe late response but they should do just fine on that head unit, I have them on a amp at about 75w rms and they sound nice for my particular setup [ KENNETH L  Aug 11, 2016 ]
This speaker wI'll work with any amp, aftermarket or factory receiver. Although they sound best when amplified with aproximately 100 watt per channel amplifier. [ william  Aug 10, 2016 ]
I Have 75watts going to mine and they sound great. I did read that they r designed for direct replacement oem. Always sounds better with an amp and separate sub though. To each is own. [ Jeff  Aug 09, 2016 ]
The grill is the same size as the speaker; 6 and 3/4 [ Jason  Jul 12, 2016 ]
It's been a while since I installed them but I think they are roughly 2x2x3/4". They are mounted in the middle of the included 5'-6' cables. Included are screws to mount them or you could use two faced tape. These speakers are excellent! The only weird thing is that they take a few hours of play to break in. [ James  Jul 11, 2016 ]
they are around 3" x 2" I have mine mounted on motorcycle lower fairings.in a car they could mount inside door beside speakers or under dash behind radio . [ RICHARD  Jul 09, 2016 ]
As far as the dimensions go, I am guessing, but I would say 3 to 3 1/2 inches by 4 to 4 1/2 inches. There are screw holes to mount. I just used Velcro and mounted them in the kick panels. [ MOSES  Jul 09, 2016 ]
They're aproximately 3"×3"×3/4". U can mount with supplied screws or what I did was use zip ties through the slots, much easier than trying to find somewhere that your willing to put screw holes. Speakers do sound great though. [ william  Jul 08, 2016 ]
They are smaller I would say probably 2 inches by 2 inches. I put the speakers in my boat and they are amazing. Used double sided tape to mount crossovers down for a cleaner install. [ Shannon  Jul 08, 2016 ]
I can't remember exactly how large the crossovers are but they are pretty small and could fit just about any where, I had placed mine behind the door panel in a spot that would be behind a raised spot of the door panel on to the door on top of the moisture barrier so that no moisture could enter them. I also had to extend the wire for better fitment on the other set of doors. It also really depends on the vehicle and how you plan on setting up with or without an amp. If you want to set it up with a amp you could put all of the crossovers right there with the amp and let just all of the wires run to the speakers as assigned by the channels. I really hope that this was helpful in any way. [ KENNETH L  Jul 08, 2016 ]
I don't know the exact measurements, but each one is roughly 3x2, very lightweight. I have some factory tabs for the wiring loom, I simply used zip ties to hold them securely to those tabs. Hope that helps. [ Steve  Jul 08, 2016 ]
If I remember correctly they are about 1.5 x2.5. I did not mount. I left them lying on base of the enclosure. They would be mounted with a screw normally to prevent movement. One could zip tie also. [ brian  Jul 08, 2016 ]
About 3 inches by 4 inches and 2 screws mount each 1 [ Stephanie  Jul 08, 2016 ]
You can check to see if this will fit your vehicle by using our Outfit My Car tool: http://www.crutchfield.com/car/carselector.aspx For additional details on fit or installation please contact an Advisor by phone (1-800-324-9695) or online chat. They will be able to pull up your vehicle and give you the details on if this will fit and what you will need for an installation in your vehicle. [ Krissy  Jun 10, 2016 ]  Staff
Thanks for your question. The SquareTrade warranty runs concurrent with the manufacturer warranty and beyond the 1 year. You can find more information on the SquareTrade link here: http://www.crutchfield.com/Promo/squareTrade.aspx [ Kenny  Apr 19, 2016 ]  Staff
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