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Polk Audio MM691

6"x9" 3-way car speakers

16 Reviews | 2 questions - 8 answers

Item #: 107MM691

In Stock

Was: $279.99

Price Break: -$120.00

Installation gear for most cars

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Our take on the Polk Audio MM691

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 MM691 6"x9" 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.

3/4" and 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.

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 virtually all factory and aftermarket stereos.

Priced per pair

The speakers have a clear and crisp sound from the mid range and tweeters but the woofer doesnt quite deliver as nicely as I would like. I have them mounted in my boat and so far they have held up pretty well against any water intrusion. They appear to be an excellent choice for marine application.

didja, Phoenix, az

What's in the Box:

  • Two 3-way 6x9" speakers
  • 2 Grilles
  • 2 Passive crossovers
  • 8 Mounting screws
  • 8 Speed clips
  • Owner's Manual
  • Product Registration information sheet

Product Highlights:

  • 6"x9" 3-way speakers (pair)
  • woven honeycomb glass fiber composite woofer cone with butyl rubber surround
  • 1" and 3/4" silk composite dome tweeters
  • certified for marine use
  • 2.7-ohm impedance for extra power (compatible with virtually all factory or aftermarket car stereos)
  • power range: 15-125 watts RMS (300 watts peak power)
  • frequency response: 30-25,000 Hz
  • sensitivity: 94 dB @ 1 V
  • top-mount depth: 3-3/16"
  • warranty: 1 year
  • Our 60-day money-back guarantee

Polk Audio MM691 Reviews

Average Customer Review:

16 Reviews

Polk Audio MM691

Written by: Dave 220lx from Olive Branch, MS on May 20, 2016

Crutchfield Customer Review (What's this?)

I installed these along with a pair of MM651 in my boat along with a ppi 900.4 amp. They sound great and look good too. They do require a lot of power though. Other reviews said it took a while to break them in to get the best sound. If they sound better with use then I will be even more pleased. Great speakers for the money

Pros: Great sound Good looks Loud Bang for the buck

Cons: Requires a lot of power

mm691 front and mm651 rear

Written by: . from Florida on May 10, 2015

These speakers sound awesome, when they work. 2 years after installing them in the stock door locations of my 2500 Dodge Ram one of the front mm691's low frequency driver just stopped working. The high frequency side is fine. The LC circuit is fine and I have never overloaded them. Also, upon removing the speaker for root cause analysis I see that the rubber surround has one small crack. In addition to this speaker having an issue, one of the rear mm651 also fried. Again the LC circuit is fine and in this case the speaker still plays, but with awful low frequency response. I spent a lot of money on these speakers and then a lot of time making them fit in the Ram. Polk brand speakers of the past were proven reliable for me, but these MM units are very disappointing.

Pros: Sound good

Cons: Poor ageing, Poor durability. Very expensive.

Good midrange and highs.... decent bass

Written by: didja from Phoenix, az on June 19, 2012

Crutchfield Customer Review (What's this?)

The speakers have a clear and crisp sound from the mid range and tweeters but the woofer doesnt quite deliver as nicely as I would like. I have them mounted in my boat and so far they have held up pretty well against any water intrusion. They appear to be an excellent choice for marine application.

Pros: Great sounding mid range and highs. Stand up well in a marine application.

Cons: Bass comes across a little less than I would like and its not long before they start to be overdriven.

Great Speakers

Written by: Mark S from Clovis, CA on February 10, 2012

Crutchfield Customer Review (What's this?)

I replaced all 4 factory speakers in my 2010 Dodge Avenger with these Polk's. After the break-in period they sound significantly better then the cheap factory ones. I have not yet added an amp or sub, and because these sound so much better, i may not. These speakers are a great replacement for a do it yourself install...It took me and my friend less then 2 hours for installation. Also, these are stable to 2 ohms and very efficient (94db) so they are louder then the factory speakers at the same volume. One note: On Crutchfield they are not listed as compatible because in the front there is a piece of sheet metal that blocks the speaker...I was able to pound with a hammer to bend it slightly so the speaker fits fine. The back was no issue at all.

Pros: Good bass, Super clean highs, balanced mid-range

Cons: None so far

I love 'em

Written by: Bill from Bedford PA on January 27, 2012

2008 Toyota Tacoma
Crutchfield Customer Review (What's this?)

I installed these in the rear of my Tacoma in a set of Sound Ordnance Bass Bunker boxes. They're paired up with a set of Infinity Kappa 6 1/2 in the front powered by a basic Pioneer receiver. The sound quality is superb. I'm hearing things in certain songs that I never heard before. Being only 3 ohms really draws the most from my receiver. I would definitely recommend.

Pros: Sale price, sound quality, and volume.

Cons: None

very good speakers!

Written by: deweys from Amarillo, TX on September 27, 2011

Crutchfield Customer Review (What's this?)

I installed these speakers in sealed MDF boxes with fiber filling in my 1970 Bronco. These speakers sound very good with this setup- lots of tight bass, mids and highs are very clean. My head unit is only feeding them 18 watts and it is more than loud enough for me- even with the top off of the vehicle these speakers drown out the exhaust and wind noise no problem. They do come with separate cross over boxes.



Polk Audio MM691

Written by: Chris M from Brookings, Or on August 15, 2011

Crutchfield Customer Review (What's this?)

A very good sounding midrange with good highs. The bass is not as described by other raters/purchasers. I bought these to replace an older pair of 6x9s that are mounted in the saddlebags of my Harley. They sound ok but I should of bought another set of my old 6x9s again.



Very pleased

Written by: Anonymous from USA on April 3, 2011

These speakers are really impressive. I knew they would be pretty good, but was pleasantly surprised with the balance of the sound and the tight, accurate punch they delivered. Mine were coupled with the MM651 front speakers. I got a chance to hear things in songs I've had for years that I didn't know existed. I put these in an older, luxury car that was very well-insulated and really was a great match for these speakers as it helped with the acoustics. I don't know how these would sound in an car without good sound insulation, they might be a bit harsh. They look pretty durable and are very lightweight, which makes it even more impressive that they have such a good bass response with the smaller, high-tech magnets. I used an amp on these and I think that makes a big difference. I also have a sub which adds that nice low end that no speaker this size can deliver. I'm not a bass-hound, but a good sub (even at low levels) can really make the experience perfect. My only complaint is that these might not be for everyone depending on the type of music you listen to. They deliver a very precise sound that might come across with a rigid sound. They don't have the warmth that some might prefer. I however usually prefer a studio monitor type sound and these deliver something more like that. Of course a good EQ can help, but I think it is just the nature of these speakers, and if I preferred a warmer sound I would take 1 star off. Overall a great choice for speakers!



6x9's? Are you kidding me?

Written by: Dave from Mobile AL on March 6, 2011

6x9's are not supposed to sound this good. I've always been told that a round speaker will sound better than an oval one. ABSOLUTE NONSENSE! I've owned top of the line separates from Quart, A/D/S, Diamond, Alpine, JL, Rockford, and a few others I can't remember. I've been doing this over 20 years. This 6x9 3-way sounds as good as any set of separates I've ever owned. Granted being hooked to a 2-way crossover kinda makes this a separate with an axis mounted tweeter. They have a "hi-fi" sound quality to them. Music is warm and well balanced, punchy and detailed. Even mounted low in the front doors the soundstage is dash level, no harsh highs, no hissy sounding ear fatiguing tweets, no mid range hole that many speakers use to make the bass sound stronger. I've been looking for a speaker that simply sounds great. I've found it. The 6-1/2 MM coax is next for the rear. I'm only amping these with 50watts/channel and they sound flawless with or without my subs turned on. I kept seeing the word WOW pop up review after review. Now I know why. WOW indeed.



Amazing Sound

Written by: RP from Nashville, TN on December 7, 2010

All I can say is wow! This is an example of why the experts always say to devote a decent part of you stereo equipment budget to high quality speakers. I installed these as part of a stereo upgrade in my boat along with a Kenwood KMR-440U marine receiver and an Alpine amp I had from the previous boat. Just for kicks, I listened to the system with the old 6x9 speakers first. I then installed the MM speakers. It was night and day. With the Polks, the mids and highs are crystal clear, and the bass is rich and deep enough that you might not want or need a subwoofer.




Written by: Richard G. from Arlington, TX on September 21, 2010

2005 Chevrolet Impala
Crutchfield Customer Review (What's this?)

Wow! I installed these last night and they are great!. I have a 2005 Chevrolet Impala which indicated that these would not fit but I decided to try any way to match my Polk in the front. They are loud. I can listen to the music outside my car with the windows up!. Good Highs and lows. Shakes my car (not like my 12" mind you) but just 2 6x9s it was impressive!. Thanks crutchfield!



Amazing 6x9s

Written by: abendroth from Houston, TX on November 22, 2009

2006 Jeep Grand Cherokee
Crutchfield Customer Review (What's this?)

I just installed these in the front doors of my 2006 Grand Cherokee. They sound great. The separation between the lows, mids, and highs is beautiful. They have a clean, crisp sound. I'm driving them with a Polk 200.4 amp. I'm very pleased with these speakers.



Clear and crisp, these speakers are amazing!

Written by: TOMN8R from Springfield, MA on May 9, 2009

I installed two pairs of Polk MM691 6x9 speakers in my '07 Charger (2 front doors, 2 rear shelf). I considered many others but liked these the best because of their amazing bass and mid-range, highs are clear and crisp. Polk used very good materials in these speakers and their construction looks like they can withstand a lot of abuse (I have a lot planned for them...). Don't be mislead by their light-weight and shallow magnets, these speakers rock hard! They may not put you in the hospital but they can break your eardrums. Tech notes: A Kenwood DNX6140 head-unit and KAC-8404 amp feed the power and tunes to the Polks. The low end is handled by two BA G310-4 subs in the trunk. Sounds so amazing I can barely hear now... !!



Polk Audio MM691

Written by: gerald from titusville FL. on January 18, 2009

I purchased 6.5's and the 6x9's to match. I replaced premium series ($500.00) 6.5's that had blown with 50 w rms and a x-over. I couldnt afford the top of the line polks, and hoped that these would tide me over till I could. AT FIRST... they sounded so horrible I couldnt believe it. I read about people saying they got better over time. They where right. After I sold the amp with built in x-over and installed diff. amp w/o x-over, I realized how much bass they really put out. The quarts couldnt compete at all as far as bass and mid bass. That extra bass pumping through them now broke them in, in a hurry. Now they sound fantastic. I wont lie and say as spacious and natural as the quarts, but the sound stage is high (right over the dash), their frequency extension is good with no harshness (the bane of Boston Pro's), and also very focused with no hole in the middle. MUCH better than I was expecting. They didnt sound good at high volume levels at first but after the break in period, now they get darn loud and sound great. The only draw back is how much my door rattles now, and the cone is kissing my factory grill making it buzz. For the price you cant beat them. Double ,triple or quadruple it and now your out of their class. Two thumbs up for me at this price.



Great Speakers

Written by: Jonathon from Maple Grove, Mn on September 28, 2008

Crutchfield Customer Review (What's this?)

I bought these speakers a couple of weeks ago and have them in and powered for about a week now, had some trouble with my amp but crutchfield support's help was amazing and greatly appreciated. These speakers are some of the best I've heard, and I've heard quite a few brands and series, They provide excellent vocals that jump out from the music, but not annoyingly so, they balance the bass out extremely well so that it isn't too much in the speakers, just mid bass that punches nicely for a set of speakers. I have them powered by the kicker ZX700.5 and that made a huge difference, definitely get an amp for these and you will be incredibly happy you made the purchase.



First time Polk user

Written by: Adam from Surprise, AZ on August 19, 2008

1997 Honda Civic

This is the first Polk product I have ever purchased and I have to say I am impressed. These things are clean and clear which is exactly what I was looking for. I do have them powered by a Rockford T400-4 amp, so that makes a big difference. The bass response surprised me. I have the rear deck in my Civic coupe lined with Dynamat and these things will still resonate the deck if I turn up the bass too high. They are tight and punchy, no booming here. That's what a sub is for. The highs are incredible as well, crisp and not ear piercing. Cymbals sound like cymbals, not like sizzling bacon like my previous speakers. All around great speakers. I liked them so much I bought the matching component set for the front of my car.




Hands-on research

What's in the box?

Download the Polk Audio MM691 manual

  • Two 3-way 6x9" speakers
  • 2 Grilles
  • 2 Passive crossovers
  • 8 Mounting screws
  • 8 Speed clips
  • Owner's Manual
  • Product Registration information sheet

Features and Specs

Design 3-way
Tweeter Design 3/4" 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 94 dB at 1 watt
Frequency Response 30 - 25k Hz
RMS Power Range (Watts) 15-125
Peak Power Handling (Watts) 300
Impedance (Ohms) 3
Top-mount Depth (Inches) 3 3/16
Bottom-mount Depth (Inches) 3 1/2

Product Research


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 Tweeter and Super Tweeter: The speakers feature 1" liquid-cooled, silk/polymer composite tweeters and 3/4" liquid-cooled, silk/polymer composite super-tweeters for clearer, more accurate mids and highs.

Neodymium Magnets: The speaker's neodymium magnets offer exceptional strength to performance ratio and are 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 supplied with two separate 2-way crossovers; one for each speaker. Each crossover input 36" 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 separate 2-way crossover network sends the appropriate frequencies to each driver for cleaner sound and better imaging. Dimensions: width = 3.515", height = 1.015", depth = 2.555"

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.

Q & A

Customer Q&A

2 questions already asked

I would not recommend this application. [ Mark  May 20, 2016 ]
The Polk mm691 speakers are marine certified and sound great. They do require a lot of power. I have these paired with mm651 and a ppi 900.4 amp they sound great and get really loud. The Polk mm651 um are one of the highest rated marine speakers on the market. [ William  May 20, 2016 ]
Not sure how they hold up to salt water and the weather conditions but I put them on the motorcycle and they held up in the rain and they sound awesome [ robert  May 20, 2016 ]
I'm not sure about boats but bought them for my car they are ok Sound is satisfactory [ RICHARD A  May 19, 2016 ]
I'd probably go with polyplaners. The Polks are great but I don't think they would stand up to long with a constant barrage ow water. [ David john  May 19, 2016 ]
I just bought them for mine.. I've head nothing but good things about them [ Michael  May 19, 2016 ]
I put them on my motorcycle and they are OK... I probably would not purchase them again because they clip fairly easily. [ Jesse Felix  May 18, 2016 ]
The included crossovers are passive (meaning they filter the frequencies post-amplification) so in most cases you'd want to leave your amp set for full-range output and allow the Polk crossovers to filter the highs to the tweeter and lows to the woofers. I hope that helps. My Bio: [ Larry  Apr 22, 2016 ]  Staff