1-888-955-6000
crutchfield.com
Crutchfield

Polk Audio MM840

Mobile Monitor Series 8" subwoofer

Zoom
  • Polk Audio MM840

    Front

  • Polk Audio MM840

    Back

  • Polk Audio MM840

Crutchfield OMC logo
We don't check this item for fit or compatibility.
Item #: 107MM840
 

Review Summary

DISCONTINUED
 
This item is no longer available to purchase.
 
Contact us for other options
 
Call   Email  
 
 
 
 
 

Our take on the Polk Audio MM840

by Gabrielle Thorndyke
Polk Audio

What's a component sub and why would I want one?

A component sub is simply a speaker that's designed to reproduce bass once it's installed in a compatible enclosure. Think about the impact of a movie soundtrack in a big theater or even in your own home HDTV setup. A component sub can add the same kind of power to the music in your car. And a car sub is not all about the boom that you hear on a street corner (although that's cool too) - you can pair a component sub with your choice of enclosure to get bass just the way you like it, from tight and punchy to fat and loose. And once you experience music in your car with a well-tuned subwoofer, you'll never go back.

Polk Audio's Mobile Monitor Series subwoofers bring out superior performance from lighter materials, so you'll get the impact you want without the extra weight of a conventional system. Advanced engineering and optimized components reproduce your sound with uncompromising accuracy, for low end that is rich and clear.

The MM840 8" 4-ohm subwoofer handles up to 250 watts RMS. A copper voice coil and neodymium magnet motor drive the polymer cone with exceptional efficiency. The carbon composite basket features a "wagon wheel" design that resists flexing during heavy excursion, so your sub hits solidly without distorting.

This sub is certified for marine use, and Polk includes corrosion-resistant stainless steel mounting hardware.

See more info on this item

Highlights:

  • 8" 4-ohm subwoofer
  • polymer cone with butyl rubber surround
  • carbon composite basket
  • certified for marine use
  • optional matching grille complements the basket design
  • power range: 100-250 watts RMS
  • peak power handling: 500 watts
  • frequency response: 26-200 Hz
  • sensitivity: 89 dB
  • top-mount depth: 3-15/16"
  • sealed box volume: 0.35 cubic feet
  • warranty: 1 year
  • Our 60-day money-back guarantee

Priced per speaker

Hands-on research from the Crutchfield Labs (what are the Labs?)

Features and Specs
Size
Loading...
8 -inch
Impedance
Loading...
4 ohms
Cone Material
Loading...
Polymer
Surround Material
Loading...
Butyl rubber
Ideal Sealed Box Volume (cubic feet)
Loading...
0.35
Ideal Ported Box Volume (cubic feet)
Loading...
N/A
Port diameter (inches)
Loading...
N/A
Port length (inches)
Loading...
N/A
Free-Air
Loading...
No
Dual Voice Coil
Loading...
No
Sensitivity
Loading...
89 dB at 2.83 watts
Frequency Response
Loading...
26 - 200 Hz
RMS Power Range (Watts)
Loading...
100-250
Peak Power Handling (Watts)
Loading...
500
Top Mount Depth (inches)
Loading...
3 15/16
Bottom Mount Depth (inches)
Loading...
4 11/16
Cutout Diameter or Length (inches)
Loading...
7 1/8
Vas (liters)
Loading...
15.4
Fs (Hz)
Loading...
35
Qts
Loading...
0.6
Xmax (millimeters)
Loading...
20
Parts Warranty
Loading...
1 Year
Labor Warranty
Loading...
1 Year
Product Research
What's in the box?

Download owner's manual

  • One 8" subwoofer
  • 1 Foam gasket
  • Eight 1-1/2" Allen head self-tapping screws
  • 8 Speed clips
  • Owner's Manual (English/ French/ Spanish/ German/ Italian/ Portuguese)
  • Online registration sheet

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 open the box, verify contents, 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.

Features
Enclosure Compatibility

Features

Basket: The MM Series subwoofers use high-tech carbon composite basket structures for light weight and maximum rigidity. They will not rust or flex like stamped steel designs.

Materials: The new polymer woofer cone and butyl rubber surround will not break down over time and will survive the rigors of harsh automotive environments.

Voice Coil: The high temperature, 1-1/2" diameter copper voice coil and polyamide former withstand the most rigorous use while maintaining extremely low distortion.

Terminals: The woofer has heavy duty spring terminals that will accept single banana plugs, pin connectors, and bare wire up to 8 gauge.

Marine Certified: Polk MM Series speakers are built to withstand exposure to moisture and UV rays, so they work well in boats and cars.

Klippel Measurement Technology: State-of-the-art laser based Klippel measurement technology is used to optimize the woofer's motor structure, voice coil alignment, and suspension to improve performance, even at extreme listening levels.

Enclosure Compatibility

Sealed Box Volume: Polk recommends using this woofer in a sealed enclosure; the ideal internal volume is 0.35 cubic feet.

 
Review this product
Great Gear Giveaway rewards card

Submit a review and then enter to win a $500 rewards card

Polk Audio MM840 Reviews

Average Customer Review:

13 people say:

Review this product:

Thanks for taking the time to share your experiences about this product. Please be sure to focus your comments on the product itself. Read our Review Guidelines for more information.

Your email won't be visible. Please use the email address that is associated with your order.
(e.g., JohnD) Your review will be signed using the display name and location
(e.g., Charlottesville, VA)

Click on a star to rate the overall product on a scale of 1-5
Rate the following specific attributes
  Value
 Sound Quality
 Ease of Use
 "Coolness Factor"
 Build Quality
1500 characters left
Attach a YouTube Review
Crutchfield Video Review Guidelines
  • Only submit videos that you made or are authorized to use.
  • Do not submit videos that contain music, video or visuals that are copyrighted and belong to someone else.
  • Please see our Review Guidelines for more information.
500 characters left
500 characters left
Filter by rating:
5 out of 5

Bad Little 8"

Written By Josh, Mississippi on Monday, July 02, 2012
Crutchfield Customer Review (What's this?)
 
I have one of these little bad boys in a homemade box in the back seat of my 96 Tacoma Extra cab with a Rockford Fosgate Punch P-300 amp monoblock and It KILLS!! Do not under estimate the power of this little 8", it hits hard and clean, no rattling. Great qualit and very sturdy Sub that sounds Amazing with any Genre of Music, I listen to Country, Classic Rock, Heavy Metal, Rap, Hip Hop, and everything else, and it sounds great with whatever is playing, I have, Polk DXI 6 1/2's in my doors and Polk MM 6 1/2's in the rear with this Sub plus a Alpine head unit and the little Alpine amp KTP145 somethin, it all sounds Awesome!
Pros:
Good, Clean, Hard hitting Bass, even though its small, it still hits really Low notes
Cons:
Nothing
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

big bass

Written By Rob M, Jersey Shore on Tuesday, June 05, 2012
Crutchfield Customer Review (What's this?)
 
clean loud tight bass, in a homeade sealed box. I need one more ,it sounds amazing.
Pros:
need I say more polk audio rules!!!
Cons:
no grill included...
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Impressive

Written By adam, Palm Coast, FL on Friday, May 18, 2012
Crutchfield Customer Review (What's this?)
 
This little sub sounds amazing. I have one in a 0.6 cu ft box mounted to my decklid. Sounds great (minus the rattles which will go away when I make a new box for 2 of these). Only 2 things I would change: The basket is plastic and I could make it bend by tightening the screws. So I had to slowly turn them, one at a time, until it was snug and level. I am unsure if it would effect anything if I didnt have it evenly snugged. The other thing is the push terminals. I am using 8 ga wire (Kicker full spec 8 ga) and the wire barely fits and I am left with a few strands that dont quite make into the terminals. Also the terminals are so close to the edge of the sub that the wires are kinda wedged against the box and the side of the sub. Overall, great product for the price. Can't wait to build the new box for the 2nd sub. I think it will easily rival my old 3 JL10W6.
Pros:
Sounds great from small package. Hits hard and plays low but is not overpowering.
Cons:
Terminals too close to the edge, plastic basket is kinda cheap. No grille included, not a big deal, but would be nice. The plastic basket is rigid, but it flexes when the screws are tightened out of turn.
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Polk Audio MM840

Written By Anonymous, laguna beach, ca on Monday, April 23, 2012
Crutchfield Customer Review (What's this?)
 
04 tundra with q logic box. Sounds great. Fit great.
Pros:
All
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Bangin lil 8s

Written By JediMaek, Oldsmar, Fl on Saturday, March 10, 2012
Crutchfield Customer Review (What's this?)
 
Bought these 8s for my fiancee's 4 dr civic and let me tell you these little things rock! We mainly listen to music with tight rapid hitting bass like drum n bass/techno/rock which is why we went with the 8s, but they will hit low and hard too playing stuff like dubstep or the occasional rap songs. Powered by a memphis 500 monoblock in a sealed box, these sounds real clean and loud. I'm going for the mm1040s for my 94 altima since I'm built a little bigger then her they should be just the ticket rattle my brains :)
Pros:
-Top build quality -Great sq -Excellent spl for 8s -High abuse tolerance
Cons:
None
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Super sickk!

Written By Resiliant, Anaheim HIlls, Ca on Sunday, February 19, 2012
 
Who said an 8in sub can't bang! Got this in my 2001 Tacoma and it fills in my music nicely. This is a great buy.. Ya digg
Pros:
#Price #Quality #Soundquality #8in
Cons:
Too good to be true
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

A very impressive 8" subwoofer

Written By Russell, California on Friday, September 09, 2011
 
I did a great deal of research before making my subwoofer selection. I had some pretty limited choices because of the small space in my 2000 Toyota Tacoma Xtra Cab. I have owned dual 10" subs, dual 12" subs and a single 12" over the years and I was curious about how a pair of 8" subwoofers would sound. I built a custom enclosure for the subs with about 0.40 cu ft of airspace for each sub and I stuffed each side of the enclosure with a little less than 0.5 lbs of polyester fiber material.

I must say that I am very impressed with the Polk Audio MM840! The Polk Audio MM840 is a very musical sub that has a very accurate response. I am very surprised at the relative volume that I can get out of a pair of these, particularly in a listening environment such as my extended cab. You won't be shaking the asphalt lose beneath you, but this sub will definitely sound very clean and accurate and it will greatly enhance your listening experience.

I would highly recommend this subwoofer to anyone who is restricted on space and wants good, clean bass. You can never go wrong with Polk Audio in my opinion!
4 out of 4 people found this helpful
Was this review helpful?    Yes | No
 
5 out of 5

Terrific bargain

Written By Chris, Pacific Tech, CA on Thursday, August 11, 2011
Crutchfield Customer Review (What's this?)
 
I bought this and the corresponding "grill" (not really a grill) to replace a sub driver whose surround had fallen apart. My top-mounting depth available was only about 4-1/8 inches, so I needed a shallow sub. The one I had before was comfortably under 4 inches.

This sub is FAR better than the old one ever was. I have to point out though that the way they got a decent "throw" into such a shallow-mount sub was to put considerably more of the sub *above* the mounting surface. My old sub used a grille that was barely half an inch high - this one is well over an inch. This may affect your choice of mounting positions.
Was this review helpful?    Yes | No
 
5 out of 5

The Little Sub That Can And Will

Written By RockinTacoma, North Augusta , South Carolina on Thursday, June 02, 2011
Crutchfield Customer Review (What's this?)
 
I am simply amazed at how great this sub performs ! I have a Kenwood 8105D Mono amp pushing it with the gain turned up about halfway . The sub even sounds great at low volumes. I was impressed at how well the sub is put together as well....heavily built and very heavy for an 8 incher ! I can't imagine a better small sub for even a little more money.
1 out of 1 people found this helpful
Was this review helpful?    Yes | No
 
5 out of 5

attention

Written By markford, charlottesville on Wednesday, July 07, 2010
 
I was limited on choices because of space restrictions, thank you Polk for coming to the rescue.I'm a big bass fan but thought I had to lower my expectations because I could only use a single 8 inch sub. I'm telling you when I turn up the stero folks begin peeking in the back of my truck looking for a PAIR of twelves. I need not say any more. The Alpine pdx 5 is the perfect companion driving my four Kenwood P680c door speakers as well. Possibly the best stero related decission I've ever made.
6 out of 6 people found this helpful
Was this review helpful?    Yes | No
 
5 out of 5

Perfect Bass!

Written By Curtis, Topeka, KS on Monday, May 17, 2010
 
I have 2 of these subwoofers in a custom box which fits easily behind the back seat of a 1998 Jeep Wrangler. The thing that I love so much about these subs is that the bass is powerful and clear. Your hearing is not completely overtaken by a ridiculous amount of vibration that sounds like a collapsing building. Bass notes are very tight and can be distinctly heard while still packing enough punch to shake your body. The magnet on these subs is on the verge of ridiculous in size and weight and can easily handle the recommended 250 watts rms at a 2 ohm load. Unfortunately I have a cheap Kenwood amp powering the two subs right now, so I assume they could sound even better with a high quality Polk amp pushing them. I definitely recommend these subwoofers if you are tight on space or don't want to shake innocent by-standers 2 blocks away while still loving the bass!
3 out of 3 people found this helpful
Was this review helpful?    Yes | No
 
5 out of 5

Like a punch to the gut

Written By Anonymous, Lawrenceville, GA on Monday, May 10, 2010
Crutchfield Customer Review (What's this?)
 
I'm not a big bass fan. I like more the thud sound, like the one the feels like a punch in the gut.

I used to have two 8'' Polk Audio db840DVC, but after I got Alpine's iDA-X305s (thanks crutchfield) the sound became so heavenly clear!! I had to get me a new Mono amp for my subs. What I choosed was the Alpine MPR-M500, but somehow the 8'' Polk Audio db840DVC was not making the cut. so I got This one. It did took a week to break in, but when it did I was so blown away I had to get another one. This so not so lil' guys have the muscle at 4ohms. so imagine at 2ohms. great buy!!
4 out of 7 people found this helpful
Was this review helpful?    Yes | No
 
5 out of 5

POLK MM840

Written By GARRY, BATTLE CREEK, MICHIGAN on Tuesday, August 18, 2009
Crutchfield Customer Review (What's this?)
 
THE POLK MM840 IS A GREAT CHOICE FOR ANYONE NEEDING A SUB TO FIT
IN SMALLER VEHICLES OR TO JUST TAKE UP LESS CARGO SPACE. IT IS
EXTREMELY WELL BUILT AND HAS GOOD POWER HANDLING. FOR AN 8" SUB
IT PLAYS LOWER THAN A LOT OF OTHER 10" SUBS. IT DID NEED SOME
BREAKING IN TIME, BUT NOW IT IS STARTING TO SOUND BETTER THE MORE
IT IS USED. THE BASS IS REALLY ACCURATE AND TIGHT, WHICH IS WHAT I
WAS LOOKING FOR IN MY BASS OUTPUT. I PREFER THE TIGHT ACCURATE
BASS OVER THE BOOMY SOUND. I DO WISH A GRILL WOULD HAVE BEEN
INCLUDED BUT THIS IS THE ONLY COMPLAINT I HAVE WITH MY PURCHASE.
3 out of 3 people found this helpful
Was this review helpful?    Yes | No
 

Add accessories for the Polk Audio MM840

We've verified that these enclosures are a good match for this subwoofer. See all categories & accessories

Sound Ordnance™ Bass Bunker Pair of sealed 8" wedge-style enclosures (Model BB82W)
5 people say
Your Price: $59.99
Add to Cart
Sound Ordnance™ Bass Bunker Sealed single 8" subwoofer enclosure (Model BB8-35S)
9 people say
Your Price: $39.99
Add to Cart
T-Spec 16-gauge Speaker Wire Black/white jacket — priced per foot
11 people say
Your Price: $0.69
Add to Cart
T-Spec 12-gauge Speaker Wire Black/white jacket — priced per foot
25 people say
Your Price: $1.99
Add to Cart
Stinger PRO Series 16-gauge Speaker Wire Black jacket — priced per foot
44 people say
Your Price: $0.39
Add to Cart
Dynamat 19100 License Frame Kit
15 people say
Your Price: $14.99
Add to Cart
Dynamat Xtreme Wedge Pack 1 sheet, 4 square feet
6 people say
Your Price: $39.99
Add to Cart
Dynamat Xtreme Trunk Kit 5 sheets, 20 square feet
12 people say
Your Price: $169.99
Add to Cart
Dynamat Dynaliner One 54" x 32" sheet (1/8" thick)
6 people say
Your Price: $69.99
Add to Cart
Metra Box Carpet Carpet roll (54" x 5 yards) — available in 3 colors (Black)
21 people say
Your Price: $39.99
Add to Cart
Polyester Fiber Stuffing Make your subwoofer think it's in a bigger box (1-pound pack)
33 people say
Your Price: $12.99
Add to Cart
Metra Speaker Terminal Round terminal cup with binding post connectors (for do-it-yourself box builders)
13 people say
Your Price: $9.99
Add to Cart
5 people say
Your Price: $9.99
Add to Cart
3 people say
Your Price: $5.99
Add to Cart
Metra Speaker Terminal Round terminal cup with spring clip connectors (for do-it-yourself box builders)
5 people say
Your Price: $3.99
Add to Cart
Metra Speaker Terminal Square terminal cup with binding post connectors (for do-it-yourself box builders)
6 people say
Your Price: $9.99
Add to Cart
2 people say
Your Price: $9.99
Add to Cart
Metra Speaker Terminal Square terminal cup with spring clip connectors (for do-it-yourself box builders)
7 people say
Your Price: $3.99
Add to Cart

Why choose SquareTrade?

The #1-Rated Protection Plan

Thousands of people have reviewed SquareTrade Protection Plans — and made us #1.

5-Day Service Guarantee & Free Shipping

We'll repair or replace your item in five business days or less after we've received it, or your plan is free. And, as always, we pay for all shipping.

Protection from Normal, Everyday Use

Repairing your average mechanical or electrical failure can cost as much as buying a new device. With SquareTrade, you're covered — including parts and labor.

3 Year Protection Plan
3 Year Protection Plan
Your Price: $29.99
Add to Cart

For a more in-depth review and enhanced detailed information on the Polk Audio MM840, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_107MM840/Polk-Audio-MM840.html ).