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Polk Audio MM1240D

Mobile Monitor Series 12" sub with dual 4-ohm voice coils

7 Reviews | 2 questions - 4 answers

Item # 107MM1240D

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Our take on the Polk Audio MM1240D

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.

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 MM1240D 12" dual voice coil subwoofer handles up to 425 watts RMS. A copper voice coil and neodymium magnet motor drives 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 sub hits solidly without distorting. The dual 4-ohm voice coils offer options for wiring a multi-sub system or drawing maximum power from your mono amplifier.

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

Priced per speaker

Product Highlights:

  • 12" subwoofer with dual 4-ohm voice coils
  • polymer cone with butyl rubber surround
  • carbon composite basket
  • certified for marine use
  • optional matching grille complements the basket design
  • power range: 100-425 watts RMS (212 watts RMS per coil)
  • peak power handling: 800 watts
  • frequency response: 27-200 Hz
  • sensitivity: 88 dB
  • top-mount depth: 4-11/16"
  • sealed box volume: 0.88 cubic feet
  • warranty: 1 year
  • Our 60-day money-back guarantee

What's in the Box:

  • One 12" Dual 4-ohm voice coil subwoofer
  • Foam gasket
  • 8 Mounting screws
  • 8 Speed-clips
  • Owner's Manual
  • Product Registration Information sheet

Great sub for the price. Perfect addition to our boat. Great sound, highly recommed.

Anonymous, Columbus, OH


Polk Audio MM1240D Reviews

Average Customer Review(s):

(7 Reviews)

Polk Audio MM1240D

Anonymous from Columbus, OH on 4/30/2017

Crutchfield Customer Review (What's this?)

Great sub for the price. Perfect addition to our boat. Great sound, highly recommed.

Pros: Great price. Sounds great.

Cons: Nothing yet.

Great sub for our boat!!

Pat from Spartanburg, SC on 6/21/2016

Crutchfield Customer Review (What's this?)

This is an awesome sub. I installed it our boat within an airtight enclosure powered by a Kenwood KAC-M8005 amp pushing 500 watts RMS at 2ohms. It sounds amazing! I love it.

Pros: Reasonably priced, well constructed and looks great! Buy the matching grill, it's a must.

Cons: None as this time.

Great Sub

K N from Cincinnati, OH on 6/15/2013

Crutchfield Customer Review (What's this?)

Packs a lot of punch. Still need to tweek, but so far very tight sounding.

Pros: Well built


Polk 1240 DVC

Nathan from Minot, ND on 12/16/2012

Crutchfield Customer Review (What's this?)

If you are on the market for a subwoofer that plays flawlessly in all fields then look no further! I installed two of these in my 2007 impala paired with the Polk PA 1200.1, words cannot describe how these things can preform! They literally rattled my rear view mirror off the windshield! The sound quality of these subwoofers is absolutely superb, I have owned and heard many other brands but none of them have came even close to Polk as far as price and quality. Before you buy you need to make sure that the box you are using is exactly the size that polk recommends on their website, I have made this mistake and sacrificed a lot of sound quality. Also, please be prepared these subwoofers are very power hungry i was feeding them nearly 600 watts each, that being said look into a dry cell battery or a higher output alternator because you will need it if you plan on using more then one of these! The bottom line, you cannot go wrong with this product!

Pros: Loud, very good sound quality, hits very good lows

Cons: Very power hungry

Stop looking now, and buy the Polk Audio MM1240D!!!!

KennyE from Stapleton, NE on 6/5/2012

Crutchfield Customer Review (What's this?)

I spent 17 years in audio electronics retail in my younger years and have heard and installed hundreds of different subs over that time. I purchased the Polk Audio MM1240D for my daughter's Blazer. She wanted subs but didn't want the cargo area cluttered with a large enclosure. I've used RF, Kenwood and JL drivers in the past, but couldn't find a 12" sub that would work in a small sealed box that fit the budget. After doing a LOT of research, I decided to try the Polk. I am familiar with the brand, but never have I owned or sold it. Recomended enclosure size is .88 cu/ft, which worked great in the custom fiberglass enclosure I built for the passenger rear corner of the cargo area. I purchased a Kenwood KAC-8105 digital mono amplifier to drive the single sub. Rated power handling for the Polk is just under 400w/rms and the Kenwood amp is rated @ 400w/rms into a 2 ohm load. Wired the dual, 4 ohm voice coils in parallel for a 2 ohm load, perfect match to the amp. Once I completed construction of the enclosure and had everything installed, the sound quality REALLY impressed me. It has a long excursion which allows it to operate well in the sealed box. Bass was hard and tight with 80's rock and country music that I prefer, but also handled the mind numbing hip hop and rap crap my daughter listens to. Two of these with a pair of these amps would be unreal! Crutchfield offers this at a discounted price which makes it a bargain. I would recommend this to anyone.

Pros: No-nonsense design, no huge plastic crap around a tiny magnet structure like so many manufacturers have today, quality wire terminals and comes with a substantial gasket to seal to the box. SMALL sealed enclosure size. Shallow mounting depth. Sounds FANTASTIC!!! I pushed this thing as hard as I could and never once did it complain.

Cons: Bought the matching Polk speaker grill and wasn't crazy about the way it fit. It doesn't fit down over the basket rim as I had expected it would. Leaves a 1/4" gap between the grill and the enclosure. Nothing to dislike about the woofer!

These subs hit hard!

SethS from Billings, MT on 4/14/2012

Crutchfield Customer Review (What's this?)

These subs hit extremely hard. I've heard a lot of different subs and different configurations but just bought two of these and have them hooked up to an infinity kappa one amp and it just blows things away. I was a little skeptical about the price at first but I will now only buy polk audio speakers as they are amazing quality for an amazing price.

Pros: Amazing quality at an extremely affordable price.

Cons: Wish they came with the grill in the picture.

Amazing sub

Chris P from Columbus, OH on 11/6/2011

Crutchfield Customer Review (What's this?)

I have the sub in a .9 cu ft. (after displacement) and filled the box about 1/3 of the way with poly fill. The result is amazing punch and clarity complemented by surprising low end extension. It hits cleaner and lower than my previous db112 (ported). Sub hasn't even been broken in fully and it totally impresses me. I am only giving it 300W for now, but I will be upgrading to the Alpine MRX to give it 500W RMS soon.

Pros: Great punch, awesome low end extension.



Hands-on research

Product Research

Enclosure Compatibility


Klippel Optimized: Using a state-of-the-art Klippel Distortion Analyzer, Polk engineers were able to optimize the woofer's motor structure, voice coil alignment and suspension for the best possible performance, even at extreme listening levels.

Polymer Woofer Cone with Butyl Rubber Surrounds: The Polymer Woofer Cones and Butyl Rubber Surrounds will not break down over time and will survive the rigors of harsh automotive environments.

High Temperature Copper Voice Coil (50mm) and Polyamide Former: High Temperature 50mm Copper Voice Coil and Polyamide Former withstand the most rigorous use while maintaining extremely low distortion for bass punch and output.

Dual 4-ohm Voice Coils: This woofer features dual 4-ohm voice coils that offer wiring flexibility. When the voice coils are wired in parallel, the woofer presents a 2-ohm load. When wired in series, the woofer presents an 8-ohm load.

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

Nickel Plated Heavy Duty Input Terminals: Nickel plated heavy duty input spring-post terminals accommodate speaker wire up to 8 AWG or twisted pairs of 12 AWG.

Preconditioning Period: Mobile Monitor subwoofers will achieve even greater performance once they are thoroughly broken in. To break in your new MM subwoofer, play 20 to 30 hours of music at moderate levels.

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.

Enclosure Compatibility

Recommended Sealed Box Volume: Polk recommends mounting this woofer in a sealed enclosure made out of 3/4" MDF with an internal volume of 0.88 cu/ft.

Recommended Ported Box Volume: Polk recommends a ported enclosure made out of 3/4" MDF with an ideal internal volume of 1.58 cu/ft using a slot port measuring 13.5" wide x 1.5" tall x 18.5" deep.

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

Crutchfield asked  
Why did you buy this?

one of the best in the market [ bruno  Feb 06, 2017 ]
It match all of my speakers that are currently in my boat as well as good power handling capabilities [ norman  Aug 01, 2016 ]
This is the perfect sub for under rear truck seat installation without having to buy a shallow mount sub. [ Curtis  Apr 29, 2016 ]

2 questions already asked

Ideally you'd want to leave some space between the back of the subwoofer and the enclosure in order to allow airflow to the coils and magnet; even as little as 0.5" of space can be helpful in that regard. The Polk MM1240D also has a mounting height of 0.9" without the grille. However, I'm afraid we don't have any mounting height specs listed when the grille is added. You may want to reach out to Polk directly in order to find that out--you can check their support website ( or call them at 800-377-7655 for more info. [ Larry  Mar 19, 2017 ]  Staff
If you made your box 17 in wide and 18 inch long and 5 inch deep , the speaker is 4.5 deep, you would have .8845 cu.ft . displacement . [ STEVEN  Mar 03, 2017 ]
Polk actually recommends .88 cu.ft. internal displacement. [ STEVEN  Mar 03, 2017 ]
ITs specs are in the owners manual and available online for free [ bruno  Mar 01, 2017 ]