Skip Navigation

Infinity 120.9w

Kappa Series 12" subwoofer with selectable 2- or 4-ohm impedance

Item #: 1081209W

Low Stock

7 Reviews | 4 questions - 5 answers

Your price: $249.99 Earn up to 250 Rewards points

Add to Cart

+ Add to wishlist + Email me alerts for this product

Scratch & Dent: $212.49

View all associated offers

Infinity Kappa subwoofers combine great-sounding bass with the wiring versatility you need to build a system that can expand to meet your changing needs. And these enhanced woofers feature superior construction that makes the thump come easy.

The Kappa 120.9w 12" subwoofer features Infinity's unique Selectable Smart Impedance design, which lets you build exactly the system you want — high-power or multi-sub — without complicated wiring. Just flip the convenient impedance switch to safely choose between 2 or 4 ohms. If you're thinking about upgrading your amplifier or adding another sub down the line, this sub makes it easy to reconfigure — and it's nearly impossible to wire incorrectly.

This sub handles plenty of power and sounds great in sealed and ported enclosures, too. The coated glass-fiber cone offers remarkable rigidity that minimizes distortion, while the thick rubber surround promotes smooth excursion. Add the hefty cast aluminum basket to the mix and you've got proven delivery system for potent low end.

To drive this single subwoofer, we recommend a mono amplifier rated between 260 and 525 watts RMS at 2 ohms. For more information, please refer to our article on How to Match Subwoofers and Amplifiers.

Product Highlights:

  • 12" subwoofer with selectable 2- or 4-ohm impedance
  • coated glass-fiber cone with rubber surround
  • cast aluminum basket
  • frequency response: 23-400 Hz
  • power range: 50-350 watts RMS (1,400 watts peak power)
  • sensitivity: 91 dB
  • top-mount depth: 6-3/8"
  • sealed box volume: 1.0 cu. ft.
  • ported box volume: 2.0 cu. ft.
  • warranty: 3 years
  • Our 60-day money-back guarantee

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.

Infinity 120.9w Reviews

Average Customer Review:

7 Reviews

Whoa! Wow!

Written by: Tracy from Twin Cities area, MN on October 9, 2013

  • "Coolness Factor"
  • Build Quality
  • Ease of Use
  • Sound Quality
  • Value

Upgraded from an entry-level 8-inch sub. WOW! I never knew what I was missing! What a difference moving up to this 12-inch sub! I finally have the boom I always wanted (but never got with the smaller 8-inch sub). Powered by a five-channel Alpine amp that matches perfectly with this sub's 2-ohm setting, i.e., 350 watts. This sub is a dream!

Pros: Awesome boom that you can feel!

Cons: None!


Written by: JuJuBee from Gloversville NY on December 2, 2011

  • "Coolness Factor"
  • Build Quality
  • Ease of Use
  • Sound Quality
  • Value

I bought these to replace my 2, 12 inch Blaupunkts that I blew apart after 6 years. I bought 2 and paired it with a 3.5 cap and a CL-1200 Amp. Im pushing a clean 450 watts by 2 at a constant 14 volts ( Hi output alt + Big 3 )and all I can say is WoW! When pushing these things will make my doors bow out from the pressure. It is insane. You will not be disappointed. These are true Infinity's in terms of the pure quality of the sound. I was hoping they dropped down to 20Hz but unfortunatly they dont and that is the only drawback. Everything from 25 and up is reproduced in a soundwave that is clean and powerful.

Put them in a ported box. Give them at least 1.5 cu ft per speaker and get ready for the ride of your life. Also you should save your money as you will get a ticket,I have three times and it has been less than 6 months!

Pros: Quality Sensitivity Clean Accurate Sound

Cons: 2ohm-4ohm Switch can move ( I Fear ) when the bass is thumping Lowest it will hit is 25Hz


Written by: Zane from Mattoon, IL on August 2, 2011

You will not be disappointed, guaranteed. I purchased just one of these to begin with, then I loved it so much I got another one. Infinity may not be known for their subs, but these will help change that. I currently running two of these on the Infinity Kappa One amp in a Sound Ordanance dual ported box. They are getting 400 watts RMS each and they handle it just fine. These subs sound absolutely amazing. Keep in mind they are SQ subs, not SPL; however they do bring the punch! Trust me. If you are looking for a sub that is hi-fidelity and hits hard, then this sub is for you.




Written by: Sam from Charlottesville, Va on September 29, 2010

I bought this sub to replace my Alpine Type-S 12inch DVC 4ohm. The Alpine wasn't blown, I just wanted a better speaker, and this thing is definitely it. It is cleaner and deeper sounding than the type-s for sure. It will hit the low frequencies in bass drops that I couldn't even hear with my old sub. I've been pushing it with a alpine m450, which is 400 watts at 2 ohms and it is plenty for sure, but it's maxed out. So I went ahead and ordered one of the new Alpine pdx-m6 600 watt amps just to have a little more head room, which I don't think I need anymore now that the sub has broken in completely. Oh well, maybe it will be even cleaner sounding. Ah... also make sure your box is decent. I thought I had blown my new sub last night because it was putting off a "blown speaker" sound, but in reality, it had blown the seals on my box that I bought from Crutchfield three years ago, and was rattling the boards against each other. Guess what I'll be buying tonight...



You Better Believe It

Written by: homerkang from Atlanta, GA on April 18, 2010

i am now a believer in Infinity car subs. About 3 years ago, i bought my first sub (see my review here: It was one of the best subs ever made. Then recently it got worn down or something, but it started to distort no matter what adjustments i made on the rest of my system. At first, i kinda doubted it, but then i decided to give this Kappa model a try coz it looked good (lol) and ordered it from here. It came 2 days later. i put it in my ported box. Set the switchable impedance switch to 2 ohms so that it can absorb about 500 watts RMS, set my amp's ISF filter to 25Hz. And waited it out during its break in period. After a week of sounding like nothing, it now sounds as good as the Boston that i had. Although it falls short of the lower bass notes than the Boston (since this one only goes down to 23 Hz compared to the Boston's 20 Hz), i can live with that because it not only sounds clean and clear, it actually makes my Polk dB6501 components sound cleaner as well. Get this sub. For the price, it is THAT good.



Sweet sound

Written by: KenM10759 from Spencer MA on April 11, 2010

Crutchfield Customer Review (What's this?)

Just added this to complete a system that includes (4) Infinity Kappa 682.9cs speakers, a Kenwood KDC-MP345U CD receiver and an Infinity Kappa 5 amplifier. Not looking for a hard-hitting, overwhelming bass, this subwoofer in it's recommended sealed 1.0 cu. ft. box is amazing. Smooth, sweet sounds without flatulence, true quality construction and great looks. The combination of the smaller speakers and amp with this sub is a near-perfect! For the combined system's price point, I cannot imagine better sound quality.



Infinity 120.9w

Written by: Dennis from Louisa, VA on October 17, 2009

Crutchfield Customer Review (What's this?)

Looks good, sounds great, good price. It gets loud and low with accuracy in the recommended sealed box.



Hands-on research

What's in the box?

Download owner's manual

  • One 12" Woofer
  • Self-adhesive foam gasket
  • 3mm Allen wrench
  • Owner's manual (English/ French/ Spanish/ eleven other languages)
  • Technical data sheet
  • Warranty and on-line product registration information

Product Research

Enclosure Compatibility


Selectable Impedance: For increased system flexibility, the woofer impedance is switchable. There is a 2 ohm/4ohm switch above the wire terminals, this provides easy configuration of the voice coil. The power handling is the same for either setting; 350 watts RMS/1400 watts peak.

Woven Glass-Fiber Cone: The cone material is extremely stiff, minimizing cone flex; this results in very low distortion and improved clarity.

Vented Polepiece: Venting the polepiece reduces air compression under the dustcap which minimizes mechanical noise and provides more constant mechanical Q for reduced distortion.

Terminal: The set screw wire terminals will accept bare wire up to 8 gauge.

Enclosure Compatibility

Sealed Box: Infinity recommends a sealed enclosure with an internal volume of 1.0 cu/ft.

Ported Box: Infinity recommends a ported enclosure with an internal volume of 2.0 cu/ft with one 4" diameter x 13.625" long port. This equates to a tuning frequency of 30 Hz. They also recommend using a sub-sonic filter.

Sealed Bandpass Box: When using a bandpass enclosure Infinity recommends a sealed rear chamber volume of 1.0 cu/ft and a ported front chamber volume of 1.0 cu/ft with a 4" diameter x 6.625" long port. This equates to a tuning frequency of 60 Hz. They also recommend using a sub-sonic filter.

Free-air Mounting: In addition to being compatible with sealed, ported, and bandpass enclosures, the woofer can be used in free-air applications. A free-air subwoofer is designed to be mounted on a baffle board, which separates the front of the speaker from the back. For instance, you could mount this woofer to a board attached to the rear deck or placed in the trunk against the rear seat. The trunk acts as the enclosure housing the subwoofer. Because there is no specific volume of air to stiffen the suspension, the free-air power handling is approximately half that of the woofer in a box, in this case 175 watts RMS.


Thiele-Small Parameters: Because the woofer has two impedance settings, there are two sets of Thiele-Small parameters:

DC Resistance (Ω) 2.1 4.3
Inductance (mH) 1.18 1.18
Vas (liters) 54.43 54.43
Qms 4.38 2.47
Qes 0.51 0.52
Qts 0.46 0.43
Fs (Hz) 27.2 27.2
Radiating Area (m²) 0.05188 0.05188
Xmax (mm) 17.5 17.5
Motor Force Factor (TM) 12.47 18.37

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.

Customer Q&A

4 questions already asked

It will stick out 0.75" past the mounting surface. [ Paul  Dec 09, 2015 ]  Staff
That amp can power this subwoofer and you shouldn't have to run the amp at full output either. [ Paul  Dec 06, 2015 ]  Staff
Thanks, Jeff. Yes, that worked. I tightened up all the connections, and it works great now! No more cutting in and out. Sub is A W E S O M E !!!!!! [ Tracy  Jan 01, 2014 ]
This sounds like a loose connection somewhere inside the box. I would recommend checking that wiring first. [ Jeff  Dec 27, 2013 ]  Staff