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Infinity Kappa 50.9cs

5-1/4" component speaker system

Item #: 108509CS

14 Reviews

This item is no longer available.

Original Price: $299.99

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Infinity built their Kappa Series speakers with improved technology and high-end materials to provide you with outstanding sound reproduction. The Kappa 50.9cs component speaker system features 5-1/4" woofers with responsive woven glass-fiber cones that won't flex during a hard workout. The Plus One design offers a larger surface area for improved low-frequency output and efficiency, while longer voice coils add a little more punch to the bass. Large magnets keep the woofers running cooler by placing more steel close to the voice coils to act as a heat sink.

Textile dome tweeters
Infinity uses the same textile dome tweeters found in many of their popular home speakers with this Kappa system, so you'll hear the music the way it was recorded with minimal coloration or distortion. The tweeters handle down to 2,500 Hz, almost an octave below the tweeters in many systems, so you'll hear more definition and detail, no matter where you sit. Infinity includes mounting hardware to install the tweeters in custom or factory openings.

Premium crossover networks
The computer-optimized outboard crossover networks employ audiophile-grade components to separate highs and lows, so that the woofer and tweeter work together perfectly. You can attenuate tweeter response by 6 dB to get the perfect sonic balance if you've mounted the tweeters in a less-than-ideal factory location.

Pre-wired crossovers eliminate a time-consuming step in your installation, and terminals at the end of the crossover wires screw directly to the Kappa woofers and tweeters, leaving no chance for incorrect wiring.

Important Note: You should use an outboard amplifier to power these speakers.

Product Highlights:

  • 5-1/4" component speaker system includes woofers, tweeters, and crossovers
  • True Four Ohm Impedance technology: speaker's 2-ohm impedance combines with speaker wire impedance for a 4-ohm load
  • Plus One® woven-glass-fiber woofer cone with hi-roll rubber surround
  • 1" ultra-high frequency textile dome tweeter with I-Mount™ and Starfish™ for multiple mounting options
  • 2-way external crossover network with tweeter level adjustment
  • direct-connect crossover dongle
  • power range: 2-85 watts RMS (225 watts peak power)
  • frequency response: 55-35,000 Hz
  • sensitivity: 93 dB
  • woofer top-mount depth: 2-3/16"
  • warranty: 3 years
  • Our 60-day money-back guarantee

Why install component speakers?

A component speaker system gives you the best possible performance from your car audio system. A system consists of separate woofers, tweeters, and crossovers, each designed to cover one specific range of frequencies. As separate components, the woofer can move freely to deliver more powerful performance, while the tweeter can be custom-mounted in a better spot up closer to your ears, revealing a whole new world of detail. Separate crossovers are far superior to the simple filters wired into full-range speakers, so the components work together for smoother, more focused sound.

Infinity Kappa 50.9cs Reviews

Average Customer Review:

14 Reviews

Infinity Kappa 50.9cs

Written by: Anonymous from Las Vegas, NV on November 28, 2012

Crutchfield Customer Review (What's this?)

Sounds absolutely great! Exactly what you would expect from Infinity and their line of Kappas. The Crutchfield advisor recommended these speakers and I'm sure glad I purchased them, They are fantastic when it comes to the mids and highs. Not so great on the lows, but thats why you get a subwoofer. :)



2001 Silverado

Written by: Brian from Indiana on May 9, 2012

I've put a set of these in the back doors of a 2001 Silverado extended cab. I filled most of the door with batt insulation and placed dynamat on the door surface. I placed the tweeters up on the door pillars facing forward. Sony head unit, Infinity Reference 6.5 components in the front doors all powered with a JL 900/5. I wasted my money on a 5 channel amp because these puppies will pound bass!! Tweeters can be extremely bright even with the -6 db setting. I had been shopping subs but after a lengthy break in period I poured the power to all 4 speakers and could not believe the sound of mirror shaking bass coming from the rears!! Love, love, love these speakers and only regret not putting Kappa's in the front doors as well.




Written by: Mike from knoxville TN on March 7, 2012

2010 Nissan Xterra
Crutchfield Customer Review (What's this?)

Great product sounds fantastic and is very loud without any distortion. Its connected to an Alpine PDX-5 amp along with a set of coaxials. Crystal clear and a joy now to drive my ride.




Written by: Donnie from Virginia Beach on November 30, 2011

Crutchfield Customer Review (What's this?)

Replaced the factory Bose speakers. Mids and highs are crisp and sharp. In my Trailblazer SS I have an Alpine amp powering the 50.9cs in my front doors, Infinity Kappa 52.9i in the back doors and a JL Stealthbox sub in the back. Now I hear things in my music that you just couldnt hear before. FANTASTIC SOUND!



Mazda Tribute/Ford escape FRONT doors

Written by: RayD from Jacksonville, FL on July 28, 2011

2004 Mazda Tribute
Crutchfield Customer Review (What's this?)

Installed into a Mazda Tribute (same as the Ford Escape) front door panels. Let me say these are nice speakers. I just wasn't impressed with the lack of any bottom end. I'm pushing 20 clean watts, but the front of my SUV had NO BASS at all. The sub was kicking, but there was a noticeable gap. I went and put the Kappa 680.9cs in the front doors (even though the site says they won't fit- they will with a layer of Dynamat behind them and you'll still have a nice ¼ inch gap behind them!) After the change, I've VERY happy. If you need something with some bass, these are not the best choice. Maybe if you pump another 150 watts they'll come to life. The crossover is a little bulky and is a showpiece by itself. Mine is in the door and I could stand for something smaller, but it works. Again, if you want bass, the 50.9cs are not the speaker- don't waste your time if you're looking for any sort of bottom end. Nice mid sound, but NO bottom at all.



Very Nice

Written by: jeff from Mansfield, OH on June 22, 2011

I bought these for my 1998 jeep Cherokee and I cant be any happier with them. Right now they are the only speakers in my car and they produce plenty of highs and mids. Of course these speakers don't produce a thumping bass. But I didn't expect them to. The bass is just right for amount of noise that comes out of these things. You can hear every detail in the music and I don't even have them hooked up to an amp yet. I've never installed speakers before but after some research and a couple hours I had them in and working great. The mounting hardware for the tweeters were easy to install and look awesome. And infinity gives you so many bracket options for the install. I used to swivel bracket so i had to drill holes and mount the tweeters in my ceiling.. Not an easy task but the final result looked like a professional installed it. Just make sure you dont cut your holes to big and make sure you cut out your ceiling fabric outline with a razor before you use your drill,or else you'll shred the fabric. I plan on buying kappa subs and more mid speakers.



Amazing Speakers

Written by: Wesstyle from South Dakota on May 28, 2011

2000 Pontiac Grand Prix
Crutchfield Customer Review (What's this?)

These are amazing...I see some people talking the highs are TOO high which to me means your system isn't configured right and this is a user issue more than a Infinity issue. The speakers are crystal clear and the highs when matched with the right rear speakers and subs fit like a glove. I would highly suggest getting these if you have the coins to do so.



Noticeable improvement

Written by: Chris from Parachute, Co. on October 26, 2010

1999 Subaru Impreza RS
Crutchfield Customer Review (What's this?)

I didn't give these 5 stars because I haven't heard a $1000 pair of speakers, but these are very good indeed. If you like crisp highs, I.E. symbals and other percussion, you will like these. Take care in the placement of the tweeters and they will treat you well. I would suggest the use of a sub-woofer as these are a little to small to deliver bass. Jazz lovers will like these, rap and hip hop, probably not. I like them very much.



Kappa all the way

Written by: 924guy from Terre Haute, IN on April 22, 2010

Crutchfield Customer Review (What's this?)

Simply amazing speakers. The tweeters are the best I have ever heard, and are very bight and clear. The wiring is great, and easy to set up. These speakers really do get the most power out of your stereo or amp, and they can handle plenty of power. The crossovers are very nice and easy to mount. The only problems I have noticed, is they really do lack bass. The are amazing with highs and mids, but simply too small for big bass. The bass they do produce is very clear and on beat, I just suggest you add a sub or two though. Besides that not much to be said. Beware the instructions included is lacking. You must have knowledge or help to install these without problems.



Amazingly articulate sound

Written by: myfloridasun from New Port Richey, FL on April 5, 2010

1993 Dodge Spirit
Crutchfield Customer Review (What's this?)

The most sensitive (which means I don't need an amplifier, as power is not wasted to drive them), clear, articulate, spatially accurate speakers I've ever heard. Breath of saxophones, brushes on snares; you can even hear where on the cymbals the drumsticks are hitting. Heck, you can almost see where the band members are standing on the stage (but don't close your eyes while driving). One caution--don't lose the tiny 1-mm or so, hex key for the tweeters, like I did, in case you have to readjust the wires to the crossover. It's a little thicker than a human hair. So don't put it on anything black, or it disappears. These speakers are worth it, as you'll save the price of an amplifier, if paired with a decent head unit like Sony CDX-GT540UI or Kenwood KDC-MP345U.



Infinity Kappa 50.9cs

Written by: Hassel from Aurora, Kentucky on November 22, 2009

I love these speakers. they were a vast improvment over my stock speakers....i have an Cadillac CTS with the bose system and i wanted more out of it so i first added these to my front doors and there little brother 2 ways to the back and was amazed! on a 4 channel alpine off a alpine deck they sound nothing short of amazing! I am hearing suddle hints and decresendos in songs i never knew exhisted. They do have to be amped to get the full force, but they are great for the price. and paired up with the right amp will sound great in any car!



2-ohm is the way to go!

Written by: KiLaHuRtZ from Essexville, MI on May 31, 2009

2008 Chevrolet Silverado
Crutchfield Customer Review (What's this?)

I purchased two sets of these for my 2008 extended cab Silverado. Powered them with an Alpine MRP-F300. With the correct tweeter placement, the sound-stage is the exceptional! For the rears, I flush mounted the tweeters up in the top of the rear door pillars. The fronts are surface mounted on the front door sails. I even surface mounted the crossovers on the doors so you can adjust the 6dB attenuation with ease. The sound feels so much richer and clearer than with my old coaxials. The two ohm feature is a must! I cannot believe that other manufactures are not following this trend. I was sceptical at first, but I took a reading at the crossovers and it was about 2.3 ohms. Took another reading at the output lines from the amp and it was 3.8 ohms. The sheer length was causing a 1.5 ohm drop in the wire! And this is in a truck, not a very long run at all. This got me thinking, with 4 ohm speakers, your amp is probably seeing more like 8 ohms. I could not believe my eyes. The last thing I want to do is run 14 or thicker 12 gauge wire in place of the factory harness. Too much work tearing everything apart. In summation, I loves these components and would recommend them to anyone looking for quality sound without breaking the bank.



02 Acura TL Type S

Written by: superputter from Minnesota on June 24, 2008

Be prepared for some serious highs! The tweeters are massive and are extremely shrill and overpowering. I have the dB set to the -6 setting and the treble on the HU turned almost all the way down and they are still overpowering. I am going to put in an 4x100 amp to hopefully bring the mids and lows into balance, but if you're not amping these things be prepared for some ear pain....

By the way, the tweeters don't mount "flush". They still stick out 3/4", but they do tilt and install is pretty easy if you have the space. It was tricky in my car (I had to surface mount in the front) but it can be done in the back seats. When surface installed, they are quite large so make sure you can put them somewhere out of the way.



Infinity Kappa 50.9cs

Written by: carlsonwa from Wisconsin on May 30, 2008

Just installed a pair of these in my buddies car....Overall a very nice speaker
now that they switched them to a 2 ohm speaker, matched them up with
the 754a 4 channel Infinity amp. Only 1 complaint, the tweeters are huge,
nearly impossible to fit in a factory tweeter location, diameter is
substantially larger and depth too than my kappa perfects. .....Make sure
you get the measurements before installing/purchasing, unless you plan on
cutting holes.



Hands-on research

What's in the box?

Download owner's manual

  • 2 Woofers
  • 2 Grilles
  • 2 Grille rings
  • 2 Crossovers
  • 2 Tweeters
  • 2 Flush-mount cups
  • 2 Threaded flush-mount adapters
  • 2 Plastic locking nuts
  • 2 Surface-mount cups
  • 2 Starfish tweeter mounts
  • Twelve 1" Self-tapping screws
  • Six 5/8" Self-tapping screws
  • Six 3/8" Flat head screws
  • Two M4 x 10mm Machine screws
  • 4 Washers
  • 12 Speed clips
  • 1mm Allen wrench
  • 2 Adhesive backed foam gaskets
  • Instructions
  • Warranty information

Product Research


Plus One Woofer Cones: The Plus One speakers use cones more surface area than other speakers of the same size. This is accomplished by using a new basket design and hi-roll surround. The Plus One design offers greater bass output and a significant increase in efficiency.

Woven Glass Fiber Woofer Cones: This woven-glass-fiber material is very light and extremely stiff, minimizing cone flex. This results in very low distortion and improved clarity. The woofers have set screw input terminals that will accept up to 10 gauge bare wire.

Edge Driven UHF Dome Tweeters: Each speaker has an Edge-driven UHF dome tweeter. The benefit is increased power handling and reduced distortion at high output. This technology also allows for better integration with the mid/woofer. The tweeter wire terminals are set screws, tightened using the included 1mm Allen wrench; they accept bare wire up to 14 gauge.

High-Output Design: The high output 2-ohm voice coil design compensates for the high in-line resistance of small gauge factory wiring and extracts every watt from factory receivers, increasing overall system output and efficiency (relative to 4 ohm speakers). The speaker's 2.0-ohm impedance combined with the impedance of your speaker wire provides a true 4-ohm load to your connected headunit or amplifier. The speakers also benefit from increased power when you upgrade the wire and add aftermarket amplifiers, designed to power a 2-ohm load.

Crossovers: Kappa speakers include computer-optimized, voice-matched crossovers, using audiophile quality air core inductors and polypropylene capacitors. The crossover slope is 18 dB/octave. Each crossover has a tweeter output switch; choose between flat and -6dB.

Crossover Connections: Each crossover has set screw input and output terminals that will accept up to 10 gauge bare wire.

Crossover Dimensions:

  • Length: 4-3/4"
  • Width: 3-1/2"
  • Height: 1-3/8"

Tweeter Mounting: The I-Mount tweeter mounting system and Starfish mounting brackets give you several different ways to mount the tweeters:

  • I-Mount Tweeter Mounting System: The tweeters can be surface or flush mounted with Infinity's innovative I-Mount system:
    • Surface Mount: Surface mounting the tweeters involves screwing the surface-mount cup to the mounting location, then inserting and locking the tweeter into the cup.
    • Flush Mount: Flush mounting is made easy through the use of the threaded flush-mount adapter and plastic locking nut. Once a cutout is made, the flush-mount adapter (with the tweeter installed) is inserted into the hole. The large plastic locking nut is threaded onto the adapter (from behind the mounting surface) to hold the complete assembly securely in place. When flush mounted, the tweeters may be angled for optimum response and imaging.
  • Starfish Mounting Brackets: The Starfish mounting brackets allow the tweeters to be installed in factory locations behind the grilles:
    • Surface Mount (behind grille panel): Once the Starfish bracket is trimmed, it is screwed to the mounting surface behind the grille panel. Then, the tweeter is inserted into the bracket and locked into place.
    • Flush Mount (behind grille panel): Once the Starfish bracket is trimmed, it is dropped into the cutout in the mounting surface behind the grille panel. Then, the tweeter is inserted into the bracket and locked into place.
    • Bottom Mount (to grille panel): Once the Starfish bracket is trimmed, it is secured to the underside of the grille panel. The tweeter must be inserted into the bracket and locked into place before the bracket is mounted.
    • Flush Mount (in-dash location): Once the Starfish bracket is trimmed, it is dropped into the cutout in the dash. Then, the tweeter is inserted into the bracket and locked into place.

Tweeter Mounting Dimensions:

  I-Mount Surface Mount I-Mount Flush Mount Starfish Surface Mount (behind grille panel) Starfish Flush Mount (behind grille panel) Starfish Bottom Mount (to grille panel) Starfish Flush Mount (in-dash location)
Mounting Height 1.316" 0.693" 1.328" 0.624" N/A 0.624"
Depth 0.552" (screw depth) 1.311" 0.552" (screw depth) 0.692" 1.370" 0.692"
Frame Diameter 2.216" 2.855" 2.221" 2.221" 2.221" 2.221"
Cutout Diameter N/A 2.360" N/A 2.221" N/A 2.221"

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.

Product reviews from the Crutchfield Labs

Video: Infinity Kappa car speakers
by Robert Ferency-Viars

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