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Infinity Kappa 63.9i

6-3/4" 3-way car speakers — for 6-1/2" and 6-3/4" openings

4 Reviews

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Item # 108639I

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Our take on the Infinity Kappa 63.9i

Infinity built the latest Kappa speakers with improved technology and high-end materials to provide you with outstanding sound reproduction. The Kappa 63.9i 6-3/4" 3-way speakers feature light, but stiff woven glass-fiber woofer cones that won't flex or distort. The Plus One design offers a larger surface area for improved low-frequency output and efficiency, while longer voice coils produce tighter, snappier bass. Large magnets keep the woofers running cooler by placing more steel close to the voice coils to act as a heat sink.

Infinity built the latest Kappa speakers with improved technology and high-end materials to provide you with outstanding sound reproduction. The Kappa 63.9i 6-3/4" 3-way speakers feature light, but stiff woven glass-fiber woofer cones that won't flex or distort. The Plus One design offers a larger surface area for improved low-frequency output and efficiency, while longer voice coils produce tighter, snappier bass. Large magnets keep the woofers running cooler by placing more steel close to the voice coils to act as a heat sink.

Infinity uses the same Metal Matrix Diaphragm tweeter found in many of their popular home speakers, so you'll hear the music the way it was recorded with minimal coloration or distortion. A super-tweeter tops off the musical spectrum by broadcasting the extreme high frequencies.

The computer-optimized outboard crossover networks employ audiophile-grade components to separate highs and lows, so that the woofer and tweeters work together perfectly. Pre-wired crossovers eliminate a time-consuming step in your installation, and terminals at the end of the crossover wires screw directly to the speakers, leaving no chance for incorrect wiring.

Note: Infinity describes this model as a 6-1/2" speaker. Most manufacturers designate this same frame size as a 6-3/4" speaker. For simplicity's sake we list it as a 6-3/4" speaker.

Installation Note: These Infinity speakers do not include screws or speed clips. You may be able to use the factory screws to install them, but it's always a good idea to have an assortment of self-tapping screws (5/8" to 1") and speed-clips on hand. These speakers don't use a standard 6-1/2" speaker bolt pattern — you'll have to drill new screw holes in either your vehicle or the included bracket in order to mount them in 6-1/2" speaker openings.

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

Product Highlights:

  • 3-way 6-3/4" speakers (pair)
  • fit 6-1/2" openings with modification
  • 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" edge-driven M.M.D.® dome tweeter
  • edge-driven UHF (ultra-high frequency) super-tweeter
  • computer-optimized outboard crossover with tweeter level control
  • direct-connect crossover dongle
  • power range: 2-75 watts RMS (225 watts peak power)
  • frequency response: 45-30,000 Hz
  • sensitivity: 95 dB
  • top-mount depth: 2-5/16"
  • warranty: 3 years
  • Our 60-day money-back guarantee

What's in the Box:

  • Two 3-way speakers
  • 2 Grilles
  • 2 Grille rings
  • 2 In-line crossovers (attached)
  • 2 Plastic 6-3/4" adapter brackets (includes GM/Chrysler 6-3/4G)
  • 2 Metal 6-1/2" adapter rings
  • 8 Machine screws
  • 2 Adhesive backed foam gaskets
  • Instructions
  • Warranty information

Featured Video:


Infinity Kappa 63.9i Reviews

Average Customer Review(s):

(4 Reviews)


saturnsl1 from san jose california on 5/27/2011

I have been out of car audio for a year and am starting over a 3rd system. I saw these things and liked the design and have always like infinity car and home audio. I was worried about power handling and I really needed a coaxial mount component for the kick panels because i get a center channel with the aiming of the tweeter. I was surprised seeing an outboard xover that was built in. I am very picky with car audio but these things rock, however they are not suitable for kick panels unless bigger then .25 cu ft. WHY...I need to vent the kicks. They just dont move in there and cannot breath. They have more mids then anything and dont think the super tweeter makes that much of a difference. I am giving them about a 100 watts a side rms. The power handling is great and are accurate and have lots of vocal and detailed highs, well built and great for the money. They are really built for right out of the box hooked up to your deck. They dont need an amp to sound well yet more power will brighten up any driver. I like the -3db button, this is a diff maker. The angle tweeters are meant for doors but you can mount with them up or down. I had them up and sound was hitting the dash because my former componets tweet were in the middle at no angle. The way my kicks are setup and i need them facing alittle down. you need to use the speaker mount to get the grill to stay on. overall i would recommend to anyone



Infinity Kappa 63.9i

Josh from Des Moines, IA on 4/21/2011

Have these installed in the rear doors of a 2000 Subaru Outback. Much easier install than the components in the front doors (Kappa 60.9cs, I posted a review on those as well). All that was needed was an adapter ring to compensate for the fact that these have a 4-bolt pattern, and the car has a 3-bolt pattern. No problems with depth/clearance. Well, aside from the fact that the adapter ring I got was too thick and had to be trimmed down. That's not the speaker's or Crutchfield's issue though. Sound is phenomenal. I've loved the sound of Kappas since I had a set of the older CMMD units (different car; sadly they wouldn't fit in the Subie). I was skeptical when they changed driver materials but these don't seem to have lost anything. The dexterity of these drivers is impressive, you can hear quick oscillations in notes that aren't detectable through lesser speakers. You really start to appreciate the artistry of the musicians more. And isn't that the point, really?



Oustanding Speakers - Some Installation Issues

Christopher from Syracuse, IN on 12/25/2010

These speakers were a perfect replacement for my 2004 Dakota door speakers. So far these have handled every type of music (i.e. hip hop, rock etc) that I have thrown at them. I'm not a huge stereophile so I can't provide all the technical details but they just sound good no matter what type of music you listen to. Installation: 2004 Dakota very easy, remove 5 screws on the door panel, lift up on the panel and it pops right off. Remove 3 connectors and the two rods for the door handle and lock and the panel is free. Remove 3 screws from the speaker and pry the whole assembly off (it's a little sticky from sealant). Attach the plastic bracket to the speaker provided with the speakers placing some foam provided in between the speaker and bracket. Attach some more foam provided on back of bracket and attach the speaker to the door after connecting wires. Replace the door panel and you are done. It really was pretty easy as installations go.



Awsome upgrade!

Stephen from Chicago, IL on 8/5/2008

Crutchfield Customer Review (What's this?)

I upgraded my factory 2006 GMC Envoy speakers with these Kappa 63.9i, and Referrence 6022si in the rear. What an improvement! Crisp highs, and full mids, and much more bass and volume that I had before...with the same facory radio. Crutchfield said the Kappa's would not fit, and I understand why...because of the dongle/crossover. I checked Infinity's website and saw that these were the same dimentions as the 6022si's....and took the chance. I had to modify my mounting to accomodate the dongle, but 20 minutes later (each) they were installed...I put the dongle under the door panel (away from the sliding window which would have crushed it had I left it in the door cavity). The rears took 15 mins without modifications. Crutchfield's illustrated instructions and the included wire adaptors made the install a snap.




Hands-on research

Features and Specs

Speaker Size
Design 3-way
Tweeter Design Dome
Impedance (Ohms) 2
Tweeter Composition UHF
Woofer Composition Woven-glass fiber
Woofer Surround Hi-roll rubber
Parts Warranty 3 Years
Labor Warranty 3 Years
Sensitivity (1W at 1 meter) N/A
Sensitivity at 2.83 volts 94.7
Frequency Response 45 - 30k Hz
Minimum RMS Wattage 2
Maximum RMS Wattage 75
Peak Power Handling (Watts) 225
Top-mount Depth (Inches) 2 5/16
Bottom-mount Depth (Inches) N/A
Cutout Diameter or Length (inches) 5 1/8

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.

Woofer Size: This speaker is marketed as a 6-1/2"; they will fit in standard 6-1/2" speaker openings, but do not use the standard 6-1/2" speaker bolt pattern. In order to install them in standard 6-1/2" speaker openings you must drill new screw holes. If new holes are drilled in the mounting surface of the car, no bracket need be used. If drilling in the car is not an option, the flange on the included metal bracket is wide enough to accommodate new holes being drilled; either in a standard 6-1/2" three hole pattern or a Ford non-symmetric four hole pattern. When using the bracket the depth becomes 2.136" and the mounting height becomes 1.360".

Edge Driven MMD Dome Midrange: Each speaker has an Edge-driven MMD (Metal Matrix Diaphragm) dome midrange. The benefit is increased power handling and reduced distortion at high output. This technology also allows for better integration with the woofer.

UHF Tweeter: Ultra-wideband UHF soft-dome tweeters are used to ensure response to 30kHz. The tweeter has an adjustable output level, +0 dB (flat) and -3 dB.

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 12 dB/octave.

Crossover Connections: Each crossover is connected to the speaker by a 6" wire. The input terminals are set screws that will accept up to 10 gauge bare wire.

Crossover Dimensions:

  • Length: 3-1/16"
  • Width: 1-1/4"
  • Height: 1-3/16"

Intermount III: Infinity's Intermount III mounting system allows the 63.9i speakers to fit a variety of 6-1/2" (with modification) and 6-3/4" applications. Two adapter rings are included for each speaker.

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.

Staff Reviews

Product reviews from the Crutchfield Labs

Video: Infinity Kappa car speakers
by Robert Ferency-Viars

Infinity Kappa is Infinity's high-performance line of car speakers. They're designed and built to give you excellent sound, especially in an amplified system.

What are the Labs?