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

Why replace your factory speakers?

The speakers that originally came in your car were made from inexpensive materials, designed to create acceptable sound at the lowest possible cost to the manufacturer. If you love music, you deserve better. Name-brand aftermarket speakers deliver fuller, richer sound with considerably more detail and nuance, and they're capable of playing louder and cleaner than factory speakers. Connect new speakers to your factory radio and you'll get the best possible sound from your dealer-equipped system. Pair them up with a new car stereo for a level of enjoyment that can rival a high-fidelity home audio experience.

Hands-on research

What's in the box?

Download owner's manual

  • 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

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 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.

Infinity Kappa 63.9i Reviews

Average Customer Review:

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Written By saturnsl1, san jose california on Friday, May 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

Written By Josh, Des Moines, IA on Thursday, April 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

Written By Christopher, Syracuse, IN on Saturday, December 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!

Written By Stephen, Chicago, IL on Tuesday, August 05, 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.

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. Watch as our experts show you why...

What are the Labs?

Get everything you’ll need to enjoy your new Infinity Kappa 63.9i

Reduce ambient road noise and your vehicle's "rattles," for better sound inside your car.
You'll need speaker wire to connect your speakers to your amp.
Keep your speakers clean and dry. They compress to fit behind your speakers.
These speaker connectors are handy if you're running new speaker wire or if your speakers have oversized terminals.
The right tools will help keep your installation simple and clean.
Dynamat 10415 Xtreme Speaker Kit

Dynamat 10415 Xtreme Speaker Kit

Two 10-in. x 10-in. Sheets

Item #: 15410415


Add to Cart
Dynamat 10435 Xtreme Door Kit

Dynamat 10435 Xtreme Door Kit

With four 12" x 36" sheets — covers two doors

Item #: 15410435


Add to Cart
Dynamat SuperLite Tri-Pak

Dynamat SuperLite Tri-Pak

Triple package — 3 sheets, 12 square feet (Model #10612)

Item #: 15410612


Add to Cart
T-Spec 16-gauge Speaker Wire

T-Spec 16-gauge Speaker Wire

Black/white jacket — priced per foot

Item #: 120SW16WB1


T-Spec 12-gauge Speaker Wire

T-Spec 12-gauge Speaker Wire

Black/white jacket — priced per foot

Item #: 120SW12WB1


Stinger PRO Series Speaker Wire

Stinger PRO Series Speaker Wire

Priced per foot (16 Gauge)

Item #: 541SPW516B


Boom Mat 6-1/2

Boom Mat 6-1/2" Speaker Baffles

Protect your speakers
Regular and slim-line sizes (Regular: 3" depth)

Item #: 696B050330


Add to Cart
XTC 6-1/2

XTC 6-1/2" Speaker Baffles

Protect your speakers (3-1/4" depth)

Item #: 237XT65


Add to Cart
Metra Female Quick Slides

Metra Female Quick Slides

An assortment of female quick slide connectors for connecting to speaker terminals

Item #: 120FQS10PK


Metra Crimp Tool and Connectors

Metra Crimp Tool and Connectors

Package contains crimp tool and over 150 pieces

Item #: 120CRIMPKT


Add to Cart
S&G Wire Cutter/Stripper Tool

S&G Wire Cutter/Stripper Tool

Cuts and strips 12- to 22-gauge wire

Item #: 18119100


Add to Cart
S&G Tool Aid 87615

S&G Tool Aid 87615

Window and Door Clip Removal Tool

Item #: 18187615


S&G Tool Aid 87650

S&G Tool Aid 87650

Door Trim and Panel Removal Tool

Item #: 18187650


Pro.Fit Hook Tool Set

Pro.Fit Hook Tool Set

Installation tools — pair

Item #: 042DM3022


Pro.Fit Trim Panel Tool

Pro.Fit Trim Panel Tool

Remove your vehicle's trim panels without damage

Item #: 042DM4022


Pro.Fit Wire Worm

Pro.Fit Wire Worm

Installation tool helps route wiring through tight spaces

Item #: 042DM4533


Add to Cart
Bojo Trim Panel Tools

Bojo Trim Panel Tools

Set of 6 pry tools — helps remove interior and exterior trim and door panels

Item #: 126CR6NGL


Add to Cart
Skewdriver Pro SPK4042

Skewdriver Pro SPK4042

Ratcheting straight and offset screwdriver set with 40 bits (Skewdriver Pro with ratchet handle, pictured)

Item #: 180SPK4042


Add to Cart
Spec Tools SQR-200a Squeeze Wrench

Spec Tools SQR-200a Squeeze Wrench

Narrow space ratchet kit with 18 sockets

Item #: 180SQR200A


Add to Cart
Install Bay 3320

Install Bay 3320

Auto-ranging digital multimeter

Item #: 1203320

Add to Cart
Install Bay IB35400

Install Bay IB35400

Premium door panel and trim tool

Item #: 12035400

Add to Cart
Bojo Trim Panel Tools

Bojo Trim Panel Tools

Set of 6 pry tools — helps remove interior and exterior trim and door panels

Item #: 126CR6LNGL


Add to Cart