A tricked out system calls for a kickin' amp, and nothing fits the bill like a KX series amplifier from Kicker! These high-end amps set the standard for clean, steady sound with MOSFET power supplies and rock-solid construction.

Versatility, power, and ultra-pure sound quality — Kicker's KX650.4 four-channel amplifier has it all! You can drive full-range speakers or components with 4 channels of 120 watts RMS (at 4 ohms), or run the amp in 2-channel mode to push your subwoofers with 325 watts per channel. And, you can trust the power ratings — they're CEA-2006 compliant!

Variable crossovers from 50-200 Hz may be set for high-pass, low-pass, or full range operation. You can adjust the front and rear channels independently for a custom tuned personal set up! And the futuristic cosmetics will definitely set your installation apart from the crowd. Grab the dash-mountable bass boost controller and select from 0 to 18 dB of bass boost at 40Hz. Protection circuits guard against overvoltage, reverse voltage, and overheating.

Product Highlights:

  • 4-channel car amplifier
  • 120 watts RMS x 4 at 4 ohms (170 watts RMS x 4 at 2 ohms)
  • 325 watts RMS x 2 in bridged mode (4-ohm stable in bridged mode)
  • cooling fan
  • 2-, 3-, or 4-channel output
  • CEA-2006 compliant
  • Tri-way capable (Tri-Way crossover required)
  • speaker- and preamp-level inputs
  • variable front and rear high-/low-pass crossovers (variable 50-200 Hz, 12 dB per octave)
  • variable bass boost (0-18 dB) centered at 40 Hz with wired remote control
  • three-way protection circuitry
  • requires 4-gauge power and ground leads and an 80-amp fuse — wiring and hardware not included with amplifier
  • 22-1/2"W x 2-9/16"H x 9-15/16"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

Be the first to review this product
Great Gear Giveaway

Submit a review and then enter to win a $350 rewards card

Review this product:

Thanks for taking the time to share your experiences about this product. Please be sure to focus your comments on the product itself. Read our Review Guidelines for more information.

Your email won't be visible. Please use the email address that is associated with your order.
(e.g., JohnD) Your review will be signed using the display name and location
(e.g., Charlottesville, VA)

Click on a star to rate the overall product on a scale of 1-5
1500 characters left
  Attach a YouTube Review
Crutchfield Video Review Guidelines
  • Only submit videos that you made or are authorized to use.
  • Do not submit videos that contain music, video or visuals that are copyrighted and belong to someone else.
  • Please see our Review Guidelines for more information.
500 characters left
500 characters left

Hands-on research

What's in the box?

Download owner's manual

  • Four-channel amplifier with two 40-amp fuses inserted in chassis
  • 2 EndKaps (installed)
  • 2 Spare 40-amp fuses
  • Remote bass level control
  • Mounting bracket
  • 2 Self-tapping screws for mounting remote level control (3/8" length)
  • 19.25' Remote bass control cable (with RJ-14 plugs on each end)
  • Four self-tapping screws (#8 x 7/8")
  • 3mm Allen wrench
  • Two 12" Speaker-level input harnesses (each with 4-pin Molex plug on one end)
  • 2 RCA dummy plugs
  • Owner's Manual
  • Warranty Registration Card (return for free Kicker decal)
  • Kicker Certified Power Certificate

Product Research

Inputs and Outputs Notes
Wiring Recommendation


EndKaps: The amplifier features two removable, cast aluminum EndKaps that are mounted to each end of the amplifier. These EndKaps protect and hide all of the wiring connections to the amplifier, and must be removed before the amp is mounted. The EndKaps can be prepped and painted any custom color you choose. They are mounted to the amp with 4 Allen-head screws (3mm Allen wrench supplied).

Forced Induction Cooling: To keep the amplifier cool, the amplifier utilizes a forced induction cooling system. When the internal temperature reaches a preset temperature, the built-in fan automatically turns on to exhaust the hot air through the top vents and draw in cool air from the side vents. As the temperature rises, the fan spins faster, circulating more air to cool the amplifier.

Top-mounted Controls: The KX650.4 features six rotary controls on the top panel: input gain control, bass boost control and crossover frequency control for both the Amp 1 section (front channels) and the Amp 2 section (rear channels). These controls can be easily accessed, even with the EndKaps installed.

Variable Crossovers: The amplifier has dual variable crossovers, one for the front channels (Amp 1) and the other for the rear channels (Amp 2). Each crossover can be independently set for high-pass or low-pass operation. The cutoff frequency is continuously variable from 50 to 200Hz with a 12dB/octave slope.

KickBass Bass Boost: The KickBass bass boost circuit provides up to 18dB signal boost at 40Hz.

Remote Bass Level Control: The dash-mounted remote unit allows you to adjust the output level of the amplifier. A 19.25' cable is included to allow you to control a trunk-mounted amp from the front of the vehicle. Dimensions: W=2.2", H=1.186", D=1.736" (2.114" including the knob).

SORT Protection Circuitry: The SORT (Short circuit, Over-voltage, Reverse polarity, Thermal) protection circuitry guards against accidents and undesired operation. If the red Protection LED illuminates, SORT protection has been engaged and the amplifier is in protect mode until the problem is resolved.

Kicker "Living Loud" Certified Power Certificate: The amplifier comes with a certificate that indicates the total maximum wattage of your specific amplifier, along with the model number, serial number, tested date, and whether the amplifier passed the total harmonic distortion, signal-to-noise ratio, and protection circuit tests. In most cases, the amplifier's certified power output surpasses the rated power.

Inputs and Outputs Notes

Gold-plated Connectors: The KX650.4 uses custom-tooled, gold-plated connectors to assure maximum power transfer and damping.

Power Terminals: The power and ground set-screw terminals can accept up to 4-gauge bare wire. The remote turn-on set-screw terminal can accept up to 12-gauge wire. A 3mm Allen wrench is provided to tighten/loosen the set screws.

Speaker Terminals: The amplifier's four set-screw speaker terminals can accept up to 8-gauge bare wire.

Speaker-level Inputs: Two high-level input connections are included to allow use with a factory radio or other receiver without RCA preamp outputs. Two 12" speaker-level input harnesses are provided, each with a 4-pin Molex plug on one end. The receiver's speaker wires will need to be spliced to the bare wires on the speaker-level input harness.

Line Inputs: Two pairs of RCA line inputs are provided to allow you to separately feed preamp signals to the front and rear channels. You can also feed signals to all four channels with one pair of RCA cables, but you will not have fade capability. There are no line outputs on this amp. Note: The line-level and speaker-level inputs should never be used at the same time.

RCA Dummy Plugs: When using both sets of high-level inputs, the supplied RCA dummy plugs must be inserted into the Amp 2 inputs in order for the fader to work properly. If the amp is being used in any other configuration, the dummy plugs should not be used.


Power Output:

  • Input Voltage at 14.4 Volts:
    • 120 watts x 4 into 4 ohms (≤1% THD+N)
    • 170 watts x 4 into 2 ohms (≤1% THD+N)
    • 325 watts x 2 into 4 ohms bridged (≤1% THD+N)
  • Input Voltage at 13.8 Volts:
    • 70 watts x 4 into 4 ohms (0.085% THD+N)
    • 135 watts x 4 into 2 ohms (0.5% THD+N)
    • 250 watts x 2 into 4 ohms bridged (0.5% THD+N)


  • Without EndKaps: Width=19.125", Height=2.375", Depth=9.506"
  • With EndKaps: Width=22.5", Height=2.535", Depth=9.921"

Wiring Recommendation

Amplifier Wiring: This amplifier uses two 40-amp fuses, so its total fuse rating is 80 amps. The Streetwires 4-gauge amp wiring kits (item #s 211PS4B, 211PS4R, 211PS4BI, 211PS4RI) include an 80-amp fuse, and will accommodate the amp's fuse rating. Other 4-gauge amp wiring kits carried by Crutchfield include a 60-amp fuse. If you are using a 4-gauge amp wiring kit with a fuse rated less than 80 amps, the fuse should be replaced with an 80-amp AGU fuse (item # 211AGU80).

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.