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Kenwood KAC-8406

4-channel car amplifier — 70 watts RMS x 4 (New Stock)

Item #: 113KAC8406

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3 Reviews | 3 questions - 8 answers

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Factory Refurbished: $129.99

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Reliable performer

Kenwood makes tough, rugged amplifiers that bring you superior sound quality along with reliable performance. Add the Kenwood Performance Series KAC-8406 amplifier to your system, and you'll hear all the tonal color, impact, and detail you've been missing, from the punch of the rhythm section to the shiver induced by your favorite singer's voice.

Versatile power

The KAC-8406 4-channel amp delivers 70 watts RMS per channel to your full-range speakers. This amp will bring new life to your factory speakers, but you'll really notice the difference when you pair it up with new aftermarket speakers or components. Switch the amp over to 2-channel mode, and you can get great performance from a set of high-power components or a couple of subs with up to 200 watts RMS per channel.

This versatile amp features separate frequency filters for the front and rear channels, along with speaker-level inputs and signal sensing turn-on, so you can put this amp to work in just about any kind of system. Aluminum cover plates protect the amp's connections and controls, giving your installation a neat, professional look.

Product Highlights:

  • 4-channel car amplifier
  • 70 watts RMS x 4 at 4 ohms (100 watts x 4 at 2 ohms)
  • 200 watts RMS x 2 bridged at 4 ohms (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • variable high- and low-pass filters (50-200 Hz, 12 dB per octave)
  • switchable bass boost (0, 18 dB at 40 Hz)
  • Class AB design and MOSFET power supply
  • speaker-level inputs with signal sensing turn-on
  • preamp inputs
  • fuse rating: 25A x 2
  • 8-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 13-3/16"W x 2-1/4"H x 7-5/8"D
  • warranty: 1 year
  • 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.

Kenwood KAC-8406 Reviews

Average Customer Review:

3 Reviews

Much better clarity and quality

Written by: kjs42 from New York on January 24, 2015

Crutchfield Customer Review (What's this?)

I was trying to find some more bass from my factory receiver with upgraded CS Kickers. This added the quality and clarity that I was looking for. And enough bass without blowing out my windows. Much better alternative than the $1,000.00 subwoofer the local stereo shop wanted to sell me.

Pros: Easy to install pretty easy directions. Has both speaker level and RCA inputs, so if I decide in the future to upgrade my head unit I want need a different amp.

Cons: The size is a little bigger then I would like. Hard to find an out of the way place. Not many options in a Wrangler.

Great improvement

Written by: Stuart from Coon Rapids, MN on July 25, 2014

Crutchfield Customer Review (What's this?)

Great improvement in sound quality and power. I had previously a Kenwood receiver and 1 pair of factory speakers and 1 pair of Kenwood speakers. The amp in the head unit didn't have the power needed to do the speakers justice and the factory amp was shot. Wired this all up and adjusted everything, I could swear I had subs in my car again. I only have 2 pre amp outs so the speaker level input let me keep 4 zone control.

I had an existing 8 guage power wires from when I used to have a sub, which is the recommend wire for this sub. the bare wire won't fit in the terminal, I had to find some connectors to make it fit.

Pros: Improved sound quality and power over stock system and aftermarket receiver. Easy adjustment. Both pre amp and speaker level inputs Separate filters for front and rear channels.

Cons: Wish it came with at least the connectors to attach the power wires, recommend guage wire didn't fit for me.

Well worth the price

Written by: Sturds from Florida on March 23, 2014

Crutchfield Customer Review (What's this?)

WOW does it sound great! I upgraded my Honda Ridgeline speakers to Polk DB6501 component speakers in front and rear the Polks sounded OK they had great Highs and OK mids even at full volume with stock Head Unit, but now they sound like a whole new system with beautiful sounds at all volumes, with the factory Head unit turned to max and adjusting the amp gain I can't hear any distortion even at max on the gain, speaker level inputs made installation a breeze just cut, splice, and rock out. Using a multimeter on the power cable it is pulling about ~400W when hitting loud bass and mids at max volume. Stock Head Unit had trouble overcoming wind noise with windows down now with volume at 60% even highway winds are no match.

Pros: Great clean sound no distortion, definitely recommend!

Cons: Not really a con, warm to the touch after ~1 hour at 80-90% max volume, cold to the touch during normal use. Bass boost proved useless in my setup, just made speakers sound terrible. (IF not using separate amp and sub it would be very helpful though)

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Two 25 amp ATO fuses (installed)
  • 2 Terminal covers (installed)
  • 7" Speaker-level input harness
  • 2.5mm Allen wrench
  • Four 5/8" Self-tapping screws
  • Instruction manual (English/ French/ Spanish)
  • Warranty information

Product Research



CEA-2006 Compliant: CEA-2006 is a system of testing and measurement for mobile audio amplifiers. This voluntary standard advocates a uniform method for measuring an amplifier's RMS power output and signal-to-noise ratio. The criteria for measuring power uses a DC input voltage of 14.4 volts and the RMS power output is measured into a 4Ω load, with 1% or less Total Harmonic Distortion plus noise (THD+N), and over a frequency range of 20 Hz to 20 kHz (for full range amplifiers). Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4Ω. CEA-2006 standards allow consumers to compare car amplifiers and receivers under the same conditions (apples to apples). Using CEA-2006 criteria, the Kenwood KAC-8406 is rated at 70 watts RMS x 4 channels with an 80 dBA signal to noise ratio. The signal to noise ratio at the rated power output (not CEA-2006 conditions) is 100 dB.

2-Ohm Stable: The amplifier can support a 2-ohm load in stereo; the 2-ohm power output is 100 watts RMS x 4 channels.

Bridgeable: Each half of the four-channel amplifier can be bridged into a 4-ohm mono load; the bridged output is 200 watts RMS x 2 channels. If you prefer, just half the amp can be bridged for three-channel operation (70 watts RMS x 2 channels + 200 watts RMS x 1 channel).

Cast Aluminum Heat Sink: The KAC-8406 utilizes a cast aluminum heat sink design to ensure the amplifier stays cool.

Protection circuitry: The amplifier features protection circuits that will turn the amp off in case of the following events:

  • speaker wire short-circuits
  • speaker output contacts ground
  • unit malfunctions and DC is sent to speaker output
  • the amp overheats

Power Indicator: When the amplifier is turned on the Power indicator (on top of the amp) lights up. This indicator turns off with the amplifier, and will turn off if the amplifier goes into protect mode.

Auto Turn-on: When using a speaker level input, the amp will turn on automatically when it senses the input signal.


Gain: To accommodate the varying range of signal levels from today's factory and aftermarket radios, the KAC-8406 features an adjustable gain control; 0.2-5.0 volts line level (RCA) and 4.0-12.0 volts speaker level.

Crossover: The four-channel amp is separated into two halves, labeled A and B. The A channel and B channel crossovers have independent controls:

  • Mode: high pass, low pass, or off (full range)
  • Frequency: rotary dial; continuously variable from 50 Hz to 200 Hz

Bass Boost: The bass boost circuit provides an 18 dB signal boost centered at 40 Hz; the bass boost is manually turned on or off.


Power Connections: The power and ground connections are 0.55" wide screw terminals. The remote turn-on screw terminal is 0.35" wide. A Phillips-head or flat blade screw driver (not supplied) is required to tighten/loosen the terminals. Spade connectors are recommended. The manual lists a minimum of 10 gauge wire for power and ground, but given the 50 amp fuse value and the current consumption specification of 35 amps, we recommend an 8 gauge wiring kit.

Speaker Outputs: The four pair of speaker outputs are 0.35" wide screw terminals. A Phillips-head or flat blade screw driver (not supplied) is required to tighten/loosen the terminals. Spade connectors are also recommended for the speaker wires.

Line Level Input: The line input is two pair of stereo RCA jacks (A-channels and B-channels).

Speaker Level Input: A wiring harness is included for the speaker level input.

Fuse: The amplifier uses two 25-amp ATO blade-type fuses.

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

Crutchfield asked  
Why did you buy this?

The bass boost is important to me, as is the size that will fit under the front passenger seat. The fuse size is better than a competitive amp at 50 amps, instead of 80. Fan cooling is a safety feature that's a plus. Total harmonic distortion is competitive. The overriding decision-making trigger for me is the controls the amp allows. [ Robert R  Dec 06, 2015 ]

3 questions already asked

Each bridged output will put out 200w RMS. The 8" kicker should be fine, I have a 300w RMS 10" kenwood sub bridged across both channels of the b output and mine sounds great. I have managed to overheat the sub once on a hot day at high volume for a sustained period of time driving my sub and a pair of 100w kicker component speakers but only once. I'm very happy with the amp in general. This soundbar you mention is a little vauge, 6 speakers in a circut can drop your ohm's down though so I'm a little worried about that. Here's something I would give a read: The specs on the amp list the output at various ohm's so you should have a decent idea if it'll be adequate once you know the requierments for the sound bar. [ GUSTAV  Feb 09, 2016 ]
From what I remember, a couple of things that cause amp to shut off. Make sure amp case is not grounded. Shorts in speaker cable. I would think maybe the higher the volume, the more power being pushed out, and the cable could be "ok" until that point is reached. Just a dumb thought. [ Kevin  Dec 11, 2015 ]
Sorry how is the system hooked up power wise? [ KENNETH  Jan 09, 2015 ]
Your in what they call cut off. How is it hooked up? [ KENNETH  Jan 09, 2015 ]
I had something similar happen to me. I have a Sony deck and discovered that I had the wrong gain setting. After I moved the gain to a higher number setting the problem went away. The system really cranks now!!! [ Aaron  Dec 29, 2014 ]
Yes it can. That is how mine is hooked up now. I forget the name of this type of hookup, but the amp is "spliced" in to be between the speakers and the head unit. So unless you install this amp under your dash, you will need to run 2 sets of wires. One set goes from radio to amp. The other set is from amp to speakers. The price is good. This amp was recommended to me from a Crutchfield rep and I am very happy with it. [ Kevin  Dec 11, 2015 ]
I think it will work with a factory head unit, you will just have to figure out the wiring color codes which should not be to hard. [ Thomas Moorhead  Dec 11, 2015 ]
Yes it can, that is the reason I purchased it. It has a feaature that senses the sound from the factory radio and then it turns on the amplifier, makin it easy to add to a factory head unit. [ nelson  Dec 10, 2015 ]