Kenwood KAC-M1804

Compact 4-channel amplifier — 45 watts RMS x 4

  • Kenwood KAC-M1804


  • Kenwood KAC-M1804

  • Kenwood KAC-M1804

  • Kenwood KAC-M1804

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Our take on the Kenwood KAC-M1804

by Buck Pomerantz

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.

Power your speakers on land or sea

Kenwood's KAC-M1804 4-channel amplifier will pump up your car's audio system with 45 watts RMS per channel — that's more than twice the power of most car stereos. The super-compact KAC-M1804 will add new clarity and impact to the basic sound system of almost any kind of vehicle on land or water, and it'll fit in a lot of places when space is tight. The amp uses plastic covers to protect its connections and features a conformal coated circuit board that keeps out moisture and salt, so the party won't stop just because of a little wetness.

Read more

Hooks up to almost any system

The KAC-M1804 comes with an RCA cable for connecting to an aftermarket receiver, but it can handle speaker-level signals as well, so you can still get input from a radio without RCA outputs. The amp senses incoming high-level signals and turns itself on, eliminating the need to install a separate remote turn-on wire.

If your receiver's power circuit is protected by a 15-amp or larger fuse (check your fuse box or owner's manual), you can tap into it to power your KAC-M1804. Otherwise, you'll have to run a power wire to the battery and install a 15-amp inline fuse as close to the battery as possible.


  • compact 4-channel amplifier for car, motorcycle, and boat
  • 45 watts RMS (100 watts peak) x 4 at 4 ohms
  • non-bridgeable, 4-ohm stable per channel
  • CEA-2006 compliant
  • MOSFET power supply and Class D amp technology
  • conformal-coated circuit board — suitable for marine applications
  • preamp and speaker-level inputs
  • signal-sensing turn-on on speaker-level inputs eliminate need for a separate remote lead
  • RCA cables and short power/speaker harness included
  • 10-gauge power and ground leads recommended
  • fuse rating: 15A x 1
  • dimensions: 6-1/2"W x 1-3/8"H x 3-9/16"D
  • warranty: 1 year
  • Our 60-day money-back guarantee

Hands-on research from the Crutchfield Labs (what are the Labs?)

Features and Specs
RMS Power Output (Watts x Channels) 45 x 4
Peak Power Output (Watts x Channels) ---
Power at 2 Ohms (Watts x Channels) N/A
Bridged Power (Watts x Channels) N/A
Minimum Impedance Bridged N/A
Minimum Impedance Unbridged 4
Best Frequency Response 20-20000 Hz
THD at Rated RMS Power 1%
Signal to Noise Ratio 74 dB
Input Voltage 14.4v
Amplifier Class D
Low-Pass Crossover Frequency N/A
Low-Pass Slope (dB/octave) N/A
High-Pass Crossover Frequency N/A
High-Pass Slope (dB/octave) N/A
Bass Boost No
Bass Boost Frequency N/A
Fan Cooled No
Fuse Rating 15
Speaker Level Inputs RCA/Bare wire
Preamp Outputs No
Width (inches) 6-1/2
Height (inches) 1-3/8
Depth (inches) 3-9/16
Parts Warranty 1 Year
Labor Warranty 1 Year
Product Research
What's in the box?

Download owner's manual

  • 4-Channel amplifier with a 15A ATM fuse installed
  • Two 38" RCA stereo patch cables
  • 5' Power and speaker output harness
  • 4 Self-tapping screws (Length=5/8")
  • Two 13.5" plastic wire ties
  • Two 4" plastic wire ties
  • Instruction Manual/Warranty sheet

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.



Compact Amplifier: The Kenwood KAC-M1804 compact Class D 4-channel amplifier is designed to boost the output and clarity of your car stereo. The amp features a conformal coating on the circuit board to protect it from moisture. This allows you to use the amp for marine applications, or on All-Terrain Vehicles (ATVs). The KAC-M1804 delivers 45 watts RMS x 4 channels at 4 ohms. It cannot be bridged or operated at impedances less than 4 ohms.

Protection Circuitry: The amplifier features protection circuitry for thermal overload, DC offset, and short circuits. The amp stops operating when it goes into protection mode. (There are no LED indicators.)

Signal-sensing Turn-on: When the amplifier is connected to a factory head unit, or an aftermarket unit without preamp outputs, you can cut off the amp's RCA input connectors and splice the head unit's speaker wires to the input wires. In this case, the amplifier's Signal-sensing Turn-on feature will turn on the amp when a signal is detected on the input. This eliminates the need to connect a turn-on lead to the amp's Power Control (blue) wire.

No Controls or Crossovers: The KAC-M1804 does not have built-in crossovers or controls. If you are connecting the amp to small speakers, it is recommended that you use the crossovers built into the connected head unit, or use bass blockers on the speaker outputs.


Amp Wiring: The Kenwood KAC-M1804 is equipped with a 22-pin DC connector on the amplifier. The included 5' DC harness, which plugs into the connector, has wires for +12V battery power, ground, power control (turn-on lead), and four speakers.

Power/Ground: The +12V Power and Ground wires are 16 AWG wires. The power wire can be connected to the car's fuse box or directly to the battery. The amp is protected by a 15A ATM mini blade fuse. If wiring directly to the battery, you can use a 10 AWG wire with an in-line 15A fuse installed no more than 18" from the battery terminal. The ground wire should be attached to a metal area close to the amplifier.

Power Control: The blue Power Control wire should be connected to the head unit's remote turn-on lead when an aftermarket unit is used. This wire does not need to be connected if you're using speaker level inputs. The Signal-sensing Turn-on feature will turn on the amplifier when an input signal is detected.

Line-Level Inputs: The amplifier is equipped with two pairs of RCA inputs on 7-1/2" pigtails for connecting stereo RCA patch cables from the head unit to the amp. Two 38" stereo RCA patch cables are included. If using a factory head unit, or a unit without preamp outputs, you can cut off the RCA jacks and splice the four speaker wires to the two inputs, maintaining the same polarity.

Speaker Outputs: The included DC harness has eight wires for connecting four speakers to the amp: Front left (white + white/black), Front right (gray + gray/black), Rear left (green + green/black), and Rear right (purple + purple/black). The amp is not capable of bridging or connecting to speakers with impedances less than 4 ohms.

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Kenwood KAC-M1804 Reviews

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5 out of 5

Great Amp

Written By Roxy85, Virgilina, VA on Thursday, June 19, 2014
Crutchfield Customer Review (What's this?)
Easy to install-very compact. Produces great sound
Install was very easy, very compact and water proof.
Was this review helpful?    Yes | No
5 out of 5

good amp for the $

Written By Eric, whitesburg ga on Saturday, June 14, 2014
Crutchfield Customer Review (What's this?)
I bought this amp to boost the sound on my pontoon boat and am very pleased. Sound quality is fantastic. I can run 20 mph and hear my radio now over the water and wind noise. Great amp for the money.
Good value
1 out of 1 people found this helpful
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2 questions already asked

This unit doesn't appear to have a "gain" control. Does it somehow automatically set the input level? Is there no way to compensate for different pre-amp output voltages on head units? [ Brian  Jul 18, 2014 ]
2 answers
  • I have a 2013 HD Street Glide. Will this amp plug easily into the factory radio or will I need to have it professionally installed? [ Brad   Jul 23, 2014 ]
  • The input level is set automatically. There are no controls. That said, I am very happy with the unit. It takes up very little space and the sound quality is excellent. [ Thomas   Jul 19, 2014 ]
My front speakers are only rated for 35 rms and my rears are 55 rms. Since there isn't a way to adjust the gain on this will it hurt front ones since it puts out 45 rms? [ Jeepfreak13  Jul 10, 2014 ]
1 answer
  • I forwarded your question to an Advisor and they responded with the following: It's perfectly fine to slightly overpower your front speakers, so the 45 watts will work in this application. If you would like to discuss further you can contact an Advisor directly by phone (1-800-324-9695) or online chat. [ Krissy Staff  Jul 11, 2014 ]

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For a more in-depth review and enhanced detailed information on the Kenwood KAC-M1804, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_113KAM1804/Kenwood-KAC-M1804.html ).