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Kenwood KAC-M1804

Compact 4-channel amplifier — 45 watts RMS x 4 (New stock)

20 Reviews | 12 questions - 18 answers


Our take on the Kenwood KAC-M1804

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.

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.

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 (Crutchfield recommends using the Kicker KISL adapter to allow you to keep the RCA leads from your amplifier). The amp senses incoming high-level signals and turns itself on, eliminating the need to install a separate remote turn-on wire.

Product Highlights:

  • 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

Powerful unit for it's size

Joseph, Pennsylvania

What's in the Box:

  • 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

Kenwood KAC-M1804 Reviews

Average Customer Review(s):

(20 Reviews)

Great amp

Joseph from Pennsylvania on 10/3/2017

Crutchfield Customer Review (What's this?)

Powerful unit for it's size

Pros: Size


Kenwood KAC-M1804

Anonymous from Glasgow, KY on 4/26/2017

Crutchfield Customer Review (What's this?)

Tucked neatly away under the dash, this little guy is all I needed to give my component door speakers that extra kick. Love this amp!



Kenwood KAC-M1804

doug from Kansas City, MO on 2/27/2017

Crutchfield Customer Review (What's this?)

Nice little amp. Seems to have plenty of output, slightly more THD than the Alpine KTP-445U that I have in the other truck - but not bad overall. Convenient size and good instructions. Ample length wiring harness. Also includes RCA patch cables.

Pros: convenient size, Adequate power, good instructions, RCA cables included

Cons: Very slightly more THD than Alpine KTP-445U.

Kenwood KAC-M1804

DAVID from Cleveland, OH on 2/14/2017

Crutchfield Customer Review (What's this?)

Great power boost to a factory or after market head unit. Gives the speakers the power they need to get full rich sound with no distortion.

Pros: Small compact unit. Fits anywhere. Easy install

Cons: None

Small but great.

EE from Altadena, CA on 10/6/2016

Crutchfield Customer Review (What's this?)

Nice to see kenwood making a small amp.

Pros: Small and good for an area with possible moisture.


Big power, small package!!

Paul from Cut Bank, MT on 4/17/2016

Crutchfield Customer Review (What's this?)

Was very surprised when I opened the box and saw such a small, smooth, compact amp with such high power ratings. Was equally blown away when I turned it on and blew my eardrums out with the pure power it produced. WOW!!!

Pros: compact, powerful, awesome specs, simple to install!!!

Cons: NONE!!!!

Perfect Pocket-sized Power!

Kevin from albuquerque, NM on 3/9/2016

Crutchfield Customer Review (What's this?)

This amplifier was a little more expensive than units that were available to me of similar power and quality, but the size of the thing sold me so I splurged a little. I'm really glad I did - I was able to hide this thing exactly where I wanted which made for a smooth install.

Pros: Small (smaller than a Nexus 6 in footprint!), perfect to drive four door speakers, super easy wiring.

Cons: No internal fan. It uses the case as a heatsink, so be careful where you place it.

Kenwood KAC-M1804

kW D from key west, FL on 2/14/2016

Crutchfield Customer Review (What's this?)

Great power from compact unit!



Nice little amp

Long Name from California on 10/21/2015

Crutchfield Customer Review (What's this?)

Works as advertised, good little amp with no frills

Pros: Small Size

Cons: No ability to make adjustments to sound on the amp. Small enough to put in tight spaces but heat is still your works enemy.

Nice addition to my Kenwood Excelon DNX692

John K from Pennsauken, NJ on 10/5/2015

Crutchfield Customer Review (What's this?)

I bought this with the Kenwood Excelon DNX692. Using the stock speakers in my Rav4 the sound is better than ever before. If you do not have amplified speakers in your car and are adding a double din head unit I recommend adding this guy to your system. I have not cranked it all the way up because the sound is really clear at a level that I can stand as it is but if I need more I will upgrade the speakers as well.

Pros: Easy to install with Metra 70-1761 Receiver Wiring Harness for the Rav4 by wiring directly into the direct fit plug. I did solder the connections for the harness and shrink wrap them but it was a fairly easy install. No splicing the car wires. If I want to sell my car all I have to do is unplug everything and plug back in the stock radio. I am taking this set up along with me in my next car. I do love Kenwood products for the high quality.

Cons: No direct fit wiring but I don't think you can get that anywhere. I was able to make my own with Metra 70-1761 Receiver Wiring Harness that I purchased with it solely for that reason.


Paul from Richmond, VA on 9/26/2015

Crutchfield Customer Review (What's this?)

Does exactly what it says. My first 4 channel amp install so took some time to figure out how to wire and ideal placement in my car. Crutchfield advisors were great in helping out with this.

Pros: Low voltage draw, lots of installation options and flexibility.

Cons: None so far.

Great little amp

BryanD from Virginia on 9/15/2015

Crutchfield Customer Review (What's this?)

Great little amp that has plenty of punch for my (4) 6 x 9's. Installed easily in about an hour. Highly recommend if you want plenty of power for the average ears were ringing when turned up and very clean.

Pros: Small, easy to install

Cons: Included hookup wires were pretty cheap. I recommend getting an aftermarket Amp install kit with better quality wiring.

Not impressed

Anonymous from Texas on 9/2/2015

Crutchfield Customer Review (What's this?)

small is right! it's only running 4 motorcycle speakers and ran for about 30 min before it started cutting out. This is at half volume and I installed 2 cooling fans to run across it. I wouldn't but this amp.

Pros: none

Cons: over heats and or cuts out in 30 min

Great little amp

Jim M from Boston, Massachusetts on 8/24/2015

This is a great little amp. Little is the key word there. I fit this little thing behind the dash above the head unit in my Expedition. TONS better than my stock stereo. But I also replaced the head unit with a Kenwood DDX672BH. So I'm sure that helps too. The speakers were the same Kicker 6x8 components that I had installed a couple of months before. 45W is only 45W so, keep that in mind. But if you need more power buy something else. But for very decent power in a tiny package, this is great.

Pros: Size Sound quality

Cons: None really

The little amp that could

Badda bing from North Carolina on 5/27/2015

Crutchfield Customer Review (What's this?)

I installed it in a marine application and this little amp really pumps out some decibels! The best thing about it was the size, easily fit behind the gauge cluster. The wiring harness has about 6' of wire and a couple zip ties included.

Pros: Compact size, 400WATTS!!!


Great, but beware of the harness hookup.

Andrew from Texas on 3/25/2015

Crutchfield Customer Review (What's this?)

Great sound. Install was a little complicated due to the harness. I wish that I had gone with a more standard setup.



Kenwood KAC-M1804

Ken A. from Georgia on 3/24/2015

Crutchfield Customer Review (What's this?)

The Kenwood amp provides clean power to my boat stereo system. Great price and quality make this Kenwood purchase a great value!




Nathan D. from Texas on 1/10/2015

Crutchfield Customer Review (What's this?)

Sound quality is awesome. I have this paired with a Pioneer AVH-X2600BT and driving two sets of Kicker speakers in my 1988 Toyota MR2, and the sound is phenomenally crisp. The highs are super clear, and the mids are delivered very cleanly. And this thing is small. No, not that small...smaller.. No, not that small either... smaller... This thing will fit just about anywhere. It's about the size of a long Kleenex box, but less than half the height. Very happy with this to drive my speakers. Works flawlessly, and with so little space in the MR2, it's wonderful to be able to fit both amps under one seat because of how compact this thing is. Amazing that it can be that small and have no perceivable detriment to sound quality. Please bear in mind that this does not have a standard screw type wire connection. It is a proprietary harness similar to what you would find on a head unit, except that the wires coming out are 16 AWG, and a 12 AWG (I believe) for the power wire. This shouldn't be too much of an issue as the power draw is very low, so there is no need for large wires. Buy it!

Pros: ULTRA Compact Size Sound Delivery Ease of Wiring Low Power Consumption Does not need direct wiring to battery

Cons: None

Great Amp

Roxy85 from Virgilina, VA on 6/19/2014

Crutchfield Customer Review (What's this?)

Easy to install-very compact. Produces great sound

Pros: Install was very easy, very compact and water proof.

Cons: None

good amp for the $

Eric from whitesburg ga on 6/14/2014

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.

Pros: Good value

Cons: none


Hands-on research

Product Research



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 pair 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, the RCA inputs will also accept a speaker level signal. The RCA jacks can be cut off, and speaker wire spliced with the existing cable, but adding a speaker level to RCA adapter is much easier (sold separately).

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.

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.

Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Good price & moisture resistant. [ C  Jul 25, 2017 ]
Kenwood quality suitable for marine use with 4 channels. [ Brook  Mar 06, 2017 ]
Product quality [ Gregory  Feb 06, 2017 ]
Recommended by an advisor [ doug  Feb 01, 2017 ]
compact don`t have much space [ clarence  Aug 08, 2016 ]
picked this item with the help of one of your online staff to go with my radio the i have now for a little more power to my speakers [ Tim  May 08, 2016 ]
To enhance the Kenwood stereo. [ Steve  Apr 14, 2016 ]
compact size with enough power for 6 speakers, again recommended by adviser. [ robert  Mar 04, 2016 ]
replacing a broken one [ Kirk  Feb 08, 2016 ]

12 questions already asked

The Kenwood KAC-M1804 compact Class D 4-channel amplifier does not have any built-in crossovers or subwoofer controls. It also can't be bridged or operated at impedances less than 4 ohms, so it's not a very good option for powering a subwoofer. I hope that helps! My Bio: [ Larry  Jul 27, 2016 ]  Staff
If you purchased the product from Crutchfield, feel free to contact our Tech Support team. They can walk you through the connections on the product. Our toll-free Tech Support number is printed on your invoice, and is also available under the "My Orders" tab in the "My Account" section of our website. If you did not purchase the unit from Crutchfield, then you may want to contact the manufacturer. You can also post your question in our forums: Or try our online support center: [ Kenny  Jul 19, 2016 ]  Staff
While you did not provide the specific year of your Harley, 5.25" is a pretty safe bet for the stock speaker mounts in the fairing. The Kicker 41KSC54 offer great performance, durable build quality, and plenty of power handling for your application: I hope that helps! My Bio: [ Ryan  Jul 07, 2016 ]  Staff
i don't think so. I connected to a kenwood stereo. If you want to connect to factory stereo, you should probably call one of the crutch field reps. before you purchase. [ Paul  Jun 25, 2016 ]
We did yes [ BRETT  Jun 24, 2016 ]
It cannot be bridged. We do have amps that can. Feel free to call an advisor on 1-800-324-9695 for help with selecting one that can. My Bio: [ Paul  Jun 30, 2016 ]  Staff
if it'll fit, it is not advertised as waterproof, only moisture proof. not sure if there would be any interference from being so close together [ jay  Dec 21, 2015 ]
Yes you can, however I didn't find it to be powerful enough. I've built a bunch of bike systems and tried this one. I was very impressed in my garage but then to get it loud enough on the bike over the sound of the motor. I also bought from Crutchfield the Alpine KTP 445U amp and IT CRANKS! I have mounted them in fairings and the power it's amazing! Your best bet is to pair it with some Polk DB speakers. Hope this helps. [ DENNIS M  Dec 21, 2015 ]
This model does require a 4 channel signal when using the RCA pre-amp inputs but this is an easy fix; you can use RCA Y-adapters to create the additional two connections from the single pair of outputs on your stereo: You won't be able to fade between the front & rear pair from the stereo but you will be able to provide audio to all four channels of the Kenwood. I hope that helps! [ Ryan  Nov 20, 2015 ]  Staff
You need to put it somewhere that will get some air circulation or where the amp can freely radiate its's heat, like just under the passenger side dash on the firewall, just above the top of the carpet if there is room, but not in direct line with the heater air. Mount it so the amp can freely radiate its heat. I would not bury it behind the dash. Under a seat is the alternative. [ JOHN  Jun 29, 2015 ]
I have it in my boat and it does run hot. I need to add some type of cooling system. I'm thinking of adding a fan or some type of ventilation to the current compartment. I think I would have this issue with any system. Not just Kenwood. Sounds great but just gets hot after a little while. Good Luck. [ James  Mar 07, 2015 ]
Have not noticed it getting hot. Should be fine for an in dash application. [ Timothy  Mar 06, 2015 ]
This will run cool but you WILL be dissapointed with the power. It is in your best interest to get the alpine KTP-445U. Same price, from Crutchfield AND it cranks!!!!!!!!! I own and used both. The ken wood is most sub par, I hate to say. [ DENNIS M  Mar 06, 2015 ]
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 ]
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  Jul 11, 2014 ]  Staff