The distinctive chrome MTX logo and heavy-duty end panels let you know that X Thunder amps mean business. Their large extruded aluminum heatsinks and anodized finish keep these durable amps running cool even under extreme listening conditions.

The X Thunder 704X amplifier pushes out 70 watts RMS to each of four speakers, or it can be bridged to run 210 watts RMS into two channels. This amp includes high- and low-pass filters that let you adjust the amp's output to fit your speaker system.

Product Highlights:

  • 4-channel car amplifier
  • 70 watts RMS x 4 at 4 ohms (105 watts x 4 at 2 ohms)
  • 210 watts RMS x 2 bridged at 4 ohms
  • CEA-2006 compliant
  • variable high-pass filter (40-8,000 Hz at 12 dB per octave) and low-pass filter (40-5,000 Hz at 24 dB per octave)
  • speaker- and preamp-level inputs
  • fuse rating: 30A x 2
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 14-15/16"W x 2-1/4"H x 9-5/8"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.

MTX X Thunder 704X Reviews

Average Customer Review:

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Crapped out on me

Written By Lee3333, NYC on Tuesday, December 07, 2010

Crutchfield Customer Review (What's this?)

Worked good for a while then a few months ago I began hearing a sound like static as
if the radio station was not tuned in right (but I have Sirius and it also happened on
CD's) Using the balance and fader controls, I pinpointed the problem to the right front
speaker. A few days later, it stopped making any sound at all. To double check, I tried
hooking up a new speaker to each of the amp outputs, and the front right one was not
working at all. When I tried bridging it, the sound level was half that of the other channel.
Since it is a little over 2 years old, there is no warranty anymore.
Amps should last longer than that

Best Ever

Written By Pastrol, Toronto, Canada on Sunday, September 05, 2010

I have abused this amp in all was possible and it just keeps on going. The most durable amp I've ever seen....

Another Great Amp From MTX

Written By Matt, Detroit, Mi on Thursday, September 03, 2009

Crutchfield Customer Review (What's this?)

Ever since buying an MTX2300 WAY BACK in the day, I've refused to buy any other brand of amp. MTX delivers more power than advertised (each amp comes with a birth certificate) and sound quality is top notch.

Some others have said they have had problems with this amp - mine has worked perfect. Although I have been installing gear for 15 years I know what I'm doing....

Right now, I have two channels bridged into a 2-OHM load subwoofer load, (that equates to 1-phm per channel) which is a big "NO NO" because it'll run "HOT". Well guess what? It NEVER shuts down. I crank it full out.... No problems.

The other two channels run front and rear mids & tweets and they get loud enough to hurt my hears without distorting.

In total, I'm running 10 speakers off this amp (2 subs, 4 mids, 4 tweets).

Too bad its discontinued.... if it wasn't I'd buy another one for my new truck.

MTX X Thunder 704X

Written By ALLEN, Atlanta on Sunday, June 21, 2009

Crutchfield Customer Review (What's this?)

Setup easy sounded good for a mounth I the winter. Least bit of heat and it is done. I am 56 and have not abused it but come on. It is in protection mode now. Maybe it will be back this winter.

Not durable at all!

Written By Francisco, Central, FL on Monday, August 25, 2008

The amplifiers controls were a breeze to use (Hp Lp filters) , and the amp put out some clear crisp loud sounds, when I first got it. It lasted for about two months before I started to have trouble with it. It would go into protect mode which it never did before, even when I wasn't playing it hard.

Then it started to loose power (i.e., 80 watts rms @ 14.4v down to 30 watts rms @14.4v) I have tested the wiring, bought new wiring just in case, tried different head units (all @ 1v pre out) even a few 4v pre out units set at 1v then to 4v. With the same results. The amps max power output was 30 watts, so I sent it in to MTX, and there customer service claimed nothing was wrong with the amp and they sent it back to me. Now I'm stuck with this junk, and out the money paid for it and out the shipping to send it in for repair.

This amp failed and was not durable with normal where and tear. MTX customer service is in itself in need of a repair. I'll never buy MTX again

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier with two 30-amp fuses inserted in chassis
  • 2 Speaker level input harnesses
  • 4 Mounting screws
  • 3mm Allen-wrench
  • 4mm Allen-wrench
  • Amplifier Performance Certificate
  • Installation sheet with warranty statement

Product Research

Inputs and Outputs


CEA-2006 Compliant: CEA-2006 is a new system of testing & measurement methods for mobile audio amplifiers. This voluntary standard advocates a uniform method for determining 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 4-ohm load, with 1% or less Total Harmonic Distortion (THD) plus noise, and at a frequency range (for full range amplifiers) of 20 Hz to 20,000 Hz. Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4 ohms. CEA-2006 allows consumers to compare car amplifiers and receivers on an equal basis. The MTX X-Thunder 704X under CEA-2006 regulations is rated at 70 Watts RMS x 4 channel with a 75dBA signal to noise ratio.

Bridgeable: The MTX four-channel amplifier can be bridged down to two channels to output 210 watts x two-channels at 4 ohm or bridged to three channels to output 70 watts x two-channel at 4 ohm to the front channels and 210 watts x one-channel at 4 ohm to the rear channel.

Heavy Duty Construction: The X-Thunder amplifier features heavy duty aluminum construction with large extruded heat-sinks for reliable sound for years to come.

Crossovers: The X-Thunder 704X has built-in independent high pass and low pass crossovers for the front (1/2) and rear (3/4) channels. The high pass crossover's slope is 12 dB/octave and is continuously variable from 40Hz to 8000Hz. The low pass crossover's slope is 24 dB/octave and is also continuously variable from 40Hz to 5000Hz. The amplifier can also be operated at full-range.

Line Level Inputs: The two pair of RCA type line-level inputs have independent gain (Input Sensitivity) control. The Input Sensitivity control will accept an input signal of 250mV to 5.0 Volts.

Speaker Level Input: The MTX 704X comes with two speaker level input harnesses. This feature makes it easier to add a four-channel amplifier to a factory radio or to an aftermarket receiver with no preamp outputs.

Power Indicator: When the power is turned on to the amplifier, the Power indicator on top of the amplifier will light up. This indicator will turn off with the amplifier and will turn off if the amplifier goes into protect mode.


Front of the Amplifier: All of the amplifier's controls are found on the front of the amplifier for easy access.

  • 1/2-Channels and 3/4-Channels Gain: 0.25V-5V
  • 1/2-Channels and 3/4-Channels High Pass Filter: On or Off
  • 1/2-Channels and 3/4-Channels Low Pass Filter: On or Off
  • 1/2-Channles and 3/4-Channels High Pass Frequency: 40-8,000 Hz
  • 1/2-Channels and 3/4-Channels Low Pass Frequency: 40-5,000 Hz

Inputs and Outputs

Front of the Amplifier: All of the amplifier's connections are found on the front of the amplifier for easy access.

  • Fuse: Two 30 amp fuses
  • Power: set-screw terminal designed to accept up to a 4 gauge power wire
  • Ground: set-screw terminal designed to accept up to a 4 gauge ground wire
  • Remote turn-on: set-screw terminal designed to accept a 16-gauge turn-on lead
  • Speaker outputs: eight set-screw terminals designed to accept 12 to 8 gauge speaker wire
  • Speaker-level inputs: Multi-pin inputs for use with included speaker level input harnesses
  • Line in: Two pair RCA inputs

Our Product Research Team

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