Rockford Fosgate R400-4D

Hi Audiophiles!, How you doing? Recently we reviewed the RF R500X1D and it turned out to be awesome monoblock amplifiers in an awesome series Rockford made. So we thought we should review more and more amps in this series to let you pick the best one for you and your car.


This time we are going to review a 4-channels Class D amplifier. It is the Rockford Fosgate R400-4D.

If you know us you would know that we really love Rockford Fosgate. They are an amazing company that makes awesome car sound system units.


We spoke before about how Rockford participated in developing the way we get amplifiers today and how they are so innovative in the industry.

Rockford Fosgate R400-4D 2



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To make the review more comprehensive and help you get the most of it, we are going to write two separated sections:

1- the technical, technology, and the features of the amp.

2- what the customers said about it and the answer for popular questions about the amplifier

So, let’s start:

Rockford Fosgate R400-4D features:


1- The design:

Thinking about who Rockford framed the amp is really a beautiful experience. The integration between the mounting options and how you are going to control the amp made you believe that the design is not just beautiful. It is also functional.


With your first look on the R400-4D, you will find the different materials and different shades of black that integrate so beautifully. With the sleek logo of Rockford Fosgate in the middle of the amp and the dashboard in the lower area of the amp and then the mounting area.


2- the price:

Here the price is a big feature. If you are going to buy the R400-4D from Amazon you will pay less than $200 and get a very beautiful 4-channel amplifier from RF. so, it is a pretty good deal for your bucks if you considered the value you get from the amplifier.

3- Controls:

As usual, Rockford gives you the power to control everything from the lower part of the amp. This would make it easier for you to manage everything you need at once and with ease.

Gain Control: The amplifier has rotary gain controls (0 to 11) for front and rear channels.

Crossovers: The amplifier features independent Butterworth crossovers for the front and rear channels. Each crossover can be set for low-pass, high pass, or all-pass (full range).


4- Power:

Basically, you will get 75 Watts RMS for every channel to power, for example, a full-range speakers or components.

But this is just the start. With the bridging capability, you could do a lot of stuff to fit with your components. For example, you can bridge the amp to 2-channel mode to drive a pair of subs.


5- Mounting:

with the toolkit, RF provide you can mount the amp in a horizontal or vertical way but mounting it right side up is the perfect setup for cooling according to Crutchfield


6- the durability:

The durability features are quite the same in every amp in this series from Rockford. the 2-position phase which gives you the option to turn it between 0° or 180° to match the rest of your vehicle’s speaker system.

The heavy cast aluminum follows the damage and the heat so you can enjoy long periods of time playing your stuff without having any problems or heat.

The Rockford Fosgate 400-4D specs:

  • 4-channel car amplifier
  • 75 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
  • 200 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • variable high- and low-pass filters (50-250 Hz, 12 dB/octave)
  • variable Punch EQ bass/treble boost (0-18 dB at 45 Hz and 12,000 Hz)
  • Class-D amplifier design
  • MOSFET power and output stages
  • frequency response: 20-20,000 Hz
  • preamp inputs and outputs
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 40-amp in-line fuse between the distribution block and the amplifier is recommended
  • 9-1/8″W x 2″H x 7-3/8″D
  • warranty: 1 year

Rockford Fosgate R400-4D 2



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Now we finished the first part of our review and now you should know the technologies and the stuff Rockford used building their beautiful amplifier.

This second part is quite small. We didn’t find so many questions about the amp. And about what the customers think about it is so repetitive.

What the people think about the R400-4D?!

A lot of people really liked the amp and thought it was a win for their car sound system. BUT, we found some angry customers who complained about the durability of the amp. It’s between 10-15 customers we found complaining about the durability so, it is obvious there was something wrong.

But something worth mentioning is that we found bought the amp in 2017 complaining about the amp till now. To avoid any of these problems always buy the amp with warranty from verified people.

Questions about the RF R400-4D:

We really found one questions repeated more than 100 times and probably you are going to ask this question too. Could it power…..(component)?

People are checking if the amp could power their components. That’s the question we found A LOT.

Hey, you got to the end of our review and you now know everything you need to know about the amp before deciding to buy it or not.

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If you have any question about the amp or want us to help you we would be so happy to do so.

check also our review for the best Rockford 4-channel amps in 2017

As Always, Enjoy Your Car Sound System.

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Rockford Fosgate R400-4D
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