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Rockford Fosgate Prime R300X4

4-channel car amplifier — 50 watts RMS x 4

21 Reviews | 5 questions - 7 answers


Our take on the Rockford Fosgate Prime R300X4

Rockford Fosgate performance in a small package. The Prime Series R300X4 4-channel amp can drive your speakers with 50 watts RMS each, so you'll really feel your tunes rockin'. Or, you could switch the R300X4 to 2-channel mode to run a couple of subs with 150 watts RMS each — when you buy a bigger amp for your subs later on, you can still use this 4-channel to drive all your speakers. Smart move.

Rockford Fosgate power for your speakers

Rockford Fosgate performance in a small package. The Prime Series R300X4 4-channel amp can drive your speakers with 50 watts RMS each, so you'll really feel your tunes rockin'. Or, you could switch the R300X4 to 2-channel mode to run a couple of subs with 150 watts RMS each — when you buy a bigger amp for your subs later on, you can still use this 4-channel to drive all your speakers. Smart move.

You can use the high- and low-pass filters and Rockford Fosgate's famous Punch boost to get maximum performance from the speakers in your vehicle. And speaker-level inputs let you hook this amp up to almost any system, even a factory stereo.

Rugged performance and value

The R300X4's heavy cast-aluminum chassis efficiently draws damaging heat away from its internal components, ensuring reliable, long-term play. The amp's built-in sensors keep track of the output current and power supply temperature, ensuring that plunging speaker impedances (they change constantly during play) or even a short circuit won't hurt anything. Your driver's seat will become your favorite place for listening to music once this Prime amp goes to work.

Product Highlights:

  • 4-channel car amplifier
  • 50 watts RMS x 4 at 4 ohms (75 watts RMS x 4 at 2 ohms)
  • 150 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) on front and rear channels
  • selectable bass boost (0, 6, 12 dB at 45 Hz)
  • Class-AB amplifier design
  • MOSFET power supply
  • frequency response: 20-20K Hz
  • preamp and speaker-level inputs
  • 8-gauge power and ground leads and a 50-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 50-amp in-line fuse between the distribution block and this amplifier is recommended
  • 13-1/4"W x 2"H x 7-3/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee

What's in the Box:

  • 4-Channel amplifier
  • Two 6" Speaker level input harnesses
  • 3mm Allen wrench
  • Four 3/4" Self-tapping screws
  • 4 Flat washers
  • Installation & Operation manual (English/ French/ Spanish/ German/ Italian)
  • Amplifier verification certificate

Scratch & Dent items may be missing non-essential accessories. In some cases the manufacturer's accessories have been replaced with generic equivalents.

Great as always from Rockford. I wouldn't expect anything less. And Crutchfield's service also great.

Stephen, Henderson, NC


Rockford Fosgate Prime R300X4 Reviews

Average Customer Review(s):

(21 Reviews)

Rockford Fosgate Prime R300X4

Stephen from Henderson, NC on 1/28/2018

Crutchfield Customer Review (What's this?)

Great as always from Rockford. I wouldn't expect anything less. And Crutchfield's service also great.



bad sound quality

joe from tehachapi ca on 12/15/2017

the sound quality is horrible nowhere near were rockford fosgate used to be. very disappointing.

Pros: none

Cons: everything about the amp.

Amp has LOTS of power

Rod from Dawsonville, GA on 7/30/2017

Crutchfield Customer Review (What's this?)

This amp really rocks, and has more power than I ever imagined it would. Coupled with the JVC head unit, 4 JVC speakers and Rockford Fosgate Punch 300-10 that I just added from Crutchfield, my Mustang is rockin' down the highway. The sound all these components generate really puts a smile on my face. I could write a book on the install, which has nothing at all to do with the equipment I selected. Main problem is working in an '07 Mustang. It's a lot like working in a phone booth. You basically have to disassemble your entire interior if you want to do it right, running wires properly and most importantly, unseen. (even had to pull the right front wheel and remove an inner fender panel to run the power cable) And of course it wasn't without calling the tech guys at CF (I believe it was 5 times) but I couldn't of done it without their help. A HUGE shout out to Wes and TJ (I hope I have the initials correct) because both were extremely helpful with a lot of issues I was creating on myself. Being an old guy still stuck in the '60's, I haven't kept up with technology like I should, and it's been a challenge trying to keep pace. Also want to thank Dolly for all her help too, along with a couple others in tech that were there when I needed them. All in all, a very pleasant experience. My first dealings with CF was back in 1988 and they were just as good back then as they are today. Rock on!

Pros: It's a Rockford Fosgate (406 RMS)

Cons: controls for adjustments could be a little better. Gets pretty warm when cranked a while.

Great Power, Beautiful Sound!

Steve from Stow, OH on 7/26/2017

Crutchfield Customer Review (What's this?)

Awesome upgrade from my factory amp! I love this amp. Very powerful and clear, will definitely purchase additional Rockford Fosgate products in the future.



major power, clean filters.

Barry from Chico, CA on 6/19/2017

Crutchfield Customer Review (What's this?)

I wanted to wait 2 weeks after having it plugged in to review the amp. I got to put my hands on it and get it toned in. I have it running 2 rear coaxial and 2 front components. It's running off a JVC KW-925bts. I have no complaints on it. It is handling over 100 degrees in the trunk with not a single over heat soo far. It is putting a lot of clear clean power to all of the speakers and it really can get loud. I think it's my speakers or crossover settings but getting up in the volume range where my ears start to hurt things can get a little distorted. I don't ever need to turn it up past 23 on my volume knob that goes up to 50, because it sounds clear and loud.

Pros: Loud and clear, clean power, handles California summer heat in the trunk.

Cons: The screws that came with it could have been security screws like the sub came with. It would have been a much better decision.

Great amp

Greg from South amboy, NJ on 4/16/2017

Crutchfield Customer Review (What's this?)

Excellent, clean sound, ran all 4 channels on 6and a half inch polk speakers... well worth the money.



Rockford Fosgate Prime R300X4

Anonymous from Lebanon, PA on 3/19/2017

Crutchfield Customer Review (What's this?)

Great power, and small enough to hide almost anywhere in my truck.

Pros: Small and powerful

Cons: None

Rockford Fosgate Prime R300X4

Luis from PR on 1/25/2017

Crutchfield Customer Review (What's this?)

Me gusta el product. I like the product.

Pros: Bueno Good

Cons: Ninguno None

Crutchfield response on 1/31/2017 Translation provided by Crutchfield's International Sales & Support team.

Rockford Fosgate Prime R300X4

Norman from Sherwood, AR on 11/28/2016

Crutchfield Customer Review (What's this?)

There many reasons this seasoned radio head has stay a loyal Rockford Fosgate fan, superior craftsmanship, performance, overall awesomeness.



Great Amplifier

Joe from Sudbury, MA on 10/18/2016

Crutchfield Customer Review (What's this?)

Unit is well made and sounds awesome. It got a bit warm on first use but after improving the Gnd connection, it was fine. I use it in bridged mode driving 2 Klipsch rock speakers out on my patio. The sound is awesome.

Pros: Great quality, great sound, versatile

Cons: none yet

Great amp

John D. from Corpus Christi, TX on 6/20/2016

Crutchfield Customer Review (What's this?)

I've alway used Rockford amps and this one rocks! Coupled with a set of Polk speakers my jeeps sound is where it needs to be for someone that has his top off 9 months out of the year.

Pros: Great bang for you buck. Quality amp from Rockford

Cons: None

Nice Amp

MikeV530 from Philadelphia, PA on 4/22/2016

Crutchfield Customer Review (What's this?)

Great amp!!! Awesome price!!

Pros: Quality, price

Cons: None so far

Excellent Sound Rediculously LOUD!!!

Audiology from NY on 4/16/2016

Rated almost 400 watts. Sound is excellent for an entry level unit. I never hear systems that run anywhere near as loud as this. Subs yes, but not everything else. Pushes my Sony 6 x 9 speakers almost like subs. I wouldn't trade my Sony speakers for Polks if they were free. In fact, I'd throw them out and get more 6 x 9 Sonys. With an amp like this driving them the only purpose for a sub is to broadcast bass and go deaf. Sound quality is amazing even at lower volumes. Plenty of headroom for my speakers runing this at 50% and under with zero gain.

Pros: Sound Quality. Pumps Bass. Max Headroom. Can Run Without Big Three.

Cons: Big. Heavy. Hard to Mount in Newer Cars with Few Flat Surfaces.

Solid functional amp

Les from Hilo, HI on 4/5/2016

Crutchfield Customer Review (What's this?)

I mounted the amp under the front passenger seat which fit perfectly and easy to get to the controls! I'm still tweaking the amp but as an amateur I configured it to a good sounding for my car. I'm running the Polk 5 1/4 speakers for the front and it sounds way better than the Sony speakers I previously were running! Maybe I'll get Polk rear speakers for a better bass! I don't have that solid bass but I don't want the loudness of a sub-woofer!

Pros: Easy to hook up and adjust the gain to the speakers!

Cons: If anything, I'm not getting to solid bass from this unit! Maybe it's my rear speakers but not much cons to this unit!

Rockford Fosgate Prime R300X4

barry from Tampa, FL on 3/30/2016

Crutchfield Customer Review (What's this?)

Very clean 4 channel sound.

Pros: seems to be very efficient.

Cons: None


r chapa from san antonio, TX on 1/30/2016

Crutchfield Customer Review (What's this?)



Cons: NONE

Terrific amp

Jontyrees from austin, TX on 1/29/2016

Just installed this to replace an alpine MRPF300 tht never impressed me. Night and day difference. This RF is sooo much better, finally the system sounds like I thought it should. I blamed head units, speakers, previously, but the problem was the two alpine amps, mrp500 and MRPF300. I replaced both with similar rated and priced RF Prime units, and the difference is staggering. Simply switched out the amps, changed nothing else. I'll never use another brand of amp than RF from now on. Oh, and the birth certificate showed 416w RMS, vs 300w rating.

Pros: Great sound, great price, good looking, adjustments on top

Cons: I didn't buy it soon enough

Great amp

Barto from New Jersey on 1/17/2016

Crutchfield Customer Review (What's this?)

Great amp, very flexible with different setups, using it to drive 6x8 Polk coaxials front and rear and has more than enough power. Very happy with this amp, Install was very easy nice size gives you lots of choices.

Pros: Great power,very clean,very flexible with different setups

Cons: None

Works great

Dennis D. from Sarasota, Florida on 1/11/2016

Crutchfield Customer Review (What's this?)

Works great. Easy setup.



Rockford Fosgate Prime R300X4

808xN8 from Hawaii on 1/4/2016

Crutchfield Customer Review (What's this?)

Excellent amp. Provides more than enough power for 6 1/2 inch front and rear component speakers that I have in the doors. Also allows me flexibility to change/ upgrade the speakers in the future if wanted. I Have the gain set at half power right now.

Pros: Small and powerful. Looks good and simple to hook up. Sound comes out clear at high volume.

Cons: Not many I can think of yet. To be picky , it could have bigger connections for wire inputs and outputs. They seem small for the power of the amp.

best amp to get for your car speakers clear sound amazing!

eddie from whittier ca on 8/9/2014

best amp to get for your car speakers clear sound amazing!




Hands-on research

Product Research



Overview: The front and rear sections of the Rockford Fosgate Prime R300X4 4-channel amplifier are bridgeable, so it can be wired in 4-channel, 3-channel, or 2-channel mode.

CEA 2006 Compliant: The R300X4's power ratings and signal to noise ratio are measured according to the uniform standards advocated by the Consumer Electronics Association (CEA). This allows you to accurately compare these specifications for all CEA 2006-compliant amplifiers, even from different brands. Manufacturers who adhere to these standards can display the CEA 2006 logo on their products and packaging. CEA2006 Specifications for this amplifier are:

  • 4 Ohms: 50 watts RMS x 4 at 4 ohms, 14.4 volts, and less than 1% THD+N
  • 2 Ohms: 75 watts RMS x 4 at 2 ohms, 14.4 volts, and less than 1% THD+N
  • Bridged: 150 watts RMS x 2 at 4 ohms, 14.4 volts, and less than 1% THD+N
  • S/N: 80 dB, measured at 1 watt output (100 dB measured at rated power)

LED Indicator: The amplifier is equipped with an LED power/protect indicator. The LED illuminates blue when the unit is turned on. It illuminates red if the thermal or short circuit protection circuit is engaged, and the amplifier will automatically turn off.

Mounting: The amplifier can be mounted vertically or horizontally using the supplied mounting screws. The amplifier should never be mounted in an engine compartment as this will void the warranty.


Gain Controls: The front and rear amplifier channels have independent gain controls. Each rotary control is labeled 1 to 11 and has a sensitivity range of 150mV to 4V when using the RCA inputs, 450mV to 12V when using the speaker level inputs.

Crossover: There are also independent 12 dB/octave crossovers for the front and rear channels. Crossover switches allow you to choose low-pass, high-pass, or full-range operation. The crossover points are continuously variable from 50 to 250 Hz.

Punch EQ: The Punch EQ bass boost circuits are individually selectable, 0 (flat), +6 dB, or +12 dB and centered at 45 Hz.

Input Switch:

  • 2-CH: when using only the front inputs
  • 4-CH: when using the front and rear inputs


Power Terminals: The power and ground terminals are nickel-plated set screw terminals and will accommodate up to 4 gauge power and ground wires.

Fuse: An external 50-amp fuse (not included) must be installed on the power wire at the battery. If a wiring kit is used which includes a fuse with a value other than 50-amps, the original should be replaced with a 50-amp fuse.

Remote Terminal: The remote turn-on terminal is a nickel-plated set screw terminal that will accommodate up to an 8 AWG wire. It's used to remotely turn the amplifier on and off.

Speaker Terminals: The four pair of speaker outputs are nickel-plated set screw terminals what will accommodate up to 8 AWG speaker wire.

RCA Input Jacks: Front and rear RCA input jacks provide an easy connection for preamp level inputs. They are nickel-plated to resist signal degradation caused by corrosion.

Speaker Level Input: Two speaker level input harnesses are included, making it easier to add the amplifier to a factory radio or to a receiver with no preamp outputs.

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?

REplacing older unit that shorted out. Daisy suggested this was as good as other in the price range and it will fit in the same place. [ Leyton  Nov 25, 2017 ]
To power front and rear component speakers [ Michael  Nov 08, 2017 ]
It's awesome [ Julietta  Oct 06, 2017 ]
Recommended by Crutchfield in order to provide the quality I was looking to achieve in my sound system.. [ STEVE  Aug 27, 2017 ]
Rockford Fosgate has never disappointed me in the past, I see no reason to not continue trusting their legacy of quality and power, even if it is the entry level line. [ Rhett  Aug 14, 2017 ]
Great amp i already have 3 [ oneil  Jun 23, 2017 ]
All the power my speakers need [ Donna  May 31, 2017 ]
It was recommended by an advisor to power my speakers [ Samuel  May 17, 2017 ]
Have used previously and it is a good product. [ MIRIAM  Jan 15, 2017 ]
I needed a good 4 channel amp for my car, since I was running a 2 channel amp. And might I took my music to another level...especially when I took the factory speakers out and added aftermarket. [ Cleotis  Sep 30, 2016 ]
Purchased this due to its reputation in the industry will not use anything else. [ Rodney  Jun 20, 2016 ]
Brand reputation and customer and Crutchfield ratings. [ harold  Jun 01, 2016 ]
The sales associate help choose this item, which after the explanation was given, it made since to choose this item. [ Lanell  May 06, 2016 ]
Brand [ Walter  Apr 23, 2016 ]
Rockford Fosgate is best brand for amps [ Alex  Mar 27, 2016 ]
are you kidding its RF [ barry  Mar 19, 2016 ]

5 questions already asked

I'm going to go ahead and recommend that you try an amp with a lower rms output. This amp pushes way more than what you actually need and you could probably go a lot cheaper as well and get great sound. If you are running 4 of these I would get a four channel amp around the 100-150 rms range. If you are running only 2 I would stick to an amp with an output no more than 100 and I would really try to find one at 60 if you can. I hope this helps at least a little! [ Cody  Dec 09, 2016 ]
Should be no problem using factory wires [ DENNIS  Mar 17, 2016 ]
THis is personal preference, you can use factory wiring, you'll just need to map out the color codes on wires to get your front and back left to right correct. Typically factory wiring is small gauge wiring, a lot of people prefer large diameter wires, believe to increase sound quality. I prefer larger than factory wires. But it's a lot of work and extra money. Most cases factory should be fine tho. I first noticed difference in sound quality in home stereo, using monster cable instead of small gauge. My ears seem to like bigger cables. Hope this helps [ Richard  Mar 16, 2016 ]
How much watts you need depends on the speakers you plan on using. This amp is 75x4 rms. I'm no expert but usually the peak output is about double the rms. I have the gain set at about 1/2 for front and rear components that rate 50watts rms. it's way more than enough, but allows for future upgrades [ Nathan  Dec 28, 2015 ]
I don't think so. [ JESSE  Sep 24, 2014 ]
We have not received any answers from other customers on your question. I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They should be able to help answer your question. [ Krissy  Sep 16, 2014 ]  Staff
I forwarded your question to an Advisor and they responded with the following: The amplifier has speaker level inputs, so you do not "need" an LOC. It can still help if you want to get the cleanest signal to your amplifier from the factory radio. If you would like to discuss further you can contact an Advisor directly by phone (1-800-324-9695) or online chat. [ Krissy  Aug 06, 2014 ]  Staff