Rockford Fosgate R2-750X5 Review: Compact 5-Channel Amp

The Rockford Fosgate R2-750X5 is a small Class D five-channel car amplifier, and at $539.99 it is a reasonable buy for a four-speaker system with one subwoofer, provided the bass channel does not need more than 350 W. This Rockford Fosgate R2-750X5 review covers the rated figures, the wiring the amp needs, one independent set of lab measurements and three rival amps. It is a current model in the Prime R2 line that Rockford announced in November 2019, and the manufacturer's site names no successor.

The catches are plain: 12 dB per octave crossovers with no DSP, a one-year warranty, and a published lab report that puts both noise figures below the rated minimums. The appeal is size and current draw: a 1.9 by 6.8 by 11.2 inch chassis and a 71 A maximum draw.

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Rockford Fosgate R2-750X5 design, build and box contents

The amp sits in a cast aluminum heat sink that measures 1.9 by 6.8 by 11.2 inches (4.9 by 17.3 by 28.5 cm), cooled by convection with no fan. The manual gives an overall length of 7.3 inches against the 6.8 inch body, so plan clearance for the larger number. The body works out to 144.7 cubic inches (model).

BestCarAudio took one apart for its lab report and describes a densely populated board, an iron-core choke on the positive input to limit radiated RF noise, and extruded aluminum hold-downs on the power supply and output devices in place of spring clamps.

Power, signal and speaker terminals all sit on the front edge, with the controls on top. The power and ground terminals take wire up to 4 AWG and the speaker terminals up to 8 AWG, tightened with the 3 mm hex key in the box. The box also holds mounting screws, 4-pin Molex pigtails for speaker-level inputs and the RLC remote level control. Wire, fuse and holder are not included.

A Protect light turns red on overheating or a short, and the amp mutes. The manual says never to mount it in the engine compartment, which voids the warranty.

Controls and features on the R2-750X5

The 2/4/5 input switch tells the amp how many input pairs are connected, so a single pair of speaker-level leads can feed all five channels. The high-level inputs accept 450 mV to 12 V and the RCA inputs 150 mV to 4 V, and the manual says to use one input type per channel, never both. Auto turn-on reads the DC offset on the radio's front-left speaker lead, so it works only with high-level inputs.

The filters are 12 dB per octave Butterworth, adjustable from 50 to 250 Hz. Front and rear channels switch between high-pass, low-pass and all-pass, and the sub channel adds an infrasonic filter from 15 to 40 Hz. The manual suggests 50 to 80 Hz for subwoofers and 80 to 120 Hz for 5.25 inch and 6x9 inch speakers. Punch EQ adds 0 to 18 dB at 45 Hz on the sub channel only, and BestCarAudio measured 18 dB at 47 Hz. Some retailer listings give the Punch range as 0 to 12 dB, but the manual and the published measurement both point to 18 dB. The RLC remote in the box controls the sub level only.

Bridging the front and rear pairs gives a three-channel mode: two 200 W channels at 4 ohms plus the sub channel, 600 W in total with the sub at 4 ohms. Rockford's feature list mentions RCA pass-through outputs, but its spec table shows no signal output and the manual states that pass-through is not available on this model. The manual wins. The spec sheet lists no DSP, app or wireless remote.

What the Rockford Fosgate R2-750X5 rated figures mean

According to our research, the manufacturer rates it at 50 W x 4 plus 200 W at 4 ohms and 100 W x 4 plus 350 W at 2 ohms, measured at 14.4 V to the CTA-2006 standard. The 750 in the model name is the 2 ohm sum. Our calculation from the rated figures gives 400 W in total at 4 ohms, so a system built on 4 ohm speakers and a 4 ohm sub gets a little over half the headline number. The sub channel holds 46.7% of the 2 ohm total.

The manufacturer also publishes dynamic power (PVC/PowerCube figures): 70 W x 4 plus 241 W at 4 ohms, and 114 W x 4 plus 426 W at 2 ohms. Against the rated figures, that is a ratio of 1.40 on the full-range channels at 4 ohms and 1.14 at 2 ohms, and 1.21 and 1.22 on the sub channel. The dynamic sums come to 521 W and 882 W.

Rockford says the power supply raises output as supply voltage rises. The ratings are set at 14.4 V, and the amp is specified for 9 to 16 V. Our calculation, assuming output scales with the square of supply voltage (Rockford publishes no curve), puts a 13.8 V system at 91.8% of the rated figures. BestCarAudio took its readings below 14 V, noting some power was left unused, mainly on the sub channel, and concludes that the amp would exceed all its ratings at 14.4 V.

What BestCarAudio published

BestCarAudio's lab report, written by Dave MacKinnon in September 2022, reports 0.02312% THD+N on the front channels at 1 kHz and 1 W, and 0.13615% on the sub channel at 50 Hz, a figure the reviewer says is nudged up by slightly high background noise. Crosstalk stays at or better than 60 dB through most of the audible range, and moving from a 4 ohm to a 2 ohm load changed the response by 0.2 dB. The crossover slopes match the 12 dB per octave rating. The reviewer's listening notes call the amp well behaved but not audiophile-grade, with slight brightness in the top end.

Noise is where the published numbers and the ratings part ways. The reviewer measured a signal-to-noise ratio of 73.26 dB on the front channels and 70.18 dB on the sub at 1 W, against ratings of better than 80 dB and 75 dB. According to AGR's analysis of published measurements, the rated minimums sit 6.74 dB and 4.82 dB above the measured values, so the ratings read as best-case figures. The reviewer ran below 14 V and still called the results far ahead of many budget amplifiers.

On current, the manufacturer gives a maximum draw of 71 A with a sine wave at 13.8 V, which is about 980 W of electrical input. That is 1.31 W in per rated watt out at 2 ohms (model, since the ratings are set at 14.4 V). BestCarAudio reports just over 60 A with all five channels at full power into 2 ohms. The 120 A fuse is 1.69 times the maximum draw.

Installing the R2-750X5: wire, fuse, fitment and setup

Fuse first. The manual requires the positive wire to be fused within 18 inches (45.7 cm) of the battery, and it lists 120 A as the fuse rating. Rockford recommends 4 AWG for power and ground. Keep the ground under 30 inches (76 cm), on bare metal, never on a seat belt bolt. Disconnect the battery negative before wiring, use grommets at the firewall, and keep RCA cables away from the power run.

Gauge matters at full current. Our calculation, from the resistance of copper wire at 71 A with a 2.5 foot ground lead (the manual's 30 inch limit), gives these drops:

Wire	Power run	Total run	Voltage drop	Share of 13.8 V	Heat in wire
4 AWG	10 ft	12.5 ft	0.22 V	1.6%	16 W
4 AWG	15 ft	17.5 ft	0.31 V	2.2%	22 W
4 AWG	20 ft	22.5 ft	0.40 V	2.9%	28 W
8 AWG	10 ft	12.5 ft	0.56 V	4.0%	40 W
8 AWG	15 ft	17.5 ft	0.78 V	5.7%	55 W
8 AWG	20 ft	22.5 ft	1.00 V	7.3%	71 W

Assumptions: annealed copper at 20 C, maximum draw and a 13.8 V supply. A 15 ft run in 8 AWG would lose 0.78 V and turn 55 W into heat, against 0.31 V and 22 W in 4 AWG.

Setup uses the C.L.E.A.N. lights. With the speakers disconnected and the radio's tone controls flat and loudness off, raise the radio volume until the C.L.E.A.N. IN light turns red, then back off until it goes dark. That volume is the clean ceiling. At the ceiling, raise each gain until its C.L.E.A.N. OUT light turns red and back it off until it goes dark. Set Punch EQ last and repeat the output step, because the boost changes the level.

Safety notes from the manual: high Punch EQ boost can push a woofer past its excursion limit, gains set too high add noise and distortion that can damage speakers, and continuous sound pressure above 100 dB can cause permanent hearing loss. Leave at least 1 inch (25.4 mm) of air around the heat sink; a trunk floor cools best. Never screw the amp to cardboard or plastic panels, and have the alternator and battery checked first.

Rockford Fosgate R2-750X5 against three rivals

Three other five-channel amps sell in the same price band. The Kicker KXA800.5 is priced at $579.95, or $0.72 per rated watt at 2 ohms. Its sub channel gets 400 W at 2 ohms and is rated for 1 ohm, and it includes a Bluetooth remote and carries a two-year warranty from an authorized dealer or the maker. Its body is about 56% larger by volume than the Rockford Fosgate R2-750X5.

The Alpine S2-A55V is priced at $499.95, or $0.93 per rated watt at 2 ohms, with 40 W x 4 plus 200 W at 4 ohms and 60 W x 4 plus 300 W at 2 ohms. Its ratings use under 0.1% THD+N, a tighter basis than the 1% used by the others. Its remote knob is sold separately, and its body is about 53% larger by volume than the Rockford amp. The Pioneer GM-DX975 is priced at $550.00, or $0.55 per rated watt at 2 ohms, with 75 W x 4 plus 350 W at 4 ohms and 100 W x 4 plus 600 W at 2 ohms and a wired bass remote. Its dimensions and warranty are not confirmed.

The Rockford Fosgate R2-750X5 costs $0.72 per rated watt at 2 ohms and $1.35 at 4 ohms. Its body is the smallest of the three with confirmed dimensions, which makes it a fitment pick more than a bass pick.

Amplifier	Price (USD)	Rated, 4 ohm	Rated, 2 ohm	Sub at 2 ohm	Per watt, 2 ohm	Body volume	Remote	Warranty
Rockford Fosgate R2-750X5	$539.99	400 W	750 W	350 W	$0.72	144.7 cu in	Wired RLC, sub	1 year
Kicker KXA800.5	$579.95	400 W	800 W	400 W	$0.72	225.2 cu in	Bluetooth, included	2 years
Alpine S2-A55V	$499.95	360 W	540 W	300 W	$0.93	220.9 cu in	Optional knob	Not confirmed
Pioneer GM-DX975	$550.00	650 W	1000 W	600 W	$0.55	Not confirmed	Wired, included	Not confirmed

Who should buy the R2-750X5 and who should skip it

The Rockford Fosgate R2-750X5 suits a system with four speakers and one subwoofer that wants a single amp and a single power run. It also suits a factory radio, since the high-level inputs and auto turn-on remove the need for a line-output converter, and tight spots, since the body is 1.9 inches tall.

Skip it if:

• The subwoofer needs more than 350 W, or its wiring ends at a load below 2 ohms.
• The plan calls for DSP, steeper filters or a wireless remote.
• A second amp has to be daisy-chained from RCA pass-through jacks, which this model lacks.
• Cost per rated watt is the goal, since a rival in the table beats it on that measure.

Rockford Fosgate R2-750X5 price and pre-purchase checks

Rockford Fosgate prices the R2-750X5 at $539.99. Prices change often, so check the current listing. That is $0.72 per rated watt at 2 ohms, $1.35 at 4 ohms and about $108 per channel.

Before ordering, check the current price on Amazon and any other seller against this list:

• Model number: the R2-750X1 is a 750 W mono amplifier from the same series, not this five-channel unit.
• Condition: the manual gives factory refurbished products 90 days of coverage, against one year for new Prime amps.
• Seller: the warranty covers the original buyer of a unit sold by an authorized Rockford Fosgate dealer in the United States.
• Bundle: a matching Rockford installation kit adds a second warranty year, and the amp ships without wire or fuse.
• Fitment: confirm the 7.3 inch overall length fits.

Final verdict and score

The rating is 3.5 out of 5. The weighted result is 3.65, which rounds to 3.5 at the nearest half point. Performance and build earn 4.0 on standard-based ratings, low published distortion and a well-built interior. Features score 3.5 for the input options and C.L.E.A.N. lights, held back by 12 dB filters and no DSP. Value scores 3.0 because one rival gives more rated power per dollar and another a longer warranty.

Category	Weight	Score	Adds
Performance and sound or function	40%	4.0	1.60
Features and usability	20%	3.5	0.70
Build quality and design	15%	4.0	0.60
Value for the price at review	25%	3.0	0.75
Weighted result	100%		3.65

Our research score is based on the rated figures and documented details above.

Sources and further reading

• Rockford Fosgate R2-750X5 product page: spec table, features and price.
• R2 amplifier installation and operation manual: ratings, wiring, fusing and warranty terms.
• BestCarAudio lab report on the R2-750X5: published distortion, noise and current measurements.
• RV PRO announcement of the Prime R2 line: launch timing.
• Sound of Tri-State product listing: dealer price.
• Kicker KXA800.5 product page: rated power, price and warranty used in the comparison.
• Alpine S2-A55V product page: rated power, price and dimensions used in the comparison.
• Pioneer GM-DX975 product page: rated power, price and features used in the comparison.