Rockford Fosgate R2-500X1 Review: Compact 500 W Sub Amp

This Rockford Fosgate R2-500X1 review answers the buying question first. The amplifier makes sense for one subwoofer in a daily driver when the buyer wants a remote level knob, an adjustable infrasonic filter and a compact Class-D chassis, and accepts paying more per rated watt than some rivals ask. Rockford rates it at 300 W RMS at 4 ohms and 500 W RMS at 2 ohms, and it is priced at $309.99.

It is a current model. The Prime R2 range began shipping in late December 2019, the R2-500X1 belongs to the third generation of Prime amplifiers, and Rockford names no successor. The R2-250X1, R2-750X1 and R2-1200X1 carry similar numbers but different power ratings, so the full R2-500X1 label is the one to match.

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Build and layout of the Rockford Fosgate R2-500X1

The R2-500X1 is a full-range Class-D mono amplifier in a cast aluminum heat sink case. Rockford lists it at 1.9 in high, 6.8 in wide and 8.5 in deep (4.9 x 17.3 x 21.5 cm), and the manual gives an overall figure of 7.3 in for the shorter side, so a mounting spot needs a little room beyond the 6.8 in body. Cooling is by convection, and the manual asks for at least 1 in of open air around the heat sink. Weight is not confirmed.

The controls sit on the top panel: input gain, low-pass frequency, infrasonic frequency and Punch EQ, plus LEDs for power (blue), protect (red) and the two C.L.E.A.N. clip indicators. Power and ground terminals use set screws and accept up to 4 AWG cable, while the remote and speaker terminals accept up to 8 AWG. A 3 mm hex key is supplied. The two positive and two negative speaker terminals are wired in parallel inside, so one pair is enough for a single subwoofer.

Protection covers short circuits and over-current. NOMAD circuitry guards against shorted speaker wire and very low impedance loads, and rollback protection lets the amplifier reduce its own demand on hard passages to spare the output devices. A dealer listing puts the amplifier, a wired remote level control with a 16 ft cable, one 7 in speaker-input harness, hardware, the hex key and the instructions in the box.

Features and tuning on the Rockford Fosgate R2-500X1

Setup revolves around C.L.E.A.N., a patented clip-indicator method. With the speakers disconnected, the source volume goes up until the IN light turns red and then back down until it clears. The amplifier gain is raised until the OUT light turns red and backed off until it clears. For test tones the manual suggests 40 Hz at -10 dB when tuning a subwoofer.

The low-pass filter runs from 50 to 250 Hz at 12 dB per octave, the infrasonic filter from 15 to 40 Hz, and Punch EQ adds 0 to 18 dB at 45 Hz. The manual recommends 50 to 80 Hz for a subwoofer low-pass and 25 to 30 Hz for the infrasonic filter. One inconsistency exists: the manual's design-features page says the mono models use 24 dB per octave, while its specification table and Rockford's product page both say 12 dB, so 12 dB is the figure used here.

Punch EQ has a practical side effect. Our calculation puts +18 dB at about 7.94 times the voltage, or 63.1 times the power, at 45 Hz, so a source signal only 12.6 percent as strong reaches the same output at that frequency. The manual says the same in plain terms: set C.L.E.A.N. OUT again after touching Punch EQ, because high boost levels can cause over-excursion.

Input options are RCA (150 mV to 4 V) or a 4-pin high-level harness (450 mV to 12 V), never both at once, and RCA pass-through outputs allow a second amplifier to be daisy-chained. Auto turn-on reads the DC offset on the front-left speaker lead and works only with high-level input. With that switch off, the remote terminal needs a 12 V switched lead. The included remote level control adjusts the subwoofer channel only.

A short fitment checklist:

• Factory radio with no RCA outputs: use the high-level input and the supplied speaker-input harness.
• Aftermarket radio with RCA pre-outs: use the RCA inputs and a remote turn-on lead.
• Vehicles with retained accessory power: the product page lists an auto-sense bypass switch for them.
• Subwoofer load: the final load must be 2 ohms or higher (the load table below shows the wiring).

Rated power of the Rockford Fosgate R2-500X1

Rockford rates continuous output at 300 W x 1 at 4 ohms and 500 W x 1 at 2 ohms, measured at 14.4 V with THD+N under 1 percent. The manual calls the standard CEA-2006, and the product page now writes CTA-2006. The page also lists dynamic power of 350 W at 4 ohms and 590 W at 2 ohms, which the rated figures work out to 16.7 and 18.0 percent above the continuous ratings.

Frequency response is 20 to 250 Hz, and the manual lists a CEA-2006 signal-to-noise ratio above 75 dB. Rockford says the P.O.W.E.R. supply raises output as voltage rises, but it publishes no rating at a lower voltage such as 12.5 V. Our research found no independent lab measurements for this model.

Maximum current draw is 52 A at 13.8 V with a sine wave. Our calculation turns that into about 718 W of electrical input at the peak. The 80 A fuse is 1.54 times that draw, which leaves room without being oversized. Rockford publishes no average music current figure.

Load options for one or two subwoofers

The loads below come from series and parallel arithmetic, not from Rockford's tests. Rockford's own wiring diagrams all aim for 2 ohms, where the amplifier gives its full rating.

Subwoofer wiring	Load seen by the amplifier	Rated output
One sub, single 4 ohm coil	4 ohms	300 W
One sub, single 2 ohm coil	2 ohms	500 W
One sub, dual 4 ohm coils in parallel	2 ohms	500 W
One sub, dual 2 ohm coils in series	4 ohms	300 W
One sub, dual 4 ohm coils in series	8 ohms	No figure published
Two subs, single 4 ohm coils in parallel	2 ohms	500 W
Two subs, dual 2 ohm coils (series per sub, subs in parallel)	2 ohms	500 W
One sub, dual 2 ohm coils in parallel	1 ohm	Not recommended

Installing the Rockford Fosgate R2-500X1 safely

The manual's installation rules shape the whole job:

1. Disconnect the negative battery terminal before starting.
2. Fit an in-line fuse holder within 18 in of the battery, with an 80 A fuse. The fuse is not supplied.
3. Use 4 AWG power and ground cable. Keep the ground under 30 in, run it to bare welded metal with the paint removed, and never use a seat belt bolt.
4. Route RCA cables together and away from the power cable, and keep power off when plugging RCA cables in.
5. Leave 1 in of air around the heat sink. Vertical or inverted mounting is acceptable, and mounting in the engine compartment voids the warranty.

A few dealer listings suggest 8 AWG wire and a 50 A fuse. The manual and Rockford's page say 80 A and 4 AWG, and the 52 A maximum draw is above 50 A, so the smaller fuse would sit below the amplifier's own peak current.

Cable length matters too. Our calculation for 15 ft of power cable plus 2.5 ft of ground at 52 A gives 0.23 V lost in 4 AWG copper (1.6 percent of 13.8 V, roughly 12 W) against 0.57 V in 8 AWG copper (4.1 percent, roughly 30 W). The model assumes pure copper at 20 C, so copper-clad aluminum kits are not covered.

Two more safety points come from the manual. Continuous exposure above 100 dB can cause permanent hearing loss, and car systems can exceed 130 dB. Rockford's warranty also excludes water damage on products that are not Element Ready, and the R2-500X1 is not described as water-resistant, so it belongs in a dry spot.

How the Rockford Fosgate R2-500X1 compares

Two mono amplifiers in the same price band show where this one stands: the Kicker CXA800.1 and the JL Audio JD500/1. The Kicker CXA800.1 is rated 300 W at 4 ohms, 600 W at 2 ohms and 800 W at 1 ohm, so it is stable at 1 ohm, and Kicker gives it a two-year warranty when bought from Kicker or an authorized dealer. The JL Audio JD500/1 is rated 250 W at 4 ohms and 500 W at 2 ohms, publishes a 12.5 V rating of 400 W at 2 ohms and has no infrasonic filter. The R2-500X1 answers with a variable 15 to 40 Hz infrasonic filter, up to +18 dB of boost and a remote control in the box, but it trails the Kicker on rated power and on warranty length.

Spec	Rockford Fosgate R2-500X1	Kicker CXA800.1	JL Audio JD500/1
Price (USD)	$309.99	$299.99	$279.99
RMS at 4 ohms	300 W	300 W	250 W
RMS at 2 ohms	500 W	600 W	500 W
RMS at 1 ohm	Not rated	800 W	Not rated
Rating at 12.5 V	Not published	Not confirmed	400 W at 2 ohms
Low-pass range (12 dB/octave)	50 to 250 Hz	50 to 200 Hz	50 to 500 Hz
Infrasonic filter	15 to 40 Hz, variable	25 Hz, fixed, 24 dB/octave	None
Bass boost	0 to +18 dB at 45 Hz	0 to +6 dB at 40 Hz	Yes, range not confirmed
Wired remote	Included	Sold separately	Sold separately
Recommended fuse	80 A	Not confirmed	50 A
Size (in, height x footprint)	1.9 x 6.8 x 8.5	2.4 x 6.8 x 8.1	2.1 x 7.5 x 9.5
Signal-to-noise	Above 75 dB (CEA-2006)	Above 95 dB, A-weighted	Above 80 dB below rated power, A-weighted
Warranty	1 year	2 years	Not confirmed

The signal-to-noise rows use different test conditions, so they are not a like-for-like ranking. The rated figures work out to $0.62 per watt at 2 ohms for the R2-500X1, against $0.50 for the Kicker and $0.56 for the JL. The Rockford is the most expensive per watt of the three, and the included remote narrows that gap only by an amount that depends on what the other two remotes cost.

Who should buy the Rockford Fosgate R2-500X1, and who should skip it

The Rockford Fosgate R2-500X1 suits a driver with one subwoofer, either a single 2 ohm load or a dual-voice-coil sub wired to 2 ohms, who wants a dash-mounted bass knob without buying one separately. It also fits a car with a factory radio, because the high-level input and auto turn-on remove the need for a line-output converter. The adjustable infrasonic filter is useful for ported enclosures, and a buyer who adds a matching Rockford wiring kit gets an extra year of warranty.

It is a poor match for anyone planning a 1 ohm load, since the manual sets 2 ohms as the lowest sub load. Two low-impedance subs that land below 2 ohms need a 1 ohm stable amplifier such as the Kicker CXA800.1. Buyers who rank a longer base warranty or the lowest cost per watt first are better served by the Kicker, and those spending less may prefer the JL Audio JD500/1. The amplifier is not bridgeable, and shoppers who want independent measurements should know none were found.

Rockford Fosgate R2-500X1 price and pre-purchase checks

At Rockford Fosgate and at the dealer Car Tunes, the R2-500X1 is priced at $309.99 (US dollars). Prices change often, so check the current listing.

Before paying, confirm these points:

• Model number: R2-500X1. The R2-250X1 is rated 150 W at 4 ohms and 250 W at 2 ohms, the R2-750X1 is rated 250 W, 500 W and 750 W at 4, 2 and 1 ohms, and the R2-1200X1 is rated 400 W, 800 W and 1200 W at the same loads.
• Rating: some dealer listings give 250 W at 4 ohms, but the manual and Rockford's page give 300 W, and the manual wins.
• Seller: Rockford's warranty covers original purchasers who bought from an authorized dealer in the United States and can show a receipt, so confirm the seller is authorized.
• Warranty length: the base term is one year. Rockford's product page says a matching installation kit adds one year, while its 2019 launch release said the kit raises the total to three years, so ask the seller which applies.
• Extras: the fuse holder, fuse, power and ground cable, RCA cable and speaker wire are not included.

Buyers who want to match the model number against a live listing can check the current price on Amazon, and should still confirm the seller's authorized-dealer status before ordering.

Final verdict and score for the Rockford Fosgate R2-500X1

The R2-500X1 earns 3.5 out of 5. It is a feature-rich mono amplifier for a single subwoofer, with infrasonic and boost controls the two rivals handle less flexibly. The score is held back by a one-year warranty, a 2 ohm minimum load, the highest cost per rated watt of the three amplifiers compared, and the lack of independent measurements.

The rubric weights performance and function at 40 percent, features and usability at 20 percent, build quality and design at 15 percent, and value at 25 percent. The weighted result is 3.475, which rounds to 3.5 on the half-point scale.

Category	Weight	Sub-score	Weighted points
Performance and function	40%	3.5	1.4
Features and usability	20%	4.0	0.8
Build quality and design	15%	3.5	0.525
Value for the price	25%	3.0	0.75
Total	100%		3.475 (rounds to 3.5)

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

Sources and further reading

• Rockford Fosgate R2-500X1 product page: rated and dynamic power, filters, fuse, current draw, size and price.
• Rockford Fosgate Prime amplifier owner's manual (PDF): installation rules, C.L.E.A.N. setup, signal-to-noise and warranty terms.
• Rockford Fosgate Prime R2 availability release: launch timing and the original kit warranty wording.
• PASMAG coverage of the Prime R2 launch: December 2019 shipping and the R2 model lineup.
• Car Tunes R2-500X1 listing: dealer price and box contents.
• Kicker CXA800.1 product page: rival power ratings, filters, size, price and warranty.
• JL Audio JD500/1 dealer specification page: rival power ratings, 12.5 V rating, filters, size and price.