Cicada Audio FLX500.4 — Compact 4-Channel Class-D Motorcycle Amplifier (500W RMS / 125W x4 @ 2Ω)
| Channels | 4 Channel |
| Power | 4x125W RMS |
| Year Range | 1998-2013, 2014-2023, 2024+ |
Fixing factory Harley audio doesn't require a competition-level build.
The Cicada Audio FLX500.4 is a compact 4-channel Class-D amplifier — the entry point in the FLX range — delivering 125W × 4 RMS at 2Ω and 250W × 2 RMS bridged at 4Ω. Same crossover architecture as the FLX700.4, same compact chassis, within factory charging system capacity. The correct starting point for a properly powered Harley audio upgrade.
Factory Harley audio clips before you've left the suburb. The built-in amplification in the Boom! Box radio was designed to a budget, not a performance target — it lacks headroom, rolls off where clarity matters, and has no meaningful output reserve once wind and road noise enter the equation at speed. The FLX500.4 solves that problem directly: real amplifier power from a chassis that fits standard Harley Touring fairing amp trays, with the crossover flexibility to drive any speaker stage configuration properly.
Who This Is For
For riders who want to fix factory Harley audio properly — not a competition-level high-output install, but a correctly specified amplifier that gives every speaker stage the power it needs to perform. The FLX500.4 runs within factory charging system capacity, fits standard amp trays, and carries the same full-range crossover as the FLX700.4. For builds that need more output per channel, or a higher-sensitivity pro-audio speaker system, the FLX700.4 is the direct step up at the same footprint.
What This Is Best For
- The straightforward Harley audio upgrade — replacing factory amplification with a proper external amp without the current draw, wiring complexity, or cost of a high-output build. The FLX500.4 makes a substantial real-world improvement with a standard install.
- Builds running 4Ω coaxial speakers — 95W × 4 at 4Ω properly powers factory-replacement and mid-tier upgrade coaxials. The FLX500.4 drives them correctly without over-speccing the install.
- Multi-way component builds requiring crossover flexibility — the full 20 Hz – 20 kHz crossover range with 48 dB per octave slope option makes the FLX500.4 a capable front stage amplifier for dedicated tweeter and midrange driver configurations, not just coaxials.
- Rear channel amplification in a two-amp system — pairing a higher-output FLX700.4 or FLX1000.4 on the front stage with the FLX500.4 on rear lids or Tour-Pak speakers matches amplifier output to the acoustic demands of each stage.
- Builds where charging system load is a design constraint — at 50A music draw, the FLX500.4 stays within factory alternator capacity on most Harley Touring models.
The Bottom Line
The right starting point for a Harley audio build that needs a proper amplifier without the infrastructure demands of a high-output system — 125 watts per channel from a chassis that fits a standard fairing amp tray and draws within the capacity of a factory charging system.
Ready to upgrade? Add to cart above. If the build needs more output per channel, the FLX700.4 is the direct step up — same footprint, same crossover architecture, 175W × 4 at 2Ω.
Power Output — What the Numbers Mean
The FLX500.4 delivers 95W × 4 at 4Ω and 125W × 4 at 2Ω at 14.4V — a fully charged, engine-running system. The 2Ω figures drive the product name: 125W × 4 yields 500W total RMS at rated voltage. For builds running modern 2Ω pro-audio motorcycle speakers, the 2Ω figures are what matter. For standard 4Ω coaxials, 95W × 4 still represents a meaningful improvement over factory output levels.
Bridged, the amp produces 250W × 2 at 4Ω — suited for a compact subwoofer, a high-output two-channel front stage, or a mid-bass enclosure in a saddlebag or Tour-Pak where maximum per-channel power is required from a 4Ω load.
Crossover and Signal Control
The FLX500.4 runs HPF, LPF, or Full Range crossover modes across the full 20 Hz – 20 kHz range with selectable slopes of 6, 12, 24, and 48 dB per octave — the same crossover architecture as the FLX700.4. This covers every standard configuration for a 4-channel motorcycle amp: high-pass filtering for fairing speakers, low-pass filtering for a rear mid-bass or subwoofer channel, and full-range operation for coaxial speakers.
At 48 dB per octave, the crossover provides clean isolation between a horn tweeter and a midrange driver — the kind of separation that keeps a front stage coherent at highway speed. At 6 dB per octave, the gentle slope suits full-range or wideband coaxial applications.
Input sensitivity runs 0.2V – 12V, covering both OEM Harley signal levels and standard RCA output from aftermarket head units without requiring a line driver.
System Integration
The FLX500.4 accepts high-level speaker output from the factory Harley Boom! Box radio directly — no signal processor or converter required for 2014–2023 models — or low-level RCA from any aftermarket head unit.
Turn-on supports three modes: REM (remote trigger from head unit), DC offset detection, and VOX (audio signal sensing). VOX activates the amplifier when it detects an audio signal from the source, handling factory Boom! Box integration cleanly without any additional wiring on platforms where routing a remote wire is not straightforward.
At 50A music-level current draw, the FLX500.4 operates within the range of most factory Harley charging systems. Maximum draw is 80A; a 50A fuse is recommended on the main power feed.
The FLX500.4 does not include onboard DSP. For builds requiring time alignment, multi-band EQ, or advanced signal routing, pair with a dedicated DSP processor upstream of the amp inputs.
2024+ Platform Notes
For 2023.5 CVO and 2024+ Harley-Davidson Touring models running Skyline OS, the FLX500.4 can be integrated as part of an aftermarket audio system when paired with a NAV-TV ZEN-H or ZEN-H Pro. The ZEN-H / ZEN-H Pro handles the Skyline OS signal interface — the FLX500.4 then receives the processed output and powers the speakers downstream from it. Without a NAV-TV ZEN-H or ZEN-H Pro, integration with a 2023.5 CVO or 2024+ Harley is not supported. For 2014–2023 models (excluding 2023.5 CVO), the high-level input connects directly to the factory Boom! Box radio.
Fitment
- Harley-Davidson Street Glide: Batwing fairing — fits standard fairing amp tray.
- Harley-Davidson Road Glide: Shark nose fairing — fits standard amp tray positions.
- Harley-Davidson Ultra Limited / Ultra Classic: Fits fairing amp rack positions.
- Harley-Davidson CVO models: Fits fairing amp rack (see 2024+ note above for Skyline OS bikes).
- Harley-Davidson Trike: Compatible — fits fairing, trunk, or saddlebag amp rack positions.
- Compatible with OEM Boom! Box radios (high-level input) and all aftermarket head units (high-level or RCA inputs).
- Run 2Ω speakers for maximum rated output; 4Ω for bridged applications.
Technical Specifications
| Channels | 4-Channel |
| Amplifier Class | Class D |
| Power Output — 4Ω Stereo @ 14.4V | 95W × 4 RMS |
| Power Output — 2Ω Stereo @ 14.4V | 125W × 4 RMS |
| Power Output — 4Ω Bridged @ 14.4V | 250W × 2 RMS |
| Total RMS Power | 500W |
| Efficiency | 80% |
| Signal-to-Noise Ratio | 91 dB (A-weighted, 20 Hz – 20 kHz) |
| THD + N | 0.1% @ 2Ω per channel (10% rated power) |
| Damping Factor | 200 |
| Frequency Response | 20 Hz – 20 kHz (±3 dB) |
| Crossover Modes | LPF / Full Range / HPF (selectable) |
| Crossover Range | 20 Hz – 20 kHz |
| Crossover Slopes | 6 / 12 / 24 / 48 dB per octave |
| Input Sensitivity | 0.2V – 12V |
| Inputs | High-level or Low-level RCA |
| Turn-On Modes | REM / DC Offset / VOX |
| Operating Voltage | 9V – 16V |
| Current Draw (Music) | 50A |
| Current Draw (Maximum) | 80A |
| Recommended Fuse | 50A |
| Weather Resistance | Outdoor-rated — moisture and vibration resistant |
| Dimensions — Chassis Only | 104 × 125 × 51 mm (4.0 × 4.9 × 2.0 in) |
| Dimensions — With Mounting Brackets | 131 × 125 × 51 mm (5.2 × 4.9 × 2.0 in) |
Australia Shipping:
- Under $500 → $19.95
- $500–$2,500 → $14.95
- Over $2,500 → FREE
- Bulky items → +$24.95 surcharge (waived over $2,500)
Fast dispatch from Brisbane. Same-day shipping on in-stock orders before 1pm AEST.
Change-of-mind returns: We accept returns within 7 days of delivery on unused, unopened products in original sealed packaging. Restocking fees apply (20–30%). Return shipping is the customer's responsibility.
No returns on opened audio gear, installed items, custom orders, or special-order products. Please check fitment carefully before installing.
Faulty or incorrect items: If you experience an issue, contact us with photos/video and your order number. We'll assess the claim and arrange repair, replacement, or refund for verified faults under the Australian Consumer Law.
Fitment assistance: If you're unsure about compatibility, reach out before ordering—we're happy to help.