Cicada Audio FLX700.4 — Full-Range 4-Channel Class-D Motorcycle Amplifier (700W RMS / 175W x4 @ 2Ω)

Power Output — What the Numbers Mean

The FLX700.4 delivers 120W × 4 RMS at 4Ω and 175W × 4 RMS at 2Ω — 700W total RMS at rated voltage (14.4V DC). That is the figure that matters for motorcycle builds where 2Ω pro-audio speakers are standard. The 2Ω figure represents real usable power, not inflated peak numbers.

Bridged, the amp produces 350W × 2 at 4Ω — the configuration for a two-speaker front stage that needs high output per channel, or for driving a compact subwoofer from the rear channels with authority.

At 80% Class-D efficiency, the FLX700.4 generates significantly less heat than a Class-AB amplifier at equivalent output. On a motorcycle with limited airflow and a charging system running near capacity, this matters for both thermal stability on long rides and for keeping electrical load manageable.

Crossover and Signal Control

The FLX700.4's crossover spans the full audio range — 20 Hz to 20 kHz — with four selectable slopes: 6, 12, 24, and 48 dB per octave. HPF, LPF, or Full Range mode selection. This is a significantly wider range and steeper slope capability than is common in motorcycle amplifiers, and the 48 dB/octave option is what makes the difference when running dedicated drivers.

At 48 dB/octave, you get clean separation between a midrange driver and a horn tweeter without bleed — the kind of control that keeps a front stage coherent at highway speeds. At 6 dB/octave, the gentle slope suits full-range or wideband coaxial applications.

For builds that need 254W per channel rather than 175W but do not require the steeper crossover slopes of the FLX700.4 — such as high-output coaxial builds — the FLX1000.4 offers more power with a 12 dB/octave crossover at 30 Hz – 300 Hz. The FLX700.4 is the correct choice when multi-way driver separation is part of the system design.

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.

Built for the Motorcycle Environment

The circuit board is conformal coated — a protective film sealing the electronics against moisture, humidity, and vibration-borne dust — and the whole amplifier is encased in an extruded aluminium heatsink chassis. On the road: road spray, humidity swings, and constant vibration are the normal operating environment for a fairing- or bag-mounted amp, not an edge case — this is the packaging that survives them.

The ICAD overload protection circuit guards the output stage against short circuits, thermal overload, and wiring faults, and two indicators handle the diagnostics: a power/protect LED that shows blue in normal operation and red in protect mode, and a dedicated clip LED that should only flash on musical peaks. If the clip LED holds solid for more than 2–3 seconds, back the volume or gain off. On the road: gain setting and fault-finding by eye — a shorted speaker wire or an overheating amp announces itself before it becomes a failure.

The crossover and gain potentiometers are detented — they click through fixed positions rather than sweeping freely, so settings are exact, repeatable, and immune to vibration drift. On the road: the crossover point set in the workshop is still the crossover point after a corrugated highway — and a known-good tune can be replicated on a second bike click-for-click.

Power and ground run through busbar-style terminals accepting up to 4 AWG wire, with 12 AWG busbar speaker terminals that clamp solid on bare speaker wire — no crimped pins to work loose under vibration. Signal input is via Molex® connectors, hooking up through standard RCA or H-D custom-terminated harnesses, and the speaker-output side can run plug-and-play through the HDFLXFO front and HDFLXRO rear H-D speaker output harnesses.

Mounting Options

Every FLX amplifier ships with two sets of mounting brackets: standard brackets (preinstalled) for flat-surface mounting, and inverted brackets that mount the amp top-face down — keeping the cooling fan on fan-equipped models facing downward with proper airflow clearance. The brackets carry multiple mounting points and can be trimmed or modified to suit a specific fairing, amp rack, or bag install without compromising structural integrity. Where there is no surface to screw into, the included 3M® locking velcro, zip ties, or straps secure the chassis directly. For 2024+ Road Glide® and Street Glide®, the model-specific 24HDAR-RG and 24HDAR-SG single-amplifier mounting systems bolt an FLX amp into the fairing without custom fabrication. On the road: the amp adapts to the space the bike actually has — factory amp tray, amp rack, or a tight custom cavity — rather than dictating it.

System Integration

The FLX700.4 sits between the source unit and the speakers in the signal path. It accepts high-level speaker output from the factory Harley Boom! Box radio directly — no additional converter required for 2014–2023 models — or low-level RCA from any aftermarket head unit.

Turn-on supports three modes: REM (remote trigger), DC offset detection, and VOX (audio signal sensing). VOX and DC offset are particularly useful for OEM integration on older Harley platforms where running a clean remote wire to the head unit is not straightforward.

At 50A music-level current draw, the FLX700.4 sits within the operating range of most factory Harley charging systems — no alternator upgrade required for most builds. Maximum draw is 80A; a 50A fuse is recommended on the power feed.

The FLX700.4 does not include onboard DSP. For builds requiring time alignment, multi-band EQ, or advanced signal routing — particularly on a Street Glide or Road Glide front stage running dedicated drivers — pair with a dedicated DSP processor upstream of the amp inputs.

A 2ch/4ch input switch lets channels 1/2 feed all four outputs from a single stereo pair — no external Y-adapters needed when running a 2-channel source into a four-channel or bridged configuration. For bikes retaining the factory Harley amplifier, Cicada's HDFiMY or HDFiM56Y-1.5 harness handles the OEM amplifier connection.

Wiring matters at these current levels: use properly sized OFC (oxygen-free copper) power and ground wire only — never CCAW (copper-clad aluminium), which carries less current for the same gauge and heats under sustained draw — and locate the main fuse within 457 mm (18") of the battery terminal.

2024+ Platform Notes

For 2023.5 CVO and 2024+ Harley-Davidson Touring models running Skyline OS, the FLX700.4 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 FLX700.4 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: Sharknose 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