Sky High Car Audio FXB 1400.4 4-Channel Amplifier

Sky High Car Audio FXB 1400.4 4-Channel Amplifier

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The Sky High Car Audio FXB 1400.4 is a compact Class D full-range amplifier built for customers who need serious speaker power without dedicating a large section of the vehicle to an amplifier rack. It delivers up to 375 watts RMS across four channels at 2 ohms while measuring only 7.01 inches long.

This makes the FXB 1400.4 a strong option for amplified door speakers, component systems, midrange drivers, pro-audio speakers, custom doors, motorcycles, powersports vehicles, factory-system upgrades and other installations where mounting space is limited.

Browse more Sky High Car Audio products, compare our complete selection of 4-channel amplifiers or view all car audio amplifiers.

Compact Power for Speakers, Mids and Custom Doors

The FXB 1400.4 provides enough output for much more than a basic factory-speaker upgrade. At 14.4 volts, it produces 200 watts RMS per channel at 4 ohms or 375 watts RMS per channel at 2 ohms.

That output can work well with higher-powered coaxial speakers, component sets, midrange drivers, midbass speakers and pro-audio systems when the speaker RMS rating, impedance and final channel load are properly matched.

Customers building a complete Sky High front stage can compare Sky High full-range speakers, Sky High midrange speakers, Sky High midbass speakers and Sky High tweeters.

RMS Power Ratings at 14.4 Volts

Four-Channel Mode

• 375 watts RMS × 4 at 2 ohms
• 200 watts RMS × 4 at 4 ohms
• 1,500 watts RMS combined at 2 ohms
• Minimum stereo impedance: 2 ohms per channel

Two-Channel Bridged Mode

• 700 watts RMS × 2 at 4 ohms
• 400 watts RMS × 2 at 8 ohms
• Minimum bridged impedance: 4 ohms

Important impedance notice: The FXB 1400.4 must not be operated below 2 ohms per channel in four-channel mode or below 4 ohms when bridged. Calculate the completed impedance of every channel before connecting the speakers.

Flexible Four-Channel or Bridged Operation

Run four independent channels for a complete front-and-rear speaker system, bridge one channel pair when part of the system needs additional power or bridge both channel pairs for a powerful two-channel configuration.

The amplifier includes selectable HPF, full-range and LP-BP crossover modes along with two-channel or four-channel input selection. These controls provide useful flexibility for several speaker layouts, but the final crossover settings should always be selected around the speakers being powered.

FXB 1400.4 Features

• Compact Class D full-range four-channel amplifier
• Full-range frequency response from 10 Hz to 25 kHz
• Operating-voltage range from 10 to 16 volts
• HPF, full-range and LP-BP crossover selection
• Two-channel or four-channel input selection
• Metal detent crossover adjustment controls
• Tiffany-style RCA connections
• Reversible Sky High emblem for different mounting positions
• Power, clipping and protection indicators
• Fanless design
• 85% rated efficiency at full power
• 95 dB signal-to-noise ratio
• 180 damping factor
• Less than 0.1% total harmonic distortion
• Thermal, overload, DC-output, short-circuit and input-voltage protection
• 4-gauge power and ground terminals
• 10-gauge speaker-output terminals
• 150-amp fuse rating
• Compatible with the SHCA modular mounting ecosystem
• Compatible with SHCA Universal Amp Key mounting options
• One-year manufacturer defect warranty

Compact Dimensions

• Width: 5.9 inches
• Length: 7.01 inches
• Height: 2.1 inches
• Quantity: One amplifier

Measure the intended mounting location before ordering and leave additional room for power wire, speaker wire, RCA cables, adjustment access and ventilation. Because the amplifier uses a fanless design, it should not be sealed inside an unventilated compartment or mounted where heat cannot escape.

Although the compact size makes it useful for motorcycle and powersports installations, the product is not identified as waterproof or marine-rated. Install it where it will remain protected from water and direct moisture.

Plan the Wiring and Electrical Support

The FXB 1400.4 uses 4-gauge power terminals and carries a 150-amp fuse rating. Power and ground wire should be selected around the conductor material, cable length, expected current demand and complete system—not terminal size alone.

Browse compatible car audio amplifier wiring kits and power, ground and speaker wire. Use properly sized fuse protection near the power source and keep the amplifier ground short, secure and connected to clean bare metal.

If the factory radio is staying in the vehicle, confirm whether the system needs a line-output converter, DSP or another integration solution before beginning the installation.

Speaker Matching and Tuning

Do not choose speakers only by their advertised peak-power rating. Match the FXB 1400.4 to the speakers using RMS power, individual speaker impedance, quantity per channel, wiring configuration and the amplifier’s output at the completed load.

Set the gain using a clean signal and treat it as an input-sensitivity adjustment—not a volume control. Use appropriate high-pass crossover protection for door speakers, coaxial speakers, mids and tweeters. Our car audio speaker tuning guide explains gain, crossover and speaker-system setup in more detail.

Who Should Choose the FXB 1400.4?

The Sky High FXB 1400.4 makes the most sense when you need strong four-channel output, bridgeable flexibility and a compact mounting footprint. It is especially useful for custom doors, high-output mids and highs, motorcycles, powersports vehicles, under-seat installations and modern vehicles with limited amplifier space.

If your speakers need less power or the installation area is even smaller, compare the other compact FXB amplifiers before deciding. If your speaker system requires more than 375 watts RMS per channel at 2 ohms, move up to a larger amplifier instead of forcing this model to operate below its minimum impedance.

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