Sky High Car Audio FMX Subwoofer Series

Shop Sky High Car Audio FMX Series subwoofers in 6.5-inch, 8-inch, 12-inch, 15-inch and 18-inch sizes. The FMX Series is built for high-output daily systems, demo vehicles, serious trunk builds, blow-through installations and light competition-style projects where the entire vehicle is being planned around substantial bass output.

FMX stands for “Forged to Perform. Built to Endure.” These high-performance subwoofers use heavy-duty motor, suspension and voice-coil designs intended for demanding systems supported by the correct enclosure, amplifier power, wiring, electrical upgrades and tuning.

FMX subwoofers are available with dual 1-ohm or dual 2-ohm voice coils. Choose the correct D1 or D2 configuration based on the number of subwoofers, wiring arrangement, amplifier capabilities and final impedance planned for the complete system.

Shop Sky High FMX Series Subwoofers

Sky High FMX 6.5-Inch Subwoofer

The Sky High Car Audio FMX Series 6.5-inch subwoofer brings the heavy-duty FMX design into a compact format for creative installations where a traditional subwoofer will not fit.

The FMX 6.5-inch can be considered for:

  • Under-seat and behind-seat enclosures
  • Center-console bass systems
  • Compact truck installations
  • Small sealed or ported enclosures
  • Multiple-subwoofer arrays
  • Custom motorcycle and powersports builds
  • Installations where every inch of space matters

A compact diameter does not eliminate the need for the correct enclosure. Verify mounting depth, cutout diameter, internal volume, cone clearance and recommended box design before beginning the installation.

Sky High FMX 8-Inch Subwoofer

The Sky High Car Audio FMX Series 8-inch subwoofer is rated for 800 watts RMS and is available with dual 1-ohm or dual 2-ohm voice coils.

The FMX 8-inch provides serious compact-subwoofer performance for:

  • Behind-seat truck boxes
  • Under-seat enclosures with sufficient clearance
  • Small trunk and hatchback systems
  • Single high-output 8-inch builds
  • Dual or multiple 8-inch systems
  • Customers wanting strong bass from a limited footprint

The correct enclosure remains essential. Do not assume every 8-inch box will provide the air space, port area or mounting depth required by the FMX 8-inch subwoofer.

Sky High FMX 12-Inch Subwoofer

The Sky High Car Audio FMX Series 12-inch subwoofer is a 3,500-watt RMS high-output model available with dual 1-ohm or dual 2-ohm voice coils.

The FMX 12-inch provides a strong combination of substantial power handling, high excursion, cone area and enclosure practicality for:

  • Serious single 12-inch systems
  • Dual 12-inch trunk builds
  • High-output daily vehicles
  • Demo systems
  • Blow-through installations
  • Ported and bandpass enclosures designed for the exact subwoofer
  • Builds supported by substantial amplifier and electrical power

The 12-inch model can be easier to package than the larger FMX options while still requiring a strong enclosure, proper electrical support and careful system tuning.

Sky High FMX 15-Inch Subwoofer

The Sky High Car Audio FMX Series 15-inch subwoofer is rated for 3,500 watts RMS and is available with dual 1-ohm or dual 2-ohm voice coils.

The increased cone area of the FMX 15-inch makes it a strong option for:

  • Large trunk systems
  • Hatchback and SUV builds
  • Single or multiple 15-inch installations
  • Blow-through systems
  • Large ported and bandpass enclosures
  • High-output daily and demo vehicles
  • Light competition-style projects

A 15-inch subwoofer needs enough room for more than the basket. The vehicle must also provide the required enclosure volume, port area, mounting depth, cone clearance and space for the box to load correctly.

Sky High FMX 18-Inch Subwoofer

The Sky High Car Audio FMX Series 18-inch subwoofer is rated for 3,500 watts RMS and is available with dual 1-ohm or dual 2-ohm voice coils.

The FMX 18-inch provides the greatest cone area in this collection and is intended for:

  • Large SUV and hatchback systems
  • Wall and no-wall builds
  • Blow-through installations
  • Single or multiple 18-inch systems
  • Demo vehicles
  • Competition-leaning projects
  • Builds with substantial amplifier and electrical support

An 18-inch subwoofer should not be forced into an enclosure that is too small simply because its basket fits. Correct internal volume, port design, enclosure strength and vehicle loading are critical.

Choosing the Right FMX Subwoofer Size

The largest FMX subwoofer is not automatically the best choice. Start by measuring the vehicle and determining how much passenger or cargo space can realistically be dedicated to the enclosure.

Choose the 6.5-Inch or 8-Inch FMX When:

  • Available space is limited.
  • The enclosure must fit under or behind a seat.
  • You are planning a compact multi-subwoofer system.
  • Preserving passenger or cargo room matters.
  • A larger FMX enclosure cannot be installed correctly.

Choose the 12-Inch FMX When:

  • You want serious output from a manageable diameter.
  • You are building a trunk, truck or SUV system.
  • You want a single or multiple-subwoofer high-power setup.
  • You have room for a properly designed enclosure.
  • The vehicle has substantial amplifier and electrical support.

Choose the 15-Inch or 18-Inch FMX When:

  • You have substantial enclosure space available.
  • Deep bass and increased cone area are priorities.
  • You are building a large SUV, hatchback, blow-through or wall system.
  • The vehicle, enclosure and electrical system are being designed around the bass stage.

Dual 1-Ohm vs Dual 2-Ohm FMX Subwoofers

The D1 and D2 versions are not different power levels. The voice-coil configuration determines the available wiring options and final impedance presented to the amplifier.

For one dual-voice-coil FMX subwoofer:

  • A dual 1-ohm model can normally be wired to a 0.5-ohm or 2-ohm final load.
  • A dual 2-ohm model can normally be wired to a 1-ohm or 4-ohm final load.

Multiple subwoofers create additional final-load possibilities. Decide how many subwoofers will be installed and what impedance the amplifier is designed to support before selecting D1 or D2.

Never connect an amplifier below its rated minimum impedance. An unsafe load can increase current demand and heat while causing protect mode, blown fuses or equipment failure.

Match the Amplifier to the FMX Subwoofers

Choose the amplifier by comparing its rated RMS output at the completed final impedance with the combined RMS rating of the subwoofers.

Before selecting an amplifier, confirm:

  • The RMS rating of each FMX subwoofer
  • The selected D1 or D2 configuration
  • The total number of subwoofers
  • How the voice coils and subwoofers will be wired
  • The completed final impedance
  • The amplifier’s rated RMS output at that impedance
  • The amplifier’s minimum stable load
  • The required power wire, ground wire and fuse protection
  • Whether the vehicle’s charging system can support the amplifier

Browse monoblock car audio amplifiers for subwoofer systems when planning power for an FMX build.

The Enclosure Is Part of the FMX System

A high-powered FMX subwoofer can still perform poorly in an incorrectly designed enclosure. The box affects low-frequency extension, output, efficiency, cone control and how the system loads inside the vehicle.

Before building or purchasing an enclosure, verify:

  • Recommended net internal volume
  • Suitable sealed, ported or bandpass design
  • Recommended tuning frequency when applicable
  • Required port area and port length
  • Subwoofer, port and bracing displacement
  • Mounting depth and cutout diameter
  • Cone and surround clearance
  • Terminal and speaker-wire clearance
  • Available space and loading direction inside the vehicle

Browse subwoofer boxes and car audio enclosures when planning the box portion of the system.

Plan the Wiring and Electrical Support

FMX systems using substantial amplifier power need properly sized power and ground wiring, secure grounds, correct fuse protection, adequate battery capacity and enough alternator output to maintain stable voltage.

Complete the installation with a properly selected Sky High Car Audio amplifier wiring kit and compare Sky High Car Audio Big 3 kits when strengthening the vehicle’s main charging and grounding paths.

A Big 3 upgrade does not increase the alternator’s rated output. A serious FMX system may also require upgraded battery capacity, a high-output alternator or additional charging-system support based on the actual amplifier demand.

Set Gain, Crossovers and Filters Correctly

Amplifier gain is used to match the amplifier’s input sensitivity to the signal source. It is not an additional volume or power control. Excessive gain can create clipping, heat and damaged voice coils.

The low-pass crossover should keep unwanted upper frequencies out of the subwoofer system. A properly selected subsonic filter can also help protect FMX subwoofers in ported enclosures from excessive movement below the enclosure’s useful operating range.

Final settings should be based on the amplifier, source signal, enclosure design, tuning frequency and intended operating range of the completed system.

Shop All Sky High Car Audio Subwoofers

Compare the FMX Series with FE Slim, FE, FXB, BMX and FXXL models in the complete Sky High Car Audio subwoofer collection.

Helpful FMX and Bass-System Guides

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