There's a Thunderstorm in the forecast, and it's headed for the wasted space in your vehicle. ThunderForms preserve all the legroom in pickup trucks and all the cargo space in SUVs. Each ThunderForm is an acoustically-designed, non-resonant, airtight enclosure, with the correct internal volume to yield optimum bass response from its subwoofer.

So what makes ThunderForms different than a standard sub box? MTX engineers design each ThunderForm enclosure for optimum performance in your specific vehicle's acoustic space. Using state-of-the-art rotational molding techniques, and exotic high-density polyethylene, MTX creates a sculpted masterpiece of a sub box, beautifully finished to blend with your interior. And they sound as good as they look, delivering bass that's tight, accurate, hard-hitting, and way down low.

This Amplified ThunderForm comes ready to install behind the rear panel (replacing the factory cargo net) of your 1997-2001 Ford Expedition or Lincoln Navigator, with a rugged 10" subwoofer and a super-efficient 100-watt amplifier already built in — so you don't have to find a spot to mount a separate amp. (The subwoofer, made specifically for the amplified ThunderForm, presents a 0.7-ohm load to the Class D 100 watt amplifier — they're a perfect match!) Speaker- and line-level audio inputs means you can integrate them into any system. They also have simple connections for 12-volt power, ground, and signal wires. 1-year limited warranty.

Vehicle-specific enclosures with subs? Say what?

Instead of the usual sub in a box, the manufacturer creates a molded enclosure that fits perfectly into a convenient spot in your specific vehicle, housing a high-quality sub. Some enclosures even include a built-in amp, for the ultimate in stealth bass. The advantages? You don't lose much space (if any), your sub is perfectly matched to its enclosure, and your enclosure has a factory look that won't tell potential thieves you have an awesome sound system. Doesn't get better than that.

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Hands-on research

What's in the box?

Download owner's manual

  • Black Amplified Thunderform with pre-installed 10" subwoofer and 15-amp blade fuse
  • Black cloth grille
  • Wiring harness (20' power lead/3' ground lead/3' remote turn-on lead)
  • Fuse holder with 15-amp blade fuse and attached wire loop
  • 1 crimp-on ring connector with red rubber boot
  • 1 crimp-on ring connector with black rubber boot
  • 1 butt connector
  • 3- 2" self-tapping screws
  • 3- flat washers
  • 9- 1/2" self-tapping screws
  • Manual
  • Warranty card
  • 1 "MTX Serious About Sound" sticker

Product Research

Inputs and Controls


Mounting Location: This enclosure mounts behind rear panel on passenger's side and replaces the factory cargo net in 1997-2000 Ford Expedition/Lincoln Navigators.

Wiring Harness: Contains a 20 ft. power wire, a 3 ft. ground wire and a 3 ft. remote turn-on wire.

Required Tools:

  • Phillips head screwdriver
  • 15mm wrench
  • 1/4" socket
  • 6" ratchet extension
  • Wire crimper
  • T50 torx,
  • 10mm socket
  • 11/32" socket
  • Ratchet
  • Wire cutters


Compatibility: This system is made specifically for the 1997-1999 Ford Expedition/Lincoln Navigator.

Built-in 100 watts RMS Class D Amplifier: The amplifier is highly efficient and designed specifically for use with the subwoofer in the enclosure.

10" Subwoofer:

  • Design: The woofer was custom-designed to compliment the efficiency of the Class D amplifier to deliver deep, low bass.
  • Materials: Laminated paper composite
  • Dust Cap: Poly material embossed a "MTX Thunderform Amplified Subwoofer" logo.
  • Surround: Foam

Built-in Crossover: The crossover frequency can be varied from 50Hz to 150Hz for a seamless transition between the output of this system and that of the other speakers in the vehicle.

Auto Turn-On Feature: When the speaker level inputs are used, the system will automatically turn on and off with the radio.

Note: The Auto Turn-on feature does not operate when the preamplifier level inputs are used unless the remote turn-on lead is connected.

Enclosure Type and Materials: The acoustic suspension enclosure is made of high density polyethylene resin which is rigid enough to resist flexing and dampens any resonance.

Note: Dimensions are taken at the widest points of the enclosure. Keep in mind that these enclosures are custom made to fit in a particular vehicle, so the enclosure will fit properly in only one specific location.

Inputs and Controls:

Speaker Level Inputs: Left and right spring-clip speaker level inputs. The manual includes the wiring codes necessary to connect the vehicle's speaker wiring to the speaker level inputs.

Preamplifier Level Inputs: Left and right female preamplifier level (RCA) inputs.

3-pin harness Input: Power, ground and remote harness.

Gain control: Rotary control that sets gain. No specification given for range of gain control.

Crossover control: Rotary control that sets crossover point (variable from 50 to 150Hz).

Fuse: There is an installed 15 Amp fuse.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.