MTX ThunderForms (with dual 10" subs)

1999-up GM/Chevrolet Extra Cab (Charcoal)

Item #: 236CXP2CT4

5 Reviews

This item is no longer available.

Original Price: $449.99

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Crinkled french fries, discarded receipts, old gum wrappers — you probably have everything in the hidden corners of your vehicle except great bass. But with custom ThunderForm enclosures, you can fill the nooks and crannies of your car, truck, or SUV with low tones that stand out.

MTX engineers evaluate the "sonic signatures" of top-selling vehicles so they can design ThunderForms as custom acoustic matches. With "rotational molding," MTX ensures that each ThunderForm fits and blends inconspicuously into your vehicle. They're made of high-density polyethylene resin to curb resonances and deliver bass that's tight, hard-hitting, and way down low.

This molded MTX ThunderForm comes loaded with two premium-quality 10" Thunder4500 speakers and mounts under the rear seat on the driver side of 1999-2004 GM/Chevy Extra Cab models, and 1999-2001 GMC pickups (3-door and Extended Cab 4-door models). It's seamless and airtight, with the correct internal volume to yield optimum bass response from the subwoofers.

The ThunderForm bolts to the floor of the vehicle, with the woofers firing downwards. There is no loss of leg room and the factory jack kit is not disturbed. It has a built-in recess for amplifier mounting. Hardware is included. For the ultimate in Thundering bass, drive one with an MTX Thunder amplifier.


  • high-density polyethylene resin enclosure
  • two 10" Thunder4500 8-ohm subwoofers
  • frequency response 35-150 Hz
  • power range 50-225W RMS per sub
  • warranty: 2 years (limited)

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.

MTX ThunderForms (with dual 10" subs) Reviews

Average Customer Review:

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awesome sound!

Written By J-Rod, Russellville, AR on Tuesday, September 07, 2010

Crutchfield Customer Review (What's this?)

speakers sound amazing! they have a clean, crisp, full sound to them. great for a nice
subtle additive for your music, or a hard hitting rattle your body full bodied base. very
little to no base bleed through to the outside of the cab. because of the direction the
subs lie it causes the sound to be "omnipresent" making it very hard to tell the subs are
behind you. set up is a breeze, just slide under the seat and hook up the speaker leads
and your done. sits just a touch too tall so the seat won go all the way down, (maybe
just a 1/4" lower would be nice) but box is strong enough to fit several people on the
back seat with out any damage.

Clean as a whistle

Written By Viper, Turks & Caicos Islands (installed in the US) on Saturday, April 28, 2007

Crutchfield Customer Review (What's this?)

If you are looking for an "invisible" audiophile type setup, this box delivers. Have one in my 1999 Silverado. Looks like part of the upholstery - but sounds like I'm thinkin' 'bout competition level sound-offs. I feel like buying another one. But I only have one truck :0) Crutchfield's hands on research made all the difference in the world when I was making the decision on what type of enclosure to get. Thanks guys!

Kicks Bass

Written By Bill, Cincinnati, OH on Tuesday, February 20, 2007

I bought this enclosure and loaded it with two Alpine SWE-1042 10" subs. My bass is powered by an Alpine MRP-M650 600 watt mono amp. This system rocks! The enclosure hides the system very well. No one knows it's even there until I turn it on!

MTX ThunderForms (with dual 10" subs)

Written By Anonymous, Lake City, Ga on Monday, September 12, 2005

these subs kick. it hides away real good...

MTX ThunderForms (with dual 10" subs)

Written By Adam, Alexandria, LA on Wednesday, March 30, 2005

Crutchfield Customer Review (What's this?)

This custom fit enclosure blends in perfect under the rear seat. It looks like the truck came with a tool box. The enclosure is so stealthy my friends didn't even know that is was an enclosure. I recommend gettin this enclosure loaded with the dual MTX Thunder4500 10's. It is already wired for fast installation. I hooked mine up in about 10 minutes and that includes the amp. This is a must by for your chevy ext cab.

Hands-on research

What's in the box?

Download owner's manual

  • Charcoal ThunderForm enclosure loaded with two 10" Thunder4500 subwoofers
  • Two 2" Self-tapping screws
  • 2 Flat washers
  • Manual
  • "MTX Audio" sticker

Product Research



Vehicle-Specific Custom Enclosure: This MTX ThunderForm enclosure is specifically designed to mount under the rear seat of your 1999-2004 Chevrolet/GMC extended cab trucks, including 3- and 4-door models. There is no loss of leg room and the factory jack kit is not disturbed.

Molded Enclosure: The molded, high-density polyethylene resin enclosure resists flexing and dampens resonance. The enclosure contains a recess on top between the woofer chambers for mounting an amplifier. The recess is 10-1/2" wide, 15" long and 3" deep with the speaker terminal flush with the bottom of the recess.

Thunder4500 Woofers: This enclosure comes loaded with two 8-ohm, 10" Thunder4500 woofers, internally wired in parallel to provide a 4-ohm load.

  • Carbon-filled Polypropylene Cones: Each woofer cone is made of carbon-filled polypropylene. Carbon adds strength and heat resistance to polypropylene; the result is reduced distortion and improved reliability. In addition, the cone is also very resistant to environmental extremes. Each woofer uses a polyether foam surround.
  • Asymmetrical Linear Drive System (ALDS): The Asymmetrical Linear Drive System consists of a flat, progressive spider that improves suspension and an extended vented pole piece that smoothes out the cone's linear motion. The result is high output and low distortion.
  • Spider Plateau Venting: Heat from the voice coil is vented through metal-mesh covered vents that surround the back of the spider.
  • Voice Coils: Each voice coil is wound on a high-temperature former to promote high power handling.
  • Strontium Ferrite Magnets: The strontium ferrite magnet yields a highly efficient speaker.
5-way Binding Posts: The gold-plated 5-way binding posts will accept bare wire, pin connectors, spade lugs, banana plugs, and dual banana plugs.


Mounting Location: This enclosure mounts under the rear seat of your 1999-2004 Chevrolet/GMC extended cab trucks, including 3- and 4-door models.

Note: The provided 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.

Tools Required: You will need the following tools to install this enclosure:

  • Powered Screwdriver
  • Wire Cutters
  • 5/16" Wrench
  • 6" Bit Holder Extension
  • #2 Phillips Head Bit
  • T-50 Torx
  • Terminal Crimpers
  • 7mm Nut Driver

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.