MTX Amplified ThunderForms

Custom-fit powered subwoofer for 2007-up Chevy Silverado and GMC Sierra Extended Cab

Item #: 23615XATTN

In Stock

2 Reviews

Your price: $549.99 Earn up to 550 Rewards points

Add to Cart

+ Add to wishlist + Email me alerts for this product

Ships Free From Manufacturer

View all associated offers

Does it fit my car?

Select your car

Find what fits your car

Crinkled french fries, discarded receipts, old gum wrappers — you probably have everything in the hidden corners of your vehicle except great bass. ThunderForm enclosures fill the nooks and crannies of your vehicle with low tones that stand out, but their factory look blends right in.

MTX engineers evaluate the "sonic signatures" of top-selling vehicles so they can design ThunderForms as custom acoustic matches. Each ThunderForm fits and blends inconspicuously into your vehicle, so you get great bass without losing any space. They're made of high-density polyethylene resin to curb resonances — they deliver bass that's tight, hard-hitting, and way down low. The airtight enclosure provides the correct internal volume to yield optimum bass response.

This amplified ThunderForm fits under the rear seat of your 2007-up Chevy Silverado or GMC Sierra Extended Cab truck. It houses a Terminator 10" sub and a cool-running 200-watt amp that's custom designed to provide optimal power without straining your vehicle's electrical system. MTX's Electronic Bass Control (EBC) lets you adjust the bass level from the driver's seat. A variety of inputs allow easy integration into your vehicle's sound system, and the included 20' power harness simplifies supplying power to the amp.

Product Highlights:

  • custom-fit powered subwoofer with Terminator 10" sub
  • enclosure fits under the rear seat
  • built-in 200-watt RMS Class-D amplifier
  • high-density polyethylene enclosure
  • variable low-pass filter (50-150 Hz at 12 dB per octave)
  • preamp- and speaker-level inputs
  • 20' power harness included
  • dimensions: 36-1/5"L x 9"H x 16-2/5"D
  • warranty: 5 years (free repair or replacement for 2 years, prorated replacement for years 3 through 5)
  • Our 60-day money-back guarantee

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 Amplified ThunderForms Reviews

Average Customer Review:

2 reviews
Review this product
Great Gear Giveaway

Submit a review and then enter to win a $350 rewards card


Review this product:

Thanks for taking the time to share your experiences about this product. Please be sure to focus your comments on the product itself. Read our Review Guidelines for more information.

Your email won't be visible. Please use the email address that is associated with your order.
(e.g., JohnD) Your review will be signed using the display name and location
(e.g., Charlottesville, VA)

Click on a star to rate the overall product on a scale of 1-5
1500 characters left
  Attach a YouTube Review
Crutchfield Video Review Guidelines
  • Only submit videos that you made or are authorized to use.
  • Do not submit videos that contain music, video or visuals that are copyrighted and belong to someone else.
  • Please see our Review Guidelines for more information.
500 characters left
500 characters left

Nice sub.

Written By Todd A, IL on Monday, September 07, 2015

Crutchfield Customer Review (What's this?)

3 might seem like a low rating but its average. Don't get me wrong, I love this sub but for the price and more for a LOC so I don't have to splice wires, it is kinda expensive. Not only that but MTX doesn't supply instructions on connecting this. They claim that they don't know what vehicle its going into so they can't supply instructions. I reminded them that this is a VEHICLE SPECIFIC enclosure so you know EXACTLY what vehicle its going in to. Anyway, I got tired of messing with them and ordered a PAC line out converter that plugs into the factory harness. Now about the SQ. That's a mixed bag. On some songs this thing hits good and sounds awesome. On other songs the bass is either muddhbor over lowering. It is absolutely necessary to connect and use the remote gain control or EBC as MTX calls it. I never had that issue with other amps. Gain was a set it and forget it deal. Probably has something to do with the factory head unit and its proprietary EQ curve. That being said, if you just want to compliment your factory system or just round out a mild aftermarket system, this is what you need.

Pros: Good SQ. Small size. Ease of mounting.

Cons: Non existent wiring instructions from MTX (Crutchfield to the rescue). Need to constantly adjust the gain as if it were a bass control.

MTX Amplified ThunderForms

Written By Anonymous, Anchorage AK on Friday, July 13, 2012

Crutchfield Customer Review (What's this?)

Nice fits perfect in my 2007 GMC Siera Ext Cab and sounds pretty good.

Pros: Already amplified and has a remote gain that mounts in an easy to reach place for quick adjustment

Cons: The instructions are terrible There aren't any wiring instructions at all so if you've never installed amplifiers and subs before ya might need some help. The remote gain rheostat is a universal length and has the male end already installed so in my truck I had a ton of excess wiring that I had to roll up, zip tie and hide under the rear seat. Also, the speaker wire it's comes with only has RCA jacks on one end.

Hands-on research

What's in the box?

Download owner's manual

  • Custom-fit pre-loaded amplified enclosure
  • Wiring harness (20' power lead/3' ground lead and 3' remote turn-on lead)
  • Speaker-level to RCA harness
  • External bass control
  • Mounting hardware
  • Installation Instructions

Product Research



Vehicle Compatibility: This MTX ThunderForm custom-fit, amplified, pre-loaded enclosure is designed specifically to fit select 2007 and later Chevrolet and GMC Extended Cab Trucks.

Note: Please refer to the Crutchfield Vehicle Selector to confirm fit for your vehicle.

Mounting Location: The ThunderForm amplified, loaded enclosure mounts under the rear passenger seat. (install hardware supplied). There is no loss of leg room.

Molded Enclosure: The molded, fiberglass enclosure resists flexing and dampens resonance.

10" Terminator Subwoofer: This enclosure comes loaded with a single 10" MTX Terminator woofer.

Class D Amplifier: The enclosure contains a built-in 200-watt Class D (digital) amplifier that allows RCA or speaker-level input. The amplifier is highly efficient and designed specifically for use with the subwoofer in the enclosure.

Built-in Low-pass Filter: The low-pass filter frequency can be varied from 50 to 150 Hz for a seamless transition between the output of this unit and that of the other speakers in the vehicle.

External Bass Control: The external bass control allows you to adjust the bass level from anywhere 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 preamp level inputs are used, unless the remote turn-on lead is connected.


5 Year Warranty Terms: Starting January 1st, 20013, this product carries a 5-Year Prorated Warranty with the following terms:

  • Years 1-2: Products found to be defective in materials or workmanship during the first two years will be, at Mitek's option, repaired or replaced by Mitek at no charge. The warranty period does not renew, but continues on from the original date of purchase.
  • Years 3-5: The purchase price of an item which becomes defective after the first two years and prior to the end of the warranty period will be prorated and credited toward the purchase of a new MTX product. The amount of proration is determined by dividing the original purchase price by the number of months in the warranty period (60), then multiplying the result by the number of months remaining in the warranty period.

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.

Searches related to the MTX Amplified ThunderForms Custom-fit powered subwoofer for 2007-up Chevy Silverado and GMC Sierra Extended Cab