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Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required

Description Warranty Information 0 Reviews Description Tailored for the 1999-2007 GM/Chevy Extended Cab, this Down4Sound PRO-FAB enclosure is designed for serious bass enthusiasts. Featuring four 8-inch subwoofer openings, it delivers precision-tuned bass output with a tuning frequency of 32.5 Hz. Crafted from premium birch wood and finished with a durable polyurethane bedliner, this enclosure is built to withstand high-performance demands. A 2.5-inch seat lift is required for proper installation. Compatibility: 1999-2007 GM/Chevy Extended Cab (Under Seat, 2.5-Inch seat lift is required BUT IS NOT INCLUDED ) Configuration: Quad 8-inch subwoofer openings Material: Premium birch wood with polyurethane bedliner coating for enhanced durability Outside Dimensions: Width: 55 inches Front Height: 9 1/2 inches Rear Height: 12 1/2 inches Depth: 14 3/4 inches Net Airspace (After Displacements): 1.29 cubic feet per side Port Information: Port Area: 10.98 square inches each Port Depth: 12 1/2 inches Tuning Frequency: 32.5 Hz Recommended Subwoofer: Optimized for Down4Sound DBz 8" Subwoofers This enclosure is the perfect fit for upgrading your GM/Chevy Extended Cab’s audio system, providing exceptional durability and bass performance for high-output setups. ****ALL SALES ARE FINAL**** View All Close Warranty Information Warranty Information Your new Down4Sound product is covered by 1 limited warranty if purchased from Down4Sound or an authorized Down4Sound dealer. This warranty does not cover improper installation, accidental damage, misuse, abuse, improper wiring, operation of unit outside of listed specifications, or any product that has been modified or repaired by anyone other than Down4Sound. Your warranty covers defects in materials and/or workmanship ONLY and is not an insurance policy. The warranty only covers the original owner of the amplifier. All warranty returns must be accompanied by the original sales invoice or receipt. You must contact us to request an RMA number prior to sending any returns via the RMA request form on our websi te. You are responsible for the cost of shipping your product back to us for warranty examination. If your product is covered under warranty, shipping back to you will be at no charge to you – if your product is replaced/repaired outside of warranty you must pay for return shipping and repair bill prior returning of the product or if no defect is found you are required to pay for return shipping only. At the sole discretion of Down4Sound your product will be either repaired or replaced when it is being covered under warranty. In the event of shipping damage due to improper packaging on products being returned to Down4Sound the customer is liable for the cost of all damages, necessary repairs, or replacement. Be sure to properly pack your return! * Extended additional warranty purchased on amplifiers take in affect from the date of purchase and must also be stated on orginal sales invoice or receipt. Refund/Return Policy: https://www.down4soundshop.com/shipping-returns/ Down4Sound - Hours of Operation Monday 6am - 9pm PDT Tuesday 6am - 9pm PDT Wednesday 6am - 9pm PDT Thursday 6am - 9pm PDT Friday 6am - 9pm PDT Saturday 8am - 4pm PDT Sunday Closed View All Close 0 Reviews View All Close

Specifications

brand
Down4Sound
model
PRO-FAB
material
birch
subwoofer size
8
subwoofer count
4
Thiele-Small Parameters

Measured at small signal levels per AES standards

Impedance:
Electromechanical
Fs
32.5 Hz
Compliance & Mass
Vas
36.52 L

Parameters measured per AES2-1984 (r2003) standards. Small-signal parameters valid within linear operating region.

Compare Prices(1 retailer)
Down4SoundAuthorized Dealer
Available
$469.99
Updated 11/10/2026
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Frequently Asked Questions

What is the Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required?

The Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required is car audio equipment made by Down4Sound.

How much does the Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required cost?

See the recorded retailer prices in the "Where to Buy" section. Prices and availability can change; confirm both with the retailer before purchasing.

Where can I buy the Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required?

The "Where to Buy" section lists retailers we have recorded carrying the Down4Sound PRO-FAB - Birch - 4x 8-Inch Ported Subwoofer Enclosure - 99-07 GM/Chevy Extended Cab – 2.5-Inch Seat Lift Required. Check each listing's availability and confirm warranty coverage with the retailer.

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