1988-1998 GMC Sierra Extended Cab Sub Box Single Ported


1988-1998 GMC Sierra Extended Cab Sub Box Single Ported

­The 1988-1998 GMC Sierra Extended Cab trucks gave birth to the under seat down fire box. This body style truck was the start of the sport truck movement and as around when car audio started its boom. The space under this rear seat is limited but there are ways to get plenty of sound out from under there. The tool box and jack storage is in the way for a full width box so this half box fits perfectly in the other half. The sub box sticks out from the front of the seat a little bit but that is the only way to get anything with a decent surface area under there. The box is half width with .7cuft of airspace which is spot on for a good 10 with up to 5 3/8” of mounting depth and leaves the tool box in place.

This is a ported subwoofer enclosure. Ported subwoofer enclosures are for customers who want louder, deeper bass with the lower bass more pronounced. Because of the ported design, the bass will not be as tight and punchy as a sealed box, but there is typically double the bass of a sealed box with the same subs and power. A sealed subwoofer box has a tight and punchy bass that is more articulate and more true to the music with a more natural sound. If tight, punchy bass is what you want then our sealed designs will be what you want.

This design is for maximum airspace and the airspace of the box can be reduced if desired. Our ported boxes are designed according to your subwoofer’s specifications. No two boxes will really be alike. At checkout, there is a “Comment” box, please give us the model number of your subs and we will build the enclosure as needed. We tend to tune our boxes low, around 34-37hz. If you have any specific requests, please feel free to let us know.

This box is made out of 3/4″ MDF and is fully carpeted in matching carpet. The nickle plated spring loaded speaker terminals are mounted on the back of the box and the speaker wires are soldered on for a solid and reliable connection.

Chevy / GMC Gallery

Contact Us About Your Options (This is only if your order requires some advanced customization. If you need a customization fee, we’ll let you know).

  • We use Stinger wire on all of our boxes.
  • Please enter the Brand and Model of the subwoofers you will be using.
  • $0.00

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Additional information

Weight 31 lbs
Dimensions 27.125 × 12.5 × 10.25 in
Total Volume (CuFt)

Mounting Depth

Fit Location


Box Finish

Number of Speakers

Speaker Sizes