GMT800 Subwoofer Box Build – Under Seat vs Custom Box

Adding a subwoofer to your GMT800 Silverado/Sierra transforms the audio experience. Here are your best options for mounting it.

GMT800 Subwoofer Locations:

Under-Seat Powered Sub (Easiest)

The most popular option for GMT800 trucks is an under-seat powered subwoofer that tucks beneath the bench seat. These are compact, self-powered units that don’t require a separate amp.

Popular options include Bazooka, JL Audio SB, and Rockford Fosgate PS-8.

Box Behind Extended Cab Jump Seat

If you have an extended cab, the area behind the jump seats offers space for a moderate-sized sealed or ported box. A 10" subwoofer in a small sealed enclosure works well here.

Custom Crew Cab Box

Crew cab trucks have the rear bench seat that can be raised or built around. A sealed 10" or 12" box under or behind the rear seat is the popular choice.

Amplifier Selection:

Whatever sub you use, pair it with a quality monoblock amp:

  • 150-300W RMS for 8"-10" subs
  • 300-500W RMS for 10"-12" subs

Head Unit:

For best bass integration, the Kissound 7" Double DIN has subwoofer pre-out connections that drive any external amp cleanly.

Tip: Set the sub amp gain properly with a DMM or bass meter — too much gain causes distortion that sounds muddy.