What we researched for this specific generation: where an enclosure actually fits, what the factory speakers are, how the factory audio is wired, and which real builds and commercial products exist for it. Confidence badges say how well each figure is sourced — this is research, not manufacturer spec.
Body styles covered: 4-Door Sedan, 2-Door Coupe, 2-Door Convertible
These are researched envelopes, not a guarantee. Measure your own vehicle — the numbers here tell you what to expect, not what you have.
| Location | trunk, through existing opening (SEDAN figures — see cargo_fitment for coupe and convertible) |
|---|---|
| Outer bounding box | Sedan: 40"W x 13"H x 34"/38"D. Convertible: 39"W x 5"H x 11"/11"D below the top's safety cover. |
| Known obstructions | SEDAN: design to 34" of depth — the pair means the space tapers and the source does not say which end is which, so the smaller figure is safe. Height is the tight dimension at 13", the same as the Panther-platform sedans, so a wide shallow box suits this car. CONVERTIBLE: the folding top's safety cover is the obstruction, and it is a hard one — 5" of usable height rules out essentially every conventional enclosure. Note the convertible's depth pair is published as 11"/11", i.e. no taper at all. |
| Usable volume estimate | 4 ft³ |
Suggested configurations for this vehicle, not prescriptions. Run the numbers in the Box Builder before you buy anything.
| Subwoofers | Sedan/coupe: powered sub in the trunk. CONVERTIBLE: a compact powered sub or under-seat unit is realistically the only option — 5" of trunk height rules out a conventional box |
|---|---|
| Box type | powered enclosure |
| Location | trunk |
| Subwoofers | Sedan/coupe: 1x12" sealed, laid out wide to work with the 13" height |
|---|---|
| Box type | sealed |
| Location | trunk |
| Subwoofers | Sedan only: 2x12" or 1x15" ported. Not viable in the convertible |
|---|---|
| Box type | ported |
| Location | trunk |
Sizes and depths below are what research turned up for this generation. Confirm against your own vehicle before cutting or ordering — trim levels vary.
| Factory speaker size | EITHER 6-1/2" OR 6-3/4" at the base of the door — the source does not tie the two sizes to specific trims or years, so check your own car. Replaceable with 6-3/4", 5-1/4" or 6-1/2" aftermarket. An adapter bracket is available. |
|---|---|
| Known obstructions | The adapter bracket MAY NEED MATERIAL GROUND OFF with a rotary tool depending on which speaker you fit. NO SPEAKER WIRING HARNESS EXISTS FOR THE MONSOON WOOFERS — the documented options are cutting off the factory connectors and splicing, or the easier route of Posi-Tap connectors that tap the speaker wires without cutting the connectors off at all. Tools vary by body style: panel tool, Phillips screwdriver, flat-blade screwdriver, ratchet and extension, and 1/4", 7mm, 13mm and/or 18mm sockets. |
| Adapter bracket needed | Available; may require grinding to fit a particular speaker |
| Tweeter | Mounted high in the door area; ON THE SEDAN specifically they are in the SAIL PANELS. Easy to reach and easy to remove. Universal backstraps make securing the replacements easier. |
| Factory speaker size | None — the rear channels come from the rear deck on all body styles. |
|---|---|
| Known obstructions | n/a |
| Adapter bracket needed | n/a |
| Factory amp / premium audio | Two systems sharing the same radio: a standard setup, and a premium 8-SPEAKER MONSOON system. MONSOON SEDANS AND COUPES ARE BI-AMPED — the amplifier sends bass and treble frequencies to the speakers through SEPARATE SETS OF WIRES, which is the same arrangement found on the 2004-2008 Grand Prix and appears to be a Monsoon-wide GM pattern rather than a one-car quirk. G6 CONVERTIBLES ARE THE EXCEPTION: they all have Monsoon, but their speakers are NOT bi-amped, so a convertible needs neither a radio replacement nor a factory-amp bypass to accept new speakers. Separately, on SOME 2005-2008 cars the Driver Information Center was built into the radio, which makes the choice of integration adapter matter for keeping that function. |
|---|---|
| Adding subs without a head-unit swap | Yes on the sedan and coupe, where the trunk has real room. On the convertible the cargo space below the top's safety cover is 5" tall, so a conventional enclosure is effectively off the table regardless of the electronics. |
| Head unit | No replacement needed |
SEDAN: 40"W x 13"H x 34"/38"D, described as plenty of room for an amplifier and a subwoofer box. COUPE: the source says a similar amount of space. CONVERTIBLE: A COMPLETELY DIFFERENT PROPOSITION — measured below the folding top's safety cover there is only 39"W x 5"H x 11"/11"D. Five inches of height and eleven of depth is not a subwoofer space in any conventional sense. Anyone shopping for a G6 sub build has to establish the body style first; the sedan figure is roughly nine times the convertible's volume.
Each link opens the tool with this vehicle already selected.
Measure your own vehicle. Trim levels, factory subwoofer options, and mid-generation changes all move these numbers, and a box cut to a researched figure that does not match your truck is wasted wood. Where a badge reads Unconfirmed, treat the value as a starting point for your own measurement, not as an answer.