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: 2-Door Coupe (targa), 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 |
|---|---|
| Outer bounding box | No change to this entry's real, deliberate finding — the source is explicit that there isn't much room for a big box, or luggage, or groceries. New: the same real, named RetroSound 8" amplified sub (2.75" tall) confirmed on both C3 companion entries also fits this real constraint. One real forum-documented behind-seat install also exists (an '86 convertible specifically): a molded plastic enclosure, ~28"x16"x10", housing a 300W 10" marine/waterproof driver — a real, larger alternative for someone willing to build custom rather than buy compact-powered. |
| Known obstructions | Confirmed, not just asserted: genuinely tight space, same category of constraint as both C3 companion entries. |
Suggested configurations for this vehicle, not prescriptions. Run the numbers in the Box Builder before you buy anything.
| Subwoofers | Compact powered subwoofer — the source's explicit recommendation, and the only option it offers for this car |
|---|---|
| Box type | powered enclosure |
| Location | behind the seats / cargo area |
| Subwoofers | Small sealed box built to measurements taken from your own car, since none are published |
|---|---|
| Box type | sealed |
| Location | cargo area |
| Subwoofers | Not sizeable from this page. No cargo dimensions are published and the source says there is not much room for luggage let alone a box — measure first and expect to give up usable space |
|---|---|
| Box type | custom |
| Location | cargo area |
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 | DEPENDS ENTIRELY ON THE SYSTEM: base cars have 6"x9" speakers; Delco/Bose cars have SPEAKER/AMP ENCLOSURES instead. Base cars can take aftermarket 5-1/4" or 6-1/2" — but see known_obstructions, because getting there means cutting metal. Delco/Bose cars cannot be upgraded piecemeal at all (see audio_integration). |
|---|---|
| Known obstructions | THIS IS A CUTTING JOB, NOT A SWAP. To fit aftermarket 5-1/4" or 6-1/2" speakers in the doors you must CUT THE DOOR PANEL *AND* THE STEEL SUBSTRUCTURE, then DRILL new mounting holes. You must also either FABRICATE A MOUNTING BRACKET or use universal backstraps, because no pre-made bracket exists. And there is NO WIRING HARNESS available, so Posi-Products connectors are needed. Four separate obstacles on one location. Tools: Phillips head screwdriver, panel tool, hex-head screwdriver, cordless drill and bit. |
| Adapter bracket needed | No pre-made bracket exists — fabricate one or use universal backstraps |
| Tweeter | n/a — no separate tweeter documented in the doors on either system |
| Factory speaker size | None — two-door car. Rear speakers are in the quarter panels on the coupe and in the FLOOR BEHIND THE SEATS on the convertible (see other_speaker_locations). |
|---|---|
| Known obstructions | n/a |
| Adapter bracket needed | n/a |
| Factory amp / premium audio | Two systems, and one of them is effectively a closed loop. BASE: not impressive but reasonably easy to work with. DELCO/BOSE: the top system in 1984 and genuinely advanced for its day, but it uses AMPLIFIED SPEAKERS THAT ONLY WORK WITH THE BOSE RADIO. The source states the consequence in the strongest terms of any vehicle : if you replace the radio OR EVEN ONE of the factory speakers, you have to replace the ENTIRE SYSTEM. There is no partial upgrade path on a Delco/Bose C4 — it is all or nothing, and Crutchfield calls replacing everything "mandatory" if you are touching the Bose system at all. |
|---|---|
| Adding subs without a head-unit swap | On a BASE car, yes. On a DELCO/BOSE car the question barely applies — adding an amp and sub is fine, but the moment you touch the radio or any factory speaker you are committed to replacing the whole system. |
| Head unit | No replacement needed |
NO MEASURED DIMENSIONS ARE PUBLISHED, and the source is unusually blunt about why: there is obviously not a ton of room for a big subwoofer box in this car — "or luggage or groceries, even." Its recommendation for improving bass while keeping what functionality exists is a powered subwoofer. Measure your own car before planning anything built.
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.