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
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, general |
|---|---|
| Outer bounding box | No independently measured raw cavity envelope found. Only the 16.7 cu ft SAE cargo figure was confirmed, and SAE volume is a luggage-fit rating, not a usable rectangular envelope — do not surface it to a user as buildable box volume. |
| Known obstructions | On Concert Sound III cars: the factory amplifier built in UNDER THE THIRD BRAKE LIGHT, centrally in the rear deck. This is the defining obstruction of this vehicle and it sits exactly where a builder might otherwise tuck an amp rack or the top of a tall rear-deck-adjacent box. Also on Concert Sound III cars: an extra pair of 4" speakers mounted immediately NEXT TO the rear-deck 6x9s, meaning the underside of the parcel shelf is more crowded than on a base car. Spare tire well. Rear wheel-well intrusions (not measured). Era-typical trunk-lid hinge gooseneck sweep should be checked before committing to a tall box — not verified on this specific model. |
Suggested configurations for this vehicle, not prescriptions. Run the numbers in the Box Builder before you buy anything.
| Subwoofers | 1x10" or 1x12" powered/loaded sealed enclosure with a conventional line output converter tapped at the rear deck speaker wiring (after the factory amp on Concert Sound III cars). |
|---|---|
| Box type | sealed or powered enclosure |
| Location | trunk |
| Subwoofers | 1x12" or 2x12" sealed, custom-built. No vehicle-specific molded Century enclosure was found — this is a custom-box car. The 16.7 cu ft trunk is comfortable for a single-12" sealed build without any real compromise. |
|---|---|
| Box type | sealed, custom |
| Location | trunk. On Concert Sound III cars, keep well clear of the center rear deck where the factory amp is built in under the third brake light, and expect the parcel shelf underside to be crowded by the extra 4" speakers flanking the 6x9s. |
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 | 5.25" full-range, consistent across the generation and confirmed by two independent sources plus a real commercial upgrade package sold under 1997-2005 Century fitment. |
|---|---|
| Known obstructions | Not documented. |
| Adapter bracket needed | unconfirmed — a real year-scoped speaker package exists (see reference_builds) but whether it ships an adapter ring was not confirmed |
| Tweeter | front (door/dash area — exact position not pinned down) |
| Factory speaker size | no rear DOOR speaker was confirmed for this vehicle by any source. Every source describes the rear channel as living in the REAR DECK (6x9s, plus 4" units on Concert Sound III), not in the rear doors. It is genuinely plausible this car has no rear door speakers at all, which is normal for a W-body sedan of this era, but 'not found' is not the same as 'confirmed absent' and it is recorded as the former. |
|---|---|
| Known obstructions | n/a — presence unconfirmed |
| Adapter bracket needed | unconfirmed |
| Factory amp / premium audio | optional-on-some-trims — GM Concert Sound III, pre-dating Buick's Bose partnership. Documented configuration: 8 speakers total — 2" tweeters, 5.25" door speakers, 6x9" rear deck speakers, and 4" speakers built in next to the 6x9s — with a BUILT-IN AMPLIFIER UNDER THE THIRD BRAKE LIGHT. That amp location is the most distinctive fact in this entry and is not something a builder would guess. Base cars run a simpler 4-6 speaker configuration without the amp. |
|---|---|
| Adding subs without a head-unit swap | Yes, and this is one of the easier cars to do it on. No factory DSP, no bass management, no premium-brand signal processing to work around — a conventional line output converter tapped at the rear deck speaker wiring is the normal approach, and on non-Concert-Sound cars the head unit drives the speakers directly, making it simpler still. On a Concert Sound III car, tap AFTER the factory amp at the rear deck speakers rather than trying to intercept ahead of an amp that is buried under the brake light. CAVEAT: no Century-specific wire colors or LOC procedure was confirmed — the approach is inferred from the documented system architecture, not read off a Century-specific install writeup. A Scosche installation guide for 1997-up Century (bk511) exists and is the right place to start for harness/dash specifics. |
| Head unit | No replacement needed |
16.7 cu ft SAE, and unusually well-behaved as a data point: the figure is reported identically from 1997 straight through 2005, with no trim or powertrain variant splitting it. Mid-pack for our Buick sedans — smaller than the Park Avenue (18.6-19.1) and Lucerne (17), larger than the LaCrosse (13.3) and Regal (14.2). Rear-seat pass-through was NOT confirmed on this car.
Outside links. Some are commercial products, some are owner builds posted on forums — the label says which. We do not endorse any of them.
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.