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: Crew Cab (unibody, only cab style offered)
These are researched envelopes, not a guarantee. Measure your own vehicle — the numbers here tell you what to expect, not what you have.
| Location | underseat, full cab (real owner-measured, broader than just the factory sub location) |
|---|---|
| Outer bounding box | Real forum-measured: width between sills ~53.5" (narrows near the pillars), track-to-back-of-cab ~13", floor-to-seat-bottom ~9" ADDED 2026-10-02 (vehicle-specific enclosure catalogues; published box footprints are lower bounds on the cavity, not the cavity): NET Audio '2006-2026 Honda Ridgeline Sub Box Sealed': 49.5 x 11 x 7.5 in (as printed; axes not labelled), 1.2 ft3, under the rear seat. ADDED 2026-10-02 — Honda (2017 and 2022 spec sheets): rear under-seat storage volume 2.9 cu ft ("2nd-Row Underseat Storage Volume"); Honda publishes no width or depth for it. A capacity rating, not a box envelope. |
| Known obstructions | Width narrows near the B-pillars — the full 53.5" isn't usable edge-to-edge for a rectangular box |
| Usable volume estimate | 1.29 ft³ |
Suggested configurations for this vehicle, not prescriptions. Run the numbers in the Box Builder before you buy anything.
| Subwoofers | 1x8" factory-location upgrade, ~0.5-0.55 ft3 |
|---|---|
| Box type | sealed |
| Location | factory subwoofer location |
| Subwoofers | 1x10" sealed, 1.29 ft3 |
|---|---|
| Box type | sealed |
| Location | underseat custom or ZEnclosures-style aftermarket |
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 | 6.5" |
|---|---|
| Known obstructions | None specifically documented |
| Adapter bracket needed | unconfirmed |
| Factory speaker size | 6.5" (Crew Cab, same as front) |
|---|---|
| Known obstructions | None specifically documented |
| Adapter bracket needed | unconfirmed |
| Tweeter | n/a — tweeter (where equipped) is A-pillar mounted, front only |
| Factory amp / premium audio | Confirmed for the start of the generation, not just the tail end. Honda spec sheets: 2017 RT/RTS/Sport/RTL 200W, 7 speakers including a subwoofer; RTL-T 225W, 7 including a subwoofer; RTL-E and Black Edition 540W premium audio, 8 speakers including a subwoofer, plus the Truck-Bed Audio System (six weatherproof exciters: two in each bed side wall, two in the bed rear wall). 2022: Sport and RTL 215W/7 including a subwoofer; RTL-E and Black Edition 540W/8 including a subwoofer, bed audio on those two. 2023-2024 (earlier finding): 540W, 8 speakers with a centre channel on RTL-E and Black Edition. No third-party brand named. |
|---|---|
| Adding subs without a head-unit swap | Confirmed straightforward via the factory subwoofer location upgrade path |
| Head unit | No replacement needed |
Unusual among trucks — Ridgeline is unibody (shares underpinnings with the Pilot), not body-on-frame. Real factory baseline: 7 3/16" cutout, only 3" of depth without modification, OEM enclosure holds ~16L (0.5-0.55 ft3) — adequate for most 8" subs but a real small starting point. Real aftermarket options: ZEnclosures sealed box, 6.50" mounting depth, adjustable 8"/10" holes, 1.29 ft3 total, 0.625" MDF; a downfire alternative fitting 2x8" or 1x10", 1.2 ft3, 5.25" mounting depth. Real DIY underseat build documented: 2x4-style frame construction, completed box 41.5"W x 8.5"H, housing a 10" sub.
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.