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 Crew Cab (unibody)
These are researched envelopes, not a guarantee. Measure your own vehicle — the numbers here tell you what to expect, not what you have.
| Location | under the rear seat, crew cab |
|---|---|
| Outer bounding box | 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 cu ft, under the rear seat; "a drop in with no modifications needed on the vehicle"; NET Audio '2006-2026 Honda Ridgeline Sub Box Ported': 49.5 x 11 x 7.5 in (as printed; axes not labelled), 1.2 cu ft, under the rear seat; drop-in. Zenclosures and Sound Off Audio print no outside dimensions (mounting depths 6.25 to 7 in). |
| Known obstructions | The RTS and RTL carry a factory 8 in subwoofer behind the rear seat (Honda 2006). NET Audio: "This box will not fit 12s due to the limited width." Zenclosures: oversized frames or magnets may not fit. |
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 | Honda 2006, RT: "one 6-inch speaker in each door" (six speakers: four 6 in door speakers plus two front tweeters). |
|---|---|
| Adapter bracket needed | unconfirmed |
| Tweeter | front-mounted (Honda 2006, RT: "two front-mounted tweeters"); exact position not printed |
| Factory speaker size | Honda 2006, RT: "one 6-inch speaker in each door" (same sentence covers the rear doors). |
|---|---|
| Adapter bracket needed | unconfirmed |
| Factory amp / premium audio | Honda, by trim. 2006 interior release: RT "a 100-Watt amplifier and six speakers (one 6-inch speaker in each door and two front-mounted tweeters)"; RTS "a 160-Watt amplifier with an 8-inch subwoofer located behind the rear seat" (seven speakers); RTL "Premium 160-Watt AM/FM/XM-ready Audio System with 6-disc CD Changer and Subwoofer (RTS and RTL)". 2008 and 2010 releases repeat RT "six-speaker, 100-watt" and RTS "seven-speaker 160-watt audio system with subwoofer"; RTL navigation is available. The factory sub changes a sub-install plan: tap its feed or replace it. |
|---|
Honda 2006 specifications: "Cargo Volume (cu. ft., underneath 2nd Row Seat)" 2.6 on all trims; 2nd row folded 41.4 (RT, RTS; 41.4/39.5 on RTL by moonroof); In-Bed Trunk 8.5. Honda's interior release, on the under-seat storage: "In the down (sitting) position, a storage area is created that is large enough to hold a medium-sized golf bag." The 2.6 is an under-seat volume, not a cargo-area figure.
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.