2019-2025 Subaru Forester 5th Gen (SK) — subwoofer box fitment

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 SUV

Where a box actually fits

These are researched envelopes, not a guarantee. Measure your own vehicle — the numbers here tell you what to expect, not what you have.

Standard Unconfirmed

Locationrear cargo area, factory custom-tuned enclosure (Harman Kardon trims only)
Outer bounding boxfactory enclosure is a sealed OEM part, no aftermarket-facing raw dimension published
Known obstructionsSheet-metal mounting bracket is tightly sized to the factory subwoofer specifically — real reported case of an 8" Kicker not fitting without cutting/modifying the mounting sheet metal

Starting points

Suggested configurations for this vehicle, not prescriptions. Run the numbers in the Box Builder before you buy anything.

Budget

SubwoofersOEM replacement (86301SJ140) if the factory HK sub has failed
Box typefactory enclosure
Locationrear cargo area, HK trims only

Enthusiast

Subwoofersquality aftermarket 8" driver within the factory enclosure — real owner consensus (SubaruForester.org) describes the stock unit as boomy at higher volume with weak low-octave output, and swapping in a better 8" driver helps but remains limited by the factory enclosure's own size/tuning; a true bigger box was NOT confirmed possible given the tight sheet-metal mount
Box typefactory enclosure, driver-level replacement
Locationrear cargo area, HK trims only

Door speaker fitment

Sizes and depths below are what research turned up for this generation. Confirm against your own vehicle before cutting or ordering — trim levels vary.

Front doors Unconfirmed

Adapter bracket neededunconfirmed
TweeterTop of dash, one each side — real, confirmed on Harman Kardon-equipped trims (2019-2024: 9-speaker/576W; 2025: upgraded to 11-speaker). Exact diameter not confirmed. Consistent with the recurring dash-corner-tweeter convention found across the rest of Subaru's lineup.

Rear doors Unconfirmed

Adapter bracket neededunconfirmed
Tweetern/a — tweeter is dash mounted, front only

Factory audio integration

Factory amp / premium audioHarman Kardon premium system confirmed, exclusive to equipped trims (base-stereo Foresters have no comparable factory sub at all). Real OEM part number confirmed: 86301SJ140 (Harman Kardon subwoofer), fits 2019-2025 — the whole SK generation shares this one part number, real evidence this is genuinely one generation for audio purposes despite any cosmetic mid-cycle changes. All sound routes through a dedicated Harman Kardon amplifier — a failed amp can present as a speaker or subwoofer problem, worth noting for troubleshooting.
Adding subs without a head-unit swapThe factory HK subwoofer itself is a direct-fit OEM replacement part (86301SJ140) for HK-equipped trims — replacing a failed unit doesn't require a head-unit swap. A genuine aftermarket UPGRADE (bigger driver) is real but constrained by the tight factory sheet-metal mount (see fitment warning above).
Head unitNo replacement needed

Known integration products

Mounting locations

Standard Solid

Real generation change from the 4th Gen (SJ, already): the SJ's build targets the space ABOVE the spare tire (replacing a factory foam bin). This SK generation's Harman Kardon subwoofer instead lives in its own custom-tuned enclosure directly in the rear cargo area, powered by a dedicated external amplifier — a genuinely different architecture, not a running change to the same bay. Real, specific fitment warning found: an 8" Kicker replacement was reported as NOT fitting without major sheet-metal modification to the mounting point — this is a tighter, more constrained factory cavity than the 4th Gen's foam-bin swap, worth flagging plainly rather than implying an easy drop-in.

Builds and products found for this vehicle

Outside links. Some are commercial products, some are owner builds posted on forums — the label says which. We do not endorse any of them.

Build it for this vehicle

Each link opens the tool with this vehicle already selected.

Before you cut anything

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.