2016-2020 Kia Optima 4th Gen (JF) — 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 Sedan

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.

Trunk Likely

Locationtrunk, through existing opening (promoted from existing notes)
Outer bounding box43"W x 18"H x 42"/35"D
Known obstructionsNone specifically documented. NOTE ON THE TWO DEPTH FIGURES: the source publishes them as "42\"/35\"" in that order, which is the reverse of how the other vehicles covered here present the pair (they read smaller-first, seats-up then seats-folded). Recorded verbatim rather than silently reordered, because assuming which figure is seats-up would be a guess. Build to 35" if you need the conservative number.
Usable volume estimate4 ft³

Starting points

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

Budget

Subwoofers1x10" sealed
Box typesealed
Locationtrunk

Enthusiast

Subwoofers1x12" loaded sealed (real example: Skar Audio)
Box typesealed
Locationtrunk

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 Solid

Factory speaker size6-3/4"
Known obstructionsNone specifically documented
Adapter bracket neededno

Rear doors Unconfirmed

Factory speaker sizeunconfirmed
Adapter bracket neededunconfirmed
Tweetern/a — tweeter is dash-corner mounted, front only

Factory audio integration

Factory amp / premium audioBase system versus an optional HARMAN KARDON system, and the difference is large. Harman Kardon cars get a factory 8" shallow-mount SUBWOOFER and a pair of speakers in the rear deck, a 5-1/4" centre dash speaker, and LOW-IMPEDANCE speakers throughout — fitting standard 4-ohm aftermarket speakers to a Harman Kardon car causes a definite, audible loss of volume. THE HARD CONSTRAINT ON THIS GENERATION: only the BASE receiver can be replaced at all. The optional navigation receiver cannot be replaced, so on nav-equipped cars the upgrade path is speakers and amplification only. Replacing the base receiver costs you factory satellite radio and the aux input. SEPARATE WARNING FOR THE HYBRID: high-powered audio gear and this hybrid system are a bad combination — speaker upgrades are the sensible route on Optima Hybrid rather than big amplification.
Adding subs without a head-unit swapConfirmed straightforward — trunk-based builds don't touch the head unit
Head unitNo replacement needed

Known integration products

Mounting locations

Trunk Solid

Real measured trunk: 43"W x 18"H x 42"/35"D. Real pricing: professional custom installations run roughly $700-900 depending on customization level. Earlier 2011-2014 generation has its own distinct spec (9.00" mounting depth, 9.125"/11.125" cutouts, 2 chambers at 0.89 ft3/chamber) — kept separate, not assumed identical to this generation.

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.