Toyota Hilux Subwoofer Box: Enclosures for Every Cab

The Toyota Hilux is one of the most popular working trucks on the market, and its three cab configurations cover a massive range of available install space. A single cab Hilux has a cavernous behind-seat area that can swallow a large ported enclosure with room to spare. A double cab has almost none — the rear seat folds up, but what remains is cramped, irregular, and tightly competed by passengers, seat mechanisms, and floor slopes. Building a subwoofer enclosure for a Hilux means knowing which cab you have, measuring accurately, and choosing an enclosure type that matches the geometry rather than fighting it.

This guide covers all three cab configurations with approximate usable dimensions, the right enclosure approach for each, driver size recommendations, and worked example designs for both sealed and ported builds. All example volumes and port specifications are calculated for common mid-level drivers — adjust for your specific T/S parameters using the simulation tools linked throughout.

Available Space by Cab Type

Measuring before you design is not optional. Hilux interiors vary by generation and market, so treat these as starting estimates — verify with your own tape measure and account for wheel arch intrusion, floor slope, and any factory trim you plan to keep.

Single Cab (Roo Bar / WorkMate / SR)

The single cab has no rear seat. Behind the front bench there is typically 900–1000 mm of lateral width, 350–450 mm of depth (front-to-back), and 500–600 mm of height at the centre, tapering toward the seat back and floor. Usable internal volume before driver and port displacement is approximately 130–160 litres. This is the most generous Hilux configuration by a wide margin. You can build a ported enclosure with a properly folded port without compromise.

Extra Cab (also called Access Cab or Space Cab depending on market)

The extra cab has fold-forward rear jump seats that are rarely used by adults. When those seats are folded up, the rear floor behind the front seats is about 700–800 mm wide, 250–350 mm of usable depth (the jump seat brackets limit depth toward the rear wall), and 350–450 mm of height. Usable gross volume is approximately 50–80 litres per side, or 90–130 litres if you use the full width. The restricted depth makes fitting a ported design tricky without compact port routing. This configuration suits a sealed build or a modest ported box in the rear corners.

Double Cab (SR5 / Rogue / GR Sport)

The double cab has a full rear seat row. Under-seat space is approximately 700–750 mm wide, 200–250 mm deep, and 130–180 mm high — a flat, shallow channel that is very difficult to exploit with a standard enclosure. The usable net volume for a dedicated sub enclosure is around 15–30 litres depending on floor profile and how far you are willing to intrude into legroom. Sealed is the standard choice here. Kick panel installs are the alternative if you want ported output without sacrificing under-seat space.

Single Cab: Behind-Seat Ported Builds

With 130–160 litres of raw space, the single cab Hilux can accommodate a ported enclosure for a 12-inch or 15-inch driver without resorting to tight port routing. The main constraint is the sloped floor — the bottom panel of the enclosure should follow the floor angle or sit on a dedicated riser to avoid wasted dead volume underneath the box.

For a 12-inch driver targeting a tuning frequency around 32–35 Hz, a net internal volume of 50–60 litres is appropriate for most mid-range drivers (Fs 25–35 Hz, Qts 0.35–0.50). A C-fold or U-fold slot port with approximately 50–60 cm² of port area per 0.01 m³ of net volume keeps port velocity below 15 m/s at rated power. High port velocity is a common problem in truck builds where builders try to maximise output by using a small port — see the post on port velocity and what happens when it gets too high for the mechanics.

A 15-inch driver in the single cab is entirely feasible. Net internal volumes of 70–100 litres suit most 15-inch sub drivers. At this volume the bottom end extension improves significantly, but you will want to verify tuning frequency choice against cabin gain. Hilux cabins are mid-size and provide substantial low-frequency reinforcement below 60 Hz — see cabin gain: the free bass you are not accounting for. Tuning to 30–32 Hz rather than 38–40 Hz typically produces a flatter in-cabin result once the cabin transfer function is applied.

Use the ported box calculator to cross-check any volume and port area combination before cutting. The port length calculator is essential once you commit to a port area — the required length changes significantly with box volume and tuning frequency, and getting it wrong by 10% shifts your tuning noticeably.

Extra Cab: Under-Seat Sealed vs Small Ported in Rear Corners

The extra cab is a compromise platform. You have more space than a double cab but less than a single, and the geometry is less regular.

Sealed under-seat: The cleanest approach for an extra cab is a sealed box that fits under the folded jump seats or beside them along the rear wall. A sealed 25–35 litre enclosure for a 10-inch driver gives predictable, tight bass with a flat impedance curve that is easy on amplifiers. The 6 dB/octave slope below resonance is gentle enough that cabin gain provides a natural lift in the low registers. For music-focused builds this is often the right call — sealed vs vented vs bandpass covers the trade-offs in detail.

Calculate sealed enclosure alignment using the sealed box calculator. For most 10-inch sub drivers with Qts around 0.5, a 20–28 litre sealed box produces a Qtc of 0.65–0.75, which is a well-damped alignment with good transient response.

Small ported in rear corners: If the jump seats are rarely used and you are willing to build an angled enclosure to fit the corner geometry, a 30–40 litre ported box for a 10-inch driver can work in each rear corner. Tuning to 35–38 Hz with a 3–4 cm diameter round port (or a slot port approximately 5×3 cm) is achievable in this volume. However, verify port length against the enclosure depth — at 35 Hz tuning with 35 litres net, the required port length for a 25 cm² port is approximately 18–22 cm, which usually fits with a straight port or a short L-fold.

Double Cab: Under-Seat Sealed or Kick Panel Options

The double cab Hilux is the most constrained platform, and most builders face a direct choice between acceptable bass from a very compact sealed build or a more complex kick panel installation.

Under-seat sealed: A 10-inch or 8-inch subwoofer in a sealed enclosure of 12–20 litres fits the under-seat channel in most double cab Hilux variants. The enclosure typically needs to be wedge-shaped or built with a sloped baffle to match the floor profile. MDF is the standard material, but some builders use 12 mm birch ply to recover a few litres of net volume from thinner walls — relevant at volumes this small where every litre matters.

An 8-inch driver in 12 litres sealed is a viable alternative to a 10-inch for builds prioritising a lower enclosure height. Many 8-inch sub drivers (Fs 35–45 Hz, Qts 0.65–0.85) are specifically designed for sealed compact enclosures. The reduced cone area is partially offset by positioning the enclosure where it couples well with the cabin floor.

Kick panel installs: For builders willing to fabricate fibreglass or foam kick panels, a small ported enclosure in each front kick panel area can provide significantly better bass extension than under-seat sealed. The kick panel space is approximately 3–6 litres per side — enough for a 6.5-inch mid-bass driver or a small 8-inch sub with a very short port tuned high (45–55 Hz). This is an advanced build technique and outside the scope of a single-post treatment, but the acoustic principles are the same as any ported build: use the ported box calculator and verify port velocity at the small volumes involved.

Driver Size Recommendations Per Cab Type

Driver sizing determines both available excursion headroom and how much port area you need, which in turn affects how easily you can route the port in a confined space.

Cab Type	Recommended Driver Size	Notes
Single Cab	12-inch or 15-inch	Space is not the constraint — driver T/S parameters and output goals drive the choice
Extra Cab	10-inch or 12-inch	12-inch sealed or ported is feasible with a careful build
Double Cab	8-inch or 10-inch	10-inch is the practical maximum for under-seat sealed

For all Hilux builds, prioritise drivers with moderate Qts (0.45–0.65) and Fs below 35 Hz. High-Qts drivers (above 0.75) in small enclosures produce a peak in the upper bass region that sounds boomy and slow in a truck cab. Low-Qts drivers (below 0.35) are designed for larger vented alignments and tend to underperform in the restricted volumes a Hilux demands.

Driver BL (force factor) matters more in compact enclosures than builders often expect. A higher BL driver maintains better control over cone excursion at the small enclosure volumes involved. See the post on motor force and why BL is not constant for context on how BL varies with excursion and what that means at realistic signal levels.

Example Sealed Design: Double Cab 10-Inch Build

This example is for a 10-inch subwoofer with representative T/S parameters:

• Fs = 32 Hz
• Qts = 0.55
• Vas = 28 litres
• Xmax = 12 mm
• Pe = 250 W

Target enclosure volume: 18 litres net (after driver and any bracing displacement, approximately 0.018 m³)

Enclosure alignment check: Using the sealed alignment equation, Qtc = Qts × √(Vas/Vb + 1). With Vas = 28 L and Vb = 18 L:

Qtc = 0.55 × √(28/18 + 1) = 0.55 × √(2.556) = 0.55 × 1.599 ≈ 0.88

A Qtc of 0.88 produces a pronounced resonant peak — this is a tight space and the alignment is pushed. If you can find 22–25 litres you will land closer to Qtc 0.75–0.80, which is more balanced. At 18 litres this driver will benefit from a high-pass filter (subsonic is unnecessary for sealed, but a HPF at 25–30 Hz protects the driver near Qtc resonance with heavy content).

Physical dimensions for 18 litres (external, 18 mm MDF):

• Width: 600 mm
• Height: 150 mm (matches typical under-seat clearance)
• Depth: 235 mm
• Internal net volume (subtracting 18 mm walls and driver displacement): ≈18.2 L

This is a wedge-unfriendly rectangular form — most builders cut a tapered top panel to match the floor slope and recover the full under-seat height. Building a tapered version with a 150 mm front height and 120 mm rear height and 260 mm depth achieves a similar net volume while fitting flush to the floor slope.

For box dimension ratios and why they matter for internal standing waves, see subwoofer box dimensions: getting the ratio right.

Example Ported Design: Single Cab 12-Inch Build

This example is for a 12-inch subwoofer installed in a single cab Hilux behind the front bench.

Driver T/S parameters (representative):

• Fs = 28 Hz
• Qts = 0.40
• Vas = 62 litres
• Xmax = 14 mm
• Pe = 500 W

Target enclosure: 55 litres net, tuned to 33 Hz

Port specification: Slot port, 60 mm wide × 80 mm tall (cross-sectional area = 48 cm²). At 500 W input and 33 Hz tuning, peak port velocity is approximately 14 m/s — below the 17 m/s laminar threshold. Use the port length calculator to verify this for your specific driver.

Port length calculation (Helmholtz formula):

Lp = (c² × Sp) / (4π² × Fb² × Vb) - correction term

Where:

• c = 343 m/s (speed of sound)
• Sp = 0.0048 m² (port area)
• Fb = 33 Hz
• Vb = 0.055 m³

Lp = (343² × 0.0048) / (4π² × 33² × 0.055) - 0.732 × √(Sp/π) Lp ≈ (117649 × 0.0048) / (39.48 × 1089 × 0.055) - end correction Lp ≈ 564.7 / 2366.3 - 0.056 ≈ 0.183 m ≈ 183 mm

A 183 mm straight slot port at this cross-section fits comfortably within the single cab depth. You can also route it as a short C-fold with a 100 mm first leg and an 83 mm return leg if depth is a constraint. For a detailed walkthrough of this calculation, see port length calculator: the math behind tuning.

Physical dimensions for 55 litres net (external, 18 mm MDF):

• Width: 700 mm (spans most of the behind-seat width)
• Height: 380 mm
• Depth: 300 mm
• Gross internal: ~67 litres
• Driver displacement: ~4 L
• Port displacement (slot port 60×80×183 mm): ~0.88 L
• Net volume: ≈62 litres — adjust depth to 270 mm or reduce width to hit 55 L net

Build the box, mount the driver offset from centre to leave port clearance on one side. RokketBox's optimizer rejects port path collisions during configuration evaluation — the design it returns is already confirmed buildable. The 3D viewer then renders the validated geometry so you can inspect the layout before cutting.

The predicted system resonance (Fb) should be confirmed by measuring the impedance curve after build. The dip between the two impedance peaks should sit at 33 Hz. If it is off by more than 2 Hz, the port length requires trimming — cutting port length increases tuning, adding length decreases it. See how to tune a ported subwoofer box for the adjustment process.

Designing Your Hilux Build in RokketBox

RokketBox accepts maximum-dimension constraints per axis, which makes space-constrained truck builds its most direct use case. Enter your driver's T/S parameters (or select from the driver database), set your enclosure type, and define the space constraints from your cab measurements. The optimizer samples thousands of configurations via Latin hypercube sampling across volume, tuning frequency, and port area (port length is derived analytically from the Helmholtz formula, not sampled), then scores each against your SPL and extension targets and returns the highest-scoring buildable result.

The key feature for Hilux builds is the maximum dimension constraints. Set the width to your measured behind-seat or under-seat width, the height to your available clearance, and the depth to your maximum front-to-back space. The optimizer will only return designs that fit. Port routing collision detection is built into the evaluation loop — configurations where the port collides with the driver or the enclosure walls are rejected before scoring, so the output you get is one you can actually cut.

If you have already chosen your enclosure type and just need to verify dimensions, the individual simulation tools do the job fast. Use the sealed box calculator for sealed builds, the ported box calculator for vented, and the port length calculator to verify port dimensions match your space constraints.

Enter your cab measurements and driver T/S parameters into RokketBox and it outputs panel dimensions you can cut directly from the result.