The largest cabinet we build

18 Inch Subwoofer Boxes

Eighteen inch cabinets, sealed and ported, CNC-cut in Tullahoma, Tennessee.

The largest cabinet we build

An eighteen is a commitment before it is an upgrade. It asks for cabinet volume a fifteen would not, and an electrical system to feed it, and in return it reaches lower with less cone travel than any smaller driver can manage.

Sealed and ported, wedge and down-fire, machined in Tullahoma, Tennessee. Each cabinet here is cut to the parameters the driver manufacturer publishes for the model it is built around.

Cut, assembled and finished in Tullahoma, Tennessee, on ShopSabre routers from Langboard Elite MDF.

Net volume for a driver-matched cabinet is calculated from the parameters the driver manufacturer publishes for that model. Where a driver has no published figure for a given alignment, the cabinet is not listed for it.

Decision Shortcut

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Curated picks matched to common build goals

Best 18 Inch Sealed

Proline X PO 18-S W RSS460HO sealed wedge, front baffle with gloss black insert and pre-wired leads, 26.0 by 21 inches.

Proline X

Dayton Audio Reference RSS460HO Box: Sealed 18" Wedge Enclosure

Sealed wedge cut for the Dayton Reference RSS460HO. Sealed keeps cone control at the bottom where an eighteen is moving the most air, and the wedge footprint leans against a seat back instead of eating the floor.

$ 399.99

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Best 18 Inch for SPL

Proline X Pro 18-P 9518LESP Professional Series ported enclosure, front baffle with slot port and branded gloss black acrylic insert, 36 by 21 inches, 73.1 square inches of port area.

Proline X

DD Audio 9518L ESP Box: Ported 18" Professional Series Enclosure

Professional Series ported cabinet cut for the DD Audio 9518L. The largest and loudest alignment we build at this size, for output in a known band rather than flat response.

$ 760.99

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Best 18 Inch Value

Proline X PO 18-S DF AA275 sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 11.6 inches.

Proline X

Ampere Audio AA-2.75 18 Box: Sealed 18" Down Fire Enclosure

The lowest entry point into an eighteen here. Down-fire puts the driver toward the floor, so it suits a build where the cabinet has to sit flat under a platform rather than lean.

$ 359.99

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Best 18 Inch for Trucks

Proline X PO 18-P W UMII18 ported wedge, front baffle with gloss black insert and pre-wired leads, 30 by 21 inches.

Proline X

Dayton Audio Ultimax II UMII18 Box: Ported 18" Wedge Enclosure

Ported output in a wedge footprint, cut for the Dayton Ultimax II UMII18. The tapered rear panel turns dead space behind a seat back into usable volume, which is what makes an eighteen viable in a cab at all.

$ 579.99

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Why Eighteen Is a Different Decision

Every size below this one is a balance between output and where the box will fit. At eighteen inches that balance is settled before you start: the cabinet is going to be large, so the question becomes whether the vehicle and the electrical system can carry it. Buyers who get here have usually already run a fifteen and want the bottom octave that only more cone area reaches.

That is also why the range is deliberately narrow. An eighteen is only worth cutting when the driver has published parameters precise enough to build around, so the cabinets here exist for specific drivers rather than as a universal shell.

Sealed or Ported at This Size

Sealed stays the right answer for accuracy and for a cabinet that has to be as small as an eighteen can reasonably be. It rolls off gently, it is forgiving of a volume that is slightly off, and it keeps cone control at the bottom where an eighteen is already moving a lot of air.

Ported buys efficiency near tuning and extends the low end, at the cost of a notably larger cabinet and a hard rolloff below the port. At eighteen inches that size penalty is the real constraint, so measure the space before you decide. A sealed eighteen that fits will beat a ported one that had to be shrunk to get in.

What These Cabinets Are Cut For

These are driver-matched enclosures. We build and stock the cabinet, and the driver is yours to supply, so the fit is to a specific model rather than to a generic eighteen inch cutout.

Current coverage spans Ampere Audio, Dayton Audio, DD Audio, Kicker and Sundown drivers, in both sealed and ported alignments. If you own an eighteen that is not listed, send us the model and the published parameters and we will tell you honestly whether we can cut for it.

Volume Is the Constraint, Not the Driver

An eighteen in a cabinet too small for it will be beaten by a fifteen in the right one. Before choosing the driver, measure the space you actually have and work back to the alignment that fits it. The cabinet decides what the driver can do.

The Range at a Glance

Four chassis types cover this size. Sealed wedge is the default for a cabinet that leans against a seat back or a bed wall, with the baffle vertical so the driver still fires forward. Sealed down-fire puts the driver toward the floor and suits builds where the cabinet has to sit flat under a platform.

On the ported side, the Professional Series is the larger and louder option, built for output in a known band. Ported wedge keeps the tapered footprint while adding port loading, which is the compromise most daily-driven trucks end up wanting.

18 inch Subwoofer Box Questions

How big is an 18 inch subwoofer box?

Larger than most buyers expect. A sealed eighteen typically needs more volume than a ported twelve, and a ported eighteen is larger again. The exact figure depends on the driver, because each cabinet here is cut to the parameters published for one model. Measure your space first and let that decide the alignment.

Should an 18 inch subwoofer box be sealed or ported?

Sealed if accuracy and size matter, ported if output near tuning matters more. At this size the deciding factor is usually space rather than preference, because the ported cabinet is significantly larger. A sealed eighteen that fits the vehicle will outperform a ported one that had to be reduced to fit.

Do you sell the 18 inch subwoofer with the box?

No. We build and stock the enclosure, and you supply the driver. That is why these are cut to specific models rather than to a generic cutout, and it is why the fit is exact rather than approximate.

Will an 18 inch box fit in a truck?

In an extended or regular cab it usually means giving up the rear seat area, and in many builds the cabinet moves to the bed instead. The wedge shapes here exist precisely for cabs, since a tapered rear panel turns dead space behind a seat back into usable volume.

What amplifier does an 18 inch subwoofer need?

More current than a smaller driver, and a healthy electrical system behind it. Match the amplifier to the driver's RMS rating at the impedance you will actually wire it to, not to the cabinet. An underpowered amplifier driven into clipping is the most common way these drivers get damaged.

Subwoofer Boxes by Brand

Every box is cut to one driver's published specs. Pick the brand your subwoofer comes from.

Drivers Built to Match

Subwoofers Spec'd for These Enclosures

The drivers below are matched to the enclosures above by Thiele-Small parameters. Buying together guarantees the alignment, port tuning, and damping work the way the engineering intended.

Image Dynamics ID8 V4 8inch Subwoofer

Image Dynamics

Image Dynamics ID8 V4 8inch Subwoofer

$ 99.99
Prodigy Audio 8 inch Subwoofer NB2 Series - Prodigy Subwoofer for car audio systems

Prodigy Audio

Prodigy Audio 8 inch Subwoofer | NB2 Series

$ 108.99 $ 115.99
Prodigy Audio 10 inch Subwoofer NB2 Series - Prodigy Subwoofer for car audio systems

Prodigy Audio

Prodigy Audio 10 inch Subwoofer | NB2 Series

$ 138.99 $ 145.99
Image Dynamics ID10 V4 10-inch Subwoofer

Image Dynamics

Image Dynamics ID10 V4 10-inch Subwoofer

$ 139.99

View all car subwoofers | Need a custom build? Contact us

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Two car audio (1 black & 1 grey) subwoofer enclosures with visible brand logo on a white background

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Proline X P8-S | Single 8" Sealed Subwoofer Enclosure | V3

$ 129.99
Proline X 6.5-inch ported subwoofer enclosure, front view with the driver cutout and slot port

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Proline X P6-P | Single 6.5" Ported Subwoofer Enclosure | V3

$ 149.99
Proline X E12-S Sealed Enclosure

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Proline X E12-S Sealed Enclosure

$ 159.99
2 10" Subwoofer enclosures, 1 Grey 1 back

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Proline X P10-S | Single 10" Sealed Subwoofer Enclosure | V3

$ 169.99

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Proline X Performance P15-S Sealed Enclosure for 15-inch Subwoofers

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Proline X P15-S | Single 15" Sealed Subwoofer Enclosure | V3

$ 219.99
Proline X PO 15-S DF VCW sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 12.2 inches.

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NVX VCW15v3 Box: Sealed 15" Down Fire Enclosure

$ 339.99
Proline X PO 15-S DF AA3 sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 13 inches.

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Ampere Audio AA-3.0 15 Box: Sealed 15" Down Fire Enclosure

$ 339.99
Proline X PO 15-S DF RSS390HO sealed down fire enclosure, front panel on 1.75 inch feet, 30 by 10.1 inches.

Proline X

Dayton Audio Reference RSS390HO Box: Sealed 15" Down Fire Enclosure

$ 339.99

View all 15 inch subwoofer boxes | Need a custom build? Contact us