What size are car subwoofers?
Car subwoofers typically come in diameters of 8, 10, 12, and 15 inches; smaller 6-inch (often 6.5”) models exist for tight spaces, and 18-inch subs are used in some high-output or custom installations.
In car audio, the size of a subwoofer largely determines how much air it can move and how deep its bass can extend, but the best choice depends on space, enclosure type, vehicle size, and your listening goals. The following guide outlines the most common sizes and how they’re typically used.
Common sizes and what they mean
Before listing the sizes, note that diameter is the primary specification for these drivers and influences enclosure design and bass reach. The items below reflect typical options you’ll encounter in retail catalogs and installs.
- 8 inches: compact footprint, suitable for small cars or tight enclosures; modest bass extension.
- 10 inches: common balance of size and output; fits many trunks and under-seat enclosures.
- 12 inches: standard choice for many enthusiasts; good bass extension with moderate enclosure space.
- 15 inches: strong bass output and deeper extension; requires larger enclosure and more trunk space.
- 6 inches (often marketed as 6.5"): for ultra-compact installations or specialized builds; limited bass compared to larger sizes.
- 18 inches: high-output, niche or competition setups; very large enclosures and substantial power are typical.
Choosing among these sizes generally comes down to the space you can devote to the subwoofer, the enclosure type (sealed vs. ported), and how deep you want the bass to go. Bigger drivers move more air and typically deliver lower frequencies, but they also require more space and power.
Practical considerations when selecting size
Beyond diameter, several design factors affect how a given subwoofer will perform in your vehicle. The following considerations help bridge the gap between the size you want and the sound you expect.
- Enclosure type and volume: Sealed boxes favor smaller subs for tight, accurate bass, while ported boxes and larger enclosures accentuate deep bass and output with bigger drivers.
- Mounting depth and space: A larger diameter driver demands more mounting depth and trunk or cargo area, which may limit options in smaller cars.
- Power handling and efficiency: Larger subs can move more air but may require more amplifier power and careful tuning to avoid distortion; efficiency (sensitivity) affects how much amp power you need.
- Vehicle constraints: Trunk shape, rear seat clearance, and available mounting surfaces influence what size is feasible and how it will impact cargo space.
In practice, the right choice balances available space, desired bass performance, and how much you’re willing to invest in enclosure design and amplification. A 12-inch sub is a common starting point for a well-rounded, room-filling bass without excessive space demands.
Summary
Car subwoofers predominantly come in 8, 10, 12, and 15 inches, with smaller 6.5-inch models and occasional 18-inch subs for specialized setups. Size affects bass extension, required enclosure volume, and space in the vehicle; the best option depends on your car, budget, and bass goals. Always pair the driver size with an appropriately designed enclosure and amplifier to achieve the intended sound.
