B&C 21SW152 – Superior 21″ Neodymium Subwoofer with 6″ Voice Coil and 4000W Handling

When the 21SW115 isn’t enough, the B&C 21SW152 takes 21-inch subwoofer performance to the next level. This flagship neodymium sub driver handles a staggering 4000 W continuous program power through a massive 153 mm (6-inch) split-winding copper voice coil — the largest coil in B&C’s entire driver catalogue. If you’re building the hardest-hitting subwoofer you’ve ever designed, this is the driver to put inside it.

The B&C 21SW152 shares the same 21-inch frame and 1680 cm² piston area as the 21SW115, but upgrades the motor significantly. The 6-inch coil pushes the Bl factor to 32.5 Tm, increases Xmax to 15 mm, and raises continuous power handling by 600 W. For builders who need the absolute maximum output from a single 21-inch driver, the 21SW152 is where the B&C range peaks.

Available in both 4 Ω and 8 Ω versions, with B&C’s recommended 190-litre enclosure tuned to 33 Hz, the B&C 21SW152 gives you a complete starting point for a subwoofer build that delivers deep, physical, room-shaking bass at power levels that push the boundaries of what a single driver can do.

Design and Construction of the B&C 21SW152

The defining feature of the B&C 21SW152 is its 153 mm (6-inch) split-winding copper voice coil on a glass fibre former. To put that in perspective, this coil is larger in diameter than most 6.5-inch speaker cones. The enormous thermal surface area is what makes sustained 4000 W operation possible — heat dissipates across a coil circumference that dwarfs anything else in the B&C range.

A ventilated voice coil gap allows airflow through the motor during excursion, further reducing power compression under sustained load. For your build, this means the B&C 21SW152 maintains its full output and tonal character hour after hour, even when driven at extreme power levels. The bass you hear at the end of a punishing set is the same bass you heard at the start.

The 32.5 Tm Bl factor is exceptionally strong — higher than the 21SW115’s already impressive 30.1 Tm. That motor authority keeps the heavy 460 g moving assembly under tight control throughout its 16 mm linear excursion. You’ll hear this as deep bass that hits hard and resets fast, with tight transient response that prevents the mud and overhang that weaker motors produce.

The double silicone spider suspension provides consistent mechanical control across the full stroke. The triple roll surround and radial cone shape are optimised for maximum excursion capability, and an aluminium demodulating ring in the motor structure suppresses distortion to keep the output clean even under extreme load.

The cone features TWP (Total Waterproof) treatment on both sides for complete moisture protection. Whether your sub is working at an outdoor festival, a humid club, or an exposed outdoor installation, the cone won’t degrade from environmental exposure.

The neodymium inside-slug magnet with T-pole design delivers 1.2 T flux density while keeping the motor as compact as possible. Despite the massive 6-inch coil and upgraded motor, the B&C 21SW152 weighs 18.5 kg — heavier than the 21SW115’s 14 kg, but still remarkably manageable for a driver of this capability.

Performance and Applications for the B&C 21SW152

The B&C 21SW152 handles 4000 W continuous with 96 dB sensitivity and a frequency range from 30 Hz to 1000 Hz. The 2.2% reference efficiency matches the 21SW115, but the higher power handling means the 21SW152’s absolute maximum SPL output is significantly higher. Pair it with a quality 2500–4000 W amplifier and your sub will deliver bass that’s felt as much as heard.

B&C recommends a 190-litre vented enclosure tuned to 33 Hz. That’s notably smaller than the 21SW115’s recommended 250 litres — the 21SW152’s 200-litre Vas and lower Qts of 0.30 allow a more compact cabinet while still achieving deep bass-reflex alignment. For builders, a smaller enclosure means a lighter, more portable sub that’s easier to transport and stack.

The EBP of 103 Hz gives you flexibility between vented and horn-loaded designs. The 21SW152 works well in both — a reflex box for clean, extended low end, or a horn-loaded enclosure for maximum SPL and efficiency when deep infra-bass isn’t the primary goal.

Builders commonly choose the B&C 21SW152 for:

• Flagship single-driver subwoofer builds requiring maximum output
• Festival and touring bass stacks needing extreme sustained power
• Horn-loaded subwoofer designs for maximum SPL efficiency
• Club installations demanding deep, physical bass impact night after night
• Builds where a single 21 needs to outperform dual-18 configurations

The driver displaces 16 litres inside the enclosure, which should be factored into your net volume calculations. At 261 mm deep, it’s 12 mm deeper than the 21SW115 due to the larger motor — a minor difference that shouldn’t affect most cabinet designs.

Specifications

• Nominal Diameter: 530 mm (21 in)
• Voice Coil Diameter: 153 mm (6 in)
• Continuous Power Handling: 4000 W
• Nominal Power Handling: 2000 W
• Nominal Impedance: 4 Ω (also available in 8 Ω)
• Minimum Impedance: 4.2 Ω
• Frequency Range: 30 Hz – 1,000 Hz
• Sensitivity: 96 dB
• Winding Material: Copper (Split Winding)
• Former Material: Glass Fibre
• Winding Depth: 30 mm (1.18 in)
• Magnetic Gap Depth: 12 mm (0.5 in)
• Flux Density: 1.2 T
• Surround Shape: Triple Roll
• Cone Shape: Radial
• Spider: Double Silicone
• Cone Treatment: TWP Waterproof Both Sides

Thiele–Small Parameters

• Fs: 32 Hz
• Re: 3.3 Ω
• Qes: 0.31
• Qms: 7
• Qts: 0.30
• Vas: 200 dm³ (7 ft³)
• Sd: 1680 cm² (260.4 in²)
• η₀: 2.2%
• Xmax: 15 mm
• Xvar: 16 mm
• Mms: 460 g
• Bl: 32.5 Tm
• Le: 1.5 mH
• EBP: 103 Hz

Mounting Information

• Overall Diameter: 547 mm (21.5 in)
• Bolt Circle Diameter: 527 mm (20.7 in)
• Baffle Cutout: 508 mm (20 in)
• Depth: 261 mm (10.3 in)
• Air Volume Occupied: 16 dm³ (0.56 ft³)
• Net Weight: 18.5 kg (40.7 lb)
• Replacement Recone Kit: RCK21SW1524

Conclusion

The B&C 21SW152 is the flagship of B&C’s 21-inch subwoofer range — the driver you choose when absolute maximum output is the only thing that matters. Its 153 mm voice coil is the largest in B&C’s catalogue, the 4000 W continuous handling is the highest, and the 32.5 Tm Bl factor ensures every watt of power translates into tight, controlled, earth-moving bass.

With a smaller recommended enclosure than the 21SW115 (190 litres vs 250), ventilated gap for reduced compression, TWP double-side waterproofing, and the choice of 4 Ω or 8 Ω impedance, the B&C 21SW152 gives you the tools to build the most powerful single-driver subwoofer your system has ever seen. Whether you’re stacking subs for a festival, building a horn-loaded infra cabinet, or designing a club install that needs to deliver punishing bass night after night, this is the driver that sets the ceiling.

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About B&C Speakers S.r.L.

B&C Speakers products are built in Bagno a Ripoli (Florence), Italy., ensuring high quality products to suite your speaker building requirements. Their 10,500 square meter facility incorporates highly sophisticated automation and quality control. Over the years they become one of the world leaders in the Professional Audio market, a brand recognized everywhere as a premium product that offers excellent value to the consumer.