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Designed by B&C Speakers

S218BP6th Order

6th order bandpass. Two driver tiers, serious low-end.

B&C's S218BP is a 6th order bandpass subwoofer using 2×18" neodymium woofers. CEA2010B broadband peak SPL of 139 dB. Open source plans, precision CNC flatpack.

Specifications

6th Order Bandpass Subwoofer — B&C Speakers

Configuration
2 × 18" 6th Order Bandpass
Peak SPL
139 dB (CEA2010B broadband @ 1m)
Frequency Range
29 – 80 Hz (processed)
Impedance
4 Ohm (2 × 8 Ohm parallel)
Enclosure Material
15mm Birch Plywood
Connectors
2 × Neutrik NL4MPR
Damping
Edilfiber (Polyester) 30kg/m³, 30mm thick

DSP / Processing

HPF: Butterworth 24dB/Oct @ 29 Hz
LPF: Linkwitz-Riley 24dB/Oct @ 80 Hz
EQ1: F = 33 Hz, Gain = +3 dB, Q = 3

CEA2010B broadband peak SPL = 139 dB @ 1m half-space.

Driver Options

Choose from 2 recommended drivers, or source your own. We can include them in your kit.

Premium£1000 / pair

B&C 18SW115

A couple of dB extra low-end extension at peak. Premium neodymium 18" woofer for maximum sub-bass performance.

Power: 1700W AES
Sensitivity: 97 dB
Impedance: 8 Ohm
Magnet: Neodymium
  • Extra low-end extension at peak
  • Neodymium magnet - lightweight
  • 1700W AES power handling
  • Premium B&C build quality
Core£750 / pair

B&C 18SW100

Excellent performance and value. Neodymium 18" woofer - the standard choice for the S218BP design.

Power: 1400W AES
Sensitivity: 96 dB
Impedance: 8 Ohm
Magnet: Neodymium
  • Excellent value for performance
  • Neodymium magnet - lightweight
  • 1400W AES power handling
  • Proven in the S218BP design

What's Included

Everything in the flatpack kit

CNC-Cut Panels

Precision-cut from 15mm birch plywood

  • Front baffle (driver cutouts pre-routed)
  • Rear panel with access panel cutout
  • Side panels
  • Top and bottom panels
  • Internal bracing & dividers
  • Mid port panel (mandatory dimensions)
  • Access panel

Hardware Kit

All mechanical fixings as per B&C spec

  • 2 × Neutrik NL4MPR connectors
  • M6 Wood T-Nuts (34×)
  • TSEI M6×30 screws (18×)
  • TCEI M6×40 with washers (16×)
  • Recessed handles
  • Rubber feet
  • EPDM stripes (3mm)

Damping Material

Edilfiber polyester damping, pre-cut

  • Edilfiber 30kg/m³, 30mm thick
  • Pre-cut to specification
  • Placement guide included

Documentation

Assembly guide and DSP settings

  • Step-by-step assembly guide
  • Wiring diagram
  • DSP / processor settings
  • Damping placement guide

Build your S218BP

Flatpack from £799. Optional drivers, stain, mounting hardware, and build service.

Lead time: 2–3 weeks (flatpack) · 3–5 weeks (subject to driver availability) (with drivers)

FAQ

What is the difference between the 18SW115 and 18SW100?

The 18SW115 (Premium) gives you a couple of dB extra low-end extension at peak, meaning deeper sub-bass reach. The 18SW100 (Core) is an excellent performer at a lower price point.

Can I supply my own drivers?

Yes. Order the flatpack without drivers and fit your own 18SW115 or 18SW100 woofers.

What tools do I need?

Essential: drill/driver, clamps (min 4), wood glue, rubber mallet, workbench, square, tape measure. Recommended: soldering iron, multimeter, orbital sander for finishing.

Is a DSP required?

Yes. The bandpass design needs HPF at 29 Hz, LPF at 80 Hz, and a +3 dB peaking EQ at 33 Hz. We provide baseline settings.

What about the build and finishing service?

We can assemble and finish the cabinet for you. Select "Build & Finish" when requesting your quote.