Continuous Power Handling
Voice Coil Diameter
Magnet Material

This next evolution subwoofer uses a new, longer, four layer aluminum voice coil. The result is more energy in the gap, higher sensitivity, lower distortion and better overall performance. The 21DS115 features a 30mm long, 4.5 inch diameter (116mm) Copper Clad Aluminum Wire voice coil. With a 1700watt AES power rating, 99db sensitivity, and over 16.5mm of Xvar, this high energy subwoofer is a significant step forward from similar models in the B&C range, even approaching the performance of our 6” voice coil alternatives.



  • Nominal Diameter530 mm (21.0 in)
  • Nominal Impedance4 Ω
  • Minimum Impedance3.1 Ω
  • Nominal Power Handling11700 W
  • Continuous Power Handling23400 W
  • Sensitivity399.0 dB
  • Frequency Range30 - 1000 Hz
  • Voice Coil Diameter116 mm (4.5 in)
  • Winding MaterialAluminium
  • Former MaterialGlass Fibre
  • Winding Depth36.0 mm (1.42 in)
  • Magnetic Gap Depth14.0 mm (0.55 in)
  • Flux Density0.8 T


  • Surround ShapeTriple Roll
  • Cone ShapeRadial
  • Magnet MaterialNeodymium Inside Slug
  • SpiderDouble Silicone
  • Pole DesignT-Pole
  • Woofer Cone TreatmentTWP Waterproof Both Sides
  • Recommended Enclosure130.0 dm3 (4.59 ft3)
  • Recommended Tuning40 Hz


  • Resonance Frequency30 Hz
  • Re2.2 Ω
  • Qes0.2
  • Qms11.0
  • Qts0.21
  • Vas274.0 dm3 (9.68 ft3)
  • Sd1680.0 cm2 (260.4 in2)
  • η₀3.4 %
  • Xmax15.0 mm
  • Xvar17.0 mm
  • Mms412.0 g
  • Bl28.8 Txm
  • Le2.4 mH
  • EBP150 Hz

Mounting And Shipping Info

  • Overall Diameter547 mm (21.54 in)
  • Bolt Circle Diameter527 mm (20.7 in)
  • Baffle Cutout Diameter508.0 mm (20.0 in)
  • Depth255 mm (10.04 in)
  • Flange and Gasket Thickness13 mm (0.51 in)
  • Air Volume Occupied by Driver15.0 dm3 (0.53 ft3)
  • Net Weight14.8 kg (32.63 lb)
  • Shipping Units1
  • Shipping Weight17.1 kg (37.7 lb)
  • Shipping Box570x570x320 mm (22.44x22.44x12.60 in)

Service Kit

  • RCK21DS1154
  • 2 hours test made with continuous pink noise signal (6 dB crest factor) within the range Fs-10Fs. Power calculated on rated minimum impedance. Loudspeaker in free air.
  • Power on Continuous Program is defined as 3 dB greater than the Nominal rating.
  • Applied RMS Voltage is set to 2.83 V for 8 ohms Nominal Impedance.
  • Thiele-Small parameters are measured after a high level 20 Hz sine wave preconditioning test.