Beta Twin 18" Sub Woofer Bass Passive Speaker 2000w RMS (B-Grade)


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£399Incl. VAT Our Price
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This listing is for a Twin 18" Subwoofer which needs painting and some minor restoration due to the odd ding in the cabinet.

Only 3 in stock - allow 5 days working days for delivery. UK DELIVERY ONLY


  • Passive 2000w RMS 18" bass-reflex PA subwoofer
  • 135 dB maximum sound pressure level
  • Deep bass down to 33 Hz through 18" BDP18 BishopSound Woofer
  • Speakon In, Speakon Out
  • Can be used horizontally or vertically
  • Rugged birch multiplex/MDF hybrid enclosure
  • 18 mm plywood cabinet with extremely durable polyurea coating
  • Easy handling through ergonomic handles and stacking dimples
  • Shock-resistant front grille to protect the loudspeaker
  • Countersunk Extra Tick "ding proof" grille to prevent grill damage when on tour
  • Acoustic foam behind the grille to prevent moisture and dust ingression
  • Painted with 4 coats textured, tough durable acrylic PU polymer paint
  • Chunky tactile steel handles

This is my most popular subwoofer delivering 135dB SPL. I only talk about RMS ratings but if you are comparing with inferior brands the BB218 program power is 4000w and the peak power is 8000w per cabinet.

We load two of the BDP18 driver into this cabinet. This superior cast alloy driver is rated at 8 ohms and has a 4" voice coil. Learn more by reading technical specifications.

I never use other people's drivers in my subwoofers. I make my own as I want to match the drivers perfectly to the cabinet and our cabinets have stood the test of time for over 20 years. We carry spares and replacement parts but rarely need them.

Remember there are no middlemen at Bishopsound. We design, manufacture and sell directly to you.

Enjoy the punchy tight bass of our best ever twin 18" sub. Bob Marley and Level 42 have never sounded as good.

Important information about subwoofers

Subwoofers are designed to reproduce low bass audio signals between 30Hz and 150Hz. Driving them with full frequencies will cause permanent damage, so they should only be operated with a passive low-pass filter, a crossover network, or an active electronic crossover or speaker management system.

  • Dual 18" PA Subwoofer
  • Woofer Magnet: Ferrite
  • Woofer :BDP18 1000w 2 x 8ohm
  • Woofer Voice Coil: 4 "
  • Load Rating (RMS): 2000 W
  • Peak Power: 8000 W
  • Max. SPL: 135 Db
  • Impedance: 84 Ohm
  • Cabinet Material: 
  • Cabinet Surface: Polyurea
  • Cabinet Construction: Vented
  • Countersunk Extra Tick "ding proof" grille to prevent grill damage when on tour
  • Acoustic foam behind the grille to prevent moisture and dust ingression
  • Rugged birch multiplex/MDF hybrid enclosure with 4 coats textured, tough durable acrylic PU polymer paint
  • Chunky tactile steel handles
  • Depth (mm): 600
  • Height (mm): 1220
  • Width (mm): 820
  • Net weight (kg): 76
  • Frequency Response (Hz): 33 Hz - 200Hz 
  • Gross Weight (kg): 82
  • Carton Dims = 75x62x130
  • Nominal Overall Diameter: 460 mm
  • Nominal Voice Coil Diameter: 100 mm
  • Magnet Weight: 125 OZ
  • Flux Density: 1.42 T
  • Weight: 11.2 K


  • Voice Coil DC Resistance Re 5.6 Ω
  • Resonance Frequency Fs 34.8 Hz
  • Mechanical Q Factor Qms 11.48
  • Electrical Q Factor Qes 0.57
  • Total Q Factor Qts 0.543
  • Mechanical Moving Mass Mms 202.6 g
  • Mechanical Compliance Cms 103.05 um/N
  • Force Factor BL 20.87 Wb/m
  • Equivalent Acoustic Volume Vas 219.7 It.
  • Maximum Linear Displacement Xmax ±7 mm
  • Reference Efficiency ηo 1.575 %
  • Diaphragm Area Sd 122.54 Cm2
  • Losses Electrical Resistance Res Ω
  • Voice Coil Inductance@ 1K Hz LE m H
  • Nominal Impedance 8 Ω
  • Musical Power 2000 W
  • Rated Power 1000 W
  • Sensitivity@1W/1m 95 d B


  • Magnet Ferrite
  • Voice Coil Winding Copper
  • Voice Coil Former Kapton
  • Cone Paper - Made In England
  • Surround Treated Cloth
  • Dust Dome Paper
  • Basket Die-Cast Aluminium



Your Guarantee is for 12 months and starts from delivery date but please read on. The warranty is recorded with the BishopSound Order number which begins with a B. Please download and keep a copy of your invoice and keep it safe.

We know problems can occur from time to time so even after 1 year I am here to help. We carry parts and we treat everyone as we expect to be treated ourselves so we will work hard to get a win win.

We still help people who bought from us at Carlsbro 30 years ago with parts (if they are available) repairs and solutions. BishopSound prides itself on treating every customer as a family friend.

In short if the problem was caused by me its up to me to fix it. If you had an accident then I will try my hardest to fix it at little or no cost to you. This guarantee is in addition to, and does not affect your statutory rights or the other right of consumer purchases.

For more information, please see our Terms & Conditions

    Get in touch with BishopSound today for professional and friendly advice. Alternatively, you can call us on 01765 698 233 or 07973 223949. If you want to send a direct email please use or

    If you have a question for Andrew use this form or Live Chat for a fast reply.