Delta 21" Birch Plywood Passive Subwoofer 1500w RMS 4 ohm

BD121S

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This 21-inch Neodymium Subwoofer is encased in my 18mm Birch Marine Plywood cabinet. This passive neodymium subwoofer delivers over 139 dB SPL. My driver in the box is 1500w RMS and 4-ohm impedance.

Use these to deliver the Sub Bass frequencies that an 18" cannot deliver. Use these at low volume under the 18" subwoofer to truly experience low frequencies.

Key Features:

  • 8mm, 13-ply birch marine plywood wooden enclosure
  • Countersunk Extra Thick "ding proof" grille to prevent grill damage when on tour
  • Acoustic foam behind the grille to prevent moisture and dust ingression
  • Point Source
  • Frequency Range = 29~150Hz
  • Impedance = 4 ohms
  • Power = 1500w RMS - Program 3000w - Peak 6000w
  • Max SPL (dB) - 139
  • Cross Over (Hz) -  80- 150 dependent on your system
  • Connection - 2 x Speakon in/out

To get even lower sub low bass plug the ports and seal the cabinet.

Marine Birch Plywood 21" cabinet finished in Heavy Duty black splatter paint it will withstand all the knocks and scrapes gathered through touring.

Fitted with my purpose made BWN21 12kg driver with its 5-inch voice coil which goes down to 27Hz.

The neodymium 21" driver is very efficient and takes modest amplification to drive it. Study our BP4k amplifier.

If you are presently using an 18" speaker you will notice a huge difference by adding  this single or double 21"

Speakon in and Speakon out enables you to link two subs together giving a 2-ohm load.

Other Features

  • British Designed 21" NEO Driver with British Paper Cones
  • Point Source Ported Design
  • Five Inch voice coil
  • SpeakON NL4 in/out
  • Easy Lift Handles
  • 2mm metal grille backed with black acoustic foam
  • Rugged birch marine plywood 18mm enclosure
  • Program: 3000W
  • Peak: 6000W
  • Carton Gross Weight = 50kg
  • Speaker Net Weight = 46kg
  • Product Dimensions = 80cm x 65cm x 77cm
  • Carton Dimensions  = 84cm x 69.5cm x 82.5cm

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.

  • 1500W (RMS) / 6000W (peak) power handling
  • British Designed NEO Driver
  • Point Source
  • 1 x BWN21 1500w NEO Woofer with Pinch Terminals
  • 5" voice coil
  • Rugged birch marine plywood 18mm enclosure
  • RMS: 1500W
  • Program: 3000W
  • Peak: 6000W
  • Nominal Impedance: 4 Ohms
  • Frequency Response: 27Hz - 150Hz
  • External Crossover to be used
  • Connections: 2 x SpeakON NL4 in and out
  • Easy Lift Handles: 2 x Steel Acrylic enamel, black
  • Grille: 2mm metal grille backed with black acoustic foam
  • Grille: Finish: Acrylic enamel, black
  • Max SPL 130dB peak
  • Ported Subwoofer
  • Countersunk Extra Thick "ding proof" grille to prevent grill damage when on tour
  • Acoustic foam behind the grille to prevent moisture and dust ingression

Speaker Driver Data

  • Overall driver diameter 548 mm
  • Net weight 12 kg
  • Magnet NEO
  • Flux Density 1.1 T

ELECTRICAL CHARACTERISTICS

  • Nominal Impedance 4 Ω
  • Musical Power 3000 W
  • RMS Rated Power 1500 W
  • Sensitivity@1W/1m 96 dB

THIELE-SMALL PARAMETERS

  • Voice Coil DC Resistance Re 3.6 Ω
  • Resonance Frequency Fs 35.0 Hz
  • Voice Coil 125mm
  • Mechanical Q Factor Qms 10.5
  • Electrical Q Factor Qes 0.45
  • Total Q Factor Qts 0.43
  • Mechanical Moving Mass Mms 335 g
  • Mechanical Compliance Cms 252 um/N
  • Force Factor BL 24.3 Wb/m
  • Equivalent Acoustic Volume Vas 260.0 It.
  • Maximum Linear Displacement Xmax ±14 mm
  • Reference Efficiency ηo 2.250 %
  • Diaphragm Area Sd 1680 Cm2
  • Losses Electrical Resistance Res Ω
  • Voice Coil Inductance@ 1K Hz LE m H
  • Magnet NEO
  • Voice Coil Winding Copper
  • Voice Coil Former Glass Fibre
  • Cone Paper
  • Surround Treated Cloth
  • Dust Cap Paper
  • Basket Aluminium
  • Depth 252 mm
  • Bolt circle diameter 525 mm
  • Baffle cut out diameter 505 mm
  • Flange and gasket thickness 15 mm

 

average rating 5.0 out of 5
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100% of reviewers would recommend this product to a friend
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Reviewed by Neal D.
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I recommend this product
Rated 5 out of 5
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5 Stars

Very nice indeed I got two plus a amp and a processor very efficient service highly recommend

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BishopSound Limited Lifetime Guarantee

Effective on all purchases from 1st January 2021

With a returns rate of less than 1% we are proud to offer the BishopSound Lifetime Guarantee at no extra cost to you

BishopSound Limited will undertake to guarantee the product will be free from defective workmanship and materials for the reasonable life of the product.

What is covered in the guarantee?

BishopSound Limited will at its discretion and expense either repair the defect using new or refurbished parts, or replace the Product with a new or re-manufactured Product of a reasonable equivalent. In all instances BishopSound Limited’s liability will not exceed the original Purchase Price.

What is not covered with the guarantee?

If we find a genuine fault or defect in your item that shouldn’t be there based on normal use, then we’ll repair or replace it for free– no questions asked. But, if that speaker has been unloved or beaten to within an inch of its life, then it might be time to buy a new one! In any case, we’ll review each case and will let you know if we can fix or replace it.

The warranty stated above is the sole and exclusive remedy and BishopSound Limited’s performance shall constitute full and final satisfaction of all obligations, liabilities and claims with respect to the Product. In any event, BishopSound Limited shall not be liable for and consequential, incidental, economic, property, bodily injury or personal injury damage arising from the product, any breach of the warranty or otherwise.

This Warranty applies to the first end-user purchaser, and only when purchased from BishopSound Direct or an authorized BishopSound Limited Dealer/Distributor on the UK Mainland listed on our website.

Additional Limitations and Exclusions from Warranty Coverage: The warranty described above is non-transferable, applies only to the Product purchased, does not include installation of any repaired or replaced Product, does not include damage to any allied or associated equipment which may result for any reason from use with this Product, and does not include labour or parts caused by accident, disaster, negligence, improper installation, broken warranty seals, misuse (e.g. over driving the amplifier or speaker, unstable, unprotected or badly earthed power sources, excessive heat or cold or humidity or inadequate ventilation), or from service or repair which has not been authorized by BishopSound Limited.

The end-user purchaser is liable for the cost of transportation and return of the Product in the original packaging. Any damages incurred during transport are the cost and responsibility of the end-user purchaser.

When purchasing BishopSound Limited products, please keep your receipt of purchase safe and retain all the original packaging, as this validates your warranty.

How To Claim

To qualify for the Lifetime warranty, in the first instance you must contact BishopSound Limited showing proof of purchase and the product code. You must be in possession of the original packing as this has the Serial Number printed on it. You will be asked for the serial number and given a return authorization number (RAN), which is required to progress with your warranty claim.

Any decision made by BishopSound Limited regarding any Lifetime Warranty claim is full and final.

How long is the product covered for?

To help give you an idea of our expected product lifetimes we’ve built a guidance table.

If no proof of purchase available product lifetime will be measured on date of manufacture.

Active Speakers - 5 years

Passive Speakers - 6 years

Power Amplifiers - 6 years

This warranty takes effect from the 1st January 2021 onward. Goods purchased prior to this date were sold with the 12 month warranty which still stands.

Only branded BishopSound Limited Products are included in the Lifetime Guarantee:

For more information, please see our Terms & Conditions

    Get in touch with BishopSound today for professional and friendly advice. If you want to send a direct email please use andrew@bishopsound.com or victoria@bishopsound.com.

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

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