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Calum Audio Ltd



Regular price £690.00 GBP
Regular price Sale price £690.00 GBP
Sale Sold out
VAT included for the UK, no taxes charged for EU or US customers. You may be liable for import taxes, contact us if you're unsure. Shipping calculated at checkout.
Build Format

The PA-121BP is a 21” bandpass subwoofer. Available as a kit, unloaded or as a loaded cabinet.

This box is especially compact and is very well suited to touring as either a main system sub, or as a DJ booth sub. The cabinet features a multi-use top hat (standard 35mm pole as well as M20 thread), making it ideal to mount an active PA speaker on top.

With a massive 1400w AES power handling and solid output down into the low 30s, this cabinet has a lot of output for the size. Loaded with an 18 Sound driver that features a carbon fibre reinforced cone, this cabinet will perform well for a great number of years.

Measurements suggest a –6db point of 32hz to 100hz with a sensitivity at around 100dB.

These cabinets / kits are built to order, please allow for a 8-10 week lead time. 

If you're purchasing a flatpack kit, please be sure to check the difficulty levels and advice in the dropdown sections below.

Features and Applications

This is a dedicated subwoofer cabinet.

Flatpack kits include

  • All panels, cut from 18mm Birch plywood
  • All the screws you need
  • All the bolts and insert nuts you need
  • Gasket tape for the access hatch
  • Wadding
  • 8 rubber feet
  • A pre-wired NL4 speakon dish, with a gasket
  • 8 metal bar handles with gaskets
  • 4 swivel casters, with heavy-duty internal mounting plates
  • Pre cut port tubing
  • A dual purpose 35mm / M20 pole mount

*Drivers sold separately*

Flatpack kit build difficulty

Beginner. No prior cabinet building experience necessary. Minimal build complexity, low number of parts. The order of assembly is obvious or there are multiple ways to successfully build the kit. All you need is a drill / impact driver and glue.

Acoustic Specifications

We recommend the 18 Sound 21LW1400 as a good standard option. This is what is in the Loaded cabinet. You can expect a frequency response of 32hz - 100hz @ -6dB with single cabinets.

Physical Specifications

  • 818mm x 606mm x 856mm HxWxD (without casters)
  • 8 metal bar handles
  • 8 rubber feet
  • 4 swivel casters with heavy duty internal metal mounts
  • Dual NL4 speakon
  • 18mm Birch plywood used throughout - 100% NON Russian plywood is used throughout our products, all timber can be traced back to the mill of origin.


UK Shipping

This cabinet is available for purchase through this website for shipping within the UK.

EU Shipping

There are a growing number of countries that can purchase this cabinet directly with shipping via this webshop. We are happy to quote for shipping to anywhere in the EU, some countries are just a little more challenging than others, so require a manual quote to be generated. If you need a manual quote then please get in touch with us.

Please be aware that you may be liable for import taxes and duties upon importing this item. If you have any questions, or your country isn't listed, please get in touch.

Global Shipping

We are happy to ship this cabinet globally, please contact us for a shipping quote.


The PA-121BP design is credited to 18 Sound. The original plan can be found here.

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