Designing a modular Voxel…

The Voxel is a small and fairly straightforward subwoofer design described in this post by its designer, Paul Carmody.

Small and straightforward that is if you know how to build speakers…

The design is a “vented” speaker, as opposed to a “sealed” one. Vented means that the enclosure is actually not airtight but open to the outside via something called a “port tube”. The black art of speaker design is about picking the right “driver” (what the uninitiated call a “loudspeaker”) for the right size enclosure and combining it with a port tube (what the uninitiated would call a “pipe”) of the right length and volume to produce something that in the end doesn’t sound like a leftover from Edison’s workshop.

While speaker design sounds like an interesting topic, this is not something I want to get into right now. For now I want to stick to “don’t mess it up by altering the design”.

Since it is not yet fully decided whether the end result of all of this will sit on my desk or end up in our living room, I would like to have maximum flexibility as to how to drive the Voxel:

Basically, there are three different ways how you can connect a subwoofer to an amplifier:

  1. The amplifier provides an already amplified signal that you can directly connect to the driver in your subwoofer.
  2. The amplifier provides an unamplified signal for the subwoofer.
  3. The amplifier has no output that provides a subwoofer signal.

To handle cases 2 and 3 you want to build an active subwoofer using something called a plate amplifier. For case 1 you don’t need an active subwoofer.

So in order to be able to handle any of the cases, I decided to build a “modular Voxel”, with the plate amplifier residing in its own enclosure. For case 1 the plate amplifier would just get disconnected.

This also goes well with the mantra of “don’t mess it up by altering the design”: Building the plate amplifier into the subwoofer requires you to alter the subwoofer’s dimensions, to maintain the right volume.


Keeping the plate amplifier separate also allows for a design that prevents heat build-up on the plate amplifier.

So firing up OpenSCAD, this is what I came up with:

This is a view of the subwoofer (to the left) and the plate amp enclosure (to the right) from the back, with the back panels of both removed.

Inside the subwoofer you can see the port tube. The grey panels on the plate amp enclosure are speaker grills, for maximum ventilation.

Here is another view from the front:

Also, as you can see my Voxel is a “righty” with the port tube exiting to the right.

So I did deviate from Paul’s design slightly after all…

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