Cajon Design – Downward Facing, Offset Sound Hole

The sound hole on this cajon is on the bottom. And most significantly, the front of the sound hole is offset from the back. In theory, because the bottom of the cajon is lower in the back, escaping sound will be focused out the front, and that is what seems to happen.

Firebox Cajon Open Hearth Model showing the large, downward facing, offset sound hole.
Looking into the Firebox Cajon Open Hearth 'bass reflex' port. This is the only sound hole on the cajon.
Looking into the sound hole from the front. This is the only sound hole on the cajon.
Interior of the Open Hearth model showing the bass port bar in front and the lower panel on the bottom towards the back of the cajon.
Interior of the Open Hearth model looking from the front to back showing the bass port bar in front and the lower panel on the bottom in the back of the cajon.

Pros:

  • As with bass reflex port cajons and ‘busking’ cajons, sound is directed forward, toward the audience.
  • There is greater tapa surface area than a bass reflex cajon of the same height because the bass port bar is lower.
  • Mic’ing the cajon is simple because the bass mic can rest on the floor on a simple foam pad or on the carpet.
  • The large opening means the interior of the cajon is readily available. You could easily pack a small suitcase’s volume of clothing in the cajon.
  • On-off snare assemblies that require access via the sound hole are much easier to access.
  • The cajon may be lighter. The large sound hole uses less wood than a conventional sound hole although the bottom bracket adds weight. Designs with less bottom bracket material are possible.

Cons:

  • The composition of your floor will effect the tone and loudness of the cajon.  I prefer it on carpet. But on a wooden floor it is louder. In some perspectives this could be listed as a ‘Pro’ – it gives tone and loudness options.
  • As with any bass reflex cajon, the tapa surface area is lower than a standard design.
  • The design is more complicated to make.
  • The design is not traditional.

Construction Tips

There are several ways to build the bottom structure, some of which are much simpler than my preferred method. I like the look of this design, there is a bar of nice wood across the bottom of the side panels.  Also, I’m using western red cedar which is not a strong wood, so I’m reinforcing it.  I’ll show some of the simpler designs in later posts.

Note that the sides of my cajons are ‘right trapezoids’, not rectangles – the box has an inclined front. So while the top of the cajon is 12×12 inch square, the bottom is a 12×14 inch rectangle. The principles would be the same for a square bottom, only the proportions would be different.

View from the back towards the front showing the left side, the bottom bracket and the bottom back panel. The bottom back panel will be glued to the lower portion of the bottom bracket.
Bottom bracket from the back. These channels are easy to rip on a table saw. Or the bottom bracket could be made by gluing 3 separate pieces to produce the same structure.
Back plate on the left, bass port bar on the right. I’ve glued a long block in the front portion of the bracket’s lower channel. This reinforces the bracket and give width for the large rubber feet.
Back to front view with the bass port bar in place on top of the bracket.
Bottom assembly from above. Back is on the bottom of the photo.

I first glue the sides to the bottom bracket,  then glue the rest of the box.

Gluing the top, sides and bottom pieces.

There are a lot of possible ways to build the offset sound hole design.  Please go wild and post some photos in the comments area.

You can hear 2 cajons with these types of sound holes in the YouTube video below. Note that I use polycarbonate for the backs of all my cajons. So the tone and resonance of these cajons will be quite different than most plywood backed boxes.

Please add your comments below.

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One Reply to “Cajon Design – Downward Facing, Offset Sound Hole”

  1. User rsnitzer on Reddit asked about plans… this was my response:
    Plans are here: https://www.cajonsmadein.com/blog/cajon-construction/cajon-plans-downward-facing-sound-hole-and-inclined-tapa/ Summary:The top is about 12×12 inches, the bottom about 12×14 and the sides are right trapezoids about 12x14x16.25 high. Cut the side pieces first as a matched pair. Then cut the bottom brackets to fit the bottoms of the sides and glue them on. Then cut the top being careful to get the front angle correct. The front angle is about 6.4 degrees, although I measure it with each one as I go along. Then figure out the bottom plate and bass port bar (with angled front). Glue everything up so all the edges in the front match perfectly. If necessary sand the back a little to get the edges to match. You want the front to be perfectly flat. Because I try different thickness of wood for the sides and top the dimensions vary. For the red cedar cajons I’m liking 5/8 inch thickness. For my plywood cajons I used 3/4 inch. I’ve tried 1/2 inch cedar but it seems weak, although plenty of commercial plywood cajons are 1/2 or less.

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