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How To Build a Cajon - Door and Feet |
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Written by Casey
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Friday, August 14 2009 14:43 |
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Page 6 of 12
The hinges were sunk into the wood so that nothing would catch when the cajon was moved or slid on its side. It's also nice to take into account the sensual aspects of touching the instrument. Supports were put in place to prevent the chiseling from fracturing any of the recently-glued joints. The hinge that meets the door lays on the inside. This creates a small space between the door and the frame against which it will lie. All along the frame for the door was glued a strip of used bicycle inner-tube rubber, which was, conveniently, just about the same thickness as the hinge, the idea being that a good seal is important and a material with some give and sealing properties was needed to achieve that. It may not be quite enough: two layers of rubber may have been better: one glued to the door, one to the frame, and the clasps adjusted to appropriate tension. Otherwise another, thicker material may be used, but as it stands it seems to work well enough.
 
  The door was a lot of work, but for an experimental cajon, it seems worth it. Of course a cruder, less-easy-to-use door could have been fashioned, although screwing into the edge of plywood is generally not realistic. The clasps, though they may appear to be casually located, are actually very carefully placed so that when the door is closed and the clasps engaged, the door is under tension against the frame. It is nonetheless possible to notice the door moving slightly when the kick is hit, which indicates that it is absorbing some of the sound despite the clasps. The shape of the clasp is such that maximum tension is reached before the clasp is fully closed, at which point the tension backs off. This keeps clasps closed when used normally, e.g. to keep a cabinet closed. In this case, they could be bent out, so that maximum tension is sustained when they are fully closed. Then they could be placed and adjusted appropriately and a better seal attained. Additionally, one could place more clasps along the top and bottom of the door frame. Make sure you give the top and bottom clasps enough distance from the framing pieces so that they can be engaged and disengaged.
 The edge of the door that meets the hinges needs to be shaped, of course, in order to allow it to open (in this picture, the door is the piece on the left, and the visible hinge is attached to the side wall). For fine-tuning the snares, it is recommended that the door be able to open wide enough to allow fiddling with the snares against the tapa while the cajon is tilted back at a playing angle, since the tilt can significantly affect the force with which the snares meet the tapa.
 I couldn't find large, tough, rubber feet with holes, so i used rubber stoppers with a screw and a large washer. I drilled a small hole for the screw, then drilled with a larger bit halfway into the stopper, sorta forced the screw and washer in there, and voila. Drilling into rubber is difficult and probably dangerous. Perhaps freezing the rubber first would help. Can't honestly remember if I tried that. :-) I think I did, and it was useless. Anyway: generally, the feet in the back are large to enable the player to tilt back. The feet in front are less important. When designing your feet, watch where you're drilling and plan ahead for the screws that will be coming through the front tapa and through the door frame in the back. I intentionally mounted the screws for the feet into the hickory frame inside, for added strength.
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Last Updated on Thursday, April 08 2010 16:01 |
Re: wood, see page 3, called, cleverly, "Wood and Frame": http://caseyconnor.org/jl/cajon?start=2 -- As far as species of wood are concerned, I doubt it makes much difference, since we're talking about laminate plywood here.
Re: Ocana, see the intro page, "Germán Ocaña".
Hi -
For the tapa, see page 3, called, cleverly, "wood and frame": http://caseyconnor.org/jl/cajon?start=2
For the snares, see page 7, called, cleverly, "snares": http://caseyconnor.org/jl/cajon?start=6
Good luck,
-Casey
@Job - see http://caseyconnor.org/jl/cajon?start=3 for info about the hole size issues. The size doesn't seem to matter so much, in my experience. The function of the hole is to "let the bass out", in a simple sense; the cajon "kick" sound is making a "thud" wavefront. Without the hole, the thud hangs out inside the box and doesn't come across as loudly. My personal conviction (as explained at that link) is that the hole isn't part of a "Helmholtz" model, where it "tunes" an air spring, so much as it just prevents the air pressure of the internal space from preventing the tapa from moving and allows the thud wavefront to escape. If the tapa vibrated like a traditional drum head membrane, then the hole might be relevant, as when playing a djembe you can insert or remove a fist in the hole to change the pitch of the drum.
Gluing/nailing: see http://caseyconnor.org/jl/cajon?start=4 -- nailing or screwing into the edge of standard laminate plywood doesn't really work, so you basically need to glue. Ocana also recommends this for the sake of a good air seal via the glue. The exception, sometimes, is the tapa, which you screw into the frame (the frame is in turn glued to the inside of the plywood). Some people also glue the tapa, but i prefer to leave mine removable.
@Richard - Yeah, generally the back panel is the same as the sides, with 12mm or thicker plywood (glued all around). It's important that the cajon be sturdy/rigid. Regarding the snares, see http://caseyconnor.org/jl/cajon?start=6 ... I agree that the string-snares are not satisfying. There are a number of other ideas on that page, as well as links.
Glad the site is helpful,
-Casey
My original design borrowed your first snare idea, but across one corner only thinking that I could have a 'slap + snare' corner plus a 'slap only' corner. The snares were not very successful: if given a lot of tension they produced a distracting sort of hum. Now I have them slack and with a few loose wires wrapped around which is OK played lightly but I am working on alternatives and will post here if I have a breakthrough.
I did find that there was a nasty resonance from the back panel even though it was well screwed on, and cured that by using frameseal (the stuff that goes around window frames) applied from the inside (with the Tapa removed). I also glued a chunk of MDF to the inside of the back panel to deaden it. The bass seemed more solid after that.
Just for fun, we put an ordinary cheap PC mic inside it and played it through a computer sound card: if you want to hear that, and see the cajon, go to youtube.com/expertanswers.
Even without a microphone I am amazed at the range of sounds and dynamics you can extract from what is just a box.
Thanks
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I am thinking about building my own canjon and your experience will be very helpful I think! Can't you create a blog or something like that and share your experience? I'm sure there is many people that will appreciate!
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Yeah same here!
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-Casey
Like i said am not a pro or anything else but love the sound of this instrument.
The one i built is 18 inches tall by 12 inches wide. i did not install any type of resonating devices in it, just pure sound from what the tapa (face) would make.
I use it for the first time today at church, like i said am not a pro, but i got good results.
Thank you for all the vital information you have share with everybody else.
Thanks