So, the wood. My impression is that the back, sides, top, and bottom of the cajon are to be made with the thickest heaviest wood you care to use, as if one were building a bass speaker cabinet. Generally 1/2-inch to 3/4-inch plywood is appropriate. I used 1/2-inch which, frankly, seemed plenty strong to handle any bass oscillations that came its way, and seems to be the most standard size used.

The front striking face, or tapa, must be rigid, but Ocaña points out that it shouldn't be too dense. The selection of the tapa wood is very important. Sounds like the typical soundboard ideal of "strong and light" comes in to play here, perhaps with more emphasis on the "strong" than you would have with, say, a guitar top, since you will be striking the tapa directly, and since there are no braces behind it. Note that the normal playing of the cajon is somewhere between a membranophone and a resonant top: in terms of the "kick" sound, you are largely relying on the force of the air generated by the compression of the space inside the instrument rather than any "ringing" of the top; but, without the ringing of the top (both at the 40-60 Hz kind of zone and the higher overtones) you have a pretty lifeless thud. Since you don't play the tapa in the center when you are making the "kick" sound (rather, more towards the top) it maybe doesn't have to be the toughest wood in the world. Many pro cajones use solid wood tops. I don't know how much that's about sound and how much that's about rare-or-fancy-wood fetish. This may be one sound application where plywood works just as well, but i really can't say. Undoubtedly you would have to know what you were doing in selecting that piece, since plywood does have the advantage of greater consistency (not to mention a higher degree of resistance to humidity, temperature, etc.)

Cajon builder Michael Kotzen weighs in on the issue of solid-wood tapas: "I’ve built quite a few solid tapas from both spruce & figured maple. They are a bit fragile, best used for studio use. Bracing helps. I generally finish both sides. The cajon in the upper left of my home page has a bookmatched figured maple tapa." Not sure what exactly he means by "bracing" in this context, but you could email him (and tell me what he says.) Similarly, other builders (luthiers, actually) have cautioned against the risk of the tapa splitting due to temperature/humidity changes or playing impact: a guitar top has substantial bracing behind it, which holds it together and strengthens it considerably, but such bracing would likely hurt a cajon's sound (although i'm interested to hear some bracing ideas...)

The plywood for the tapa can seem hopelessly flimsy when you first evaluate it, but once it is all screwed down to the face it should do fine. This cajon used 1/8-inch birch 3-ply. There were alternative "strong and light" plywoods at the supplier. I would consider using a thicker wood for the face, but again, without playing lots of cajones, i'm not sure. All of the candidates seemed to have much more flexibility along one axis than the other (presumably because with 3-ply, the two outer layers of wood are aligned in grain, with only the single inner layer at 90 degrees to those). This undoubtedly affects how the top resonates (maybe for good, maybe not); i took a guess and cut the tapa so that the outer grains ran vertically. If thicker wood could be used for the tapa, then perhaps 4-ply wouldn't have this issue, for whatever that's worth. "Aircraft-grade" plywood sounded tempting, but my rough information on that is that the grains of the plywood layers are not 90-degrees to each other; so it's not as rigid and even more biased to flexibilty along a certain axis (apparently because the wood is intended to be shaped.)

It seems that there must be some technique to shaping the tapa, but i found no information. Ocaña does have instructions on how to flatten the tapa of store-bought instruments, so perhaps flat is best. I did iron my tapa (low heat, no steam) before affixing it, as he recommends doing for tapas that are warped.

The unglued wall pieces are also shown freestanding to illustrate the basic idea.

Marking and cutting the hole...

One way to look at the cajon is as a Helmholtz resonator. Not sure how accurate that is, really, since the volume of air in the cajon isn't doing to much resonating, but assuming that the air spring's oscillation after a strike influences the kick sound, one might infer that the size of the hole would affect the "pitch" of the kick. The original plan was to keep the disc cut for the hole and use it as an adjustable slider that could narrow or widen the hole. Testing it out, it seemed largely irrelevant. One might then infer that the size of the hole doesn't matter so much. Even so, intuition tells me for some reason that perhaps this hole was a little too big (it was scaled up a bit because of the general oversized nature of this cajon.) The exit hole for bass reflex ports is often shaped in certain ways. It may be worth experimenting with those ideas. It's also tempting to wonder if the internal reverberance of the cajon maximizes the energy delivered from the tapa: perhaps the frequency is low enough that it doesn't matter, but perhaps some shaping of the cajon or strategic insertion of wood inside would help keep those waves coincident (in-phase). One wonders too how the location of the hole affects this, if at all.

The hole on this cajon is on the side, close to the floor. A cajon has the most punch when played against a wall, or especially in a corner. This leverages the bass effect: when placing subwoofers or a bass amp in a room people often choose corners or, failing that, against walls, because bass frequency waves, with their long wavelengths, are less susceptible to canceling each other out when reflected off of nearby surfaces and redirected in a similar direction. Thus one can "collect" the energy emanating from the cajon in all directions, bounce it out of a corner, and focus it into the room as a unified force. If played in the middle of the room, the waves go everywhere, and their reflections of walls may intersect out of phase, thus reducing the bass sound dramatically.

Thus, one sees the wisdom of having the hole in the upper back: you can play against a wall or a corner. When you get up against the wall and tilt back on the cajon (a common playing style) the hole is right where it should be. There may be advantages to having the hole in the side; I wondered if it somehow improved the bass by forcing the internal aerodynamics to a lower resonant pitch. Perhaps it is easier to mic on stage because a player tilting forward and back can't accidentally change the distance to the hole from the mic (nearly as much, anyway). But having the hole on the side makes it difficult to find an appropriate place to sit to maximize the bass sound: you're always facing along the wall unless you're lucky enough to find a corner (harder than you think).

I don't recommend the snare setup depicted here. Read on for more info.

Ah, the snares. Perhaps the strings weren't thick enough (classical guitar "A" strings), perhaps they shouldn't have been so far up in the corners (longer strings = more mass), perhaps my notion of the "snare" sound is different from typical cajonares, perhaps my tapa is warped; but the snares seemed ineffectual, even after considerable tweaking. Here, anyway, is how they are set up. The image on the left shows the tapa before screwing and the various pilot holes in the tapa and the internal frame. The red lines show where the tapa screws will hold it (there are only three along the top of the tapa, the middle one was already screwed in once, thus the hole looks larger). Also visible are six large holes in the frame in two sets of three (which will hold the zither pins from the inside) and, above each of them (actually below them in the image; one is indicated with the blue arrow) is a small hole through which will pass a snare string (i broke and lost drill bit in the string hole rightmost in the picture, thus a secondary hole had to be drilled). Leading from the exit of these snare string holes is a groove where the string will lie (as demonstrated by the yellow line.) The string passes along the inside face of the tapa, through the groove, into the string hole, and finally wraps around the zither pin on the inside-face of the hickory frame. On the other side of each string, it passes through a similar groove and through another small hole; it is simply knotted on the other side of the hole to hold the string. The grooves are cut to both prevent the string from pressing or bulging the tapa (which could also affect the seal) and so that the string is not unduly stressed as it is tensioned or released. It may be a good idea to grade the entrances to the string hole so there isn't such a sharp edge for it to pass over. I have broken one string so far in my snare tweaking, and it was at this edge. Werner wrote in to say that he used a temporary small helper board screwed into the frame to act as a "pretend tapa". He then used blocks to hold the strings against this temporary board. Once those blocks were permanently installed, with the strings passing over them, he removed the temporary board and installed the tapa, which in turn had a nice close fit with the strings.

There are many, many variables in the instrument that affect whether or not the snare works well, not to mention a wide variety of opinions as to what a good snare sounds like, so it's hard to say what kind is best.

Standard zither pins (a.k.a. "tuning pins") are available online or, better, from your local friendly music store. The proper way to use them is apparently to drill the hole and then hammer them most of the way in (screwing them in can apparently cause them not to hold their tune as well over time.) It's probably not crucial in this application since the snares will never be at particularly high tensions. Ocaña describes the tension as just enough to hold them against the face to cause a rattle. [read on, below...]

The rattle setup was a good start: an edgy, barky snare, but the rattles are, well, rattly, and the snare sound was still on the short side and lacking in higher-frequency shimmer. I took old "E" steel guitar strings (.52 or .54 inch diameter, not sure which it was), carefully unwound the wrapping from the core, and gradually made 10 5-inch long pieces that i joined with some hammered copper 12-gauge wire and electrical solder to form a somewhat fancier custom snare that went in the other corner (the strings were slackened and just pulled out of the way). Two zither pins were used to mount the snare assembly: the top pin could be used with a string tied to the strategic bend in the wire (near where the actual snares connect) as a tensioner of the snare, but it didn't seem necessary, and is not done in this picture. (The old classical guitar string snares with some rattles are still hanging around loose in the picture, they are not contributing to the sound.) A whole lot of time was spent straightening and tweaking with the very finest degree of accuracy the lie of these snares so that they sounded but did not rattle excessively, etc. The combination of the two snare systems sounded nice. (Note that the snare tweaking was done after construction was finished, since you need to test it with the real instrument, but it's included here out of order.)

However, the best snare system, in my humble opinion, is to purchase a snare drum snare, clip off one end of it (in so doing, you probably want to shorten it to an appropriate length, as they are quite long), and then figure a way to mount it in your cajon. This is what i have done, and it's my favorite system by far. Perhaps it's not a traditional cajon sound, but it's what i was looking for. I have mounted it on the same copper wire which i use to tension, position, and otherwise adjust the lay of the snares against the tapa. This alignment is crucial, and tricky, and requires tweaking, (and some re-tweaking, especially while traveling with the cajon). Perhaps there is a nifty way to have it lay correctly and never fall out of alignment. I seek this method, but have not found it yet. In the mean time, it's like tuning your guitar: a nice moment to get in touch with your instrument before playing. :-) Pictures of this system are forthcoming; it's essentially the same as my "home-made" snare described above, but a lot more effective. If there is too much tension towards the tapa, or too steep an angle, the snare wires curve up to the tapa and then continue bending and "reflect" off the tapa face. If the tension against the tapa is too weak, or angle is too slight, the wires won't make good contact. Remember to adjust this while the tapa is leaning back (if you play with a backwards lean).

There are, of course, many other snare designs for the cajon, (see the other links section, as well as the readers respond section.) Some use snares all the way across the center of the face, which i would expect to reduce the separation of the kick and snare sounds. Many cajones (such as those from Meinl) allow the snare to be disengaged completely, to allow a more hollow, ringing high sound. I didn't bother, given my personal intentions for the instrument.

In the further notes (english translation, without images), Ocaña says: "I hope ... that percussionists would restring their cajones, just as guitarists change strings on their guitars, to get their own, personal sound."

Ocaña suggests you take a swallow before you hit it the first time since you may well be disappointed. It's true. But play around with it, stick it in a corner and play it, get used to your tapa and how to strike it, and it's true character will likely reveal itself to be a lot better than your first impression. After giving it some time and practice, i have grown to love this one as it is, and i haven't taken it much further than the original design (e.g. by coating the inside with glue as Ocaña suggests, trying other tapas, placing wood inside to direct the waves, whatever). The snare, though: You will probably want to spend some time on your snare.

Ocaña recommends not gluing the tapa. Apparently some builders glue it, probably because it's easier to make but possibly because it seals better. Many cajon players, myself included, like the top corners of the tapa to be free (thus the lack of screws there, or with glued tapas, the lack of glue in the top third) in order to get a slapping sound as the tapa corner hits the frame (Inserting paper shims in the corners to raise them up a tad may help you get a good corner sound.) So the seal may not be as gravely important as it's made out to be, but perhaps the overall seal over the perimeter of the tapa really does matter. Having the corners lifted with shims in conjunction with slightly loosening the screws that abut the corners didn't seem to affect the bass sound much, as compared to no shims and all the screws tightened.

Ocaña recommends being generous with the number of screws. The tapa of this cajon lifts off a tiny amount at the edges, probably because of a slight, natural deformation from the tension of the screws. I am confident that the seal is nonetheless good. Drilling pilot holes is probably a good idea for the tapa screws to as to avoid splitting the hardwood frame. Before affixing the tapa, of course, you want to ensure (through sanding, if necessary) that the internal frame is appropriately flush with the edges of the plywood sides, top, and bottom. (I may even have tapered the plywood back a hair to make sure that the tapa contacted the frame fully, which may also help explain the slight gap between the tapa and the plywood.)

Straight-up organic locally-grown homemade fresh-squozed beet juice was used to dye the wood. As for the tapa, Ocaña recommends rigid finishes only as oil would soften or dampen the resonance. Not sure if he feels the same about the other faces: I think he advocates using similarly rigid finishes on the interior at least (or the glue method he described). It's hard to imagine that it matters on the external non-tapa faces. Anyway, given the horrid environmental and health aspects of most finishes, beet juice was used. As for finishing the tapa, it was left unfinished and we'll let nature slowly break down the plywood (which, of course, is itself full of toxic glues and will probably last lifetimes.) After the beet juice dried, a light pass with unrefined walnut oil, which is purported to be a "true drying finish", and is about as natural as it gets in that department, was applied. The inside is also unfinished.

Beet juice fades very quickly. A test piece faded dramatically after a week or two of mild sunlight. But it's beautiful, and you can always add another coat. Once totally dry it does not rub off on your clothes, though if it got wet it may well. I don't know if the walnut oil will make it harder to re-juice. I keep it under a cloth when not playing it in the hopes that the fading has more to do with ultraviolet light. Maybe the oil will help if in fact it has more to do with oxidation. Time will tell. After three weeks it still looks very strong, as opposed to the test piece, so maybe the combination of oil and storing under a cloth will work. Update: After 1 year the cajon was still nice and red, though it could maybe have used a fresh coat. After 2+ years it's more pinkish now. Still nice enough, but definitely ready for another juicing. This whole time i've kept a cloth on it to cut down on the UV.

The finish work basically involved making the edges meet up through the magic of sanding. All three of the top non-tapa edges were all generously rounded - it's definitely worth it! After sanding, the moisture in the beet juice will cause the wood to regain a rough texture, so don't spend too much time making it perfectly smooth, as obsessively fun as that is. Apparently you can sand, wet down the surface with water to bring out the grain, let it dry, then sand again, and this will cut down on the roughening phenomena.

Isn't it so beautiful?

Mark's Cajon

"As far as the inset on the port hole I made the hole too big and did that to make it smaller and am thinking of doing the same to the other one.It worked out really well and I think it looks good the way I did it.I went by the dimensions of the Meinl except taller. 12" by 12" by 20" I used 1/8" birch for the tapa. I used woodfiller and sanded with 220 and finished with 4 coats of polyurethane and then polished with a wax that I purchased from woodcrafters. As far as the screwing pattern I was not thinking when I placed the screws on the corners but it seems to work well anyway. I've moved the snares several times and I think I've found the right way."

Jeffo's Cajon

"I also had the same problem as you, regarding the strings: no effective snare sound coming out of them. What I did was to run three strings (times 2) from top to bottom. Actually, from bottom to top, using Guitar claviers (is that the word?) on top, to helping "tune" the strings. It works VERY nice, I got a real snare sound (oh, and I use BASS strings, something like the 4th, or the E for folk guitars, they are thicker and ressonate better). My cajon is a 18mm plywood, VERY thick for the standards and the front cover (Tapa) is 6mm, also thickier. Microphonated it has a very impressive sound, deep bass and a good snare sound."

Returning to the strings problems, the only disadvantage is that the strings keep breaking frequently, that is, after a "nervous" session of 2 to 3 hours some of them brake.

[...] it got a very nice PU varnish finish and laser engraving on the tapa.

[...] new snare system I put in. After a 3 hour session everything seems allright this time. I copied the MEINL system from a picture I found over the web!

As for the claviers I used, I came to the conclusion that there is no need for frequent tuning in the strings. Once you do the first tests and find the sound is ok, you will probably never want to play with the tuning again...at least that is my feeling. So, the simpler the system, the better...I think.

[Casey asked: Regarding the strings; do you have a good separation between the bass sound and the "snare" sound? I know that some people don't want that, but I do, and so I didn't want to run the strings from top to bottom...]

I do like the separation since I was a drummer in the past [...] and the cajon sound was the perfect bass/snare I was looking for.

My cajon has a very distinct snare sound going crisper and crisper as you go to the left/right upper tip (i guess all cajons are like that) and the bass in the middle is deep as I expected. The Bass and the snare have the strings "slap" along and I like it, just like the flamenco cajons I've been listening on the net. For the extra snare on the upper tips I heated the cover with a blower and bended just a little bit (2 to 3mm gap), so I also have the wood cover hitting the cajon and making a distinct sound."

John's Cajon

"I made mine of solid wood [3/4" poplar], with a 1/8" plywood front. I used 1" x 12" + 1" x 6" glued/butted/clamped together [with 'biscuits'] to get enough width. I also used a side sound hole & decided to angle the front/back in a trapezoid shape, with the two sides being parallel. My thinking was that the sound on the left striking side [11" deep] would be a little higher pitched than the right [13" deep], kind of like 2 congas. I was also thinking that the natural megaphone shape would help force the air/sound towards the hole. I used a snare drum spring, duct-taped to the inside top of the front piece just before I re-assembled the front, after applying the finish [outside only] to the whole thing (no stain, just gloss Verathane). Since the sides/top/bottom were all solid wood, I didn’t need to make an inside frame to attach the drum face – I just screwed it directly to the sides."

"I wanted it to be the same height as the stool I usually sit on to play congas, to serve a dual purpose. The inside height was already 19" & the thickness of the top & bottom added 1 1/2" + I added a block of wood [3/4"] under each [3/4"] rubber bumper on the bottom – so it came out about the right total height [22"]. I also personalized it with some [water-slide-off] decals on the bottom of the front. I made the graphic designs in PhotoShop and printed them on decal paper with my computer printer."

"I've only played a couple caĵons at music stores, and then only for just a couple hits each time & to check out their construction & spring setup, mainly. So - I’m not an expert at the sounds produced, or in playing. However, I think mine sounds good; I was satisfied with the sound and with the snare effect. However, I think that the low/high and megaphone/projection effects are probably minimal; maybe not worth the trouble of the irregular angles, which probably provided the most challenges in making it. I’ll have to play it awhile, though, before I get used the all of the possible sounds it can produce."

...

"I've played my cajon a couple of times now, but still need to learn more about its particular areas, sounds, etc. After having played it a little, I do think that my trapezoid/angled sides have some effect on the tone and pitch. Since the inside dimensions vary from left to right, it has a lot of varied playing area & tones – from left to right, up & down, middle versus edges, etc."

"My [drum] snare has a lot of zazz to it - which I mostly like. I’ve found that I can control/lessen the amount of after-effect snare noise by playing technique; either pressing on/muting the tapa after striking it, and/or putting my (socked) heel against the face at the bottom as I play. So far, I would liken my playing style to that of a drummer on a traditional trap set – with my right hand placed lower on the tapa, playing the kick drum parts, and my left up top, doing the snare."

"My right hand is generally cupped most of the time [to produce more of a bass/kick sound] – and my left mostly does slaps. After-touch-muting with my right hand helps reduce the snare sound on the bass-sound hits. Since it's in close proximity to the tapa, I can kind of leave the right hand lightly engaged most of the time, to press on the tapa and control the snare sound. I was considering rigging up some device to engage/disengage the snare springs on & off the tapa – which has some access through the (side) sound hole. But I already have congas and bongos, so if I want to play percussion sounds without a snare, I would tend to just use those."

"So for my cajon, I think I will probably leave the snare permanently affixed. I may go in and stretch the snare just a tad and permanently attach it to the sides -- I currently just have the ends duct-taped to the face, with about as much [minimal] stretch as that process allowed. However, that method allowed for plenty of contact for all of the springs, and like I said -- it has a lot of snare effect if I just strike the tapa and let it vibrate. To access and adjust the snare I would need to take off the tapa, so I thought I would play it awhile before I did anything semi-permanent."

[update] "I finally got around to permanently affixing the (drum snare) springs to the inside of my cajon instead of the duct tape I used for awhile. ... I found a simple solution. I had some plastic furniture door magnets in my junk drawer that I adapted for use – I just popped out the magnets and used the plastic housing. I fed the plastic tapes that came with the drum snare through the slots on the ends that they usually go through, and trapped the (then doubled-up) tape under the plastic door hardware on each side of the inside/box – as you can see, a few inches down from the top of the box. The door hardware had adjustable slots, so that you could adjust/move it back and forward a little by loosening the screws (and then re-tightening) – and also adjust the tension on the springs just a little by pulling on the ends of the plastic tape. I used this method to adjust the closeness of the hardware and springs to the front edge of the box/tapa. I just experimented around, holding the tapa against the box & seeing how much spring contact there was & adjusted both sides equally to get the amount of spring contact I liked before I screwed the tapa back in place."