August, 2001
KORIMBA
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NOTE: 12 additional photos
and a sound sample of this instrument are available. Click
here for information.Korimba is a name that I coined for an instrument I came up with and have been experimenting with for a while now. Quite simply, this Korimba is (as the name implies) a cross between two African instruments -- the 21 stringed Kora and the Kalimba (also known as Thumb-piano). It plays (and is tuned) like a Kora*, but uses 21 metal Kalimba-type twangers (made from lawn-rake tines) in place of the Kora's 21 strings.
Click HERE to see a photograph of this instrument.
Click HERE for construction illustration.
The biggest challenge was to develop twanger mounts that were orientated 90 degrees from that of the Kalimba to allow "side plucking", like the strings of a Kora, while still enabling the sound to be conducted efficiently to the sound-box. A lot of experimenting has been done with this thing & I anticipate a good deal more -- check back on this web-site for updates. The twangers are plucked on their sides, near (but not at) the tips. One nice thing about the field of musical instruments is that by no means has every musical instrument already been invented! You or I could invent an instrument a day for a long time to come. MATERIALS USED Right and left sides - 3/16" plywood. I found some old panelling that worked fine. Front and back - 1/8" plywood. From an old door in my case. Twangers - 3/16" by 1/32" thick spring steel. I salvaged these from old lawn rakes. Other widths and thicknesses should work as well -- lengths would likely be different from what is shown here. If you used different type twanger stock, you'd have to experiment a bit to get right lengths. I have noticed a big difference in volume and tone by using different gauge & width twanger-stock. If you get a bad tone with one type, try another. Twanger mounts - I used 1/4" long hardwood dowel pins bought at Ace hardware. These are Tietbond-glued into very snug holes. The middle mounting member for each of the 21 twangers is a 6 x 3/4" pan-head screw. "Resonator" - I used a 7" diameter by 1&7/8" high cookie tin. CONSTRUCTION NOTES The body is glued together using titebond wood glue and 8 small blocks of wood in each corner for strengthening. Try your best to mount the dowels so that the twangers will be as parallel as possible. It's fairly critical that the metal screws be located properly so that the twangers are sprung just the right amount to stay in place & not let the twangers buzz, but yet not be so "tight" as to make tuning difficult. I suggest experimenting with some scrap here before drilling holes in the real thing. If you ever find that a twanger is loose, or buzzes, an easy fix is to remove the existing screw & replace it with one size larger diameter. Twangers can be cut to length simply by breaking them (carefully) with your fingers while held in a vise-grip. Use a grinding wheel to round off and dull the otherwise sharp twanger ends. I found the box as described not to be quite as loud as hoped -- A rather goofy, but quite effective, soundbox was fashioned out of an old 7" diameter, 1&7/8" tall cookie tin. I silicone glued this tin to the open top of the instrument (locate this tin as far back on the instrument's open top end as possible, so not to interfere with twanging fingers). Then, carefully, using a stout utility knife, I cut a rectangular hole into the cookie tin's bottom, just a bit smaller than the large opening at the top of the instrument wooden part. Into the cookie tin's top I made a 2" diameter soundhole, positioned as far away from the player as possible (so as not to be positioned over & thus gazing at the ugly rectangular hole with it's maw of screw-tip "teeth"). This cookie tin resonator at least doubles the volume & the tone is quite nice. To lessen the natural tendency for the tin to vibrate loudly at certain musical pitches, I wedged what amounts to a sound-post from tin's floor to inside of the cover - located this as close to center of the tin as possible --- then secured this post as well as the entire cover with silicone glue. I may replace the tin with some sort of small wooden box at a later date, but for now I am happy with it as is. If I do replace it, it will be for aesthetic reasons --- altho as you can tell by my webpage, such considerations have bothered me little in the past. DIMENSIONS: - Both side panels measure the same - 6&7/8" heigth & 4&1/4" width. - Front and back panels measure the same - 6&7/8"" high by 3" wide at the top, tapering to 1&5/8" wide at the bottom. - Bottom rectangle is simply cut to fit on the four "wall" panels. - Top is left open - cookie tin resonator covers the top. - See illustration for details of handle & twanger mount dimensions. TWANGER MOUNT LOCATIONS, TWANGER MEASUREMENTS & TWANGER PITCH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I am not at all fond of the metric system of measurement, but I begrudgingly admit that it occasionally can be of some use. Such is the case here. So all measurements in the chart below, concerning dowel placement are indicated in millimeters. LEFT SIDE: Refer to chart immediately below and to the accompanying illustration. Note that all 21 twanger mounts are made identically. Try your best to mount the dowels so that the twangers will be as parallel as possible to each other and to the Korimba's top & bottom). Note: this only shows the placement of one of the two dowels that make up an individual twanger mount The other dowel is mounted 1&1/2" due left of the first dowel, & the screw is mounted midway between the two but exactly 1/4" higher (center-line to center-line). | distance | distance | | from the | from the | left | center | center | | musical side | of dowel | of dowel | overall | twanger | pitch dowel | to | to | twanger | vibrating | of this number | "edge 1" | "edge 2" | length | length | twanger * --------|----------|----------|---------|-----------|-------------- #A: | 54 | 160 | 165 | 112 | C (2 octaves (topmost| | | | | below Mid. C) mount) | | | | | | | | | | #B: | 54 | 147 | 140 | 90 | G (2nd G below | | | | | middle C) #C: | 54 | 134 | 135 | 84 | A (2nd A below | | | | | middle C) #D: | 54 | 121 | 130 | 81 | B (2nd B below | | | | | middle C) #E: | 48 | 108 | 119 | 72 | D (1st D below | | | | | middle C) #F: | 42 | 95 | 111 | 65 | F (1st F below | | | | | middle C) #G: | 36 | 82 | 106 | 57 | A (1st A below | | | | | middle C) #H: | 29.5 | 69 | 101 | 52 | C (middle C) | | | | | #I: | 23 | 56 | 98 | 46.5 | E (1st E above | | | | | middle C) #J: | 17 | 43 | 96 | 41 | G (1st G above | | | | | middel C) #K: | 10 | 31 | 93 | 37 | B (1st B above (bottom | | | | | middle C) mount) | | | | | | | | | | RIGHT SIDE: Refer to chart immediately below. Note that all 21 twanger mounts are made identicallly. Try your best to mount the dowels so that the twangers will be as parallel as possible to each other and to the Korimba's top & bottom). Note: this only shows the placement of one of the two dowels that make up an individual twanger mount The other dowel is mounted 1&1/2" due right of the first dowel, & the screw is mounted midway between the two but exactly 1/4" higher (center-line to center-line). | distance | distance | | from the | from the | right | center | center | | musical side | of dowel | of dowel | overall | twanger | pitch dowel | to | to | twanger | vibrating | of this number | "edge 3" | "edge 4" | length | length | twanger * --------|----------|----------|---------|-----------|-------------- #L: | 51 | 147 | 128 | 76 | C (1 octave (topmost| | | | | below Mid. C) mount) | | | | | | | | | | #M: | 45 | 134 | 121 | 66 | E (1st E below | | | | | middle C) #N: | 39 | 121 | 118 | 60 | G (1st G below | | | | | middle C) #O: | 34 | 108 | 113 | 53 | B (1st B below | | | | | middle C) #P: | 28 | 95 | 108 | 48 | D (1st D above | | | | | middle C) #Q: | 22 | 82 | 105 | 44 | F (1st F above | | | | | middle C) #R: | 16 | 69 | 100 | 40 | A (1st A above | | | | | middle C) #S: | 10 | 56 | 92 | 35 | C (1 octave | | | | | above Mid. C) #T: | 10 | 43 | 90 | 34 | D (2nd D above | | | | | middle C) #U: | 10 | 31 | 89 | 32 | E (2nd E above (bottom | | | | | middle C) mount) | | | | | | | | | | * The Korimba's overall pitch is one octave below that of a Kora. The lowest few notes on my instrument could be a bit louder/clearer. I'm experimenting with different twanger-stock & will report any findings here. In the meantime, I find these few low notes sound best if plucked at twanger's end using fleshy part of your thumb. If your twangers do not lie as parallel as you would like, the offending ones can be made parallel by careful, but forceful bending into shape once the instrument is more or less tuned. Dowel pins can be trimmed shorter once you see where the twangers lie. Looking at the accompanying illustration, it appears that the dowels are mounted at a slight angle --- this is not the case (it was just easier to draw it that way) --- the dowel holes should be drilled perpendicular to the surface of the sides. Dennis Havlena - W8MI northern Michigan my webpage: http://www.ehhs.cmich.edu/~dhavlena/
