- Mon Apr 30, 2018 5:19 am
I'm a bit late, but here's a couple tips: (btw I understand wanting a non-skin head, I'm vegetarian too, and working on prototype plant-based heads for djembes and congas, more on that later)
Key tuned wood-shell djembes:
1.) If you ever decide to upgrade, I saw Motherland Music carries real djembes (wood shell) with lug-tuners instead of rope.
2.) Improving synthetic heads
a)-adhesive weather stripping foam strips aligned in spiral/vortex pattern
b)-gluing paper to underside of skin
You're spot on with adding foam inside the bowl, but is it spiral-oriented?
Foam in bowl alignment:
First, make sure the foam is aligned properly: I was taught to use 3-4 strips of weather proofing foam and align them vertically on a diagonal, so as to mimic the "spiral" carving pattern, which may help the air and soundwaves "vortex" out of the bowl. Either that or the diagonal angle ensures contact with all the soundwaves, but it's very effective.
Glue paper, not foam, to head:
I wouldn't use any foam on the head however, instead I'd glue paper* on the under side (while the head is off the djembe, so the paper gets stretched onto the shell as part of the head/membrane). Here's why:
I suppose it might be obvious that Remo already does a similar thing to the top of their synthetic heads (glues fibrous plastic "paper" veneer onto the core solid plastic membrane), which is why fiberskyns sound better than a piece of unmodified plastic sheeting, but here's explanation for how it works...
First: Consider one of the issues with the tone being caused by a lack of "air" in the core of the plastic membrane(a good djembe or conga skin, by contrast, is fibrous with some air in between the fibers). So this lack of air results in a "uniform" and "simple" tone, with few "dry" overtones, which contributes to the lasting ringey sustain. (in real skin the variety of competing overtones drain energy off the fundamental quicker due to cross-interference, a single tone can sustain longer because it's resonating without interference, a similar concept is applied to Mantio conga skins to increase sustain, but only to a certain degree, too much uniformity of tone sounds boring)
By gluing paper on the underside of the head, you force the vibration to travel through paper fibers and air, which creates various dry overtones, thus reducing tonal uniformity and ringey sustain.
This however is assuming the glue was diluted, so when the water dries it left airspace in the paper. If the glue is too thick, it will fill the air spaces.
Depending on the thickness and amount of paper, the sound can be changed a little or a lot. I'd use reversible glue (softens when wet) so you can undo it if you don't like the result.
Another benefit of glueing it on when the head is removed, so the paper gets stretched when you put it back on the shell, is that it will act as part of the membrane, rather than merely as a dampener. This would help with the tone, because it's vibrating in an integrated way, across the whole drumhead.
Second: This also adds mass to the head, so it won't sound so "bright", as fiberskyns do otherwise. Real goatskin is denser, because protein is heavier than plastic, and they tend to be thicker than fiberskyns as well, so the tone is lower and warmer.
*: What kind of paper? Depends on what you have access to. Theoretically brown paper bag would be better than smooth white paper, because it is coarser, meaning the fibers will be larger, and thus have more air spaces between them. But it might be too thick. You could sand some of it off, or use layers of tissue paper instead.
How dilute can the glue be? Very. If you're using something like Elmers (PVA based glue), it's very thick, so I'd mix it with a lot of water. Perhaps 1:5? Not sure, I'd experiment with a small scrap to make sure it's still enough glue to hold.
How to prepare the head? The underside of remo fiberskyns is absolutely smooth (unlike the top), so I'd sand the bottom of it, so the paper sticks to it. A light sanding with fine to medium-fine paper is ideal, to avoid taking material off the head. I don't think this would hurt the sound, in fact sanding alone should improve the sound I suspect, just by roughing the membrane-to-air interface. Remember natural skin is very rough on the bottom, often pieces of fiber hanging off etc.
What if the paper makes it sound dull? If you only glued one side of the paper, and the paper wasn't saturated with glue, then you may need to add some dilute sealant, or dilute oil, to the underside of the paper at the end to reduce some of the dryness (a little dryness is good, too much is not - it's a fine tuning thing).
Dilute shea butter is the perfect oil. (diluted in household cleaner made of orange oil so the dilutant evaporates away)
As for sealant, you can dilute some glue, or if you're not vegan, nonfat milk makes a good sealant, as does eggwhite. Vegan natural glue options include sticky rice starch, acacia gum/gum arabic, and wheat glue.
Just remember not to add to much sealant or oil, the idea would be to add a tiny bit and see if it's enough, and only add more if needed. Adding too much is easy to do.