dleufer wrote:ome drums just taper off. I've noticed on all the Ghanain drums I've reskinned, the bowl just goes like a V on the inside.
The reason for this is that Tweneboa (which is what most Ghanaian djembes are carved from) is very soft. If the sidewalls of the bowl would be thinner, chances are that you'd end up with cracks.
Rhythm House Drums wrote:So a bit of a correction to above... The sound hole in the djembe will determine the pitch of the bass...
Not just the hole, but the shape and volume of the bowl, and the diameter and length of the stem also determine the bass. A djembe is a Helmholtz resonator, meaning that the bass frequency is determined by the proportions of the shell.
Rhythm House Drums wrote:a big hole means a higher bass note and a quicker hit (more attack, more volume, less sustain) while a smaller hole means a lower (deeper) bass note that lingers longer (less attack and more sustain).
This doesn't line up with my experience. Generally, I've noticed that djembes with a large hole have louder bass that has more sustain, and djembes with a smaller hole have a quieter bass with less sustain and more attack. Not sure why our experience differs here? I might not have enough data points, or there might be other factors that affect this? Certainly, skin thickness enters into the equation. In my experience, thinner skins have longer sustain and tend to go "boiing" more than thick skins. (That's despite people having reported the opposite.)
As usual, lots of variables here that are difficult to control...
Rhythm House Drums wrote:The slaps are a direct relation to the tension of the head.... as is all the notes, but the slap more so.
A correction here: the frequency of the bass is independent of the tension of the skin. Try it.
Basically, the drum itself has a resonant frequency that is determined by its shape. That frequency obviously stays constant. The skin has a bass frequency that is determined by the skin's tension. Lower tension means lower frequency. The issue is that the skin's bass frequency is higher than the drum's resonant frequency, so they fight each other to some extent. The drum wins and forces the skin to vibrate at the fundamental that's determined by the drum, not the fundamental of the skin.
The closer the drum's and skin's resonant frequencies are, the louder the bass will be, and the longer its sustain. As you tighten a skin, its resonant frequency moves further away from the drum's resonant frequency. The skin is still forced to vibrate at the drum's frequency but, because the two are further apart, both volume and sustain of the bass decrease at higher tension. Tighten the skin too much and you will reach a point where the bass almost disappears: no body, very short sustain, and very quiet.
In contrast, tones and slaps depend on the tension of the skin because they are higher-order modal vibrations that are too far from the shell's resonant frequency to be affected by it. Tighten the skin, and both tones and slaps go up in pitch.
Djembe-nerd wrote:Also, what thickness of cow skin do you prefer for a bass djembe , medium or thick.
I'd go for thin. You'll get fuller tones that way at low tension because a thin skin has less internal friction (and therefore dampening) than a thick one. A thin skin also should give you longer sustain, which seems to be what people look for in a bass djembe. If you can, use a shell with a big round bowl. (All the bass djembes I heard in Mali were big and fat.)