When initially spec'ing a particular drum, we select a bearing edge design primarily (a) to affect the sound and, in some cases, (b) to improve the ergonomics for varied playing positions.
Basically, we manipulate the bearing edge geometries to change the contact between the head and the shell. Do we want more energy being transferred to the shell or to the head? The shape and the amount of contact affects the resonance and the sustain, ultimately makes the drum sound brighter or warmer.
The alternatives typically each emphasize a particular sound quality, so it should not be surprising that the ultimate choice involves comprise. That is, each design does something different and it's probably not wise to think that there is one "best" design for all drums.
Our Cooperman Classic model frame drums represent, for us, a benchmark - a traditional sound palette that brings out the woody shell tones while offering a range overtones, from articulate teks to resonate pahs and dums. https://www.coopermanframedrums.com/collections/tars
A traditional bodhran might have a fatter contact point to deaden the overtones and emphasize a thuddier tonal range, while a riq might get a sharp contact point to emphasize bright, articulate teks.
Tom Callinan playing bodhran (not stick playing technique for thuddier tone)
Yousif Sheronick showing finger playing technique for articulation.
Other, specialized designs in our line include a "rolled" edge on our Marla Purple Haze model, and a "hybrid" edge on our Asheville Rhythm series drums.
The rolled outer edge on the Marla 12” was chosen primarily for ergonomic reasons. By way of comparison, the hybrid edge on the Asheville drums was chosen primarily to create a unique tone and responsiveness.
At the time the Purple Haze was designed, Marla was exploring Turkish split-finger techniques and she wanted to hold the drum tucked under her arm more like a doumbek. The rolled edge is inspired by goblet drums, more so than typical frame drums. We paired an ebony drum head material head material was to bring down the brightness of the small diameter drum. So, the combination of the bearing edge geometry and the drum head material work together to achieve both ergonomic and sound internationalities in a small diameter drum.
Our Asheville Series has a “hybrid bearing edge” that is intended to bring forward the teks and the kahs. The artistic director of the Asheville Rhythm group (River Guerguerian) plays the drums in ensemble venues, and, in some ways, this design is jazzier and more modern than it is traditional. The combination edge design is not as "rolled" as the Purple Haze model, so the edge sounds, the Tek and Kah, have a clear and more defined sound. It doesn’t take a lot of effort to get a nice open Tek sound. Still, for a lot of people, it’s easier on the hands than the traditional edge of the Cooperman Classic, because your fingers roll over the top.
The compromise is that the drum tends to be more sensitive to any discrepancies in the tension of the drum head. That means that you might have to tune more often.
We've focused mostly on external geometries, but then there's also unique internal geometries - the inside scoop (versus a 45 or 30 degree angle) used on our Todd Roach hybrid tambourine accommodates. (See Pic). This design allows the player to squeeze the head material to create pronounced pitch blending.