BY RHETT HENDRIX | FROM THE SUMMER 2019 ISSUE OF DRUM!
There are a remarkable number of factors that come into play to create the final sound when a drumhead is struck. Some of these factors are commonly understood, like head choice or shell material. But you’re probably not familiar with “bearing edge apex diameter,” or BEAD. This rarely discussed measurement has a tremendous effect on a drum’s tonal range, resonance, and overall performance.
The bearing edge apex is the highest point of the bearing edge, and is determined by measuring from the apex on one side of the shell directly across the center to the apex on the other side of the shell. This can vary depending on the profile of the bearing edge as well as the actual shell diameter. Believe it or not, a 14″ drum is not 14″ in diameter—it can be anywhere from around 13.75″ up to just a hair under 14″.
BEAD is so important to a drum’s sound because it determines which part of the drumhead first makes contact with the drum shell. For example, if the BEAD on a 14″ shell is 13 15/16″, the bearing edge will be in contact with the steepest part of the drumhead collar. This creates a fair amount of tension before the head is seated properly on the shell, causing the pitch of the drum head to be relatively high before it can be evenly tuned, thus greatly reducing the tuning range and versatility of the drum.
Ideally, your drum’s bearing edge apex should make contact with the flat playing surface of the head just inside the collar. Most heads have a flat playing surface roughly 0.25″ in diameter below the head’s stated size, so the ideal BEAD is right at or just under 0.25″ below the drum’s stated diameter. This enables the drumhead to be fully seated and resting flat on the bearing edge before being tensioned. But the BEAD shouldn’t be so small that the bearing edge apex is in danger of being hit by your sticks.
If your drums have a limited tuning range, your BEAD might be a bit too large. If needed, have a professional recut the bearing edges to the ideal BEAD measurement and you will find yourself with a much easier-to-tune, better sounding, and more versatile drum set.