N.B. Before beginning this process, make sure that the drums are acclimated to the environment, the room is quiet and at a stable, comfortable temperature (roughly 72–78°F), and no air is circulating directly above the drums. (see Environment and Timpani Pitch)
Synthetic heads ONLY: The cleaning and conditioning described below applies to synthetic (plastic/Mylar™) heads only. Do not use glass cleaner or vinyl protectant on natural skin heads.
Preparing the Head
Before you start the tempering process, clean the surface of the head thoroughly with a non-caustic glass and surface cleaner to remove any salt, dirt or grease which may have accumulated. Excessive dirt and other unwanted residue can keep the head from vibrating evenly. If the head shows any dryness or damage from indirect sunlight or heat, evenly apply liberal amounts of a vinyl protector such as Armor All®; let it set for at least ten minutes, then work the protectant into the head evenly, and then completely wipe off any excess. (If you use a protectant, test a small area first to make sure that it won’t damage the coating of the head.) It is recommended to do this both before and after you have completed the tempering process. The vinyl protector will help restore some of the natural elasticity in the head. It helps to apply this to the heads routinely to keep them flexible. The heads come from the factory with a film coating on them but it dissipates over time. Be sure that the protector has been worked well into the head and that no excessive residue remains.
Reducing Tension Before Centering
For spring-balanced / balanced-action timpani (Ludwig, Yamaha, Adams, Ajax, Majestic etc.), set the foot pedal all the way back to the floor with the heel of your foot. This will remove most of the head tension and should place the drum near the low end of the MSR. For drums with a master tuner, loosen until the drum is at its threshold of pitch.
Center the Head and Check for a Uniform Collar
The head can become off-centered simply by moving the drum improperly. If the head is not centered, loosen each lug the same amount and center the head on the drum. Loosen in small, equal increments (opposite lugs in a star pattern) only until the head can be nudged; do not drop one side dramatically, or the hoop can cock and the collar can bind. Before measuring, bring the counterhoop down evenly (finger-tight) so it is seated uniformly. Measure the distance from the lip of the bowl to the counterhoop at four points on the drum (north, south, east and west) making sure that they are exactly the same. With a felt tipped pen, place a small mark on the head directly at the point where the lip touches the bowl at these four points (NSEW). Use these marks as reference points to make sure that the head is always centered..
Before the Head Is Mounted
It is best to place these reference marks on the head before it is mounted on the drum. In that case you would simply measure the diameter of the drum at two adjacent points at the lip and then the diameter of the head. You then find the difference of these two measurements and then divide that number by two. Use this measurement and mark on the head at four points (NSEW) measuring from the very edge of the head in towards the center. When you mount the head, center the head on the drum making sure that the NSEW marks are right at the lip. For more information on this process, please see my article on mounting Mylar™/synthetic heads.
Return to a Low Working Pitch
Return the lugs to the low note position of the MSR (the lowest and highest pitch at which you want the instrument to sound) once the head is centered. For drums with a master tuner, leave the instrument at its threshold of pitch. Next step will be to set the range of the instrument.
Why Centering Matters
If the head is not centered, the drum cannot be tempered properly and will never be able to create a desirable overtone series throughout the range of the drum. This crucial step, which is often overlooked, is easily fixed and “makes or breaks” the overall sound of the drum. This process helps ensure even seating and a consistent boundary condition around the rim, which reduces split partials and supports stable pitch. It also helps stabilize the behavior of the lower modes (including mode (0,1), the membrane’s true fundamental), which, although not heard as the pitch, still influences how the pitch-bearing preferred modes behave. The principal tone (what we perceive as the pitch) is determined primarily by mode (1,1), which is the second partial of the vibrating membrane.
Image courtesy of Yamaha Corporation
Takeaway: Centering the head preserves a uniform circular boundary condition at the bearing edge. When the head is off-center, the system loses symmetry and paired modes can split, creating “falseness,” pitch instability, and uneven lug-to-lug response. A centered, evenly seated head makes your lug adjustments translate into a more symmetric tension field, so the drum can clear properly and hold a stable pitch center across its usable range.