Working Principle: Provided the physical integrity of the head is sound and the mechanical/geometry tolerances of a timpano are within reason, accurate head centering and even low-tension stretching help preserve a strong, sustained principal tone in the extreme low range of the drum. This, in turn, makes it easier to maintain usable harmonicity (near-harmonic partial alignment) throughout the functional playing range of the instrument.
1) Determine centering marks. Take half the difference between the diameter of the bowl (measured diametrically from lip center to lip center) and the diameter of the head. (Example: if the bowl is 28” and the head is 31”: a) 31” − 28” = 3” b) 3” ÷ 2 = 1.5”. The centering marks will be 1.5” in from the edge of the head.)
Place a centering mark at eight points on the head. The distance between each mark is the circumference of the head divided by eight: X = πd / 8. These marks should line up dead center on the lip of the bowl at eight equidistant points around the head if the bowl is in round. The marks can (if desired) correspond to the individual lug positions when the head has been mounted. The larger the bowl, the more tolerance deviation is likely to be found.
If the bowl is found to be not in-round (or the bearing edge is uneven/out of plane), steps should be taken to repair or replace the bowl. Proceed to the next steps only if the bowl is in-round and the bearing edge is even (in plane). If the bowl is in-round, but the head is not evenly centered, it will not be possible to tension the head evenly throughout the range of the drum. This centering step is crucial in the overall outcome of the mounting/tempering process.
Note: When you tap near each lug you are hearing a tap tone, not a true “local pitch.” Lug-to-lug tap comparisons can help you get close, but final clarity depends on the membrane behaving symmetrically as one vibrating system.
2) Prepare the lip of each bowl (if needed). If minor pitting is encountered, use varying grits of wet/dry silicon carbide paper to smooth the lip. Final polish with 1200 grit. Always use a “shoe-shine” motion when working with abrasive materials on the lip of the bowl in order to keep the striations in the same plane as the head as it moves across the lip.
3) Low-friction interface (PTFE spray or PTFE tape). If the bowl is already equipped with PTFE (Teflon) tape, steps 2 and 3 may be omitted unless the bearing edge needs repair. Clean the tape thoroughly with a non-caustic solvent to remove dirt/grime and buff with a lint-free cloth.
If you are using PTFE spray (instead of tape): after thoroughly cleaning the lip with mineral spirits, apply PTFE spray in multiple thin coats. Allow each coat to dry completely and then gently buff with a lint-free cloth. Once buffed, test the surface for squeaks using a strip of old head by moving around the drum in a shoe-shine motion.
4) Prepare the underside of the head (head-specific note). Even though the underside of Evans Strata heads is smooth, a #00000 fine steel wool can be used lightly to prepare the inside of the heads. It is recommended to prepare Remo Renaissance heads in this same manner because they can be prone to noise when using PTFE as a lip lubricant. Wipe the underside of the head clean of all residues before mounting.
5) Counterhoop liner and head centering in the hoop. Check the counterhoop liner for wear or severe channeling and replace if needed. Center the head inside the counterhoop with temporary cardboard tabs (if necessary). Once preliminary tensioning is complete, remove the tabs. The insert ring will make an indent in the liner material, helping to keep the head centered in the counterhoop.
6) Mount and center the heads. Mount and center the heads using the centering marks described above. Align the centering marks on the head with the tension rods on the counterhoop. Once mounted, seat the heads and apply preliminary tension by hand or via the use of a DrumDial™.
Caution (synthetic heads): If you “find the best playing spot” by rotating a mounted head, do so only in small increments and be prepared to re-seat/re-balance afterward. Rotation can disturb seating and tension distribution.
With the pedals set at the lowest functional pitch of each drum and the master tuning rod engaged at approximately ten percent only, set a consistent tension at each lug point with the DrumDial™. You may find that some tension rods don’t engage at very low tension. This is OK, an even reading is the objective. When mounting new heads, the author likes to end with a DrumDial™ reading between 65–70.
Once lug tension has been equalized (by hand or with the DrumDial™), begin tempering using an electronic tuner or your ear, if you can discern extremely low pitches. Bring the head up to the initial pitch (at each lug point) with the individual tension rods as follows: 31/32 = B1, 28.5/29 = D2, 25.5/26 = F2, 22.5/24 = A2. The initial pitch should be approximately one octave below the highest note you will be using on that particular drum. At this point, each drum should have a clear, sustained principal tone, although the drums are not really usable yet because they are still not in range.
Real-world settling guidance: If tolerances are weak (common on older/institutional sets), let the drums idle at low pitch for up to two weeks (if possible) and check/restore the initial pitch daily using the tension rods only. If you don’t have that window, give the heads at least 2–3 days. Drums with better tolerances typically stabilize faster. Once the head has had a chance to do gentle stretching, it will be easier to temper.
7) Bring into normal range and refine. After the heads have had a chance to do some initial stretching and conform/seat to the bearing edge, with the pedals set at the lowest functional pitch of each drum, use the master tuner to bring the drum up to the pitch set for the normal pedal placement.
Temper the drum by finding the virtual pitch at each lug point using an electronic tuner or your ear (if developed to that point). For more information on Virtual Pitch and Timpani, please visit the Virtual Pitch & Timpani section of this WEBook.
Notes: The objective is to get the heads to stretch slowly and evenly without over-stretching any part of the head. As the drum is played regularly, the original centering marks will move as the head begins to stretch. It is important not to put too much tension on the head via the pedal or master tuner until the head has seated to the lip at low tension. Once a head is unevenly stretched at any point to any significant degree, the integrity of the principal tone can be diminished, especially in the low range.
Practical longevity note: excessive large-range cycling, heat, direct sunlight, and water/humidity can shorten head life. Avoid heat guns, hair dryers, irons, and direct sunlight. Most premature failures come from environmental stress and over-cycling rather than “normal use.” Applying a head-safe surface protectant may help keep the surface from drying out, but avoid products that leave heavy residue or become slippery.