Additional Air Holes
Historically, most drums have been vented with a single air hole. Yamaha engineers studied bass drum dynamics and, with the Absolute Series, provided the customary top vent hole one the player's side, and then added holes located around the front end of the shell. The additional air holes permit additional air, the result of "internal combustion", to escape, providing a distinctly more comfortable beater action, more controllable on the rebound. The reduction in beater vibration and backlash in particularly noticeable when an intact head without a hole is used on the audience side.