Re: What effect does a resonance hole have on the bass drum sound?
You get more projection of sound, and the beater has less rebound, but there is a loss of tonal warmth. The reason the hole is offset from the center is that much of the low-end sound that you hear from a bass drum is generated from the sound vibrations resonating back and forth between the center of the beater head and the center of the resonant head, therefore no center = no resonance. Also, sometimes a hole is needed for internal placement of a microphone. Any hole up to 4 1/2 inches will have an effect on warmth and projection, 5 inches is often needed for micing, and anything over 7 inches defeats the purpose of even having a resonant head.
My kit: Pacific wood, Evans oil, Zildjian bronze