This tutorial looks at building x0x style kick drums in Reaktor, based on the sounds of the classic Roland TR-808 and TR-909.
The tutorial goes over how to calculate Freq and Q (Quality Factor) from reading schematics. The video also shows how to modify the Core static BP filter to use Q values instead of Resonance.
- To see how to do the same thing for BandWidth (BW), see this video
- The video also points out these tutorials for building a TR-909 Kick