Check this out. Schlogwerk makes a tube to put in the sound hole of your cajon called the Cajon Bass Tube. It increases… | Bass, Diy musical instruments, Cajon drum
Amazon.com: Schlagwerk BC460 2 in One Booster Boxx Bass Cajon: Musical Instruments
Keepdrum Pad Sitzauflage Schlagwerk CBT 10 Cajon Bass Tube