Piezo contact mic resonance comparison

A comparison between a resonance of a diy piezo with no added weight (''naked'' element), diy piezo covered with hot glue, and JrF C-series piezo. All contact mics were plugged into Radial Engineering StageBug SB-4 Piezo preamps, and recorded with a Focusrite Scarlett 6i6 2n Generation sound card with the same gain on each channel.