Here are some piezo tweeter measurements.
The KSN1005, KSN1038, KSN1177 are CTS products.
The MPT100 is an unknown copy of the KSN1038, with a bit longer horn.

KSN1005 #1
KSN1005 #2
KSN1005 with 44ohm parallel, 0.47uF in series

KSN1038 #1
KSN1038 #2
KSN1038 #3
KSN1038 #4
KSN1038 #4 with 22ohm parallel, 0.47uF in series

MPT-100 #1
MPT-100 #2

KSN1177 #1
KSN1177 #1 with 44ohm parallel, 1,5uF in series
KSN1177 #2
KSN1177 #3
KSN1177 #4
KSN1177 #4 with 44ohm parallel, 0,47uF in serie