The plasma tubes generally ionize at 80 kHz but we allow a margin for tube manufacturing variables and different operating ambient temperatures. Spooky2 Central will actually work down to 0Hz but the tube ionization is so brief that it cannot be detected. The maximum frequency is about 3.6 MHz, but again this depends on many factors like the length, spacing, and orientation of the white wires feeding the tube, tube type and more. Adding a high-speed gate (about 20 Hz) increases the operation range. We have run a Spooky2 Central at 8 MHz using a short wire and 20 Hz gating.
Source: Spooky Central Q&A