It's a differential output, measured stator to stator, so the absolute maximum if the design allowed for it would be 2 * power supply voltage peak to peak. The Blue Hawaii will output 1500vpp, slightly less than 2 * it's 800V of power supply (the bottom of the waveform will clip first because of the type of design, same with the Stax 007t). At 800Vpp, SPL w/ Omega II is 106dB, so this would be louder than that. Max output of KGSS & Stax 717 are both around 1200vpp, Stax 007t is probably somewhere around 950vpp