This was recorded using the built-in microphone of the OnePlus 6T placed next to the B&W CM10 S2 tweeter. The noise is inaudible at 20 centimeters or more. The speakers are hooked to NAD M17 power amp, which is connected to NAD M17V2 processor.
1. The hiss goes away 100% when the processor is muted.
2. If the processor is disconnected, then the noise floor of the amp is heard from the tweeters the above mentioned hiss goes away.