Video: noise floor and tweeter hiss, what do you think?

Simple answer. This idle noise or hiss is usually from the pre-amp or amp having high gain. This can be knocked down by putting an attenuator on the cable going into the amp. All my systems are dead quiet and only a couple of times have I had to attenuate the signal. 

XLR or RCA but in a lot of applications the RCA has less gain so unless you have a long run an RCA cable will help a little compared to XLRs. A 10db attenuator usually is enough but each system is different. As long as you can’t hear it from your listening chair you are good. I’ve only used RCA attenuators but your link looks fine. To be more specific, it’s the gain, the noise floor, plus loudspeaker efficiency that are the things that add up to the noise level at the speaker.

A Discussion About Idle Hiss – Upscale Audio