Low level hissing noise coming from drivers is normal sound associated with speaker operation. All the active speakers amplifiers generates sound which is heard through the speaker elements. This is called self generated noise level, which is <5 dBA or even <3 dBa for latest Genelec products. This is a very low noise level and most of the active speakers on the market are not capable of such a low base noise.
In a very quiet room and listening to it closely, the normal self generated noise can be heard if there is no other sound or music in the background.
If you feel the noise is too loud, with certain models you can slightly adjust it to lower from the input sensitivity trimmer that is located on most models on the rear panel of the speaker. However when you do this, you have to remember that after that you have to raise the volume from your sound source, and also your sound source can generate some noise. With SAM-series of speakers, the sensitivity and noise may be lowered from the GLM.