I just purchased a Slim Stage 30 and Bravius 8A sub woofer combination. When the sub woofers level is increased to about 33% I start to notice an audible sound from the sub (I know this sounds weird) like air rushing down a open chimmeny flue. I can hear it from my viewing position. It gets louder when I continue to increase the subs sound level control. I notice it while viewing the TV or the blue-ray player. I am using opitcal audio inputs to the soundbar (from TV and blueray) and connecting the included mini to RCA cable to the LTE, using the white RCA end to sub. I do not believe this is sub woofer hum caused by a ground loop becuase I only hear the noise from the sub woofer when there is an active audio input. I have the sub crossover set to 120 and the bars crossover left at the default of 115.
I am hoping this is not normal since it is noticible during quieter moments of the source audio. It is not a dramatic sound but enough to be audible from 6 to 8ft.