You need a quality power conditioner like the Shunyata Denali and room treatments.
From Soundstage's review:
But those tracks, and others, showed me that I had to be a little careful with the S5’s extreme highs. Like the mids, they were exceedingly clear, but they were also designed to be neutral -- there was no subtle rolloff in the highest frequencies, as there was with the V2, which was a tad polite up top. As a result, the S5 sounded quite lively on top, even a little hot, depending on the recording. This wasn’t a problem in my room, which is very large, and has a carpeted floor that absorbs some of the highs. What I experienced with the S5s, even when listening on the tweeter axes, was a clean, thoroughly extended top end not at all unlike the XO Cericas’, which was also prominent. In a room more reflective than mine, the S5’s lively top end might have to be compensated for with speaker placement (less toe-in, meaning listening farther off the tweeter axis), and/or
absorptive materials.
From Soundstage's review:
But those tracks, and others, showed me that I had to be a little careful with the S5’s extreme highs. Like the mids, they were exceedingly clear, but they were also designed to be neutral -- there was no subtle rolloff in the highest frequencies, as there was with the V2, which was a tad polite up top. As a result, the S5 sounded quite lively on top, even a little hot, depending on the recording. This wasn’t a problem in my room, which is very large, and has a carpeted floor that absorbs some of the highs. What I experienced with the S5s, even when listening on the tweeter axes, was a clean, thoroughly extended top end not at all unlike the XO Cericas’, which was also prominent. In a room more reflective than mine, the S5’s lively top end might have to be compensated for with speaker placement (less toe-in, meaning listening farther off the tweeter axis), and/or
absorptive materials.