Mid-size stand-mount in the 600 S3 line — same 25 mm Titanium Dome tweeter as the rest of the series, here driven by a 165 mm Continuum cone instead of the 130 mm unit in the 607. The bigger cabinet pushes the low end into the low 50s Hz at ±3 dB and lifts sensitivity to 88 dB, making it the easier load of the two passive bookshelves in the family.