The SACD filter threw me for a minute, in part because there's a typo on page 28 of the manual. The filter is unrelated to the bass management crossover. Instead, it is a low-pass filter that can be set to either 50KHz or 100KHz (page 28 lists the default as 50Hz rather than 50kHz, which is what threw me off until I looked at page 42). The bass management crossover defaults to the THX standard of 80Hz (not 80kHz). The upper limit of human hearing is 20,000Hz (or 20kHz), but SACD supports much higher frequencies. The 3910 provides a low-pass filter that throws away everything above 50,000Hz as a courtesy (since most electronics aren't designed to bother with frequencies that high), and it provides an optional low-pass filter setting of 100,000Hz in case you don't want that courtesy for some reason. I'd leave the SACD filter at the default value of 50kHz.