Playing files of a "decade" of test tones from the Stereophile CD and measuring SPL with a Radio Shack sound level meter,
I have a persistent 10 dB peak at 200 Hz at the listening position. In Amarra, I selected "Bass Reduce" and three sliders appear.
I typed in 200 Hz for one freq and zeroed the attenuation on the other two.
Q is defined as center freq divided by bandwidth. Bandwidth is defined as the 3 dB-down freqs on either side of center.
I previously measured nearly flat at 160 Hz so I chose 180 Hz for the 3 dB-down point and 220 Hz on the other side, so bandwidth is 40 Hz.
Q, then, is 200/40 = 5 which I typed-in, setting attenuation for the 200 Hz center freq at -10 dB.
At the listening position the SPL now measures flat for the 200 Hz tone -- and the system sounds WAY better on music:
Voice articulation and imaging are dramatically improved, and overall bass response sounds "right."
I reported my experience to Sonic Studio Support and they validated this approach. They noted that the other sliders could be used to
simultaneously deal with similar peaks (or troughs) at other frequencies.
