Good question, Roscoe, as I should have clarified that statement further.
If I position the window cursor close to the direct sound arrival, say within 3 ms or so to cite an extreme example, and then look at the frequency response on the next screen, there will be a downtrend in the frequency response below something like 500 Hz, roughly speaking. Presumably that occurs because the short duration of the window doesn't make it possible to sufficiently capture low frequency information. (Consider that 3 ms is less than one cycle of all frequencies that are below 1/0.003 = 333 Hz).
If the window cursor is then moved way out, to say 20 ms or so, the frequency response shown on the next screen will show a substantial rise in bass response at many low frequencies, with perhaps a narrow dip or two at certain frequencies.
Intuitively it seemed to me to make sense to set the lower frequency limit of the calibration around the inflection point below which that decrease or increase in bass response starts to occur for the chosen window duration.
This is all consistent with a comment Nyal had made to me that a common mistake is to correct to too low a frequency relative to the duration of the truncation window, the result being an excessive bass boost.
And consistent with various statements in the calibration manual, the subsequent room corrections should be a more suitable means of addressing the bass region, or at least most of it.
Best regards,
-- Al
If I position the window cursor close to the direct sound arrival, say within 3 ms or so to cite an extreme example, and then look at the frequency response on the next screen, there will be a downtrend in the frequency response below something like 500 Hz, roughly speaking. Presumably that occurs because the short duration of the window doesn't make it possible to sufficiently capture low frequency information. (Consider that 3 ms is less than one cycle of all frequencies that are below 1/0.003 = 333 Hz).
If the window cursor is then moved way out, to say 20 ms or so, the frequency response shown on the next screen will show a substantial rise in bass response at many low frequencies, with perhaps a narrow dip or two at certain frequencies.
Intuitively it seemed to me to make sense to set the lower frequency limit of the calibration around the inflection point below which that decrease or increase in bass response starts to occur for the chosen window duration.
This is all consistent with a comment Nyal had made to me that a common mistake is to correct to too low a frequency relative to the duration of the truncation window, the result being an excessive bass boost.
And consistent with various statements in the calibration manual, the subsequent room corrections should be a more suitable means of addressing the bass region, or at least most of it.
Best regards,
-- Al