Frequency over time. Drivers aren't perfect and don't stop immediately, and enclosures don't absorb all acoustic energy perfectly. A perfect CSD would look essentially like the measured frequency response with an immediate drop off. What you see instead is decay over time across the frequency spectrum.
Y axis is SPL, X axis is frequency, and Z axis is time. CSDs are often used to find ringing or verify FR measurements because there can sometimes be dips in FR that don't actually exist.
LOL! @Hands beat me to it. Now I know how @cskippy felt :P
Read these "rules" AND introduce
yourself before your first post
Being true to what the artists intended
(opinion / entertainment piece)
Comments on Profile Post by lcmusiclover