I just finished a fashion show where I used (4) QSC KW181 single 18″ subs in addition to the venue’s Meyer Sound 700HP dual stacks for low end. During the setup it was discovered that one of the Kw181 cabinets has an issue. Today while I had a few spare minutes, I measured the (3) functional cabinets to verify they match and also as a baseline for verifying the malfunctioning cabinet after it is repaired.

Here are (3) overlapping traces with the mode switch on NORMAL.

Here are (3) overlapping traces with the mode switch on DEEP.

Here is a comparison of the same cabinet with the mode switch in both positions (NORMAL & DEEP).

Note that when the polarity switch is reversed, the frequency response (measuring only one cabinet at a time) is unchanged but the phase response has rotated 180 degrees.