A sub-30 ms Haas delay widens a mono signal but is mono-incompatible and lopsided

By the precedence (Haas) effect, a copy of a signal delayed under ~30 ms fuses with the original as one sound localised toward the first arrival, so delaying one side widens a mono signal. Above ~30 ms it breaks into an audible echo (sharp transients can flam below that). Drawbacks: it comb-filters and weakens in mono, homogenises the sound, pushes it back, and feels lopsided because the precedence effect hears the dry signal as the source and the delay as a reflection.

Examples

A mono guitar with a ~20 ms delay panned opposite sounds wide in stereo but combs and loses level in mono, and pulls attention toward the dry side.

Assessment

Describe the Haas mechanism and why Haas delays cause mono-compatibility problems and a lopsided image.