Back slot

A short, narrow slot parallel to the stud axis that breaks through the back surface of the horn. Back slots are used to lower the resonant frequencies of nonaxial resonances in wide bar horns.

Back slots are usually machined with a narrow blade. They are often positioned about midway between normal slots. They generally do not extend farther forward than the back of the normal slots -- i.e., the back slot length is generally less than the rear web length.

Also see —
Back slot width
Circular back slot
Face slot
Saw slot