Slot web ratio
|Slot web ratio||=||Front web length|
|Rear web length|
For shaped bar horns, the front web length is generally about 12 mm at 20 kHz for reasonable front web stress and the slot web ratio is approximately the inverse of the horn gain. This results in a rear web that is longer than the front web, thereby yielding a relatively short slot that minimizes problems with adjacent nonaxial resonances while still giving reasonable rear web stress.