Wayne Parham Messages: 18784 Registered: January 2001
Illuminati (33rd Degree)
15 1/8" is an inside dimension. The port shape can be anything, but the Helmholtz formula is a simplification that only describes straight ports. That doesn't mean a curved or bent port is a problem, it's just that you want to measure impedance of the finished cabinet to confirm the resonant frequency is right.