Port tuning

With 4 string 40Hz tuning is usually too low. That minimizes excursion at 40 Hz, whereas the power bandwidth has the most demand above 60 Hz. Even with 5 string best results usually come with 45 to 50 Hz tuning, which still gives adequate output to the fundamentals while giving the maximum sensitivity and displacement limited power handling within that 60 to 100 Hz bandwidth where power demands are highest.