My box tuning is off?

[45js45]

I use the port calc @psp-inc.com.When I goto play some test tones the box is supposed to be tuned @33hz but is loudest at around 40hz.I figured in all displacements.Box is 4.05 cuft after subs and ports,it is for 2 12s....2 4" ports at 12.6' in length.Pioneer TS-w303R subs.We are very happy with the output but I cant figure out why it is tuned higher than what I built it for.

[SpeedEuphoria]

cabin gain

[kushy_dreams]

Your peak will be a little bit higher than your port tune. I was playing around with a term lab today and peaked at 52-55hz and the port tune was 35hz

[45js45]

Sooooooo,next time should I tune lower......like 30hz?

[RAM_Designs]

It depends on the box/subs as well as the vehicle it's going in. The box itself is going to peak around 3-5hz higher than tuning(again, sub/box dependent). Then throw it in a vehicle and everything will change. I can tune as low as I want in my truck with seemingly any sub, but it'll still peak at 57hz because the cabin gain is just so high in the 50's. I had three "sq" 18's tuned to 32hz and still peaked at 57hz.