first off i want to say i'm new and hello to everyone.i'v been reading the topics here for a while and i finally decided to join. ok i have 2 kaption audio spl104d's and right now there in a small sealed box. over the winter i want to put them into a ported box. i email the company and they said for a ported box it should b 1.7 cubeic feet inside with a port 4 inches wide and 12 inches long. so if i were to build this box what would the frequency of it be. and what would i burp it at. also with the sealed box i got now aroudn 41 hz there a "dip" it sounds lower then 40 and 42. is that the resonate frequency of my car. its a 94 cavalier.

 

1.7 cubes with a 4" x 12" port is tuned to about 36hz. Not sure about the other questions though, sorry...