I've been jumping around on the internet all day today reading this and that about bass speaker cabinet calculations. The stuff i've come across hasn't lead me to any sort of clearity in understanding things yet. I'm proving to be quite inept at the current time. Basically, I'm trying to get a grasp on the abilities of the 2x15 Acoustic made cabinet I have. It is ported, but I don't know for what frequency. I have taken measurements and calculated the internal volume (thanks Autocad). As well, I've gotten Perfect Box and another DOS based speaker buider program. I've been playing around with these programs, but I really don't know what to put in for the vent frequency, so my graphs are about worthless. So here's what I'm looking to find out. How can I figure out the port tuning from the given size? Here is a screen shot of the autocad drawing I made. The organe color represents the inside surfaces of the cabinet. I'll probably wake up tomorrow and find that I've just asked the most stupid question in the world. If so, just slap me, and I'll go on my merry way.