i have made my box up to the right dimensions and all but is there a way of telling how deep i have to put my 6 inch tubing into the box to get a gud result ... or is it just by testing :S

the only and last part im confused on :(

Whats the tubing for? A port?

Google sub box catulation

Google sub box catulation

Or more specifically port length tuning

Well it all really depends on box size whether or not the sub is suited to potted or sealed and what hertz it can go and what u want to go

Download WinISD

You should have used like the 'RE box calculator' (google it). Its gives you all the measurements for the box and the port (As you need to tune to a specific frequency). I dont know how a little round port like this is gonna do with a 2000wrms sub.. (From your other thread, i assume thats the sub your putting in)......