What size port and how far in should the tube go and where on the box is best to put the port. what size box do you think would be best? And its not really a noise its like a thump pulse. and it doesnt do it with car off. It only pulses when i turn the power up .and doesnt get worse when the volume is up or down. I can look at battery guage on dash and see it go up and down every time it pulses head unit is a jvc -kd g230