I am planning on building a ported box for a 15" quatro. I've been playing with WinISD, and it looks to me like a 5.5 cuft box ported at 20.12 Hz will work best. I am thinking about making a slotted port with an opening of 2"x10" and length of 21". WinISD predicts the air velocity peak of 73.8 ft/s at 16.5 Hz. Will this produce port noise? Do my box plans look good, or am I missing something else? Thank you.