bulding 2x15'' and 2x10'' cabs - need advice

[BRAILLE]

I'm currently designing 1 2x15'' and 1 2x10'' bass cabs. I have almost everything I need I'm just touching up on the design of the cabs. I'll post more information about the demensions of the cabs later. As for right now I was curious if anyone could reccomend me ports/vents and where to position them on the 2x15" cab? I'm trying to get these cabs to have a very low frequency response.

Thanks!