I think you are right he is low on port area. Hard to fix now that the box is built. I was talking about because he has around 15 sq inches of port per cube so a lot of people assume that will be real peaky. the box models out to have a peak, but nothing noticeable by ear, it does have the steep drop off on the low end, but with the subsonic filter, it should boost those frequencies. so it if he notices any difference in frequencies, i would say its because of the acoustics of the vehicle. This