I am tuning my Lanzar opti1533d subwoofer 4.5 @ 37 and my group delay seems crazy high. It is peaking at 61 ms. My sub seems to hate vented boxes. The EBP is 39.175257731959. That doesn't make sense for a Lanzar opti1533d. It is a SPL sub right? Am I not getting something here?