I have my new sub hooked up using the two RCA jacks going to a Y and then to the single sub pre out on my Yamaha HTR 5860 receiver. The only problem is that the top jack on the sub does not allow the pin to go into the jack far enough to make contacts. It sounds good but what am I missing? Also the subs grille seems bowed in the middle both at the top and bottom! Normal or what, and if normal why??