I have the kicker app on my iphone that lets my select a frequency and it will play it over my stereo. I have the crossover at the lowest, which is 50hz, yet i can here up to 110 hz comming from the sub. Any ideas why?

I have 2 kicker solo baric 10 l5's and a 1000 watt kicker amp

 

A crossover is not a brick wall cuttoff. It has a slope (6db, 12db, 24db, etc). This means that as the frequencies double (or halve for a HP crossover) they will be reduced in output by that amount.

So, if your amp's crossover is 12db, that means that at 100hz it will be 12db quieter than at 50hz, 24db quieter at 200hz, 36db quieter at 400z, etc.