Numark headphones delayed slightly

Hi, I have noticed that the headphone jack seems to be delayed slightly compared to the master output. Its very slightly out of sync.

I like to mix cueing the other deck by comparing in one ear.

Could it be the headphones I am using or am I missing something?

Thanks

Andy

I should note - I am using a rather dated ipad 2.

Cheers

nevermind i found out it was the pc as i was running through that