For those that sync their iPad music thru the system there is a FREE music equalizer that allows adjusting the frequencies of your music library while using BlueTooth!
The app come with an equalizing graph, contains radio stations from all over the world and as mentioned, allows equalizing even while BlueToothing.


https://itunes.apple.com/us/app/deno...520604518?mt=8

Give it a try cuz it's FREE!