iPhone 5 audio/headphone output is not very good

Hi - I use iphone 3, 4 and 5 and the audio output quality seems to diminish more and more through each upgrade of iPhone. iPhone 5 is the worst.

trying to listen to itunes playlists with the iPhone 5 through top quality speakers and cable is a poor exerience, listening to the same itunes playlist through the same speakers and cable with the iphone 3 and 4 has much better sound quality. Does anyone else suffer the same experience? the main reason I have Iphone is to help me with my work in music industry!!