with one, u can have sertain frequencyz sound better and louder. i personally like 32-35 to get those low bass hits in songs. if u tune higher, the bass will sound different.
an easy example i can think of now would be grabbin a cup and place ur ear by where u would drink from. u will notice a sound, and the closer its to ur ear, the lower it sounds. if u move it slowly far from ur ear, the sound will have a higher pitch i think i just got my self confuced, but give it a try man, lol