high treble left vs. bassy right speaker ?

i just noticed that the let speaker plays out higher treble sounds and the right speaker carries more bass. is this suposed to be a design of the speakers so they balance out when the output balance of both is equal (ie at the centre of the left-right bar) ?

i ve pulled it to the far left and obviously the let speaker has higher frequency - treble sounds and when only the right speaker is on, i can hear the bass thumping which is missing on the left. anyone has the same experience ?