Edirol MA-20D's bass buzzing?

[Acoustic_Daddy]

Hey guys

Ever since i bought my Edirol monitors from the local music shop, the right speaker has bass buzzed a bit, like, you hear a crackling/buzz when certain parts of a song happened.

It's a very low volume buzz, and is hard to hear, but is evident when you stick your ear right up to the side of the cabinet. The left one doesn't do it at all.

At first i thought it was some interruption from the computer power supply, or a vibration in the computer cabinet (the speaker sits on top of the case) but then i swapped around the 2 speakers (left and right) and the buzzing still happened in the right speaker, in a different position completely.

My question is, is this a normal thing? It's a very low audible sound, and unless you have super mixing ears like mine, i doubt you could hear it.

Am i entitled to take them back and ask the shop owner for a please explain?

Anyone else had experience with this?

Cheers,
Acoustic_Daddy