Lemon oil works for me,S7horton has 1/2 of it right also.Extreme dryness will cause cracks depending on many variables,thickness,type,temps,changes,finish etc. etc......common MDF with a veneer[common in speakers]could use a little TLC.1.5" solid wood[unusual for speakers]won't be cracking much if at all,figure what you have,google wood finishes,then go to the yellow pages under furniture,make some calls,listen and learn,then go and score 1 or 2 products and try out.Wood is so interesting you can't go wrong investing a couple of hours and 15-20$.Need to know what you have first,good luck,now get to work....
