I'm having a problem with my 12" tom. First I bought coated ambassadors for all the toms, I used them at a gig on Saturday and they seemed fine. Today I took the 12 and moved it where the 10 would be, wanting just a four pc. setup. For some reason it lost most of it's resonance, I took the head off and retuned it, but it still sounded like a thump. When I held it by the rim with my fingers it resonated like mad, but after placing it on the tom arm it went flat again. I noticed if I did not tighten the wing screw to tighten it on the arm it came alive again, but was moving around. Does anyone have an idea why this might be happening? BTW, it's a new Mapex Meridian birch kit, thanks.