I have a pair of Tannoy Mercury MX3 front speakers and a pair of MX2 rears. The MX3 floorstanders have a forward facing bass tuning port and the MX2s a rearward facing one. They came with foam bungs in them which I assume were just for protection in packaging so I took them out. Now I've read that perhaps that isn't what should be done. So, what's the difference between having them bunged up or not? I still have the foam bungs. Michael.