I just bought a secondhand IMR R1 (non-zenith) and as I was experimenting with the filters, I noticed I'm not hearing any sound signature change with the other filters then I found out some of the filters have no "filters". Only the the orange and pink has. I can't contact the person I bought this from, so, since I'm using the blue filter, is it normal that it doesn't have anything on the filter, mesh or foam? So which filter normally doesn't have any "filter"if any? The blue, black and copper doesn't have any kind of filter. Obviously, the copper was tampered with. Also, is it normal that the pink has a foam only and no mesh? Again, bought it used and the seller didn't disclose the damage to me.