Our podcast recording setup is a Behringer multitrack mixer with 4 preamps and we have 5 microphones. I have made peace with the fact that two microphones will have to occupy the same track. How would adding a Y XLR splitter and plugging two dynamic microphones into one preamp affect sound? Would the signal be split and I would have to extra boost gain/volume? Is there a way to estimate by how much?
if your mics are getting phantom power via the Behringer interface, then I'm not sure a splitter would work. Or two mics needing phantom power from a single preamp would probably draw too much current (never good).
A passive split with dynamic mics should work as long as the load of both mics combined is within the specs of the Behringer unit. The gain coming from both mics thru the splitter will certainly be less compared to having only 1 mic connected; it depends upon their impedance and the gain range of the Behringer unit. The correct way to do the split is to isolate one of the mics, e.g., using a transformer, otherwise you can hum/ground loops. There are inexpensive passive boxes to do this - just search for passive mic splitter.