Low cuts should ALWAYS be used. At what freq? It depends-on many different factors-the room (today I highpassed at 350Hz-don't ask-------)
The use of high pass filter use on vocal mics can't be overstated in live PA use.
Before you EQ the channel, roll up the high pass to remove low end and see how it sounds.
No adjustable high pass?, use channel strip low frequency EQ control to cut.
Don't look at the number, just listen. As Ivan said, it could be quite high!
Also, hi pass is very helpful to "clean up" monitor sound and reduce the low frequency spill from monitors to the house.
All that low end swimming around just muddies the water
A slight (note: slight) boost at 2.5 to 3k(wide band)can bring vocal "forward" in the mix.
