Traditional floor wedges are regular speakers that aim upward. Wedgehorns are designed specifically to accentuate the vocal range from 250 to 800Hz, to cut through high instrument levels on stage.
The chart shows a single Wedgehorn 8, loaded with an Eminence Beta 8 woofer and a six element melded array, measured half-space.
Which Wedgehorn? It depends how close you are to your PA mains. Below 200Hz or so PA output is omni-directional, so you hear the low end of the mains even if you're behind them. The Wedgehorns fill in what you don't hear coming back at you from the PA. The larger the stage you're on the less you'll hear from the mains, so the larger the Wedgehorn you'll need. This chart compares the W6, 8 and 10.
As you can see the W10 has higher sensitivity than most PA main cabs.