Our square dance club has been using an L1 Compact in a temporary venue. We have just returned to our regular venue, a renovated 1950's style gymnasium, all hard surfaces. Echo makes it difficult to understand the caller's voice. We had a line level output from the caller's mixer going into channel 2 on the L1. We had the speaker set up using both extensions on the floor of a stage about 3 feet above the gymnasium floor, putting it a couple feet above the dancers' heads. If we only use one extension or use no extension and place the speaker on a table it would be about at the height of the dancers' heads. The mixers used by the callers only have a "tone" control for mic inputs, not real EQ capabilities. We have considered using a Mackie Mix 8 to give us more EQ control. Because it is a historical building we can't do any type of acoustic treatment. Are there things we can do with the speaker (e.g., cut bass way back, change the direction the speaker is pointing, etc.) to reduce the echo?
Using EQ will help, but it may not make a drastic difference. Every little bit helps though. Rolling off the bass to filter out unnecessary audio will tame the space a bit.
Ideally, the distance from the L1 speaker to the dancers' ears is as short as possible. It's a game of inches, but this will give the maximum "signal to noise ratio" of direct sound versus reflected. This means having the speaker at ear height and as close to the dancers' as possible.
It's also important for the microphone to be as close to the caller's mouth as possible, which also will increase the signal to noise ratio.
These are very small things that might add up, but ultimately, you're still working against the acoustics of the space.