Back to the OP's question, the problem you are having is one of "suitable listening distance". It's the same problem faced by designers of studio monitors. There are nearfield monitors and farfield monitors. The largest Nearfields you see are usually 8" woofer two way systems. 2 way systems with larger low freq drivers are extremely difficult to design crossovers for due to the difference in radiation patterns between the LF and the HF.
You will also see that NF monitors use dome tweeters instead of horns in order to have a radiation pattern that matches the woofer better. The idea is to have (as much as possible) spherical radiation from both drive units at the frequencies they are playing. The small woofs will give you a much higher possible crossover point before they begin to narrow their radiation pattern.
How this all pertains to your drum monitor is that the drummer is sitting in the "nearfield" and you at the desk are not. The Eons are not designed with nearfield listening in mind. Therefore the drummer is getting a wildly skewed, lumpy frequecy response. To the credit of the eons, most 15" x 1" horn pro audio cabinets will have this same problem. A 15" woofer is a great compromise between acceptable freq response and high efficiency, but it typically makes a terrible low/mid for a 2 way cabinet.
My suggestion is to either back the monitor up several feet, or run a 3 way drum fill with a sub and a small 2 way cabinet. A 10/1" monitor on top of an 18" sub works pretty well, given that all the components are of decent quality. If you can find a small monitor with a conical wave guide you might be a little better off than one with a rectangular horn, but as always, give it a listen to see if it sounds good up close.