Typically the folks trying to operate ball field systems have very little (if any) knowledge on how to operate a sound system.
The ones who think they know how do the most damage and after the first few months it seems the system never operates consistently (game to game) ever again. (cut to scene two where the school thinks the system is crap, bad mouths the install contractor, and throw more money away on a whole new system instead of sending the press box folks to a simple "audio basics" course at their local music store.
My latest systems for ball fields are R Series cabinets from Community and power amps from Crown, Biamp and Lab Gruppen (depending on speakers, required volume, and client's budget).
Community has some great .pdf files on their site showing speaker choices, throwing distance, power required, and mounting locations. Check this out:
http://www.communitypro.com/files/literature/guides/R_SERIES _AP_GUIDE.pdf
For venues that have a qualified audio operator I will put in a small line mixer or a rack mounted 6-8 channel Soundcraft mixer.
Again, most do not have a clue what to do with a mixer and 9 times out of 10 it leads to feedback, signal clipping, and system damage.
Most prefer the Biamp Nexia units I've been installing. Once the install technician sets it up, the operator only has 2 buttons/knobs to adjust. One is a selector (source selection) and the other is volume (of the selected source). Essentially that's all they need control over. - Volumes -
There are no external knobs or buttons on the Nexia. No LCD screens to burn out or fail. (although there is a new wall controller coming out this month that does have a LCD screen on it - Installing one next month if all goes as planned) This ensures consistent performance and and simple operation of the sound system game after game no matter what level of experience the announcer has with PA systems.