Re: When setup is important?
I think part of the answer to the "Should I" question involves accurately defining the extent of the problem.
By throwing out a lot of suggestions, people may help with that part of the exercise, even if the bulk of any remedial work might take a different form in the end after any modelling etc. you might do.
And just to add to the speculation, have you been able to ascertain yet what the orientation of the horns currently is?
I haven't used that exact box but have read various posts on fora suggesting that rotating the horns so the "down" tilt becomes an "out" tilt when using flat fronted or tight packed boxes can help mitigate (albeit not completely solve) combfiltering, which if it has been done in your case may be part of why it doesn't seem as bad as your initial visual impression led you to expect?
Anyhoo, back to the "should I" part, as well as looking at what potential improvements you can actually make to the sound, I'd have to suggest trying to get a feel for what other benefits (beyond your own satisfaction at a job well done) you might realise.
For example, would improving the overall sound of the room likely attract better bands/more bands/more drink sales etc.? Allow you to run at lower SPL's improving neighbourhood relations (not that you mentioned that being an issue, just trying to widen the net of possible benefits here)?
Assuming a non-infinite budget, would the cost of any improvements be better spent elsewhere - maybe improving mic selection, upgrading desk/monitoring/some other aspect of the system?
Without potential improvement in some other area, I'd be reluctant to ask an owner to invest in something that only I would ever notice.
Maybe try out the "one box unplugged" for a low/moderate volume show and get the owner/manager alongside you to see if they notice the improvement anywhere near as much as you might?
HTH,
David.
