It all depends on where and when mono summing takes place. Mono is not simply throwing L+R together and sending it back out as an identical signal over both L+R outputs.
So, if – for example – the PA is summed to mono through a professional summing amp and your controller has a far more basic way of creating a mono signal, you’d still end up with two different sounds.
I hardly bother with EQ-ing tracks anymore. First of all I’d rather spend the time not necessary to create transitions watching/interacting with the audience and determine were I am going next. Second, if the EQ is bad because it’s an old track (that either lost a lot due to deterioration of the original medium, like tape or vinyl or because that was just the best sound they could produce in the era), I’d keep it to reflect the “sound of the times”.
Generally speaking, sound engineers will EQ for stereo and then do a quick check on a simple mono speaker. What you are suggesting means re-EQ-ing everything from stereo to fit a mono output better. While commendable, I think it’s waisted on the majority of your audience who are there to drink, dance and flirt (not necessarily in that order).
The way I look at it is that I bring tracks in their original form, which is in stereo for which they have been optimized. If a venue owner decides mono is a better option, it’s up to him to provide the best possible conversion from stereo to mono. This can be done with the right equipment and with room EQ for example and will still sound a bit different from the original stereo source. And it’s not my job or responsibilities to change every track to compensate for the absence of a stereo PA.
Just my two cents though.
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