Hi, Live Systems Engineer here,
If you are only deploying a basic full-range LR pair, the mixer will be fine, as all you need is a a basic compressor/limiter and EQ.
The second you add subwoofers, fill speakers, etc.., you will want outboard DSP for routing and control, to handle crossover, delay, EQ, compression, limiting etc.... and leave the mixer free for strictly mix purposes
Disclaimer, I am not a sound engineer I am working on the acoustics in a wedding hall and have brought the RT60 time of a 2.5 to 3.5 sec hall to 1.4s flat from 100hz to about 2k with a slope downwards in an approx 3000 meter3 volume. Of course using, REW and a pair of speakers rather than the sophisticated Dodecahedron spekears and acoustic mic.
Simulation shows that with the venue filled with 300 people with the new chairs should bring it down to 1.1sec or even lower.
Well, this is going to be for a one off event. I just want to be sure that the DSP in the touchmix is enough to provide decent sound. The speakers will be the QSC KW122 which has onboard DSP and the KS118 subs I think also do.
No offense, you are approaching system design logic from a wildly overly-analytical, impractical/backwards lens.
Intelligibility is determined by the incident(direct) to reflected/ambient noise ratio. Concern over RT60, DSP filter taps, measurements and corrective EQ when you are using a pair of consumer QSC powered mains over consumer QSC subs for a one-off event is absolutely absurd.
My next goal is to find a sound sytem that I deem appropriate to sound good enough for that hall to allow the owner to ascertain if he wants to spend more on the acoutsics or not. I feel the VRX he usually rents at least in my amatuer opinion is that too much sound will still bounce around and with a point source we can direct the sound to the dance floor, with a minus 3 or 6db being covering to the seated audience.
This makes no sense.
First, and most importantly, focus on designing a system using controlled directivity sources which smoothly cover the intended listening area with minimal boundary illumination.
Hypothetically, lets look at an exaggerated, yet technically simplified (without boundary interactions) situation.
You have a venue, 2x 90Hx60V speakers, and 2x 18" subwoofers and ample time and equipment for whatever rigging arrangement you desire.
- Option 1 (right), speakers on poles over the Subs, tweeter at 7ft
- Option 2 (left), speakers flown along ceiling, at 18ft, inline delay to rear speaker, pointed down at audience, flown central subwoofers (granted you'd never do this arrangement with only 2 speakers, but I want to keep the comparison equivalent)
- Option 1 has a horrific SPL gradient, and tons of back and side-wall illumination, has problematic misalignment, and has wildly uneven subwoofer coverage
- Option 2 has a much smoother SPL gradient, less wall illumination, flawless alignment, and flawless subwoofer coverage
Due to the smoother SPL gradient, and proper alignment, and less wall illumination, option 2 will have significantly more average intelligibility and consistency across the entire audience region, regardless of the room.
In the time, energy, and money it takes you to setup your 2x tops on poles over 2x subs system, take measurements, deal with REW, design EQ filters, realize you messed up somewhere and start again, realize REW is inadequate for live sound use, purchase SMAART+an interface+professional measurement mic for $1800, start your tuning process for the 3rd time, meticulously find all the points to place acoustic treatment, tune again, your show starts, you realize you spent all of that time and it didn't translate at all now that the venue has bodies on the floor, people in the front row are complaining about it being far too loud, and people on the sides complain about no bass, and people in the back are experiencing an awful incident:reflected sound ratio and its completely unintelligible...
...I could have installed a far, far more capable system with highly optimized placements, and tuned it solely by ear, 3 times over. Not suggesting you tune by ear or deploy ridiculous inline mono delay setups, I'm just trying to prove my point that your priorities are completely misguided.
99.999% of people only care about 3 things
- hearing the audio
- not having to walk around to find a spot where they can hear the audio because of poor coverage or dominant reflections.
- good bass
Coverage (and therefore its ability to push reflections outside of audibility) is 500x more important than obsessively perfect tonality.
Here’s a system I deployed this weekend. Way way way worse RT60 than your venue. But guess what? It sounded flawless. The reason? Flawless placement to reduce wall illumination, cardioid bass to reduce room effects, and so on.