A couple of weeks ago I sat in with a group that came through town and I heard the best on-stage monitors I've ever heard, no squeals, no chirps, plenty loud, and very natural sounding. I asked the sound guy how they got such a good sound and he said they had tuned wedges designed and built. My question is how do you tune on-stage wedges?
"Tuning" covers a lot of ground when it comes to speakers. I'm not really sure what the guy meant about having the wedges tuned when they were built, but there are aspects of construction that are important for how monitors will sound and perform:
- The volume and type of the enclosure, along with whether there is a port or duct and the size, shape, and positioning of the port or duct are the basic design parameters that affect how the finished speaker sounds, given the same drivers. When designing floor monitors, there are interesting challenges here because you want the drivers to be an angle and you have fewer options when it comes to the shape of the enclosure.
- Monitor wedges are very different from PA speakers turned sideways. Every time I see marketing of a PA speaker that says, "And this can be used as a stage monitor also", I roll my eyes. To get the best performance and gain before feedback, monitors have to have very tightly controlled coverage. Ideally a monitor creates a fairly narrow beam of sound that just ends after ten feet or so. That ideal can never be realized, but choosing the right horn geometry for the tweeter and better phase alignment of the drivers will go a long way.
- Crossover type and frequency can have a huge difference on the final sound, and this is another are where monitors should be designed differently from PA speakers. High end wedges usually support bi-amping, so that you can take more control of the crossover and also mate each power amp better to each driver and get higher effective power bandwidth.
- There are many advantages to building powered enclosures (downsides include cost and weight) that apply to monitors just like any other enclosure. Built-in active crossovers and bi-amping and better driver damping are just the most obvious advantages. These could have been powered wedges, while many lower-cost wedges are passive (I still don't know why this is true).
After the wedges are built and put on stage and powered, there is a process often called "tuning" were the overall sound is adjusted using equalizers to both eliminate feedback and create the best tone. Old pros would swear by 31-band (1/3 octave) graphic equalizers for both tone shaping and feedback elimination, but digital technology has made this a whole new world. Automatic digital notch filtering systems for feedback, and digital parametric equalization built right into aux (monitor) outputs of digital mixers make it much easier to create great sounding monitors than it was in the old days.
As the other answer says, stage monitors now can be tuned using a white or pink noise source and analysis software that can automatically adjust the EQ or provide information and recommendations for manual tuning by an engineer.
Most likely what you experienced was a competent engineer or engineering team using a combination of the knowledge above and experience with those exact monitors to do a great job. Finding the right equipment is not easy because market forces sometimes drive spending towards products that have bells and whistles over products that just sound awesome, so custom building was probably a major contributor, and it also speaks to the experience of the engineer(s).
You can 'tune' a PA (including monitors) for maximum volume before feedback. In the broadest sense this includes choice and positioning of microphones, FOH speakers and monitor speakers, and eq adjusted for each setup in each different room. This last is probably what the guy was talking about.
Well-chosen mics and speakers, and their positioning, make a lot of difference. I prefer to 'tune' the system to sound GOOD rather than to just be as LOUD as possible though. Sounds like your guy had the equipment and skill to do this.
I am not sure what this particular venue did, but by playing white noise played through the speakers, and then analyzing it with a spectral analyzer, one can be used to identify the acoustic qualities of a room or area of the stage, and then that information can be used to equalize output to quiet louder or resonant frequencies, and boost the quieter ones.