The point was to increase the excellence in sound quality in the house, by removing the excess stage volume from the house mix, thereby allowing the sound board operators to get a cleaner mix overall and have more absolute control over the room volume. We can determine the exact volume level that we want in the sanctuary and hit it with consistency, keeping total volume limited to a level that is right in that sweet zone: where it's loud enough to be felt, but not offensive in any particular frequency range to where anyone complains about the volume. To be completely honest, the sight of a sound engineer prowling the sanctuary with a sound pressure meter does instill confidence in our church goers that we are being sensitive to the sound level and keeping it in control (which we are in fact doing). If you don't have your sound engineer equipped with a SPL meter, I highly recommend the investment. Or use a free smartphone app like the aptly named "SPL Meter" on iPhone. Its performance is within a couple dB of a real meter, close enough for the desired purpose.
Back to the in-ear monitors...
By having direct control over their personal monitor mix, each musician is able to determine how much of any particular instrument or voice they need to hear, and take the front-of-house engineer largely out of the picture. They can each save their own preferences in the system and log into a personal monitor profile, eliminating the need for lengthy monitor mix tweaks. Our sound checks are down to less than 5 minutes total. Game changer for our mid week rehearsals and our weekend sound checks!! We get so much more time to actually rehearse together rather than fuss with mixes, it's wonderful!
Another benefit is that due to the clarity of the in-ear system, each musician is far more aware of their own instrument/voice and its dynamics. The musicianship of the whole team has increased exponentially, as there's nowhere to hide from poor musicianship when the sound is so crystal clear.
Our particular system has the ability to do multitrack recording on SD memory cards on each individual workstation. Our musicians can record the live worship sets or rehearsal (or both!) and export the raw .wav files into any music editing software and review/mix/remix it to their heart's delight. It allows me to review each music session and determine where we need to concentrate, as far as continuing to develop our musicians' skills and cohesion as a band. Or simply to export a good worship song recording as an mp3 and share it!
A final benefit is that by dropping the stage volume (an average of 20dB) and using sound isolating earbuds (which also drop sound by 26dB), we're saving our musicians' hearing. No ear splitting OSHA violating noise levels, even when we're rocking out!! We tried a wide variety of different earbuds of price ranges from $20 up to $700, and found happily that the best bang for the buck was right at the $100 level. Shure SE215's are amazingly the most full range flat response earbuds of the entire Shure line (no need to get the dual driver SE325's or triple driver SE435's - they simply don't sound better than the SE215's.) The close in performance and price models were the Sennheiser IE6's. They didn't quite fit the majority of our musicians ears the way the Shures did, but the sound quality was hard to tell apart. Very crisp..
In order to facilitate getting our in-ears (we went with the MyMix system) we bought it piece by piece over the course of the whole year (and then some). First month we bought the analog/digital converter for our board. Next month we bought the ethernet switch & router. Next month we got a couple of workstations and cables and actually had the drummer and bassist on the system. Next month we got two more workstations and got the electric guitarist and keyboardist on there. The next month we got two more, so on and so forth. We still are in process of getting more components - the goal is that my mid spring 2013, we'll have a complete setup for all musicians and vocalists, and budgetwise it will have been spread over a year and a half. Made it a lot more tenable for our financial oversight board to approve, rather than a single big purchase.