Typically vocalists express a sudden change in the tone of their own voice when using earphones for the first time. Our WL mentioned earlier would have certainly noticed this. He didn’t hear much of his voice through air conduction any longer, due to occlusion.
Before the vocal microphone is mixed into the in-ear mix most of what a vocalist hears the bassy/muffly sounds of their voice due to this bone conduction. For this reason, vocalists often have the toughest time adjusting to wireless personal monitors.
So a vocalist using in-ear monitors is certainly going to need to hear others on the stage (such as the band or orchestra) in their monitor mix, but usually needs a lot more of their own vocal. This helps overcome the occlusion. The vocal will often need to be, by far, the loudest thing in their mix.
If vocalists do not hear sufficient level of their own voice, the bone-conducted tone of their voice is predominant and they are uncomfortable. Ever heard a vocalist trying “ears” for the first time say, “I sound really weird.” This is probably why. Instrumentalists using professional, sealed earphones also experience isolation, but they do not have the challenge of their instrument being mounted in their skull :>), and hence, don’t have to deal with tonal distortion due to bone conduction.
So because of the isolation provided by proper earphones, artists no longer hear sounds naturally as they traditional have with wedges. If there is something they want to hear, it must be deliberately routed to their monitor mix. It becomes critical that the sound tech auditions the monitor mix with earphones of preferably the same type. And, mix adjustments that required four or five knob “clicks” with a wedge might need only two or three “clicks” (or less) in great earphones. Sonic details are simply much more obvious.
Consider a worship leader with a choir behind him: in a wedge application, he may hear plenty of the choir naturally, without any choir being folded back. But with “ears,” he will certainly want the choir mixed in his mix if he intends to hear them at all. So the acoustic isolation offers wonderful control, but requires increased attention and effort.
Full Vs. Partial Mixes
A straight-up full IEM mix might sound much like the front of house mix, a commercial CD mix, or similar, have every element processed and blended at the proper “finished product” balance. A typical IEM mix intentionally omits non-essential elements (for that particular user!) so that the remaining elements may be monitored clearly, without unnecessary “clouding” from a busy mix. Clouding is sometimes also loosely referred to as “crowding.”
For instance, a bass player’s IEM mix in a modern worship band setting will certainly have his bass, the kick drum, the basics of the rhythm section, the lead vocal, and maybe a few other things he may request. But it might omit the choir mics, orchestra sounds, background singers, playback devices, “talking heads,” or other elements that are not really essential in helping him get the pitch and time cues he must focus on.
It is often helpful to remind each other (musicians and techs alike) to contrast the terms “listening” and “monitoring,” and remember the purpose of stage monitoring. This can sometimes become a race for the perfect full mix in a user’s wireless personal monitor, when oftentimes that’s really not the point at all (if it were, we could all save a ton of money and effort by routing the main PA mix to all IEMs, but that would be a disaster…)