Third problem... worship leader has very small ears and most IEM's are pretty huge, even customs. We shall see where we end up.
This could certainly be an issue as well; if you do not get a proper fit and a tight seal there will be problems with volume and low end.
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For universal ears look into Comply Isolation tips.
I second the recommendation for the KZ's for decent cheap ears.
The ZST is about $18, and it is a dual driver model. It has pretty decent low end. The ZST does not like being driven hard.
The ZS6 is about $48, and it is a quad driver model. It gets more it goes lower than the ZST, however the top end is about 6dB too much in my opinion.
I had a pair of both years back, and I actually preferred the ZST, it was flatter. However there are those that would prefer the ZS6.
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I knew a vocalist who would always DIME their IEM pack; at one point a coworker, noticing this, suggested the vocalists give the manufacturer of their custom IEM's a call, sure enough the company had accidentally installed the wrong set of molds, and thereby this vocalist had never had a good seal.
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If you do not have a decent set of cans I recommend that. They can be a good reference when checking IEM problems, as IEM sound is so dependent on the unit and the persons ears.