The proximity effect is another area of mike response that buyers should think about. They all vary, and a lot of what makes your decision for you depends on how you (or whoever is going to use the mike) actually use the mike. Particularly for 'guest' singers, you see vastly different mike to mouth distances, often varying wildly for the same person!
So a mike with as little proximity effect will keep things more consistent. While we, as pros, may be aware of mike technique, many others are not. A mike with the best feedback rejection, and with the least proximity effect is often the best choice for others sitting in...
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An arranger is just a tool. What matters is what you build with it..!