If you are starting out make sure you know that...

At you risk.

This is a humble advice I wish I knew or followed since beginning recording in my teens. Unfortunately or fortunately it took me 25 or so years to realize a simple truth.

Even a few inch microphone distance can play a tremendous role in sound quality. The whole timbre of the subject recorded is changed.

For example even if the mic chain has bass, mid bass correction (to reduce bass, mid bass heaviness to listener's brain) changing the mic distance from 24in to 18in can give a seemingly hotter signal at the expense of change of quality.

 Al Scmitt who has recorded so many masterpieces including Africa byToto, on his book On Vocal and Instrumental Techniques emphasize the importance of mic distance. The great recording engineers were lucky to learn this way as at that time not many equalizers were available although the quality of them was excellent.

So the humble advice is use your ears and brain and make sure the monitoring system sounds correct, amazing, on legendary recordings!

Also you might like to make sure that the sound absorbers are seen by the mic, i.e. are at the back of the singer. 

See for example Amy Winehouse while she was recording Back to Black with producer Mark Ronson.

The microphone is the ribbon microphone RCA 77DX 

P.S.

Why just a few inch or change of angle make a difference?

The frequency response curve of the microphone changes, for example due to proximity effect, due to different angle etc.

Other matters needed to be taken into account:

The frequency response curve of our brain depends of the intensity of the wave displacing out eardrum. See Equal Loudness Curves also known as Fletcher Munson Curves

The frequency spectrum of voice depends on effort (low softly or low loud the singer sings).

The objective is flat frequency response not from production microphone to reproduction loudspeaker but in a much broader sense from producer's brain to listener's brain.

Further Reading:

Elements of Sound Recording - Frayne, Wolfe

Sound Picture Recording and Reproducing Characteristics, D.P. Lowe, K. F. Morgan - Journal of the Society of Motion Picture Engineers