When I sing low in my range (notes around G2-A1), I often get a really resonant, airy sound that is quiet enough that it cannot be heard when singing in a group setting. How can I make these notes louder? Should I try to produce a sharper tone?
It's difficult to get as much projection and power in the low end of your range because to sing low notes - you must relax your vocal chords - which entails relaxing all the muscles that control the vocal chords.
If I'm singing Johnny Cash or Josh Turner I will usually use a microphone and take advantage of the proximity effect. As I get to the lower and quieter end of my range, I hold the microphone closer to my mouth.
To get more volume on the lowest notes when singing without a microphone, you will need to push a more powerful blast of air across your relaxed vocal folds. One way to do this is to tense your abdominal muscles as if you were bracing for a punch in the stomach. This will effectively produce a more forceful contraction of your " diaphragm" and your pelvic floor muscles.
Some people are able to get a slight boost in volume on the lowest end of their range by turning their head sideways. I am not sure why it works but it works for me as well.
You may find that when singing your lowest notes, a slight smile as you sing them will brighten them up a bit.
Whenever you sing, you should spend some time warming up your voice with some easy vocal exercises to get all the muscles that contribute to vocalization moving around with minimal stress. Then they will be more relaxed and resilient when you start testing the limits of your range.
You may find some useful information in this Music Stack Exchange Question as well: How to Extend your Lower Range on Stack Exchange Music
Finally a vocal coach or teacher may be able to help you develop some techniques and give you some exercises to help you expand your range.
Good luck and mostly have fun singing.
The fact that you are projecting in your high range but not in your low range makes me suspect you are singing too much with your throat and not enough with your diaphragm. It should be easier to project in the low range because you can more easily relax your whole instrument, but if you let your diaphragm relax also, then you won’t push the air that you need to project. No matter what note you are singing, you want everything to be open and relaxed except your diaphragm, which should be pushing air. That is where all of your power comes from.
A great exercise is to lay flat on your back on the floor, which tends to put your whole instrument in a relaxed state that is ideal for singing. Then place a hand flat over your diaphragm and focus totally on it, let your belly expand as you pull in a full breath, and push air through some big fat long low ahhhhhh notes. Psychologically, it can help to imagine your hand is sort of pushing the air out, but you really let your diaphragm do the pushing. Over time you should be able to project any note in this way, with the entire instrument relaxed except the diaphragm pushing air. High note, low note — doesn’t matter.