WOOD SELECTION
When selecting wood the top is the most important to think about. Adirondack spruce is probably the favorite among many builders for tonal qualities. Adirondack is stiff and has strong, clear tones. Carpathian spruce's quality is very similar to Adirondack. Italian spruce is also another spruce that is stiff. Sitka spruce is the most used top for guitars today. It's stiff ( depending on quality)flexible, and durable.
Engelmann spruce is a good substitute for German spruce. Engelmann has a tone of sitka and cedar combined. Cedar and redwood are softer and warmer sounding. redwood seems to be able to take a little more abuse than cedar.
The back and sides are the reflectors. The top is for producing good tone and the back and sides are for reflecting good tone. The denser woods tend to project sound better than mahogany. If you want a mahogany guitar to be louder, use a good stiff top. You may read that brazilian rosewood is the best wood to use for back and sides. The positive things about it is most of it has been sitting around for years. Another is the tonal quality. The down side is it is very expensive and getting harder to come by. There are quite a few woods that are equal in tonal quality to brazilian rosewood. The two I have used is cocobolo and macassar ebony. The other woods are ziricote, madagascar rosewood, and amazon rosewood. Prices of these substitute woods are sometimes a third to a quarter of the price of brazilian rosewood.
The bottom line is to use a good top and choose what type of back and sides you want to be your reflectors.