I remember back in my old Hi-Fi Stereo hobby days all the terminology and ideas that were used in describing stereo sounds. Some of those ideas and terms apply to acoustic guitars as well. In general like if you are comparing two guitars (A-B-ing), the louder guitar will sound better at first examination and also personal taste and style of playing always applies to any opinion.
Balance...
In a well balanced guitar, all the notes have equal power. The guitar
will not be bass heavy, overly bright sounding or have too much midrange.
Cutting Power...
This is a hard one to describe. Cutting power is the ability of a
guitar to be heard while playing with other instruments. This is not
accomplished by volume alone but by being able to fit in and fill up empty
spots. This term is usually used when describing a guitar in a bluegrass
group. The flat picker will break into a lead and you can hear every note
while others are playing.
Dynamic Range...
The quality of a guitar to go from very soft to very loud with minimal
effort.
Presence...
The best way to think of presence is "Surround Sound." When you
play the guitar loud or soft, the complete quality sound of a fine guitar is
definitely distinguishable from a poorly made guitar.
Separation...
When a guitar has good separation, you hear the individual notes in a chord
very distinctly.
Sustain...
Sustain is the time a note keeps sounding with good tone after you pick the
string. If the note fades out quickly, the guitar has poor sustain.
Tone...
Your guitar has a fundamental frequency of vibration and overtones that are
similar to all other acoustic guitars but it also has its own combination of
tones depending on what it's made of and how it's built. Technically, no
two acoustic guitars sound exactly the same even if they are the same model and
manufacturer.
Volume...
Simply put, some guitars are louder than others. As mentioned above, don't
make the mistake of thinking one guitar sounds better than an other just because
it's louder. All things above need to be considered.
Bob, Gman ( o )==#