Check out the thread " What would your perfect speakers sound like ".
ELEMENTS THAT AUDIOPHILE SPEAKERS REQUIRE
I was thinking about the key elements that make a great speaker, and came up with this short list;
1, Tonality - a speaker needs to be able to reproduce instruments accurately. A harp needs to sound like a harp. The strings need to sound as if they are plucked.
2. Accuracy - the speakers must be flat across their stated bandwidth...+/- 3 DB 1
3. Dynamics (Attack and Decay) - to effectively portrait the music, the crescendos and Diminuendos must be accurately represented. This keeps one interested and involved in the music.
4. Imaging - to some folk, this is not essential. Certainly it is not as essential as the previous three requirements, but I appreciate a proper stage image.
5 Resolution - the ability to resolve and portray inner detail and nuance of the music.
6. Matched - electronics must match the speakers impedance, sensitivity and overall sound.