"Bloom" is a term that can be good or bad, depending on degree. Just as "bass" can be overdone, so can "bloom". I think of bloom as the overtones and air around an instrument or voice. As someone said, it's 3-D rather than a one-dimensional cardboard cutout.
Bloom is generally pleasing and, just as with bass, some systems add too much. Ideally, a great system can extract and present the bloom in a recording without adding more than is really there. It's hard to judge what's right. ARC, Lamm and most other high end tube designs don't add bloom, but I do hear it in some of the lesser tube designs. Some users prefer that sound and it tends to be euphonic.
Dave
Bloom is generally pleasing and, just as with bass, some systems add too much. Ideally, a great system can extract and present the bloom in a recording without adding more than is really there. It's hard to judge what's right. ARC, Lamm and most other high end tube designs don't add bloom, but I do hear it in some of the lesser tube designs. Some users prefer that sound and it tends to be euphonic.
Dave