This article is from the Audio Professional FAQ, by with numerous contributions by Gabe M. Wiener others.
It depends upon who you ask. There are speakers called "monitor"
speakers that are found almost exclusively in homes and never in
studios.
The purpose of a monitor speaker is to monitor the recording and
editing process. If you buy the concept that they are but one tool in
the process (and probably the most frequently used single tool at
that), and if you buy the concept that your tools should be flawless,
than the requirements for a monitor speaker are easy to state (but
hard to achieve): they should be the most neutral, revealing and
unbiased possible. They are the final link between your work and your
ears, and if they hide something, you'll never hear it. If they color
something, you might be tempted to uncolor it incorrectly the other
way.
There is another camp that suggests that monitor speakers should
represent the lowest common denominator in the target audience. The
editing and mix process should be done so that the results sound good
over the worst car speaker or boom box around. While such an idea has
validity as a means of verifying that the mix will sound good over
such speakers, using them exclusively for the process invites (as has
been thoroughly demonstrated in many examples of absolutely terrible
sounding albums) the possibility of making gross mistakes that simply
can't be heard in the mixing process. [Dick]
 
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