I have to admit, I have never used pro monitors in my home. But, I am assuming (yes, assuming) that they would be more accurate
in a home environment than would a standard home system. I also assume that they make good speakers, then label them monitors, for whatever my opinions are worth. I admit that I am currently using home speakers, a pair of Technics SB-L200, in my main system until I get the parts for my DIY speakers. Now for some speculations with a foundation in actual knowledge: both home and pro speakers should ideally have a low amount of intermodulation and harmonic/nonlinear distortion, period. Some companies, however, *cough*Boze*cough* either underestimate the importance of harmonic distortion, or purposely add it, due to the fact that a certain amount of distortion, particularly the second harmonic, adds a degree of perceived "musicality" (note, tube amps add second order harmonic distortion, this is why they sound more musical than solid state), but any harmonics, however musical, reduce accuracy, and are thus in my opinion, the opinion of studios, and what should
be your opinion, a bad thing. So if we have a theoretical set of speakers, one the perfect monitor, the other a perfect home system, both will share these characteristics (besides the obvious efficiency, power handling, etc):
1. No nonlinear/harmonic distortion or intermodulation, which is linked to rise/fall times
2. Close driver spacing, optimally a coaxial setup (or true fullrange, if one could be made that does not "beam", a.k.a. have poor performance off-axis) so as to combine into a point source at the nearest range possible and have the best performance off axis. If directionality is required, waveguides or horns may be implemented.
3. As flat as possible a frequency response in their intended environment.
As we can see, 3, frequency response, is the only one where environment, home or studio, comes into play. If a designer is creating a monitor for a treated studio, he may (more speculation in this part) wish to engineer it to be flat in an anechoic chamber, which would resemble a full 4 pi radiation pattern. A home speaker, on the other hand, may be placed on a floor, resulting in 2 pi radiation, mounted on a wall, again 2 pi, on the floor against a wall, resulting in pi radiation, or in a corner, resulting in half pi radiation. If free space 4 pi radiation is assumed, mid field or far field frequency response would be flattest with full baffle step compensation, or BSC (look it up, others can explain it better than I). Against a wall, radiating in 2 pi or less, BSC is unnecessary (as any sound that "leaks" behind the speakers is reflected back, this however causes early reflections, reducing sound quality). In a 4 pi radiation, near field environment, such as what should exist in the ideal studio, and as such how most monitors are/should be designed, partial BSC is what is used to achieve the flattest response (in the near field, the "leakage" of the lower frequencies behind the speaker cabinet is less apparent, the closer you are to the speaker the less effect it has).
So in conclusion, the only difference between my "ideal" monitor and home speakers are the amount of baffle step correction applied. That being said, many speaker designers simply ignore BSC, and the results are acceptable. And if you did want to adjust the level of BSC, so as to convert a monitor for home use or vice versa, it would not be that difficult, requiring only a change in value of one inductor in some instances. (The instance I am referring to is a 2nd order electrical passive crossover). My question now is, where do DIY speaker fit in the debate? Oh wait, they're better.