Once again some wise words from Duke. The path length of 11 feet or the 10 msec rule of thumb is something you need to consider whatever speakers you have. The rule also applies where you sit (do not sit near a wall). This is one of the reasons that you find main speakers built directly in to a wall in most high end studio setups (no spurious reflections).
One concern with Omnis is the necessary mounting and shapes of the speaker box - inevitably there are often edge diffractions of the sound from mounting posts and many of these designs use surfaces to deliberately reflect or disperse the sound (Beolab 5 for example). Therein can lie a weakness in this type design. The result can be that certain frequencies may collapse to the speaker (as secondary reflections color the sound) even if the majority of the sound is natural and wide open. It is worth auditioning to carefully check for these issues - cymbals can often hint at this issue due to their broad frequency content. I found the Beolab to sound very open on airy on some sounds and less so on others - I wonder if there is not a 3 to 6 db SPL drop and edge diffraction occurring as certain frequencies reach the edge of the reflective discs. Overall the speaker sounds great but these coloration will be of concern to some listeners.
All speakers are trade-offs, Omnis are wonderful sounding but there are some compromises (as with any speaker).
One concern with Omnis is the necessary mounting and shapes of the speaker box - inevitably there are often edge diffractions of the sound from mounting posts and many of these designs use surfaces to deliberately reflect or disperse the sound (Beolab 5 for example). Therein can lie a weakness in this type design. The result can be that certain frequencies may collapse to the speaker (as secondary reflections color the sound) even if the majority of the sound is natural and wide open. It is worth auditioning to carefully check for these issues - cymbals can often hint at this issue due to their broad frequency content. I found the Beolab to sound very open on airy on some sounds and less so on others - I wonder if there is not a 3 to 6 db SPL drop and edge diffraction occurring as certain frequencies reach the edge of the reflective discs. Overall the speaker sounds great but these coloration will be of concern to some listeners.
All speakers are trade-offs, Omnis are wonderful sounding but there are some compromises (as with any speaker).