There are two classes of speakers: ones designed for uniform power + polar response with a monotonic decrease in total output above some frequency, and ones that don't pay enough attention to it.
The former class has the potential to be exceptional when the rest of the design is well done.
In-room performance from the later group of speakers is going to be more room and placement dependent with excellent performance unlikely. Unfortunately most speakers fall into this category due to the way they mate a dome tweeter which starts with low directivity to a mid-range that's becoming directional with a large fraction of a wavelength between them so there's a characteristic notch in total power response.
The Harman group with Floyd Toole, Sean Olive, and Kevin Voecks has put a lot of effort into researching this going as far as applying a computerized speaker movement system to blind tests. The results are that listeners prefer uniformity regardless of musical genre, country of origin, and experience as listeners.
Most of the good class of speakers (Revel Ultima Salon 2, B&W Nautilus Prestige, Beolab 5, MBL, Ohm Walsh, the RAAL Requisite Eternity, Linkwitz Pluto) get there through uniformly broad dispersion. The more conventional examples use acoustically small drivers + baffles and keep the drivers close together. The less conventional use drivers which have 360 degree output in the listening plane.
Your brain does a pretty good job at ignoring reflections that resemble the direct sound, although such speakers are going to suffer some from being close to walls and objects which create early reflections.
The solution to that is narrower controlled dispersion.
Some speakers achieve moderate directivity down to the bottom of their output using acoustic cancellation, with either dipole or cardioid radiation patterns. Such designs have 1/3 the total power output for a given on-axis SPL compared to conventional speakers at low frequencies. To be mathematically correct, a dipole has a cosine alpha polar response which means -3dB at 45 degrees off-axis, -6dB at 60 degrees, -12dB at 75 degrees, and no output 90 degrees off axis. "dipole" speakers with acoustically small radiating surfaces get close with -20dB nulls. The Linkwitz Orion, Audio Artistry line, and NaO take this approach. Planar speakers aren't really dipoles since they're acoustically large at higher frequencies which results in an irregular lobed response. Lyngdorf crosses to conventional woofers at 300hz so they don't count completely. The Jamo R909 baffle and drivers are probably too big to be acoustically small.
Some achieve higher directivity (10dB vs. 4.8dB for the dipoles) at higher frequencies using wave guides which are getting acoustically large compared to the wave lengths involved. Examples would be the Audio Kinesis speakers, Gedlee Abbey/Nathan/Summa, and Danley Sound Labs unity/synergy horns. Anecdotally, Earl's wave guides seem to the only speakers which Orion owners prefer.
Emerald Physics has combined a dipole at low frequencies to a wave guide at high.
