Asking questions about improving the speaker/room interaction is, imo, asking the right questions. The speaker and room form a system, and these two parts of the system do not always work well together. But they can.
In my opinion the best approach is to examine what causes negative room interactions and try to address those causes. I realize that's more complicated than simply replying with "monitors are better" or "floorstanders are better", but play along for the next few paragraphs.
Standing waves in the bass region are inevitable from any given bass source within the room, but their peak-and-dip patterns can be de-correlated somewhat and thus minimized by having multiple bass sources spread around the room. This results in multiple dissimilar standing wave peak-and-dip patterns, whose sum is smoother than any one of them alone. A floorstander designed with this in mind can spread the bass sources further apart than can a stand-mount speaker simply because there's more physical distance available within a bigger box. But if the design doesn't spread the bass sources apart, then a floorstander has no inherent advantage over a stand-mount in this area.
In some cases the ability to make broad adjustments to the shape of the low-frequency response can be useful to deal with too much or too little boundary reinforcement. User-adjustable port tuning would be one way to do this.
Reverberation is beneficial in many ways if done right. It enriches timbre, spaciousness, sense of envelopment, and even clarity. What is reverberation "done right"? Well, what you get in a good recital hall would be an example: the reverberant field is spectrally correct, diffuse, arrives after a fairly long time delay, and decays smoothly across the spectrum. Some of these characteristics are largely room-acoustics-dependent, but the loudspeaker system can either work with or against the room based largely on what it's doing off-axis. Imo the floorstander format offers more opportunity for the designer to do a system that works with rather than against the room, but if he doesn't do that, then once again a floorstander has no inherent advantage.
Slap echo is a room acoustics problem, but a relatively uniform and somewhat narrower than normal radiation pattern, along with aggressive toe-in, will help avoid undesirable strong early sidewall reflections. Some rooms are simply inherently brighter than others, and a low-distortion means of adjusting the high frequency balance of the system can be useful.
Getting a good speaker-room interaction is something I have put a bit of study into. In my experience speakers that do a good job of getting the reverberant field right tend to be more engaging and less fatiguing long-term. But I'm certainly not the only designer to attach high priority to getting the reverberant field right (which admittedly can mean different things to different designers).
Duke
dealer/manufacturer
