I haven't heard the B&O Beolab 5 yet, but seriously doubt the lenses are mere marketing drivel. They address a problem that most loudspeakers have.
Briefly, very few loudspeakers generate a reverberant field that has approximately the same spectral balance as the first-arrival sound. This matters because the ear derives timbre not only from the first-arrival sound, but also from the reverberant energy. Driver beaming is the main culprit; it affects more than just the high treble. For example, in a typical loudspeaker when we cross over from the midwoofer (which is beaming) to a small tweeter, the radiation pattern flares out again and we have excess reverberant field energy in the lower treble region compared to the rest of the spectrum. Under most listening conditions, such off-axis response anomalies are audible and detrimental.
The lenses used in the Beolab 5 address this issue by reflecting the midrange and tweeter's outputs uniformly over a 180 degree horizontal angle. As a result, the reverberant energy has very nearly the same spectral balance as the first-arrival sound. This contributes to natural timbre and long-term fatigue-free listening.
Now I might quibble about the width of the radiation pattern used in the Beolab 5, but imho getting the reverberant field right is a fundamental requirement for natural timbre and something that relatively few loudspeakers do well.
Note also that DSP correction works best with a loudspeaker having a uniform radiation pattern. You see, DSP corrects for the microphone location only; if your speaker has an on-axis dip but an off-axis peak at a certain frequency, boosting that frequency to equalize the on-axis response would be a step in the wrong direction. DSP cannot correct the radiation pattern - it works best when uniform radiation pattern is an innate characteristic of the loudspeaker.
I would expect the Beolab 5 to sound very natural when set up correctly, and not be fatiguing over the long haul. In my opinion it's not the only speaker likely to have these characteristics.
Duke
dealer/manufacturer