“I cannot state with certainty what might be the factor for this. However, I do wonder if the narrow vertical directivity is one such factor (or even the factor). The majority of speakers I have heard thus far generally exhibit a vertical radiation pattern in the neighborhood of ±40 to ±50°. The Perlisten S4b, however, has a radiation pattern from ±20° ±30° thanks to the tweeter/midrange waveguide assembly. The center-to-center spacing of the midrange drivers is approximately 103 mm which yields a beaming point of approximately 850 Hz (using 1/4-wave; or ~1700Hz using 1/2-wave). The use of this vertical array with smaller drivers could, in some ways, be considered like a ribbon tweeter where the narrow width allows wider horizontal directivity, but the taller height limits the vertical radiation”

Audiograde Editors Choice review for S7t LE
“Uncompromising loudspeaker that offers exceptional performance”