Disclaimer: I am finally down to Danganronpa's second last pair!! Oh you have no idea how bad I wanted to talk about this manufacturer..
Ever since Ultrasone introduce their proprietary technology, S-Logic™, the legitimacy of their claim has been disputed quite heavily within the headphone enthusiast community.
"...In studying the past, it is clear that S-Logic is the only way to influence stereo or channel tone signals to produce a 3-dimensional auditory event without any digital, binaural processing..." from http://ukrtech.com/root/faqfileref/27049.pdfAccording to the manufacturer, S-Logic™ is an acoustic passive filter that promotes a front-localized surround sound. In short, this is done by creating an accurately controlled acoustic passage through an opening at the bottom part of the front baffle, and the reflected sound wave originated from the port yields directional pinna notches along the frequency spectrum.
|B&K 4128C's HRTF characteristic: 0° / 45° / 90° / 135°|
CON: There's a good amount of linear distorton in the treble due to a lot of baffle reflections.
ON SECOND THOUGHT #1: According to Ultrasone' patent documents and their white papers, the goal of S-Logic™ is quite simple: It is to create a front-localization. Dr. Florian M. König of Ultrasone thinks the in-head localization of headphones is located at the 45° above the listener's sagittal plane, and once it is brought down to the front subjectively, an effective front-localization is achieved.
|Ultrasone S-Logic™ in action on two different individuals|
Front: 260 Hz-550 Hz, 2.5 kHz-6 kHz
Rear: 700 Hz-1.8 kHz, 10 kHz-13 kHz
Above: 7 kHz-10 kHz.
has been proven to be highly ineffective in 1986. However, since HFI-780 still seems to be diffuse-field oriented as seen below, the peak at 10 kHz is most likely a linear distortion.
J. Blauert, "Sound localization in the median plane," Acustica, vol. 22, no. 4, pp. 205-213, 1969-1970.