I would like to re-open discussion on three-dimensional sound reproduction by means of a pair of properly designed loudspeakers.

Time coherence had been a major passion of late Jim Thiel and the Thiel successors continue to follow the path of the founder of the Thiel loudspeaker company. Having owned over the last 20 or so years CS6, CS2 and CS1 each in the first version and still owning a pair of  SCS4 for my small listening room featuring a fine coaxial chassis I can understand and appreciate the advantages provided by time coherence.

Starting with the Munich High End Show 2012 I made the acquaintance of the FA5.3 of Foerster Audiotechnik of Germany also claiming time coherence as one of the top priorities. I recently visited FA at their manufacturing site near Munich to listen to the bigger brother FA3 of the FA5.3 which excelled at the 2012 show with a surprisingly holographic but nevertheless musical sound in an acoustically well prepared show room. The FA3 which did not surprise me sound-wise after the very good impression I could gain from the FA5.3 is my favorite candidate of a big floor standing loudspeaker for my main listening room since it does nearly holographic wonder on all kind of music without neglecting all the other parameters of sound reproduction over the whole frequency spectrum needed to finally arrive at convincing music reproduction.

How does FA provide 3D sound out of only two loudspeakers? One aspect obviously is individual positioning of the chassis not in the kind suggested by Jim Thiel using a slanted baffle board but by shifting position of the tweeter – a Manger transducer in case of the FA3 – in combination with a special construction of crossover I could not get further information. In addition each pair of loudspeakers finally is said to be tuned by ear in the literal sense (don’t know how) in a time consuming process using recordings of acoustic instruments as for instance an acoustic guitar. The outcome is nothing but overwhelming in my opinion since the sound is precise without ever being aggressive and completely natural, pin-pointing at the sound sources and reproducing them in the correct dimension. Dynamic of the FA3 is nothing but awesome.

The 3D ability of the FA loundspeakers is mirrored by the step response shown at the website of FA for the FA5.3: http://www.foersteraudiotechnik.de/zeitrichtigkeit_en.htm

FA claims the FA3 to feature the only Manger system operating time-coherently. This is said to be shown by  the time of the zero-crossing of the step. 

Further requisite for time-coherence is said to be same polarity of all chassis a requsite nearly never realized  by loudspeaker manufacturers and may be the reason why manufacturers desist from publishing the step response of loudspeakers.

Receiving remarks on the above would be appreciated.

Does anyone know of an alternative working approach to attain at 3D sound out of a pair of loudspeakers?