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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: Esoteric UX-1, Yamamoto YDA-01, Ancient Audio Lektor Prime, Raysonic Audio CD228 [on loan], Red Wine Audio Isabellina HPA as fixed-level DAC [on review], Wadia iDock [on review], Apple iPod Classic 160GB
Preamp/Integrated: Esoteric C-03 (transistor), ModWright DM 36.5 (valves), April Music Stello Ai500 [on loan]
Amplifier: Yamamoto A-09S, FirstWAtt F5, ModWright KWA-150, Octave MRE-130 monos, FirstWatt J2 [on loan]
Speakers: ASI Tango R, Zu Essence, Pearl Ballerina 301-8" [on review], Amphion Helium 510 [on review]
Headphones: Audio-Technica WHT-5000, Sennheiser HD800 w. ALO harness, Grado PS-1000, AKG-K702 with ALO harness
Headphone amplifier: Yamamoto HA-02, Woo Audio Model 5 with EAT 300Bs, KingRex HeadQuarters [on loan]
Cables: Complete loom of ASI Liveline
Stands: 2 x ASI HeartSon 3-tier, 2 x ASI HeartSong amp stands
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive use of Acoustic System Resonators, noise filters and phase inverters, Advanced Acoustics Orbis Wall & Corner units
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review Component Retail : €515 or $745 outside the EU, €595 inside the EU (includes VAT)


"Headphones", Jan Meier of Corda headphone amp fame contends, "are so unnatural that some people can't ever adapt." That's because with headphones, each ear is isolated to listen only to one channel. In real life and even over regular speakers, such isolation between the ears does not occur. Each hears what the other does. The difference is merely one of minuscule time delays and loudness attenuation (the closer ear hears the sound first and a bit louder than the ear which the head shadows). Our ear/brain mechanism uses arrival time and loudness differences between these cross-fed data to firmly allocate fixed points in space from which specific sounds arise. To get a really precise fix, humans automatically turn their heads back and forth. This adds additional difference points from altered perspectives.


The biology of our head and ears additionally reflects and absorbs certain sound components. These interactions change with the direction of the arriving sound. Related sonic colorations create further data points for directional hearing. Lastly, unobstructed ears receive both direct and reflected sounds. By virtue of their distance from us, conventional loudspeakers involve the room they're in. Hence our room's sonic signature overlays the 'pure' recorded signal.


Now take headphones. Not only do they eliminate natural reflections of sounds before they reach our ears but they also isolate and shield one ear from the other. The left ear only hears the left channel information, the right only the right. This disables the natural cross feed mechanism whereby our brain 'sees' from where sounds arise.


As Jan Meier contends: "All the mechanisms of directional listening are missing when we use headphones. The sound at the right ear will no longer reach the left ear and pinnae reflections no longer interfere with the original sound wave. Moreover, the headphones are directly attached to our head and so head movements no longer add information. Reverberation too is absent and as a result, the sound from headphones seems to stick to the inside of our head and ears to create an unnatural sound field. The brain misses logical directional cues which creates mental stress. Some people cannot tolerate this and are unable to use headphones."


To solve this obvious dilemma, AKG's infamous K-1000 winged ear speakers allowed the user to angle each driver far enough away from the ears to break the hard seal between them. The other ear "listened in" to the opposite channel. By simulating the natural crossfeed which occurs automatically with unobstructed ears, these headphones imaged far more outside the head than conventional ones.


The famous 'all things headphone' company HeadRoom in Bozeman/Montana has popularized their electronic crossfeed circuit which attempts to simulate natural crossfeed with clever signal manipulation. Each channel injects data into the opposite channel by a predetermined amount of signal strength and time delay. Jan Meier of Meier Audio has developed his own circuit which he calls natural crossfeed.

"For optimal performance the natural crossfeed filter needs to see two low-output-impedance input buffers and two high-input-impedance output buffers. If the output impedances of the source are relatively high or if the input impedances of the load are relatively low, strong interactions occur with the filter network and the filter characteristics change considerably. A unique feature of our crossfeed circuitry is that it 'recognizes' the virtual positions of instruments and singers in a recording. The sound of an instrument in the middle of the soundstage will be equally present in both channels to not receive any crossfeed. A crossfeed signal is only generated for instruments that are not placed at the center. The more off-center the instrument, the stronger the crossfeed and the longer its delay.


This guarantees that the filter has no influence on the sound of more central performances (mono signals). This feature is called natural crossfeed and results in more precise imaging than can be achieved with more conventional crossfeed filters that even produce crossfeed with mono signals [and as a result, can diffuse image focus and attenuate the low bass - Ed.]."