Stereophony purified...
...finally, simply and truly 3D.
Stereo purification based on individualized HRTF measurement, automatic 3D audio filter design, BACCH® 3D Sound processing, advanced sub-millimeter head tracking, and a dynamic 3D audio sweet spot...
...virtual reality for the audiophile.
"I heard a spatial representation that was indistinguishable from real life."
Robert Harley, Editor, The Absolute Sound
"The reverberation on the recordings was now a stable,
solid halo around the performers, just as it is in reality."
John Atkinson, Editor, Stereophile
Most Significant Product Introduction at CES 2015
"This is no hat trick; it's true 3D audio that can literally put a whisper in your ear."
Allan Taffel, The Absolute Sound
"One of the biggest and most mind-boggling moments of CES 2015.
The 3D-ness of the presentation was absolutely startling.
...[it] literally dissolved both the speakers and room..."
Michael Lavorgna, Editor, AudioStream
"When you experience the full effect of Dr. Choueiri's engineering, you will see the future and know that it is now."
Herb Reichert, The Audio Buzz
"Sound quality did not suffer one iota: this was all about reproducing
an authentic soundfield, which it achieved in spades."
Ken Kessler, Soundstage! Hi-Fi
"Better sounding than stereo, better than 5.1, better than 10.2!"
Bob Katz, Grammy Award-winning Audio Mastering Engineer
The BACCH® Stereo Purifier (BACCH-SP) is a state-of-the-art, high-definition, digital audio processor that yields highly realistic 3D sound imaging from a pair of stereo loudspeakers.
At the heart of the BACCH-SP is BACCH® 3D Sound technology developed at Princeton University, which purifies stereo audio signals from the crosstalk inherent in loudspeaker-based playback, allowing the listener's brain to receive the proper psychoacoustical cues that are needed to localize recorded sound sources realistically in 3D space.
The BACCH-SP is the most advanced digital audio processor for music playback today as it incorporates, for the first time outside the laboratory, a number of advanced technologies that combine to offer what amounts to a virtual reality sound experience for the audiophile. These technologies include:
  1. Individualized tonally-transparent crosstalk cancellation filters (called BACCH® filters) designed from quick calibration (impulse response) measurements made by the listener using calibrated binaural microphones placed in the listener's ears.
  2. Real-time adjustment of the 3D audio sweet spot through high-resolution tracking of the listener's head position (even in pitch darkness) using a 3D infrared camera and advanced custom-built head tracking software.
  3. 64-bit audio processing through a dedicated multi-core CPU running custom-built algorithms and optimized convolution engines.
  4. Wi-Fi control of all BACCH-SP functions through an intuitive iPad controller on a dedicated iPad that serves as the sole remote control.



The BACCH-SP produces an individualized BACCH® filter for each listener from quick impulse response measurements with calibrated in-ear microphones. The BACCH® filter purifies the audio from the crosstalk that corrupts the proper transmission of ITD and ILD cues to the listener, leading to truly 3D sound imaging with zero tonal distortion.

The BACCH-SP tracks the listener's head in real time using an infrared sensor and adjust the audio sweet spot to move with the listener for a seamless 3D sound stage.

individualized BACCH® filter generation
64-bit processing
sub-millimeter head tracking
31-band 1/3-octave speakers equalization
8th-order 3-band crossover network
display of crosstalk cancellation performance
test signal generation
multi-I/O switching and pristine AD/DA conversion
Stunning 3D audio...
...tailor-made for your head.
Manufactured in Princeton, NJ, USA.
Digital In: S/PDIF (RCA), USB
Word Clock In & Out (BNC)
24-bit Audio, 64-bit Processing | Sampling Rates: 44.1, 48, 88.2, 96, 176.4, & 192 kHz
Dedicated iPad as Remote Control | Remote Technical Support, Maintenance, and Software Upgrades via the Internet
Integrated DAC, ADC, and Three-Level Preamplifier
Analog I/O: XLR, TRS, RCA
SNR: 113 dBa, THD: <-105 dB, <0.0005%; Channel Separation: >110 dB; Max Input Level +19 dBu; Input Impedance: 10 kΩ
Professor Edgar Y. Choueiri
Photo by Josef Astor
Edgar Choueiri, who conceived, designed, and developed the BACCH-SP, is Professor of Applied Physics at the Mechanical and Aerospace Engineering Department of Princeton University, and Associated Faculty at the Department of Astrophysical Sciences, Program in Plasma Physics. He is also Director of Princeton University's Engineering Physics Program and Chief Scientist at the university's Electric Propulsion and Plasma Dynamics Lab, a leading research laboratory in the field of advanced spacecraft propulsion. He is also the director of Princeton University's 3D Audio and Applied Acoustics (3D3A) Lab.
Professor Choeuiri is a world-renowned leader in the field of plasma physics and plasma propulsion for spacecraft. He is the author of more than 225 scientific publications and encyclopedia articles on plasma rockets, plasma physics, instabilities and turbulence in collisional plasmas, plasma accelerator modeling, space physics, and applied mathematics. He has been the Principal Investigator (PI) in more than 30 competitively selected research projects (including two space experiments), funded by NASA, the US Air Force, the National Science Foundation, and other governmental and private institutions. He is Fellow of the American Institute of Aeronautics and Astronautics and the recipient of many awards and honors, including a knighthood.
An avid audiophile, acoustician, and classical music recordist, his decades-long passion for perfecting the realism of music reproduction has led him to work on the difficult and fundamental problem of designing advanced digital filters that allow natural 3D audio to be extracted from stereo sound played through two loudspeakers, without adding any spectral coloration to the sound (i.e. without changing its tonal character). He was able to solve this problem mathematically by applying analytical and mathematical tools he uses in his plasma physics research. The resulting patented method lies at the heart of the BACCH-SP.
For more information on the 3D3A Lab, BACCH® 3D Sound, and related press and media coverage, visit:



Innovative Audio Video

150 East 58th Street

Manhattan, NY



Audio Concept

Södra Agnegatan 29

112 29 Stockholm



Absolute Sounds Ltd.

58 Durham Road

SW20 0TW, London


The BACCH-SP is an audiophile-grade BACCH® 3D Sound digital processor manufactured by:
Theoretica Applied Physics
Princeton, NJ, USA
BACCH® is a registered trademark of Princeton University.
US Patent 9,167,344 (Spectrally uncolored optimal crosstalk cancellation
for audio through loudspeakers). Granted October 20, 2015.
US Patent 6,243,476 (Binaural audio for a moving listener) is
licensed exclusively to Theoretica by the MIT Media Lab.
The lyre player in the Theoretica logo is reproduced from an ancient Greek black-figure
pseudo-Panatheanic amphore painted by the "Princeton Painter," circa 530 BC.
The amphora is the property of Theoretica Applied Physics.
The Theoretica 3D Arpeggio, heard by clicking the Theoretica logo, was created by permission
of the composer, Michael Levy, using an audio excerpt from "Hymn to Hermes" played by the composer
on a replica ancient Greek lyre. From the album "The Ancient Greek Lyre," available on iTunes.