Reviewers' ChoiceTheoretica Applied Physics, based in Princeton, New Jersey, has the most revolutionary digital signal processing (DSP) technology you’ve never heard about. The company’s website states that this technology, the Band-Assisted Crosstalk Cancellation Hierarchy-Stereo Purifier (BACCH-SP), uses digital interaural crosstalk cancellation (IXTC) to create “unprecedented spatial realism . . . [thus] allowing the listener to hear . . . a truly 3D . . . sound field that is simply unapproachable by . . . existing high-end audio systems.”

Mere marketing hyperbole? In a High End 2016 show report, SoundStage! veteran Brent Butterworth concluded that a BACCH-SP demo he attended was “one of the most convincing and dramatic I’ve heard in my 26 years of attending audio shows.” Also at that demo, SoundStage! founder Doug Schneider said that it was the best sound he’d heard. Brent’s report on the BACCH-SP demo at High End 2017 was no less glowing.


Having heard several IXTC products over the years, I wanted to check out Theoretica’s BACCH-SP for myself. As luck would have it, I found out that it would soon be demonstrated at an audio dealer nearby. My SoundStage! Global article on that demo appeared last year. Briefly: I arrived to find a playback system that included a Theoretica BACCH-SP adio, which includes a built-in digital-to-analog converter ($23,800 USD base price). When the demo began, the attendees, me included, were astounded. The BACCH-SP adio enabled that already accomplished system to create shockingly realistic and correctly placed three-dimensional (3D) images. As if that weren’t enough, the adio pulled off another startling feat: It caused music played through a pair of headphones to appear in sonic character and location as if it were coming from the system’s floorstanding speakers.

With the pillars of my audio foundation shaken, I requested an adio review sample.

Lions and tigers and IXTC, oh my!

Crosstalk is an audible artifact created by virtually all stereo playback systems. It occurs when sound from the left channel reaches the listener’s right ear or sound from the right channel reaches his left ear. Crosstalk hinders the human ear-brain system’s ability to fully decode the spatial cues preserved in most stereo recordings, thus preventing the listener from experiencing aural images and soundstages that are convincingly 3D.

IXTC generally sends an inverted and delayed canceling version of the left-channel signal to the right-channel speaker, and vice versa. In this way, images are freed from the area between the speakers and become much more realistically 3D.

Over the years, IXTC technologies that function in the time domain have been designed by such audio pioneers as James Bongiorno, Bob Carver, and Ralph Glasgal. Their attempts have varied in sophistication and effectiveness, and often suffered one or more downsides, such as spectral coloration and the creation of a too-narrow 3D sweet spot. Likely for these reasons, IXTC technologies have not been widely adopted.

Enter Theoretica’s founder and the brains behind the BACCH-SP technology: Edgar Y. Choueiri. A leading plasma-physics and spacecraft-propulsion scientist and an audiophile, Choueiri is a Professor of Applied Physics at Princeton University’s Mechanical and Aerospace Engineering Department; an Associate Faculty of Princeton’s Department of Astrophysical Sciences, Program in Plasma Physics; Director of Princeton’s Engineering Physics Program; Chief Scientist of Princeton’s Electric Propulsion and Plasma Dynamics Lab; and founder and Director of Princeton’s 3D Audio and Applied Acoustics (3D3A) Lab, which studies human spatial hearing.

Choueiri states that, while working in the 3D3A Lab in 2009, he developed a digital IXTC filter that he called a BACCH filter of unprecedented effectiveness, and that did not suffer any of IXTC’s downsides. According to him, this filter, which operates not only in the time but also in the frequency domain, also corrects for numerous problems inherent in stereo signal reproduction that are unrelated to imaging (e.g., comb filtering).


The BACCH filter is predicated on comprehensive measured samples of the head-related transfer function (HRTF) taken with sinewave sweeps. These sweeps cover the entire listening chain -- the stereo system’s components and loudspeakers, even the listener’s head, torso, and ears. The ears are measured by BACCH-BM binaural microphones placed in the ear canals, like in-ear monitors.

To run the BACCH-SP filter, Choueiri designed the software and hardware that formed the basis of the three audio components Theoretica currently makes. He claims that, except for the size of the 3D sweet spot, the first generation of his IXTC system worked perfectly. That spot extended quite far behind and in front of the listener -- up to two meters in each direction, and farther with speakers that are not highly directional. However, as with many past IXTC technologies, the sweet spot was quite narrow, extending only about 4” on either side of the listener’s head.

To address this limitation, Choueiri developed a camera-based mechanism to work with his BACCH-SP system. This mechanism laterally tracks the position of the listener’s head and continuously repositions the 3D sweet spot, so that the listener hears uninterrupted 3D sound. With this mechanism, the sweet spot ends only at the point(s) that the camera loses sight of the listener. This allows the listener to move around on a large sofa without ever leaving the sweet spot. Listeners sitting outside the spot hear traditional stereo sound.

However, while the head-tracking mechanism permits the 3D sweet spot to move laterally, that spot is still wide enough to accommodate the head and ears of only one listener. Nonetheless, Choueiri states that, except when using highly directional speakers, such as horns and electrostatics, as many as five people can experience much of BACCH’s benefits -- if they sit single file, one behind the next.

Next, Choueiri brought the BACCH technology to headphones by developing the optional BACCH-HP (for headphone) module. This, he says, creates a filter that enhances the stability and realism of binaural and traditional stereo recordings played through headphones.

As I experienced at the dealer demo, the BACCH-HP module also does something unfathomable: it perfectly emulates, in sonic character and location, the sound of freestanding speakers, even very expensive ones, through even inexpensive headphones. Remarkably, the BACCH-HP module seems to eliminate headphones’ main weakness: the experience of hearing the sound inside the listener’s head. I couldn’t tell that the sound was not coming from the speakers. Want your friend to hear your system and speakers through his system and headphones? He can do just that if he has a BACCH-HP module and both you and he have given Theoretica permission to electronically transfer your BACCH-SP filter to his BACCH component. With the touch of a button on Theoretica’s iPad app, the sound is then reproduced through your friend’s headphones in your system’s version of 3D.

BACCH is also compatible with traditional stereo and binaural recordings, both of which contain spatial cues, otherwise corrupted by crosstalk, that allow the brain to perceive a sound’s location in 3D.

According to Choueiri, BACCH-SP is far more effective than other IXTC technologies because it’s measurement-based and, in working in the frequency domain, it separately cancels IXTC for each frequency. Indeed, after hearing a BACCH demo, Tesla’s Elon Musk awarded the 3D3A Lab a research grant to optimize the sound systems installed in Tesla cars. Further, BACCH products are the only ones that have been approved by Princeton to bear a seal stating they were invented at the university. This seal appears on the BACCH-SP adio’s rear panel.

Still, like other IXTC products, BACCH-SP is not without limitations. First, while the technology is claimed to improve the imaging abilities of any stereo speaker pair, those with high sound directivity will yield the best results in a reflective, untreated room. However, Choueiri asserts that even low-directivity speakers fed a BACCH-SP-processed signal will produce greatly enhanced imaging in typical listening rooms, and spectacularly enhanced imaging in rooms treated with sound-absorption products.

Second, Choueiri states that traditional stereo recordings range from those that preserve natural spatial cues (e.g., well-recorded acoustic jazz and classical performances) to those in which the spatial imaging is artificially constructed by recording engineers using panned sources (e.g., most multitracked pop-music recordings). For the former, Choueiri states, BACCH creates the same realistic 3D images as do binaural recordings, except that the locations of sound sources within the 3D soundfield may vary from their actual locations to a degree insignificant for music-listening purposes. For the latter recordings, Choueiri states, BACCH frees the fabricated image from the area around the speakers and projects it in 3D.

Third, BACCH was not designed for a group of people to simultaneously listen to 3D music, except in the unlikely case where they sit one behind the other. Only the listener whose head has been tracked will benefit from the technology; other listeners sitting outside that narrow spot will experience ordinary stereo sound.

Finally, while BACCH improves the imaging of stereo recordings, it has no effect on monaural recordings, which don’t contain the requisite spatial cues. BACCH may also not substantially improve stereo recordings whose content is mostly monaural.

Pay no attention to the IXTC behind the curtain.

Theoretica makes three BACCH-SP audio components: 1) the dio (digital input/output), a 3D digital processor with no DAC ($19,800 base price); 2) the adio (analog/digital input/output), with DAC and ADC ($23,800 base price; $34,430 as configured for this review); and 3) the Grand, with practically every known audio input/output format, including AES/EBU and AES3id ($54,000 base price).

Lacking only a power amplifier and speakers, and controlled by an Apple iPad (included) with the BACCH-SP app preinstalled, the adio’s small size and spartan front panel -- it has only a single button and an amber LED power indicator -- make it look like an all-in-one “lifestyle” audio component. It is anything but.

The adio’s heart is its 64-bit, multi-core central processing unit (CPU), which runs the BACCH filter’s proprietary algorithms, and the so-called optimized convolution engines that numerically apply the filter to the digital signal. The adio’s sigma-delta DAC and ADC each operate at resolutions of up to 24-bit/192kHz. The adio’s word clock times those converters, and can serve as a master clock to control external digital devices. (There is also a clock input for slaving the adio to an external master clock.) The BACCH-SP adio has a linear power supply made by MSB Technology, a preamplifier with a digital volume control and three selectable impedance levels, and a headphone amplifier.


The adio provides two ways of processing a digital input signal: 1) at the signal’s native sampling rate, or 2) up- or downsampled to 24/96. Analog inputs are sampled at 24/96 through the ADC. Since Choueiri is an avid collector of analog master tapes, he ensured that, in addition to an input for an external phono stage, the adio includes one for analog tape decks. In fact, the adio can apply a digital version of Dolby A professional noise reduction to a similarly encoded incoming analog signal.

The adio includes Roon compatibility, and can be configured as a Roon core or endpoint player to stream Tidal and Qobuz. It has a 250GB solid-state hard drive that is generally non-user accessible and comes pre-loaded with a collection of binaural recordings from Chesky Records, who consult with Choueiri on their binaural recording projects. To accommodate the user’s own collection of music files, the adio can be connected to a NAS drive.

The extremely sleek iPad app permits the control of settings such as on/off and input/output selection, and adjustment of volume, mute, and digital crossover, as well as settings specific to BACCH-SP. The app also displays a huge amount of helpful information, including the adio’s internal temperature and that of 16 of its critical components (e.g., its CPU). If the 3D Audio Analysis Software Toolkit option is purchased ($1000), the app will display XTX and IR measurement plots (see below).

When used with its individually equalized BACCH-BM (for binaural microphone, included), the adio can make binaural recordings. Up to three such recordings, each up to 15 minutes long, can be stored on the internal hard drive.

The adio’s rear panel offers an enormous range of connections. The digital ports comprise: USB in; S/PDIF optical out; Ethernet, for attaching a NAS and allowing Internet audio streaming, remote tech support, and firmware upgrades; and word clock (BNC) and S/PDIF (RCA) inputs and outputs. On the analog side are one pair each of RCA, XLR, and TRS (tip/ring/sleeve) inputs and outputs, the latter commonly found on pro audio devices. Also on the rear panel are a headphone jack, a fuse bay, a 110/220V selector, an IEC power inlet, and two BACCH-SP-specific connectors: a USB port for the head-tracking functionality, and stereo XLR mike inputs.


Choueiri says that Theoretica’s frequent releases of free firmware updates containing improvements and features render the adio future-proof.

My review sample of the BACCH-SP adio contained all of the available options:

  • BACCH-BM Pro binaural microphone ($1630)
  • 64-bit digital crossover software with individual band attenuation, configurable to accommodate subwoofers and bi- and triamping ($2000)
  • Infrared camera for head tracking; works in any lighting condition, including complete darkness, at distances of up to 6’ 6” ($1000) (The webcam included standard with the adio works in dim and brighter light at distances up to 26’.)
  • BACCH-HP headphone module ($3000)
  • 64-bit, 31-band digital equalization software, to allow the adio to compensate for room modes and speaker colorations ($2000)
  • 3D Audio Analysis Software Toolkit, to create XTC and IR measurement plots. An XTC plot shows room-related crosstalk information. An IR plot displays such things as room reflections. ($1000)

Add all those to the BACCH-SP adio’s base price of $23,800, and the total comes to $34,430. The adio weighs 24 pounds, and measures about 17.5”W x 3.25”H x 13.25”D. Its case, also manufactured by MSB Technology, comes in standard finishes of matte black or silver; other finishes are available for an additional charge.

We’re off to see the IXTC wizard, the wonderful IXTC wizard of Oz.

Edgar Choueiri visited my home to oversee setup of the BACCH-SP adio. Using its four supplied metal cones and coasters, we placed the adio on a Symposium Acoustics stand. We then screwed the standard webcam (later replaced by the optional IR camera) onto the tripod, and connected it to the adio with its supplied cable.

After booting up the adio and its iPad, we heard the sound of a Greek lyre, which is generated whenever the adio is booted up. (A lyre is part of Theoretica’s logo.) We configured the adio’s inputs and outputs from the iPad app’s main screen so that the adio could receive an analog signal from my SACD/CD player-DAC, perform the necessary processing, and pass that analog signal along to my preamplifier.

Next we set up the head-tracking functionality, which requires pointing the infrared sensor toward the listening position and choosing a setting in the app that sets the physical limits of a virtual box in which the adio looks for a human head.

The head-tracking setup process completed, a crosshair centered on a point representing the position of my head appeared on the iPad. Thereafter, the crosshair followed my head’s position in real time. In preparation for the two-step process of creating our first BACCH filter, I positioned the BACCH-BM binaural mikes, which we connected to the adio via long, included XLR cables.


We then made my first BACCH filter, a roughly two-minute process. I sat in the center of the sweet spot (my sofa) and pressed a button on the app that sent a five-second exponential sinewave sweep through each speaker. A recorded voice (Choueiri’s) then instructed me to move to the left edge of my sofa, but not to leave the camera’s field of view. Two more sweeps were triggered, at which time we repeated the process for the sofa’s right edge. The adio then processed the measurements, created a filter, and stored it in one of its seven erasable digital bins.

We were now ready to listen to 3D music. Choueiri noted that while it’s best that each frequent listener make and store his or her own BACCH filter, anyone else listening to any of the filters would enjoy much of the adio’s imaging benefits.

He also pointed out a button on the app that bypasses BACCH processing, for easy A/B comparisons of its effects. Not being a headphone guy, and having auditioned the BACCH-HP module at the dealer demo, I didn’t further test that feature.

The adio’s excellent owner’s manual made setup surprisingly easy, and technical support is handled directly by Theoretica. Customers with any problems e-mail Theoretica and, Choueiri told me, typically quickly receive a phone call from the company.

Toto, I’ve a feeling we’re not in Kansas anymore. We must be over the IXTC rainbow!

My time with the BACCH-SP adio revealed that it’s no mere parlor trick. It transformed my stereo system’s ability to reproduce aural images, and thus my immersion in musical realism. Still, giving in to my inner geek, I began with nonmusical test tracks from one of the binaural recordings preloaded on the adio’s internal hard drive: Dr. Chesky’s Sensational, Fantastic, and Simply Amazing Binaural Sound Show! (24-bit/96kHz FLAC, Chesky).

In addition to musical tracks selected from the catalog of Chesky Records, the Sound Show includes test tracks featuring microphone, tone, and channel checks, as well as recordings of David Chesky talking while walking around inside the former Manhattan church that his label uses as a recording studio; wielding a buzzing electric shaver around the sides of a binaurally miked kunstkopf, or dummy head; and of “Edgar the Barber” talking while snipping a pair of scissors around the dummy head, as if giving it a trim. The barber is Edgar Choueiri.

When I hit Play on the adio’s app, my room’s acoustic was supplanted by those of the large church, with its tall ceiling and pronounced reverberations. As Chesky walked, his voice clearly moved from one end of the church (it seemed many yards behind my speakers), to a point midway along the church’s length (where my speakers stood), and then to the church’s other end -- which, at alternating times, seemed only a few inches from each of my ears. The scissors and shaver clearly circled the dummy head, moving from front to back and from top to bottom of the head.

Similarly, using the adio’s internal recorder, we recorded Choueiri as he clapped his hands, talked, and whispered, all while circling me at varying distances. Playing this back was mind-blowing: Starting midway in the left half of my room’s front wall, Choueiri’s voice moved around me leftward to a point midway on the left sidewall, then to a few inches from my left ear, and finally behind me. This procession was then repeated on the right side of the room, all with rock-solid stability and eerie realism. When Choueiri’s voice was at 9 o’clock, I hit the Bypass button and his voice reappeared at 11 o’clock, roughly behind the outer edge of the left-channel speaker.


After this stunning technical demo, I was ready for some music. Stereo imaging from a standard two-channel system can be breathtaking. Still, such systems suffer drawbacks. First, they create the impression of some invisible force drawing musicians and even audience members to the area between the speakers, even if those images do occasionally and dramatically escape out into the room. With the BACCH-SP adio and the right recording, that invisible force was switched off like a flashlight -- performers were unshackled from their fixed positions between the speakers and now were discrete in width, depth -- and, where appropriate, even height.

Second, for music recorded before a live audience, traditional stereo systems can reproduce reverberation sufficiently well to create a good sense of the original venue’s space. But there’s a big difference between providing a diffuse feeling of space and reproducing reverberation itself as part of a clear and distinct 3D sound. The adio did the latter, and the result was vastly more reverberation, sonic fullness, and immersion in the music and what seemed to be its original soundfield than I have ever experienced from a standard stereo system.

The BACCH-SP adio could work its 3D magic with recordings of many or only a few musicians. Take “Sweet Papa, Mama’s Getting Mad,” from jazz trombonist Wycliffe Gordon’s Dreams of New Orleans (24/96 FLAC, Chesky), another Chesky binaural recording preloaded on the adio’s hard drive. In this duo recording, Gordon, here playing trumpet, is in the left of the soundstage, with Matt Munisteri on guitar on the right. The adio placed Gordon and Munisteri separately, each against the appropriate wall of my room, each far from the left or right speaker. Even more remarkably, while Munisteri was on a lateral plane with the speakers, Gordon was positioned many feet into the room.

Further, the reverberations created by the sounds of the two instruments were so clear that it was almost as if Choueiri had suspended dedicated reverb speakers in mid-air. As if all that were not enough, there was impressive snap detail from Matt Munisteri’s guitar, and, from Gordon’s trumpet, gorgeous, metallic brilliance infused with overtones.

The BACCH-SP adio produced breathtaking 3D sound from Chesky’s binaural recordings, without exception. For example, in the Adagio -- Allegro con brio of Beethoven’s String Trio No.3 in G, Op.9 No.1, performed by the Baillie String Trio (24/96 FLAC, Theoretica), the adio placed the players, recorded in a small chamber-music room with a solidity and dimensionality I had never heard before: violin on the left, straddling the left wall and closest to the audience, viola at middle rear, and cello on the right, but not quite as close to the audience (and me) as the violin. The reverberations of sounds made by the instruments, the performers’ bodies, the audience, and what sounds like the cello being plunked down on a bare wooden floor -- were stunningly and, for me, unprecedentedly real. Again, 3D considerations aside, the leading edges of notes were clean and precise, and the cellist’s lower-frequency bowed notes were powerful, vibrant, and beautifully dark.

Traditional stereo recordings from my own collection did not, in every instance, yield the same dramatic 3D results. The level of improvement varied, and the soundstaging of a few that have poor stereo imaging to begin with was not greatly improved. However, the vast majority of traditional stereo recordings I played were improved to some degree or another, most of them significantly.

The soundstage of “Gloria’s Step (Take 2),” from the Bill Evans Trio’s Sunday at the Village Vanguard (16/44.1 FLAC, Riverside/Original Jazz Classics), unfolded stunningly. Evans’s piano at extreme right was also well into my listening room at 2 o’clock or greater. Scott LaFaro’s double bass was at left and clearly in front of the left speaker, though not as forward as the piano. Paul Motian’s drums were slightly to the left of center, behind the other two instruments. His snare and cymbal work seemed to reverberate more or less uniformly in the room, and the piano notes reverberated very clearly off the right wall.

The BACCH-SP adio also produced striking 3D sound with “Perfect Sense, Part I,” from Roger Waters’s Amused to Death (16/44.1 FLAC, Columbia), an album so well recorded that it already seems to be in 3D. But with the adio, the opening screaming -- rabid, unexpected, and chilling -- reached so far toward my listening position that I felt I could touch the face producing those sounds.

With these stereo recordings and others, I noticed no anomalies of instrument placement, though I did check a few album covers that pictured the recording venue and performers.

I eagerly turned to my collection of electronic music. Here, as with recordings of acoustic instruments, the BACCH-SP adio reproduced aural images with remarkable solidity and depth, those images now appearing far from my speakers, and with greater apparent space between synths. In any track on Daft Punk’s Random Access Memories (16/44.1 FLAC, Columbia), electronic sounds danced around robotic, auto-tuned voices, spanning the soundstage with a palpability that made every other system’s reproduction of them seem diffuse, lacking in air, and two-dimensional. Low-frequency pulses radiated far along the room’s sidewalls.

Also, with neither binaural nor traditional stereo recordings did the BACCH-SP adio create any unusual linear distortions, a holy grail of IXTC technologies. In this regard, the tests performed with the adio’s internal recorder served as a means by which to compare its sound to a live reference point -- such as Choueiri’s voice.


The BACCH-SP adio’s 3D sound can be disorienting at first. We get used to the sounds not only of our stereo systems but of our listening rooms, and to a large extent, those are what the adio removes from the sound. For example, as indicated, the adio works best where room interaction is minimized. The adio didn’t bring only the performers into my listening room -- it brought their recording venues as well.

The BACCH-SP adio’s sound was far more immersive than that of a traditional stereo system. This meant that, rather than viewing the performers from, say, the tenth row, I heard more of the perspective of the microphones, wherever they were placed. This means that you may learn that, during the recording of your favorite Neil Young album, his acoustic piano sat in the middle of the recording studio.

Outside of 3D audio, I was a bit taken aback by just how good the adio’s DAC and preamp stages were. I have seen no other component with a built-in preamp that offers so many features and connections.

[sign on road to witch’s castle:]
witch’s castle, 1 mile. if you’re a hardware manufacturer, i’d turn back if i were you!

IXTC is not marketing hyperbole, but probably the most important development in the reproduction of soundstages and aural images since the invention of stereo, in 1931. Indisputably, Theoretica’s BACCH-SP technology, which I highly recommend, is at the bleeding edge of IXTC’s continuing evolution, and so effective that it has convinced me that the future of audio playback is not in incremental advancements in electrical circuit design or the operation of mechanical hardware, but in DSP technologies that fool the brain in increasingly sophisticated ways.

My only question: How long will it be before we witness the death of traditional audio systems, and the birth of neurorealistic ones that operate through the direct interface of a computer with the human brain’s auditory centers? The latter may still be a ways down the road, but my time with Theoretica Applied Physics’ BACCH-SP adio has led me to believe that such a breakthrough may be closer than we think.

. . . Howard Kneller

Associated Equipment

  • Amplifier -- Esoteric Grandioso S1
  • Preamplifier -- Esoteric Grandioso C1
  • Sources -- Three-box Windows 10 music server with JPlay player, Linn Kazoo control software, JCAT USB and Ethernet cards, JCAT USB Isolator, HDPlex 200W linear power supply, and Apple iPad Mini 3; Esoteric Grandioso K1 SACD/CD player and Grandioso G1 master clock generator
  • Other electronics -- JL Audio CR-1 active subwoofer crossover
  • Speakers -- YG Acoustics Kipod II Signature
  • Subwoofers -- JL Audio Fathom f113v2 (2)
  • Interconnects -- Synergistic Research Galileo UEF
  • Digital links -- Mad Scientist Audio Black Magic (USB), Synergistic Research Galileo LE (USB) and Galileo (BNC)
  • Speaker cables -- Synergistic Research Galileo UEF
  • Power cords -- Synergistic Research: SR25 (power conditioner), Galileo UEF, Atmosphere Level 3
  • Power conditioners and distribution -- Synergistic Research PowerCell 12 UEF SE and QLS power strips
  • Isolation devices -- Silent Running Audio VR fp Isobase. Symposium Acoustics: Osiris Ultimate and Standard racks, Segue platform, Roller Block Series 2+ equipment support system. Synergistic Research: Tranquility Bases, MIG 2.0 footers
  • Room treatments and correction -- Synergistic Research: Acoustic Art, Atmosphere XL4, Black Box, HFT and FEQ devices; GIK 2A Alpha diffusor/absorber acoustic panels, WA-Quantum Quantum-Sound-Animator
  • Misc. -- Synergistic Research Active Grounding Block, Blue fuses, and Electronic Circuit Transducers (ECTs); Mad Scientist Black Discus Audio System Enhancers and Graphene Contact Enhancer, Hi Fidelity MC-0.5 Magnetic Wave Guides, Telos Quantum connector caps, f.oq damping tape

Theoretica Applied Physics BACCH-SP adio 3D Sound Processor
Price: $34,430 USD (as configured).
Warranty: Three years parts and labor.

Theoretica Applied Physics
417 Alexander Street
Princeton, NJ 08540
Phone: (609) 532-1023