Sunday 8 October 2023

Stereo Crosstalk Cancellation (XTC): A review by STC. And trying out uBACCH,, and AmbiophonicDSP VST plus Foobar foo_dsp_ambio plugins.

Hey everyone, it has been very busy as expected through September here at the Archimago household. As a result, I haven't been able to spend as much time on the audio hardware hobby (still very much enjoying the music of course!).

Over the years, you might have come across the term "crosstalk cancellation" (XTC) for speaker playback, words like "ambiophonics" or acronyms like "BACCH" may have passed by in your readings (for example great discussion on Reddit). For this blog post, let me ask an outspoken advocate of XTC to join for some guest content to discuss the reasons and techniques, and later on, we'll talk about a few DSPs one could try at home to experiment...

Take it away STC for Part I, I'll be back with STC for Part II, then I'll talk about trying some of the DSP options in Part III:

Part I: An introduction to XTC (by STC)

Crosstalk cancellation is an attempt to deliver stereo sound as it was meant to be played without the interaural crosstalk errors with loudspeakers (see Keele, 1986 for a technical exposition). Many listeners may not realize how much realism their high-end stereo hi-fi system is lacking until they hear a system with crosstalk-cancelled (or XTC for short) playback. It is like comparing a photo of a window with a view to an actual window looking out at the scenery. Or like watching Avatar in 2D versus 3D.

Is XTC the same as immersive or 3D audio? No, it is not, but the distinction is now slowly blurring with spatial audio incorporated with immersive audio. Immersive or 3D audio produces sounds from different directions providing envelopment with the aid of additional channels and loudspeakers while XTC produces the sound as if there are tens of speakers creating the frontal stereo stage extended across 180° if it's there in the recording. Most newcomers expect a bigger stage with XTC and often wrongly adjust the parameter to force one. XTC only applies to the interaural crosstalk errors in stereo reproduced via loudspeakers. It is a correction system and can enhance the sound unlike MQA or Dolby Pro Logic. It can be used with immersive/multichannel content as well.

In my opinion, immersive audio is good when you have visual cues to help your brain create the sonic scene. Formats like quadraphonic can create a very natural 3D sound with XTC, that would be great for home theater setups. It can produce sounds from anywhere in the 360° circle around you, as if the sound sources are in the room with you. Sony's 360 Spatial Sound Mapping with their 4 speakers system is heading towards that direction.

Crosstalk cancellation is not a new concept. The most basic way to do crosstalk cancellation is just to put a physical partition between the two speakers, but that is not practical. Atal & Schroeder's "Apparent sound source translator" patent filed in 1962 suggested a technique with signal processing. Despite being around for a long time, audiophiles have ignored it presumably because some think that any signal processing is "bad" for high fidelity sound.

[Ed: of course, rational audiophiles here at the Musings don't hold on to such silly phobic myths.😉]

One example of an early consumer XTC device is Carver’s Holographic line of processors, preamps, and amplifiers which came out in the early 1980's based on his 1979 patent (see Carver's Q&A ad on Sonic Holography on page 69). 

XTC's intent is not to change the original sound. The goal is to conserve the sound waves that are intended to be presented to the ear on the same side, but reduce the crosstalk that reaches the opposite ear. You can see the illustration here.

The impractical physical mattress-between-the-ears approach. ;-) On the right we see some old photos from back in the day when they were experimenting with this (Keele, 1986 paper).

In some ways this is like listening with headphones since each ear only hears the corresponding speaker. You may think then that the sound of speakers with XTC is like the experience of listening with headphones, but that would be wrong. Listening to stereo sound with headphones is actually unnatural because it bypasses the role of the pinna, thus creating a soundstage inside the head.

To understand why, we need to know how our ears and brain work and how stereo creates an illusion of sound images.

The purpose of stereo and multichannel formats is to re-create the sound scene of an event as if you were there in person. The most accurate way to do this is to record the sound with microphones inside your ears and listen to the recordings with headphones. These recordings are called binaural. Assuming the recordings are done in high fidelity, they will sound exactly like the original event to you and only you. Some users may perceive a closer realism if their Head-Related Transfer Function (HRTF) is similar to the person's (or dummy head's) HRTF that made the binaural recording. HRTF is a result of how one's head and ears (pinna, ear canal) interact with the sound that arrives towards us, therefore for each of us, the effect will be somewhat different. Individual parameters include Interaural Time Difference (ITD), Interaural Level Difference (ILD) and pinna frequency shaping among perhaps other complexities. Readers are advised to look up the HRTF topic elsewhere (such as this paper) for a better understanding.

An example of the variations in frequency response among 8 individuals due to HRTF. See here for source. Notice most of the variation happens in the higher frequencies.

For any one of us, when sounds are presented around us horizontally, the head/pinna changes frequency response to help with localization starting from ~1.5kHz.

Stereo attempts to re-create the scene by capturing the ILD (and sometimes ITD). Since the sound waves are coming from loudspeakers, they will be modified by the pinnae of the listener which give additional cues to the brain to localize the direction of the sound. This sound is more natural compared to stereo listening with headphones since three separate cues can be delivered to the brain - ILD, ITD and frequency shaping by the pinnae. Headphones do not replicate the pinna's role as the sound is delivered directly to the ear canal without natural modifications by the pinna. Unlike headphones though, the crosstalk errors limit the realism due to a constant secondary sound heard by the opposite ear, again, this is the interaural crosstalk error which will always present as a delayed sound of ~220μs (with maybe -3dB attenuation), damaging the localization and blurring the sonic image.

There are stereo width enhancement techniques that aim to create a more spacious and realistic sound stage from two loudspeakers. However, most of the existing methods, such as SRS, compromise the fidelity of the sound and introduce artifacts or distortions. Rather, crosstalk cancellation/XTC has emerged as a high-fidelity solution that leverages digital audio processing. Crosstalk cancellation eliminates the unwanted interference between the left and right speakers, allowing each ear to hear only the intended sounds. This creates a binaural effect that simulates the natural hearing of sound sources from different directions as captured in the stereo recording.

There are various products that implement crosstalk cancellation using different algorithms and names. Many products use the Recursive Ambiophonic Crosstalk Elimination (RACE) algorithm, which was developed and made public for free by Ralph Glasgal and Robin Miller in their 2006 paper. The RACE algorithm is based on the principle of "ambiophonics", which is a term coined by Glasgal at least since the late 1980's to describe the binaural reproduction of two-channel sound using loudspeakers. The term ambiophonic therefore is meant to distinguish this crosstalk cancellation approach from the conventional stereo ("stereophonic") playback, with its inherent limitations in creating a realistic soundscape. The Ambiophonics Institute was a pioneering organization that promoted and supported the research and development of ambiophonics and related technologies.

A picture of Ralph Glasgal's sound room circa 2019.

The Ambiophonics Institute was also where Edgar Choueiri of BACCH was involved, working alongside Ralph to improve the crosstalk cancellation. Ralph’s RACE algorithm is incorporated in many other products. BACCH evolved using a different approach called Band-Assembled Crosstalk Cancellation Hierarchy through impulse response convolution.

[Ed: we can see convolution techniques used in various papers over the years such as this one, or this one. Here's an article from 2010 showing Choueiri's "ambiopole" speaker arrangement discussed below, and one of Choueiri's early videos more than a decade ago about the technique and the Princeton lab. Repository of publications here.]

RACE uses the original signal and inverts it and reproduces it delayed via the opposite channel speaker, so that the secondary interaural crosstalk from the first speaker and the inverted signal arrive at the same time at the unintended ear, thus reducing crosstalk level. This process is repeated until the signals reach above 60dB attenuation. This can be achieved by anyone with a DAW using delay and an effect such as "Ping-Pong" plugin that allows adjustments in microseconds. [Ed: for those using Reaper as a DAW, check out this discussion.]

The original RACE block diagram. Notice processing within the 250Hz-5kHz band, recursive 60-100us delay with inversion for each pass. Bass <250Hz and higher frequencies >5kHz are typically unaffected by the DSP.

The theory of cancellation is well documented by Ralph Glasgal and Robert Miller's Filmaker website who also worked with Glasgal in the early stages. Since early 2023, Glasgal (92 years old in 2023) has closed the Ambiophonics Institute but the archival contents are still available here. Check out Glasgal's Ambiophonics: Beyond Surround Sound to Virtual Sonic Reality book for more (free PDF here). Also, see this 2019 article with a visit to Glasgal including some fascinating background on his life.

BACCH is said to use different levels of cancellation based on frequencies as head shadow attenuates higher frequencies more than the lower ones. BACCH's approach is similar to the RACE "ping-pong" effect but implemented in a convolver using impulse responses for the contralateral signal attenuation.

In the end, what’s the audible difference between BACCH and RACE based products?

Unless you have access to the various products implementing XTC from SoundPimp (demos here), uBACCH, Neutron MP, etc. you are at the mercy of opinions and subjective claims; as usual, it's best to experiment and try for yourself.

IMO, the best cancellation can be achieved without spending $$$, such as with a DAW or music player with DSP. The trick is how to get the tonal accuracy. Audiophiles can make bees fly around the head with free XTC software and some know-how. The ability to achieve this using standard 2-channel audio content is something that should not be expensive but one will need to make an effort to understand how this works so you can implement it well in your own room and own system.

Part II: Benefits and the ambiophonic set-up (by STC & Archimago)

In this next section, let's talk about what we expect to hear from a properly set-up XTC/ambiophonic system.

STC's system: Sound Lab electrostatic speakers, powered by Crown XLS amplifiers. Custom implementation of RACE.

Notice that the speakers in an ambiophonic system are typically placed not in something like a 60° (ITU-R BS.775-3) equilateral triangle arrangement. Rather, they're much closer at around 20° apart in front of the listener. 

We can see this kind of closely-spaced arrangement in the papers by Glasgal like this one showing the most basic "ambiopole speaker pair" spaced 20-30° apart fed with standard 2-channel input through the XTC processor:

Notice that there's also the potential to use captured concert hall impulse responses to re-create ambiance using various surround speakers, spaced every 15-30° for example. (You can see some of this work capturing concert hall impulse responses in presentations like this from Farina.)

As you can see in the paper, there are many other layouts and processing options that can be considered such as adding a rear ambiopole speaker pair (see "360° Localization via 4.x RACE Processing" AES 2007) which can be used to convey multichannel like quad or 5.1 content. Glasgal also discussed the use of height channels in what he called "periambiophonics" with captured "upper hemisphere" soundscapes.

While I will stick with discussing just the 2 speakers up front, STC indicated that he also has some small Panasonic "rear ambiopole" speakers, fed a similar signal as the front, to expand the 360° panorama. Also, he has a stack of amplifiers powering his surround speakers when playing music in his "virtual concert hall".

Stack of Line5 A960 amps...

You might be wondering why the 20-30° closely spaced front speaker layout. This is for psychoacoustic reasons since human frontal localization via the pinna is poor compared to the sides (the pinnae as direction-finding mechanisms are most sensitive to sounds coming from 30° off-center). With both speakers closer up front, the crosstalk correction mechanism can assume minimal pinna coloration and relative independence from the listener's head size and shape. Furthermore, this speaker arrangement could inherently reduce side room reflections, improve center imaging, and reduce comb filtering. 

Here's STC's take on some of these elements:

1. Reflections - Glasgal was aware that RACE XTC reduces the impact of sonic reflections and he shared his thoughts about it within the archives. RACE is a recursive signal of in-phase and out-of-phase effects separated by ~80μs so the reflections can get cancelled by itself. BACCH is also recursive since that's what the convolution engine does.

2. Comb filtering - comb filtering will always exist when two sources produce the same signal. In stereo you are always hearing 220μs of comb filtering and no one complains. In ambiophonics, the cancellation is supposed to reduce or eliminated the comb filtering as the ears only hear a reduced level from the other side. Of course, the comb filtering is already happening from the two signals traveling from the speakers to a certain extent. I have done many listening tests with music students, non-audiophile music lovers and musicians on my system, all of them preferred the XTC version as the sound is more detailed and refined.

3. Centre Image - This tends to be excellent with ambiophonics. My own XTC will be slightly different from a DSP like AmbiophonicDSP [Ed: we'll talk about this below] but listeners (music students) have preferred the XTC version as it sounds more natural compared to typical stereo speaker placement. The question is whether it's the same or better than mono vocals or center channel solo vocals. Listening tests need to be done and since my children are grown up now, I do not have virgin ears to explore this further!

As usual, the results can vary between systems. For example, my setup is literally 1.5 x 1.8m of radiating electrostatics surface listening from about 2.4m away which could be very different from what you use. I am very familiar with AmbiophonicDSP and despite giving all the parameters of my listening system, some users cannot seem to achieve the intended sound quality with their systems. One guy who was a recording engineer was shocked at how well AmbiophonicDSP worked on my system. At that time I was using Harbeth speakers, but he could not get it done correctly in his studio. So it can vary! Just too many variables and sorry to say this, but I am beginning to suspect not all audio engineers are equally made. Some cannot even seem to get the speaker angles correct. 😂

[Ed: Indeed on that last point! ;-) Sadly, some audio engineers apparently can't even tell that their DR4 dynamically compressed mastering sounds like crap...]

Also see "What to expect to hear with Ambiophonics" by Robin Miller.

Another perspective on crosstalk cancellation from Floyd Toole; the thread is interesting as it proceeds into discussions of BACCH and back-and-forth with Choueiri.

A comment about listening to audiophile vocal recordings with speakers spaced closer from Glasgal.

Part III: Try XTC for yourself (by Archimago)

Thanks STC for the information above! Great stuff and I hope the background on crosstalk cancellation (XTC), ambiophonics, and BACCH intrigues you, dear audiophiles. I know the terminology might be quite alien to many readers although I think the concepts should not be difficult to grasp.

In Part III then, let's get into it and see if we can try this for ourselves. First, it's important to space out the speakers so they're close to that 20° angle to the listener. For me, in the living room, I have some small Tannoy Mercury mX2 speakers that I can move around temporarily like this:

As you can imagine, normally these speakers would be on either side of the 65" TV which is connected to my gaming computer. The speakers are powered by a Denon AVR-3802 receiver from decades back which still sounds excellent. You can see on the screen that I have JRiver 64-bit running with the "Universal BACCH Filter" (uBACCH) plug-in window open. The software I'll be discussing are all Steinberg VST plugins which can be used in digital audio workstations (DAW) or playback software supporting this standard like JRiver.

First, let's go to the download/purchase link for BACCH Labs' uBACCH where you can find a 14-day trial of the VST plug-in for Mac or Windows. Install the file. Afterwards, on my Windows machine, using JRiver's DSP Studio, I click on "Manage Plug-ins..." and find the uBACCH directory where the .vst3 file lives (in my case, "C:\Program Files\Common Files\VST3\BACCH Laboratories"):

Now open up the uBACCH window and you can play with the very simple "u-BACCH Angle" setting to find the best value for your set-up:

My speakers are 20° apart (+/-10° off center) so putting that angle for the setting turns out quite nicely as expected. Notice the uBACCH filter also has the "Tuning" button which you can click on and that will play some pink noise so you can fine-tune the effect. Unfortunately, there's a bug somewhere and JRiver needs to be playing music in the background in order to hear the pink noise sound. Here's what it looks like to have the L channel playing the pink noise while I slide the angle width adjuster around:

What you want to hear is the lateral R/L sounds emanating from just beyond that corresponding ipsilateral ear, and as little sound (crosstalk) as possible heard by the other ear. BACCH Labs has a video discussing this.

To test out how well the plug-in works, have a listen to some binaural content. One of the tracks to check out is "Edgar (Choueiri) The Barber" found on Chesky's Sensational, Fantastic, and Simply Amazing Binaural Sound Show! (Binaural+ recording**). This binaural track should sound "3D". You should be able to hear the spatial movement of the scissors corresponding with the narration, and if it's working well, you should even hear the scissors moving behind your ears during those portions of the demo.

So that I can listen to music from a variety of sources (including Roon), JRiver has a handy WDM driver you can turn on so all your computer audio can be piped into the output device through the DSP:

24/48 sounds great already. Feel free to process at 24/96 if you prefer. As usual, for DSP precision, 24+ bits are beneficial. Samplerate is not nearly as important.

You can set Windows' default audio output to the "JRiver Media Center" device as I did above. With this, I was able to achieve a similar experience playing the Virtual Barber Shop off YouTube hearing a wide spatial field, reasonably good tonality, and portions where the voices and sounds seeming to be coming from behind my head; it's an older recording so resolution isn't the best.

Overall, I found uBACCH worked quite well and sounded good. Do not confuse BACCH Labs who sell uBACCH (US$399) with Theoretica Applied Physics and their BACCH products currently only for MacOS along with more expensive standalone versions.

US$400 for a software audio plug-in isn't cheap though, so let's see if we can find some free/inexpensive options.

Here's a free one, check out by Weldroid, released initially in 2010. The links on the page might not work to download from any more, so try this link. Note that it's a 32-bit plug-in so it'll only run on the 32-bit version of JRiver.

While this one did expand the width of the soundstage, it definitely wasn't as good as uBACCH for the "behind the head" effect or impression of being spatially enveloped when listening to my music. Feel free to play with the control knobs to see if you can fine-tune the results to your system. Hey, it's free! ;-)

Finally, let me direct you to this 32-bit VST plug-in that I fear unfortunately might not be available to purchase anymore - AmbiophonicDSP (only US$10 last published price, released initially in late 2009 - link provided for info even though I think no longer sold).

It works very well (as mentioned above by STC) and I quite like the "Jazz / acoustic" preset in the drop-down menu. STC suggested increasing the "Space" knob to further expand the spatial envelopment. I found that going up to 3-4 was good but beyond that I started noticing some mild distortion with sustained decays in my system, Also, push the "Zentrum" knob higher if you want to strengthen the central image, especially if voices sound too recessed. YMMV.

[Note from STC: I was using JRiver and AmbiophonicDSP but when I upgraded to JRiver 25, I had issues with it and also the virtual concert hall using surround speakers (or "domestic concert hall" - DCH). I did implement DCH with JRiver and there is a complete guide in the old Ambio website. The best part with JRiver was I could use various inexpensive USB DACs and implement DCH using their Zones. Unfortunately, after the upgrade to version 25 the sync wasn’t possible. JRiver was unable to resolve it and thankfully forced me to finally learn to use a DAW to created my own crosstalk cancellation procedure!]

Clearly the DSP widened soundstage, achieved good clarity, I did not hear any distracting coloration (unless parameters moved to extremes), and that "surround" behind-the-head effect was at least as good as uBACCH in my simple Tannoy set-up. Make sure to have a look at the user guide for more details and recommendations on the values of those settings; for example, depending on the listener-speaker angle, set the delay closer to 250µs as you get towards 60° if you're not able to pull speakers together. 

Beyond just binaural samples like the virtual haircuts, when listening to music, it's easy to hear the pleasant, natural, expansion of the soundstage. For example with classical music, it can sound as if one is sitting and watching the orchestra unfold in front with the various instrument sections - I really enjoyed Reference Recordings' recent Tchaikovsky: Symphony No. 5; Schulhoff: Five Pieces for String Quartet (2023, DR12). At other times it can be startling to hear sound effects in some mixes I didn't pay as much attention to before. For example the rain and thunder at the start of aha's "Crying In The Rain" (off East of the Sun West of the Moon) is rendered with a jarring presence of the raindrops falling around me, nice expansion of the soundscape with the thunder claps apparently above and behind my head.

Vocals like Adele on "Make You Feel My Love" off 19 sounds well defined in space as a tighter center image, the voice seeming closer and more forward than I'm typically used to. The tonality of typical audiophile female vocals like Lori Lieberman's Truly (2022, DR11) and the piano solo "Sonata in Darkness" (from The Batman) sounded pleasing as well. Also, check out some of the QSound encoded CDs out there - Madonna's Immaculate Collection, Roger Waters' Amused To Death, Sting's Soul Cages, Pink Floyd's Pulse, even Def Leppard's Yeah!. They really "pop" as intended.

You might also want to have a listen to The Cowboy Junkies' Trinity Session (1988, DR12) which was recorded with a single Calrec ambisonic omnidirectional microphone (more on the album here). In fact, have a look at the list of ambisonic recordings out there in this FAQ which includes Holly Cole's Girl Talk (1990, DR14). It can be quite surprising the amount of spatial depth and details captured in these. (Whether you're pro or against using ambisonic microphones, here's an interesting discussion.)

Although I have not tried it extensively yet, for those using foobar2000, there's foo_dsp_ambio plugin released in late 2011. It's no longer under development, here's an alternate download link. Good alternative if you don't want/have VST processing; I'll probably use this most often on my desktop machine.

Within the reasonable settings I used, I didn't detect unpleasant tonal distortion or "phasey" anomalies across the audio spectrum using these DSP plugins which I've heard some listeners complain of. Make sure your processing/playback is at least 24-bits and the parameters are optimized for your system.

Enjoying the sound of crosstalk cancellation? 😯


It has been fascinating jumping into the world of crosstalk cancellation and ambiophonics these last few weeks while chatting with STC about it. Appreciate the collaboration, STC!

There have been all kinds of products out there already featuring stereo width expansion over the decades. Most of these play with phase to artificially widen the stage rather than proper crosstalk cancellation (XTC) to remove the unintended sound reaching the opposite ear. These days, in the 21st Century, with the ubiquitous computational power of modern computers where even a Raspberry Pi should have no problem implementing 2-channel RACE in hi-res, we can do XTC in DSP with good results like the VST plugins above so long as the speakers are arranged appropriately and we tune the settings to match.

I've heard criticisms around using crosstalk cancellation as being unnatural because in the studio, the engineers and artists typically are not recording and mixing while employing XTC. I think this is a true and fair statement. The sound achieved is quite likely not "as the artist intended" or at least "as the artist heard" in the studio. Having said this, I'm not sure I actually care much about what the "artist intended" these days especially with pop studio productions. When it comes to rendering soundstage, I care more about whether the reproduction sounds interesting, entertaining and "cool"! Employing XTC, Madonna's "Ray of Light" is almost psychedelic with AmbiophonicDSP and I've not heard New Order's "Blue Monday 1988" sound so expansive before. I'm pretty sure I don't care what Madonna or New Order "intended" all those years ago in the studio. 🤔

Due to the front speakers being close together, they act as a common/center channel if the listener is further off to the sides. The sweet-spot for hearing the enveloping "surround" effect is reserved for those sitting centrally and narrower than typical ~60° stereo arrangement so it won't be as satisfactory if you have 3 or 4 people sitting side-by-side. I suppose one could arrange a few rows of chairs behind each other to have a few listeners within the central axis, but that would be a little odd in most domestic listening rooms - my wife and kids will have none of that.

Alas while I quite enjoyed the sound, as a pragmatist, unless I have an ambiophonics-specific set-up in one of my rooms, I would not be able to keep my speakers in that exact 20° orientation since all my sound systems here at home feature a screen and the speakers typically positioned on either side of the TV/monitor. Furthermore, since I've been listening to quite a bit of multichannel content these days, a standard 5.1 or 7.1 "bed" speaker layout with or without height channels would still work best.

[Note from STC: For home theater, transparent acoustic screens can be used to visually hide speaker placement. However, when vision is involved, auditory cues take a secondary role. There are research papers (like this) exploring changes in sound quality perception when accompanied by video. Furthermore, most of the positional information is predetermined by the eyes and the surround sound reinforces that localization.]

For those Tannoy speakers in my main living room, one solution I can do is to keep the speakers on either side of my TV but sit further back to listen. With the speakers 5.25' apart, sitting on the sofa 13' away will give me +/-11.4° or 23° between speakers and listener which is within the 20-30° layout. When I do this and activate the DSP, the sound is not as clear, the center image not as stable, nor is the "surround" effect as convincing as sitting closer due to the suboptimal layout and room acoustics, but I still experience a good amount of soundstage envelopment. A reasonable compromise, I think!

It's pretty cool watching a movie with XTC to expand the auditory "surround" experience using 2 speakers:

Excellent sounding "Diva Plavalaguna" scene (start at 1:27) from The Fifth Element.

For completeness, I want to mention that XTC has also been implemented in devices like the miniDSP products. Polk has their Legend L800 speakers (which I had a listen to at RMAF2019). On a web browser, Aria3D is also based on the RACE algorithm; I see the page is still up but I'm having difficulties accessing the demos on Chrome these days, you might have better luck. The same founder has another project called Magic Audio which works.

Of course check out the BACCH systems which have been promoted to audiophiles over the years. The recent TAS review of the BACCH-SP provides a good description. Starting at US$20k for a system like that without DAC functionality clearly represents quite a significant investment, but it does allow for further listener customizations like measurement of HRTF, head-tracking, and special headphone filters. BACCH4Mac is more affordable starting at about $1,000 for what looks like the generic DSP playback only. I wonder what is the difference between something like a Mac Mini running BACCH4Mac Intro and uBACCH VST playing in JRiver given the price difference.

[By the way, with "universal" BACCH VST plug-in, I was curious if I could measure the difference between different settings like 20° vs. 60°. Yup, we can capture an impulse response, overlap and show the change:

I suppose someone with BACCH4Mac Intro could capture the impulse response on that with the same angle settings and compare to see if it looks like uBACCH VST above.]

As usual, I'll leave it to you to experiment, audiophiles. I hope this article provided a reasonably comprehensive launch pad to help understand the technique and points you to some interesting audio experiences if you have not tried this before.

You might be very surprised by what you hear in your existing 2-channel audio library!

Further reading: A Psychoacoustic Rationale for the Subjective Evaluation of Stereophonic Sound Systems by Reviewers and Audiophiles (Ralph Glasgal)

Also check out Home Audio Fidelity's X-talk Shaper as another great option for DSP processing.


** I want to add an extra comment here about using binaural recordings and listening with the ambiophonic set-up and processing.

Strictly speaking, even though they can sound very good with ILD and ITD information, binaural recordings are not the most proper content for best reproduction through the ambiophonic system. Binaural recordings are done typically with a dummy head + pinnae which are supposed to represent some kind of "average" human HRTF.

Neumann KU 100 Dummy Head binaural mic ~$9.5k.

With ambiophonic listening, we would be using our own ears/pinnae, so we actually do not need those pseudo-ears imparting pinna frequency shaping in the recording. This is why if we look at Glasgal's 2003 paper, he showed a prototype "ambiophone" microphone that looks like this:

Notice that the mics would be inserted where the holes are on either side of that central "head". The top in particular is tapered to reduce capturing ceiling reflections. A pair of these can be used to capture front and rear hemispheres. See Glasgal's comment here. More on the ambiophone from AES 2001.

This means if we listen to a binaural recording with the HRTF of a person or dummy head including pinna coloration, the tonality sounds bright with speakers and thru ambiophonics. You can hear this on pure binaural recordings like Stax's The Space Sound CD, the binaural mix of Jean-Michel Jarre's Oxymore, Lou Reed's Street Hassle among others over your speakers.

Interestingly, Chesky's "Binaural+" Series recordings (of which "Edgar The Barber" is one) are supposedly made for both headphone and speaker listening. It looks like an EQ has been applied on these recordings as discussed in this 2013 Sound & Vision Chesky interview indicating the change (thanks STC for the link):

S+V: How do you process the recording so it plays back on speakers?

DC: We add a diffuse EQ filter so that you can play it back on speakers. Without that filter, the sound will rip your head off, it'll be ridiculously bright. We do it in Sonic Solutions. We have a filter algorithm that was supplied by Edgar [Choueiri]. This makes it theoretically flat again.


To end, with all that's going on in the early fall season at work and in the family, it has been hard finding time for the audio hobby. ;-) I consider this a good thing since it also means, ironically, that I'm enjoying the music more even though in shorter spurts! More just listening to the music and thinking about things than having the time to actually write stuff.

For other interesting reading material, check out Whit Turner's JWTAudio blog. It's always good to look around and see what others have been working on!

Have a great October, audiophiles. Hope you're enjoying the music.

Oh yeah. Happy Canadian Thanksgiving 2023, eh?!


  1. Nice review of a neglected subject that has been around for a long time.

    The easiest way to experiment ‘natural’ XTC if you have two adjacent rooms with only a wall between them and doors close together, is putting one speaker in each room and sticking your head near the wall with one ear in each room, so to speak…I did that a long time ago and the result was ear-opening indeed. Incredible how much stereo music is messed up by crosstalk!

    Later, around 2008, I experimented with the RACE algorithm using AudioMulch on a Windows XP system (see this partial image: With two speakers close together, the result was interesting for music with a wide soundstage, not so much with the more static piano modeling software that the image shows.

    The positioning constraints and limited use made me decide finally that the best way (for me) to get rid of crosstalk was using headphones, pinna or not…

    Now I’m more into multi-channel with Dolby Atmos, so stereo crosstalk is no longer a problem ;-)

    1. Hey Gilles,
      Great hearing from you!

      Yeah, I've been wanting to spend some time trying out ambiophonics for awhile now. It was fortuitous a few weeks ago on Audiophile Style in the Immersive Audio forum discussing this with STC and we got into this path about putting an article together. Plus with uBACCH demo available, I thought it would be fun making sure to include that in the overarching discussions.

      Wow, that's quite the thing to have your 2 speakers on either side of the room wall! Yup, must have been "ear opening" - just make sure nobody closes the door on you, eh? :-)

      Obviously, while multichannel approaches the "surround" soundstage effect differently than XTC (with its own pros and cons), I can definitely see myself doing what STC has done in his sound room if I just was listening solely to a 2-channel hi-fi rig (maybe not quite ready yet to have all the extra DHC ambience channels ;-)! Heck, I'm even tempted to set a small system upstairs just for 2-channels like this so I can experience the way all my stereo music should be heard!

      What I find fascinating is that the effect of XTC is well beyond stuff that many audiophiles rave about or argue about like fancy audio cables, tube amps, LP vs. digital, expensive brand names, etc... Yet, as you say, this topic is remarkably "neglected" in audio writings when I think it really should have a place of prominence as a key deficit of the typical stereophonic layout we should be exploring for true "high fidelity" reproduction!

  2. I have experienced with similar approach of placing speakers in two adjacent rooms but did not perceive as good as the DSP method. Even the partition method doesn’t yield got separation unless it is at low level.

    You actually get good immersive and 3D sound when you incorporate Ambiophonics to Dolby or DTS setup. I used to demo transformer movies by converting a few of my ambiance speakers to meet the 7.2 setup and it can really sound amazing. You can. Also add the Miniambio or MiniDSP to the HT like all sound production the sweet spot is for only on listener. Even, in IMAX theater if you move around you would notice that the best sound is still in the middle slightly towards the back.

    Stereo is anti social and meant for only one person for the best sound. Even multi channel is still for one man listening for the best sound.

    p.s. Commenting requires third parties cookies anable in the privacy settings and for securities reasons I don’t think that’s safe. Perhaps, URL or non Google account posting enabled?

    1. Hey ST,
      Glad you made it on the messages... Yeah, I guess I could try using something like Disqus for comments (haven't looked into this in awhile, I assume it's still working for Blogger). Thought about it earlier on, but too lazy after all these years...

      Would be interesting to hear a combination of XTC across a multichannel setup. Regardless, when it comes to multiple speakers, there probably will always be a single "best seat" in the soundroom. :-)

      I can't find much these days other than the user manual, I assume the miniAMBIO has been discontinues awhile back?

    2. I have no idea why they made miniAmbio in the first place! Probably, it had 64 bit processing compared to Minidsp but the Ambiophonics plugin was also a single to be used with Minidsp. Subsequently, they put a notice that the Ambiophonics plug-in would not work with the HD version. Actually, it should work but with doubling of the sampling rate the delay adjustment would be half so there could be a problem. Even with JRiver, you would notice the AmbiophonicsDSP would change the delay values when you play higher resolution files causing the XTC not working correctly. I noticed this problem in early days of JRiver because on and off the XTC wasn’t working correctly. When I reported to Ralph, he was surprised and after some thoughts on it he told that it could be a problem with sampling rate as his algorithm was calculated based on sampling delays of 44.1. I believe he contacted Horowitz but nothing happened.

  3. My programs which I use to run VST plugins (SoundForge, Adobe Audition) cannot see this vst3 BACCH plugin. They can see other vst3 plugins, but not this one, it's strange.

    1. Hey fgk,
      The BACCH VST3 is seen by Adobe Audition 14 here but greyed out so like you, not working.

      I wonder if it has to do with 32-bit vs. 64-bit? Maybe jBridge might help (not tried):

      Definitely with JRiver, uBACCH VST only runs in 64-bit version. I wonder if it might be good for BACCH Labs to offer a 32-bit build as well if this is what's needed for extra compatibility especially since it's just being used for audio playback. Not like uBACCH actually needs to take a lot of memory nor much processing power.

    2. Hi Archimago,

      Thank you for your advice!

      I am yet to meet a single person who was able to successfully install and use jBridge.

      I wrote to uBACCH asking them to explain why their plugin refuses to cooperate with Adobe Audition 64-bit. Also asked them to release a vst2 version and a 32-bit version.

      I tried once jRiver and I did not like it, I use Foobar2000.

    3. Hey fgk. Let us know if the BACCH folks get back to you!

  4. A quick note from a reader E-mail. It looks like some DACs like the Weiss DAC50X devices have XTC features incorporated in the device. Check out section 2.3.10 in the manual:

    IMO this would be a great feature on future DACs (forget silly EQ stuff like "tube sound" and such ;-).

    Likewise, I think it would be an amazing feature in software like Roon. For example, put a RACE XTC processing option in the "Speaker setup" section in Roon Muse DSP so folks can place their speakers ~20-30° and just turn this on for instant ambiophonics specific to the endpoint. This would make life so much easier for those Roon users who want to go beyond standard 60° stereophonics!

  5. Thank you Archimago and STC for putting this up! I have read myself the papers by Keele, Glasgal, and Choueiri, and now you have shared some more reading material, and even a first-hand experience. I will try one of these approaches for sure.

    I'm curious how much the directivity pattern of the speakers used and room treatments affect the perceived realism. I suppose, reflections do not help. Bock and Keele were doing their experiments outdoors.

    1. Hi Mikhail, you’re welcome but the credit should go to Archmago. In theory, I was using Harbeth and it worked great. New speakers dispersion is flat up to 30 degree and it shouldn’t make any difference. It should work in most rooms just like how BACCH doing it during the AV demos.

    2. Just a quick note, yeah reflections will not help; probably a fair general statement with hi-fi playback unless one is a Bose fan. :-)

      I agree with ST regarding the dispersion characteristics generally good to 30° with many speakers. Currently even listening to my Emotiva B1+ on the desktop with slight toe-in but still suboptimal placement at around 45° using the ambio DSP in foobar sounds good.

      Another example, for jazz lovers. If you like Sonny Rollins' Way Out West, have a listen to track 1 "I'm an Old Cowhand" in ambio. In stereo, his saxophone sounds almost mono-left panned to me and Shelly Manne's percussions right-panned. With ambio, the space around the instruments is much more nuanced and I can imagine a full 180° hemisphere in front of me where the sounds are emanating from.

      BTW, there is a 5.1 mix of this album from 2003 I think; not the best as I recall but I should have a listen to it again and compare with the ambio presentation.

  6. Nice review. Do you have a surround setup, and if so would you consider reviewing available software stereo-to-surround upmixing options? I'm using and enjoying the old freesurround plugin for 32-bit foobar2000 these days, its a nice change from the staid Dolby Surround Upmixer that AVRs come with these days (which is a downgrade from the excellent Dolby Pro Logic II (Music) upmixer they used to come with.

    1. Hi Steven,
      Yes, I do use my 5.1.2 setup for music these days (and movies as well). Quite a lot of Atmos stuff coming out now so can't miss out on that ;-).

      Interesting, will have a look at FreeSurround! Thanks for the tip. Of course the beauty of ambio is that we can enjoy much of that expanded soundstage with just 2 speakers.

    2. I'd be interrested to hear you comparative impression of ambio vs upmixing, though they are surely very different beasts.

      Freesurround is one upmixer (rather old), other tools -- that aren't foobar plugins, theya re standalone software/packages -- include Plogue Bidule (also old), SpecScript is a modern one that I've also had great results with,

  7. Very good explanation, Arch. One question I've posed on places like ASR regarding the Bacch system is why we would want systems like my Smyth A16 Realiser to replicate the sound of speakers playing in a room, as well as crude attempts to introduce crosstalk to headphone systems to get the sound "out of your head", and at the same time want to create a system for speakers which eliminates crosstalk so as to make them sound more like headphones.

    You are actually the first person to actualy clear that up for me. We want to be able to use the pinnae to shape sound whether for speakers or headphones, and the reason my A16 works so perfectly is because it exactly captures the HRTF I uniquely possess. Headphones don't capture the clues from our pinnae, so they result in sounds inside the head which is what the Smyth brings to the party for me with its exact capture of my HRTF for the systems I've measured.

    OTOH, speakers playing in a room introduce interaural crosstalk error by creating a delayed sound from room reflections which blurs images. It's this distortion, and this distortion alone which Bacch4Mac, uBacch, and other ambisonics programs remediate. Knowing that, it would be interesting to see if someone could develop a metric for it. Is it more present in same speakers systems than others? More liable to exist in stereo than in multichannel? Is it even possibly a benefit in stereo, creating ambiance where none would otherwise exist given the limitations of the format?

    In short I think it would be great to see a more systematic, analytical, and quantitative, measurement based approach to the issue.

    inside the head.

    1. Greetings Phoenix,
      And congrats on the Smyth A16!

      Exactly... The "magic" of making something sound "real" is ultimately how well we reproduce the sound fed to our brains so that the brain interprets the sound as similar at least, but ideally identical to what it would be like if the waves hit our ear drums in real life.

      As discussed by STC, the only way to make that subjective experience seem genuine and wholly "ours" is to make sure the stimuli are precisely time and level accurate, along with the necessary fingerprint pinna filtering which our brains have been trained on all our lives to sound like something we would interpret as being external; unlike unnatural unprocessed headphone listening.

      The Smyth creates the illusion with its measured PRIR and HPEQ I believe, then uses the DSP to virtually re-create the sound of the environment in a way our ears find "personal" through headphones.

      With XTC and ambio, it's at least an easier job since we're still using our own pinnae. Let's move the speakers closer to the front (where we expect the main content to come from anyways) to reduce the coloration from front/side-firing 60° speakers, and remove/reduce the crosstalk distortion so we can benefit from the full 180° hemisphere. Plus if there's something a bit more in the content (like binaural cues), then we might even experience it as coming from behind.

      It would be cool to hear what the full BACCH system sounds like at some point with my own measured HRTF; I'd be curious how wide one can keep the speakers apart while achieving accurate soundstage and without tonal coloration.

      Yeah, would be interesting being able to quantify how "real" something sounds. Alas, as we get deeper into the psychoacoustics beyond measurements of electrical parameters and distortions, we're encroaching into the subjective "brain-reality" matrix ;-).

    2. If I remember correctly, Smyth does not XTC. I remember the developers where I. Touch with Ralph for a possible coding to incorporate Ambio but I wasn’t paying much attention then as I thought headphones already without XTC. Unless the discussion was about Smyth XTC for speakers as they have all the right tools to measure the ears and pinna like Apple, BACCH or Samsung.

    3. Hey ST,
      The Smyth is a headphone system as far as I am aware. No need for XTC. More about creating a binaural feed to the headphones to externalize/virtualize the sound in a room.

      I think they use in-ear microphones to capture the room impulse response and headphone EQ.

    4. Archimago, the discussion was to implement this with speakers for crosstalk since Smyth measures personalized response and therefore theoretically is should do better cancellation. In any case, that is similar to BACCH implementation. IME, playing with EQ affects the 3D because of phase changes and I am just curious how they are actually implementing this with BACCH. the funny thing with hearing is that you just accept whatever things experts say without a chance to check the validity.

  8. That's correct. The Realizer does however output 16 channels of line level analog audio which can include audio decoded for Atmos, DTS-X, or Auro 3D. Unfortunately it doesn't do the other things a regular Atmos receiver does like individual channel level adjustment, PEQ and the like.

  9. Thanks for this article ! FYI I have been working on developing crosstalk reduction algorithms for some time and provide convolution filters (from generic ones to tailor made based on HRTF measurements) as alternative to BACCH system. I also made a video to demonstrate the negative impact of crosstalk for stereo setups :

    1. Thanks for the comment and video link HAF!
      Nice work on the filters...

  10. Well thanks for this, guys, even if you've put me in a quandary.
    I've read about these processes in the past, but haven't been able to try them till now. My stereo speakers are integrated with my surround system, and are too far apart for optimal XTC, it seems.
    So I tried the Soundpimp demo and was impressed -- enough to install the uBacch trial to hear what it did to known tracks. Very positive to almost neutral on a variety of sources. First impressions, maybe someone can give theirs on some of these:
    - LEDR: big increase in depth, less wobbling on height movement
    - Meeting by the River (Water lily): wow, main instruments are larger, closer and Ry Cooder's lines are much easier to make out (Bhatt's instrument is consistently louder.)
    - Trinity Sessions: another wow (despite the rough highs), Margo T. sitting 2 feet in front of speakers, reflections clearly located in the distance.
    - Mahler 5th, live recording on Water Lily: seemed to be heavy on the right, light on the left, with violins quite muted. That damned cougher on the left was at least separated (in front) of the orchestra.
    - Montserrat Figueras, Ninna Nanna (Alia Vox): goosebumps... she and her(?) finger cymbals move around quite believably, and the accompanying instruments clearly located behind (and beside) her.
    - Muddy Waters, Folk Singer: very stable images, less artificially 2-track sounding, bass fiddle stable (not expecting that)
    - Rebecca Pidgeon's Spanish Harlem: you'd have to put a gun to my head to make me listen to that again.
    Telefunken recordings from the 60s showed a big spatial improvement.

    Tracks that were not so drastically affected included Rolling Stones' Love in Vain, Laurie Anderson's Strange Angels and Monkey's Paw. The Stones track has zero ambience, Anderson's have gobs.

    So anyway, yeah, unquestionably dramatic improvements on most material.
    Now what am I gonna do? I could stay with my integrated 2.0/5.1 system, with sub-optimal stereo performance (and best music listening restricted to one spot), or split them up and lose some living space. Wouldn't want to spend $400USD in the first case... although when you think about it, we've all spent that much or more on hardware that brought fewer benefits. I guess I'll have to move my L and R speakers to the ideal XTC spot within the next 2 weeks. If it's not worth the money and bother, I'll use one of the free or cheap VST options for occasional dedicated stereo listening.
    I'll keep checking the posts here. Thanks again: this is for me the most valuable source of audio suggestions, wisdom and thoughtful opinion.
    All the best

    1. Phil, it has been years to read impression like yours. Thank you. BTW, could list your speakers and the distance ( triangle ).

    2. My pleasure. ST.
      Speakers are reconditioned Martin Logan SL3s, 2.15m apart (C to C), listening position 2.8m, so I set uBACCH to 24 degrees.
      After further listening, I don't think it's worth it for me to set up a separate stereo configuration. It's the narrowness of the sweet spot that's a killer for me: turning one's head is a problem, as is sitting too much off axis. I will install one of the lower cost alternatives for occasional solo concentrated listening.
      It would be ideal for a home studio or desktop setup.

      Generally, I think more minimally miked sources seem to work best (or is that just my prejudice?) Pretty much any Water Lily recording will come alive with this treatment. I'll have to try the classic RCA living stereo recordings.
      Thanks again, both of you, for this interesting and fun article.

    3. Thanks for the info. Tall speakers seemed to be better in projecting the 3D image giving better externalization.

    4. Thanks for giving this a try Phil!
      Indeed there are some amazing recordings out there to try out and the effect can be mind-blowing form "just" 2 channels. Those high-quality, well recorded, natural dynamic range recordings like the Water Lily Acoustics ones definitely are a "must try" for anyone giving this a go. :-)

  11. As I was reading your article, I was remembering a video where Dan Worrall presented a trick to get "depth" on stereo mixes. However, he never mentioned anything about surround sound or ambisonics:
    I suspect that what he was doing is something similar to what happens in the Ambisonics/XTC technology (with the difference that in the video the delay/phase change is only applied to the Mid side of the stereo image)

    1. Interesting phase plug-in and using the center/side processing!

      Looks like he's primarily doing center-image delay compared to the side R/L side content which accentuates the image including how it's perceived using headphones.

      This is clearly a different set of processing effect than true XTC though. Interesting trick for guys in the studio though!

  12. @Avitronic Ambisonics is not Ambiophonics or XTC.

  13. Somebody sho'nuff put the pedal to the metal on those uBacch prices!!! From $400 to $1, nothing flat. OUCH!

    1. Wowzers. Yeah... I think that's a bit too much.

  14. Looks like they are more interested in selling the tech to manufacture to incorporate XTC in their product. Apple phones already doing head tracking and XTC itself is a simple algorithm where we can do it with delay, invert and attenuation. Looks like uBACCH not targeting audiophiles. Even if they make it available for free not many going to take up the offer.

  15. Thanks for the update. So typical. By the time most of us regular folk figure out what's up the train has left the station. And when the next one comes we can't afford the ticket. :)

  16. XTC is not new and it is more like a revival like Carver’s Holographic Amp. Polk and TAcTalready done it before. Minidsp sold it for $100and AmbiophonicsDSP at $10.The price is not going to change the number of the users. Only change of attitude of audiophiles determine the succes or failures of BACCH or any XTC.

    1. I'm certainly surprised by the asking price for the BACCH systems in general. Hmmm... An unfortunate bit of "high end" price creep?

  17. Hi, I've recently compared u-BACCH VST3 plugin to the solution of crosstalk cancelation provided by Home Audio Fidelity ( on the same configuration with JRiver Medía Center 31 and its Studio DSP. The solution provided by Home Audio Fidelity is based on measurements, whereas the one proposed by u-BACCH is not. On my system, I prefer the Home Audio Fidelity solution which is by far less expensive than u-BACCH plugin. It goes further in terms of soundstage (fullness, 3D, localization, sound quality.... etc.).

  18. For those interested, SoundPimp appears to be vaporware, a dead product, or a scam. The only things that work on their website are the buy button and the demos. Also, the phone number appears to be out of service and they do not respond to emails. I tried to buy it, didn't get a download link or key, and have raised a claim with PayPal. Caveat audiophile.
    The best low-cost options appear to be 32-bit VST plugins. I wouldn't bother with homeaudiofidelity as they only supply a set of filters, not a DIY app, so it's a charge any time you move or change anything in your system.
    There's a chance that someone might release plugin code that could be recompiled as 64-bit VSTs.

    1. @PhilFromTo, I have forwarded your frustration to Dr Janson of Soundpimp. It was a government funded research and I still have their VST. The VST plugin is 24/196 so the DAW need to set for 196 sampling. Let’s hope for the best.

    2. I generate convolution filters as I combine crosstalk reduction with room correction. If there is some interest, I can quite easily develop a plugin to apply crosstalk reduction only

    3. If I were better at predicting market interest, I'd be quite a bit wealthier. However, with uBacch now priced out of the home market, I think there might be interest in a reasonably priced 64-bit VST XTC plugin, as many of us music lovers/audiophiles who are not DSP-averse already have convolution or PEQ capabilities. (Certainly, I'd be interested.)
      Right now, I'm using the free 32-bit plugin with the very nice and reasonably priced DDMF Bridgwize 64 to 32-bit bridge (thunker?) and it works quite well, I think, but hard to say whether other XTC implementations might work better.

    4. @PhilFromTO, Dr.Janson of Soundpimp contacted me about your problem. They had server migration issues. Please contact them again or email directly to

  19. Home Audio Fidelity, please do it. I personally think the cheaper version should be freely available. perhaps, you also want to write something about your XTC here or forums such as Audiophilestyle.

    1. I agree.

      HAF, would be great to have an alternate to something like uBACCH which as others have noted, have priced themselves out of many audiophile budgets! Heck, even when they were at US$400, that'll need some commitment to put money down given that $400 could buy some good headphones or even desktop speakers.

      A modern 64-bit VST just for crosstalk reduction priced reasonably with easy fine-tuning and any other parameters you think we might enjoy I think would be very welcome! I'd certainly happily make use of something like this.

      With I hope ongoing discussions of and the value of subjective "immersion" of sound quality, I do hope that more audiophiles become acquainted with the benefits of XTC and increase the general interest. Thinking outside of the typical "2-channel cul-de-sac" sound and into a greater sense of depth I believe should be the quest of the modern audiophile who seeks an experience beyond the typical. XTC should certainly be in our "armamentarium" of techniques to try if not also going multichannel...

    2. Thanks for your support, I will investigate this xtalk plugin... It is not xtalk but I already have a plugin to re-position sources for stereo setups, working with both speakers or headphones (Soundstage shaper

  20. For those of us who don't live in the financial stratosphere---or, who are unwilling to spend large sums on the technology---the HAF approach is much appreciated. As is the flexibility on offer.
    HAF is also providing a great learning platform for newbies and anyone struggling to get a better understanding of the many faces of digital audio.
    Let's hope the conversation here continues to progress.

  21. FYI, the plugin development is progressing well... a snapshot of the GUI...

    1. Hi there! The link is not working.

    2. You just need to copy/paste the http address as I am not sure I can a hyperlink in a comment

    3. Thanks. All good now.

  22. As a preview, here is the link to download my plugin
    You can find versions for Windows & MacOS

    1. Thank you HAF will test it next week. BTW, can I share the link?

    2. Hi HAF,
      I've installed the 64-bit VTS3 on my W10 PC laptop and can confirm that it works with J River and also with JRMC's WDM driver. This has been a problem with other plugins: the WDM driver crashes. In the next day or 2 I will have a chance to install it on my media PC and report on how it sounds.
      Hang tight, looks very promising. Nice to have a proper manual too!

    3. Great, thanks ! looking forward getting your feedback

    4. Hi again
      I've tried the plugin with JRMC on Windows 11 and found no problems. I'm at a bit of a handicap when it comes to evaluating the audible effect: whether it's because of a headcold or something messed up in my system, the apparent width on the left is reduced. This has nothing to do with your plugin, as the AmbioOne shows the same defect.
      But as far as I can tell it works fine. I find the interface easier to understand than the AmbioOne and can hear no tonal balance issues or distortion.
      I hope my hearing/system gets fixed so I can enjoy the XTC experience.

    5. Thanks Phil for confirming this. This is exactly the reason why XTC must be done with ears and not by measurements as we hear differently between left and right ears. Furthermore, like your hands, legs and eyes your ears too are different between the two.

      There are ways to address this but the first step is to place speakers closers.

    6. Thanks for your feedback PhilFromTO ! Hope this will motivate others to have a try

  23. Hi Thierry, I haven't been to this site in awhile but I want you to know I did get around to testing the Room Shaper plugin. Had no luck on Foorbar2000 or my main player Audirvana Origin. I finally dusted off my JRiver26 and it worked perfectly. The most dramatic effect was cleaner/tighter bass. The overall effect was quite nice.
    Still trying to find time this weekend to solve my polarity issues. Will get back with you soon for proper testing and analysis.
    Thanks for all the good stuff you're doing.

    1. Oh, I forgot to say that the bass was no longer BOOMY, which can very quickly get on your nerves. With Room Shaper the BOOM got BOUNCED :)

    2. Thanks for your feedback ! I am really proud of the innovation brought by Room Shaper to lower the impact of the room