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Future Tech at Capital Audio Fest 2023 | Special Show Report

Alan Taffel, Lance Profyt, Jacob Heilbrunn and I recently travelled to Washington, D.C. for the Capital Audio Fest. Alan and Jacob will file their own reports. In this video, I’ll be reporting on something a little different from the product introductions I focused on in parts 1 and 2 of my roundups. Let me explain.

While at the show, it seemed clear to me that there is a “standard high-end audio model”. What I mean is that certain technologies have been voted on by “the people” and “the industry” and now represent much of what is on display. For example:

– Loudspeakers with forward-facing cone drivers in a cabinet.
– Solid state class A/B amplifiers.
– Digital streams.
– DACs using ESS or AKM chips.

Etc. Etc.

This is a good thing, to a point, in that it allows refinement of these technologies to a very high degree. It is also a good thing because markets usually coalesce around good price/performance answers. It is a good thing because it allows investment in a supply chain that has some certainty of demand and ROI.

But, the possible issue here is this:

Some unconventional ways of approaching audio may have a hard time getting up to critical mass. Since unconventional means are not per se desirable, the issue comes when those unconventional means are needed to move the state of the art forward.

I think we may be at such a point, so I thought I would approach this show with a question in mind:

“do I hear, or hear of, new technologies, or old low market share technologies, that might be a key to future progress?”

In this video, I will review my thoughts some of those. This material is therefore somewhat speculative. It is not intended to declare that some different technology is “The Answer” or “The Future”. It is intended to give consumers some, possibly new, thoughts about technology they might investigate further.

Again, I am not judging that these technologies are breakthroughs or ready for prime time. I want to bring them to your attention so that you can do that. And I think new or distinctive technologies are interesting and fun.  I hope you do too.

Okay, let’s go over some of my technical highlights.


Theoretica Applied Physics: BACCH processor

We’re starting with this amazing device because it helps to start at the beginning. At the beginning, I think, is a common fundamental misunderstanding of the issue with stereo. “Stereo” here means the 2-channel recording and playback concepts we use to reproduce a sense of space and position.

I will try to keep this simple; for more detail check out Andy Quint’s review of the BACCH processor, and stay tuned for my upcoming coverage of the BACCH for Mac software version. Also check out my previous review of the Linkwitz speaker which aims at some of these same problems.

The Issue: The soundspace we hear from stereo recordings is not what it could be in terms of accurate rendition of the space or performer positioning.

The late Siegfried Linkwitz described the issue as being that our experience, and hence our objective with stereo, seems to be to create a miniature stage in between the speakers, where miniature performers are playing. I should add that this objective isn’t exactly easy to achieve, as often we actually get miniature performers who are playing inside the left and the right speakers.

The technical problem is that we seem to be stuck with improving a good but imperfect model of the soundspace. There would seem to be something in assumptions, or in our recordings or in our playback technology or all of the above that is limiting the results we can get.

Linkwitz, who started professional life as a Hewlett-Packard RF scientist, and Edgar Choueri of Theoretica, who is director of the electric propulsion and plasma dynamics lab at Princeton, have thought hard about how to address this issue. And my experience is that their answers are interesting. (Maybe we should replace the phrase “it’s not rocket science” with “it’s not audio engineering” to indicate problems that are simpler than the really challenging stuff, like audio?)

In reading some of their work, it strikes me that a fundamental common denominator of their work is borderline earth-shattering if you care about high-quality music reproduction. The earth-shattering idea, in my words not theirs, is that the data to place the performers in a realistic soundspace is on the stereo recording already. The work of the stereo system is not to screw up that data and/or it is to correct screwups that are inevitable.

Let me contrast that with common assumptions. One common assumption is that the stereo equipment in your listening room is critically responsible for additively creating a sense of spaciousness that is missing from the recording and therefore needs to be enhanced. Linkwitz and Choueri would say that is wrong. They say the data is on the recording already, you just need to present it properly to the listener.

Another sometimes common assumption is that we don’t have the complete data needed on a stereo recordings, so to really get the soundspace right, you would need a multi-channel recording (and playback) system. Again, these scientists say that stereo can get much of the job done, and in practical terms do a better job than multi-channel.

And, they point out that in any event most of recent musical history (1950-2023 and beyond) is encoded in two-channel recordings, so it would be preferable if we could work with those. Maybe Taylor Swift could re-record her work in another format, but we’re not getting Elvis or Cream or Bernstein or Miles back to do new recordings. And the music industry has a terrible history of deciding on new technologies.

I have the entry-level BACCH system on review right now, but I stopped by the Theoretica room at Capital Audio Fest to hear the big BACCH processor set up by Dr. Choueri playing through Janszen speakers. My system has Theoretica’s head-tracking customized to my exact listening position and for my head shape. Yes, that matters, but listening to the generic version at CAF still produced some of the amazing soundspaces that I hear at home.

What are we talking about when I say “amazing”? The generic BACCH can produce an image of a performer at 90 degrees left or right, well outside the speaker positions, with no problem. Or it can place performers pretty much anywhere else in between, if that’s where the performer was when the recording was made. Again, this is using standard stereo recordings. Just for reference, standard “between the speakers” stereo is plus or minus 30 degrees left or right from the listener. With BACCH at CAF, I heard plus or minus 90 degrees. That is a 200% increase in possible soundspace width. Now it is very important to note that the BACCH doesn’t force the soundspace to be that wide. It simply allows that (or wider). The recording engineers set the soundspace size. So, if the performers are in a 40 degree arc, they should be presented that way with BACCH. Or if recorded in an 80 degree arc, they should be presented that way. Come back for my BACCH review for a discussion of whether you want that soundspace with current recordings.

A simple explanation of what the BACCH processor does is easy to say, but not so easy to understand:

The BACCH processing system cancels certain acoustic crosstalk signals that were not in the mic feed but are automatically added when played back via two speakers. Remove that crosstalk and you hear something very much like what the mics heard.

On demo the result is almost shocking, especially if you come into the demo with the idea that stereo is set up to present an image spread between the speakers. Your reaction, I imagine, would be “how does it do that?” And if you don’t also have the idea that “the data on performer location is already on the recording”, you think the BACCH is additively faking it. Not so. It is subtractively getting back to the mic feed.

I will expand on this in upcoming pieces, but the BACCH software may be a key to a better future presentation of soundspace. I don’t think that is as simple as it sounds, but it is a source of hope in my mind.


Viva: Nuda Horn Loudspeakers

In the Audio by Oz room, a new speaker was on demo, the Viva Nuda Horn loudspeaker. This is a primarily horn design, with horns for the lower mids and upper mids and treble. Accompanying these two drivers are an active cone woofer and a super tweeter. The industrial design is also interesting in that the speakers, while large, are not super tall and do not take over the room as much as traditional wideband horns do. The Viva horns were, naturally, driven by Viva tube amplification. They produced a suitably dynamic sound on a variety of large-scale classical music, and they do make you wonder if the magic of horns is something that should be studied more.

When I say “the magic of horns”, I mean the frequent sense they give of realistic dynamic transitions, much of which is in the micro-dynamic or mid-dynamic realm.  Not everything is Mahler, though this thought applies to Mahler’s macro-dynamics too.

Horns in the old days were often derived from 1950s designs because then we only had low power amps and had to have high efficiency speakers. Materials technology then wasn’t even close to what we have today. Nor was measurement technology. And we have vastly bigger amps now. And better psychoacoustic science. So, it is interesting to contemplate what modern horns could do. This may be a good example of a technology that “the people” voted against 50 years ago, when the tech was limited and the high-end was tiny, but which now could work if only it could be developed. I am hopeful that the companies trying to move the ball downfield, like Viva and some others, get increased traction.


Von Schweikert: Active Bass Traps
Nemesis: Room Treatments

One obvious problem at Capital Audio Fest was bass. Actually, having measured many rooms, I would say that one problem with most real rooms is…bass. Rooms have walls and domestic dimensions and this means they have bass resonances that create peaks and dips and blur in musically important regions (e.g. 30-150 hz).

While being bugged by the resonances of hotel rooms, little did I know, Von Schweikert was showing their new VR-55 Mk II speaker with their upcoming bass trap system. Don’t confuse this with the active bass system, also optional on the VR-55.

I’m probably massively oversimplifying, but Damon Von Schweikert explained that they have designed a pair of separate woofers not to create low-frequency extension (which the VR-55 doesn’t necessarily need), but to be placed and operated to function as active bass traps. That means the VR-55 MkII will have an upgrade that can tame the inevitable peaks caused by room dimensions…without overwhelming the room with visually obvious treatments. The bass was about as clean as I heard at the show without seeming rolled off.

I believe Von Schweikert’s intention is to offer this active bass trap system with multiple models. The Von Schweikert active bass trap system should be available in the first half of next year with pricing tbd.

On this same subject, I have recently reviewed (upcoming on YouTube) the PSI AVAA C214 active bass traps and they work too. So, I am optimistic that this is a technology that could gain momentum partly because it helps with a real problem and partly because it fits with real living environments. I didn’t actually notice the Von Schweikert active traps when I entered the room, for example.

Another related example of such “hidden in plain sight” technology were the Nemesis diffusors. When I went into the Estelon and darTZeel room, I noticed a picture on the wall…of the Beatles. I thought “Oh, that’s a nice touch”, thinking it was just a big, dramatic photo. But no, the Beatles were printed on the acoustic surface of the Nemesis panels. These are designed to work at low frequencies, as are all bass traps, but Nemesis says they are focused more on diffusion than absorption. In the event, the bass was better controlled in this room than in most of the other small hotel rooms. Maybe the Nemesis panels work?


Larsen: Model 9 speaker

I got to hear the Larsen Model 9 in the Dr. Vinyl room. This is an interesting speaker that tries to solve a problem that almost no other current speaker in the high end really aims at, at least the way Larsen goes about it.

In simple terms, the Larsen Model 9 tries to remove the influence of the room on the sound. There are multiple ways the Model 9 does this, first by requiring a specific placement in the room: against the front wall and away from the corners. The drivers seem scattered about the speaker with only a tweeter really directed toward the listener. But, this is not randomness; Larsen is trying to get consistent spatial output across all frequencies (constant directivity).  By placing the speaker against the wall, bass is no longer omnidirectional (it has a quarter-sphere radiation pattern I believe) and the speaker-boundary interference response is eliminated or at least put at a frequency above where the woofer operates. The midrange is angled to create a very early reflection, inside the Hass window, from the front wall that your ear integrates and doesn’t hear as a reflection. Then there are three tweeters, two aimed up and one facing forward. Again, this complex system is designed to create uniform power response in the room. The placement of the speaker aids this goal and is intended to move many reflections either in or out in time so that they are not confusing your ear and brain.

My listening time was brief, but these speakers have something attractive going on. First, performers don’t seem to come from the speakers, rather, they are in the room. Second, my listening position was not at the apex of a triangle between the speakers as I would normally prefer with conventional stereo. And yet, the sound profile seemed balanced and was somewhat like sitting toward the side of a concert hall – not my preferred spot, but enjoyable.

To summarize: these are speakers that must be placed in a position that does not take over the room. Ideally, they require few or no room treatments. Their sound can be enjoyed by listeners outside the sweet spot.

Very interesting. Robert E. Greene reviewed these in The Absolute Sound and has more technical and listening thoughts at the link.


Diptyque: 140 Mk II planar magnetic speaker

Fidelity Imports demoed a new Diptyque speaker, the 140 Mk II. Diptyque uses push-pull dipole planar magnetic drivers. I’m speculating, but it would appear that the push-pull approach allows for enough excursion to extend the bass into the 50hz or maybe lower range. Alan Taffel was more circumspect than I was about the bass level, so I think this needs some additional investigation.

As a reminder, bass is hard with dipoles because they naturally have a bass roll off below a frequency set by the baffle width. This rolloff has to be compensated. At some combination of low enough frequency and high enough level you reach an excursion limit. And you reach it faster than with many traditional cone woofers because the compensation required is larger by the time you reach the mid-bass.

The Diptyque 140, like the larger Diptyque’s we heard at Axpona, delivered satisfyingly balanced mid-bass with good dynamics. The rest of the frequency range sounds pure and smooth. While not a small speaker, the shorter stature of the 140 might also make it a fit in more living rooms.

This is an impressive speaker, and at $25,000 seems potentially quite competitive.

Part of this thought comes from the comments I made at the beginning about the problem of stereo. Linkwitz was quite clear that constant or nearly constant directivity is an element of equipment design that helps render stereo soundspace more true to the data on the recording. Dipoles are one way to get closer to constant directivity than what is generally what occurs with cones in a cabinet. A typical cone speaker will have omni-directional bass and then more energy delivered forward at the top of each driver’s range. A dipole comes closer to having a figure 8 radiation pattern at all frequencies.

The weakness with dipoles tends to be the bass cancellation or roll-off effect, which has made it hard for dipoles to appeal to listeners who like the bottom few octaves to be realistic. You could get around that with very large panels, but that is unacceptable or impractical for many. Or you could add a sub, but constant directivity goes out the window. Hence, the Diptyque 140 is exciting because it brings the controlled directivity idea together with possibly satisfying bass that upsets room modes less than traditional speakers.

I hope we have a chance to review these.


Bacheaudio: 002 speakers

Bacheaudio was demonstrating their 002 loudspeaker. A semi-unconventional design, the 002 features an active 10” woofer with a bass level adjustment. A level control hardly seems like a breakthrough, until you consider the large variations in output below 100 hz experienced in real rooms with real seating positions. It practically defies logic that the low frequency output of a speaker should be held constant in all these cases. But, most speakers and electronics stacks do not allow this adjustment.

The woofer is crossed over to a 10” paper cone mid-woofer. The main driver is an 8” bamboo fiber midrange/tweeter which is run without any crossover. To support frequencies above 10 kHz, a Fostex super tweeter is used, and this also features a level control.

The goal is to create a high efficiency speaker with controlled directivity. Rated at 96db at 1 meter, the efficiency is high enough to allow use of SET or other low-power amplifiers. Bache demoed the 002 with a 15 watt per channel Alexus Audio SET amp.

The sound was nicely dynamic, with good balance and imaging. I was surprised at the smoothness of the response in the sweet spot. This speaker made me wonder about the potential for high sensitivity (as with horns) and controlled directivity (as with horns or dipoles or omnis) to mix dynamics with spatial accuracy. And to fully exploit the dynamic possibilities, it would be interesting to test speakers like these with bigger than SET power.

The Bacheaudio 002s are priced at $22,500 per pair including the bass amplifier and your choice of a variety of solid wood finishes.


Legacy Audio: Aeris XD speakers

Legacy Audio introduced the Aeris XD loudspeaker at Capital Audio Fest. There is so much interesting technology in this speaker, I probably can’t do it justice, but I’ll try.

The Aeris has a powered bass system, using two 12” woofers per speaker, with 750-watt class D amplification for each driver. So, to be clear, you have 1500 watts per channel for low frequencies. The remainder of the speaker is passive, with a 10” mid-woofer, 8” midrange, 4” AMT tweeter and 1” AMT supertweeter.

If you think about it for a bit, those are rather large drivers for their assigned frequency bands, but Bill Duddleston, Legacy’s chief engineer, is aiming for a controlled directivity pattern. What is particularly interesting is that he is designing for a cardioid output pattern. Cardioid means the speaker output is mainly to the front and drops off to the sides and rear of the speaker. But, I think, the big point for spatial performance is the controlled directivity goal, if you tie back to Linkwitz’ thinking that I mentioned before.

Now, achieving cardioid radiation is tough with cones in a cabinet, but Duddleston has used driver size, side radiation (as with a dipole) and his not-so-secret weapon, which is DSP. Legacy has long partnered with Bohmer Audio to create time-domain correction software. In this case, part of what the software is doing is cancelling the lateral and rear radiation from the speaker in areas where a pure acoustic approach is insufficient.

Legacy then uses their DSP system to do room correction in the bass because, as we’ve noted, bass is a big problem in real rooms. Duddleston showed me interesting measurements of bass wave propogation over time, and you can see in those charts that normally the timing of bass arriving at the listener is, to put it mildly, wrong. Which means delayed relative to the input signal…and delayed in a complex way. Unless it is corrected, likely in a complex way, as with DSP.

On a track I know well, from Shelby Lynne’s Just A Little Lovin’ album, the Aeris XD demonstrated a remarkable combination of bass power and detail.

Then, touching on the last element in our trifecta of issues, the drivers Legacy has chosen for the Aeris lead to high sensitivity. In this case, the sensitivity is 95 db for the standard 2.83 volts @ 1 meter. I don’t know that this sensitivity is critical to dynamic realism, but it seems to help. That help may simply be that realistic amplifiers can deliver high dynamic range. That is, the dynamics of sensitive speakers may not be something inherent to high sensitivity per se. To put that in perspective, I recently did a calculation that some low-efficiency systems would require 4 kilowatts of power to produce certain dynamics. As I said then, “not going to happen”. So, high sensitivity may allow real amplifiers to produce high dynamic range.

The Aeris XD is priced at $23,400 per pair with the Wavelaunch DSP processor. You can upgrade to the full Wavelet II preamp, crossover, processor as well.

The Aeris XD checks all the technical boxes, so I would very much like to hear it in residential surroundings with low background noise and ample time to explore a variety of music.


MBL: 101e MkII speakers with MBL 9011 amplifiers

This room was full of products that have been around for a few years. But I stopped anyway because I wanted to see if the rapid progress of the industry in the past 8-10 years had left MBL a bit less special. Not really, to put it mildly.

I suspect MBL has made more improvements along the way than their model numbering indicates. In any event, the sound in the MBL room was glorious in a way that could be the envy of many.

Since we are talking in this report about spatial presentation and the problems of stereo as commonly practiced, let me say that a standout thing in the MBL room was the ability of the 101 speakers to place an image in virtual space in a way that is at least unusual and perhaps unmatched except by the bigger MBLs.

Now, I should add that my view is that some intuitive explanations of how the MBLs do this are likely wrong, although I stand to be corrected. If you think about the theme of controlled directivity or constant directivity, you instantly recognize that a true omnidirectional speaker might be the ticket. Bass with cone drivers wants to be omni, so why not build omni midrange and high-frequency drivers? Most other approaches to constant directivity are only going to get part way there.

MBL has gone all the way with the 101, at least in the lateral plane, and it seems to work like a charm. The driver system in the 101e Mk II has been under development for over 30 years, which may explain why it is unique. There are, of course, other ways to do a full range omni.

But the attractions don’t end there because the detail of the 101e sound is excellent and the tonal density is well above average. The bass definition is also pretty high (though this was not the ideal room for bass and yet the 101s were top tier among show demos on the tracks I heard). There is no obvious tech underpinning to this, as there is with some other systems we’ve discussed, however. Execution still matters.

The other area we’ve talked about that the 101e Mk II doesn’t offer is high sensitivity. MBL has a solution, it would seem, which is to use the giant, ultra-wideband MBL 9011 amps. From past experience, these amps are an important element to the overall impressive and beautiful result.

The MBL 101e is priced at $91,000 per pair. The 9011 amplifiers are $128,200 per pair.


Personal Best of Show

For reasons I’ve touched on, I don’t like the best of show idea. It is illogical. At a show, rooms are different from each other. OEMs don’t all have the choice of rooms sized properly for their equipment because rooms are chosen by historical precedent. Noise levels vary. And noise levels are almost always high (about 15 db above my listening room for example). Seating positions vary when we are there. My brain and ears vary based on what I just heard 5 minutes before. I don’t have time to hear the 100 or so tracks I regularly use for reviewing. I don’t get to visit every room or anything like it.

And then there is the issue of what is best for you? Is a Porsche 911 GT3 the best? The best off-roader? If you have small room, is the XVX Chronosonic the best speaker? If you have a large room and low sensitivity speakers, is a 100 watt tube amp ideal?

You get the idea.

However, I understand that some people would like some sense of a “winner”. Football has a winner. Politics has a winner. So, reminding you of all the issues I just rattled off, I’ll get off my high horse and pick two personal winners:


  • First, the Fidelity Imports room where they demo’d the Q Acoustics 5050 speakers with the Unison Research Unico Nuovo class-A integrated and Innuos streamer/dac. Potentially coming in around $6500 for the entire system, I liked the sound and the price point. At a show where “big” is a draw, there aren’t a lot of demos in this price category, but this system just sounded musical and seemed like an outstanding value.
  • And I was impressed with the MBL room. We have awarded similar MBL systems best of show in the past, so my choice is hardly insightful. But, as a listener who prizes a sense of virtual reality, the MBL system goes as far in that direction as anything I heard.


Now back to our regularly scheduled sanity, or insanity, depending on your interests.


A Simple Summary

In my view, the industry is to be praised for a relentless pursuit of musical accuracy. In the last 15 years, progress, in what would seem to be a mature field, has taken off in meaningful ways. This direction is, perhaps, more appealing to those with a connoisseur’s mindset, but it is an artistically-motivated endeavor and one that I find admirable.

At the same time, audio faces some challenges in advancing the state-of-the-art. I think the Capital Audio Fest showed that work is being done in areas that might move the ball way down field. And, perhaps most positively, it showed that the massive historical recorded library of musical artistry is in a technological form that could be the backwards-compatible platform for huge strides forward.  I certainly hope so.


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