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For those interested in the BACCH system, my article on how it performs in my system appeared in the October issue of audioXpress magazine.

https://audioxpress.com/news/audioxpres ... cal-design

Tom,

Thanks for sharing the link, but you buried the lede. What's the 3 driver (2 way speaker?) on the cover? Influence someone to build eggs? Is it a full range driver on top with two woofers?

I have no idea where the egg speaker came from. It's not part of my article. I have not read the whole issue yet, but have not found a reference to it.

I auditioned BACCH at Tom’s place yesterday. Tom switched it on and off while the music is playing, making the comparison easy to hear.

With BACCH engaged, the soundstage expanded significantly, instrument separation improved, and the presentation became enveloping, engaging and more enjoyable, though slightly forward. Switching it off made the stage seem to collapse and recede. The difference was obvious.

BACCH is supposed to be tuned to each individual and I heard these benefits in a system that was personalized for Tom. I am sure he can hear more enhancements with BACCH.

If I have BACCH in my system, I will never turn it off.

Thx, Tom for hosting me and the demo.

I tried it, with assistance from their engineer, but unfortunately heard very little effect, We determined that this was due to a serious imbalance between my right and left ears. I have what used to be called "nerve deafness" in my left ear which severly limits the frequency response. While the system was in place I invited my audio buddy, who is an audio engineer and has "golden ears", over to hear it. He could clearly hear the effects, but he's an old-school audio guy and felt it had an electronic signature. But the key thing here is that if your hearing is in any way deficient, the benefits of BAACH may be lost on you. I will say they were actively helpful and dedicated to trying to implement the software. YMMV.

More on where the egg speaker photo in the October issue of AX came from. This from the editor, Joao Martins:

Hi Tom

I’m answering this one since that was my work - or better said AI's work.
I actually created that room background illustration drawing for the Lutz article (you can see it in the same issue, with the MTM speakers.

For the cover, I actually wanted to use your Egg speaker on that same background, but the light on the original room photo we had didn’t look right.
When I asked Adobe to use AI to “harmonize” the speaker layer with the background (normally it does that very well), the result was as shown.

I thought it was funny and I ended up using it because it didn’t take so much space.
I guess if someone builds those speakers for real, they can call it “Hallucinations”.

Maybe I should have shared that story.
I’ll add it to the next issue’s editorial


AI strikes again!

Possible reasons for Grover's inability to get the full effect of BACCH can be due to his frequency limitations in one ear. This is from my article in AX that describes the differences in how HRTF responds at different frequencies:

To vastly oversimplify HRTF, there are three
dominant factors that affect the ability to retrieve
depth, width, and height information from a sound
source. They are interaural level differences (ILD),
interaural time differences (ITD), and spectral
changes primarily from comb filtering caused
by the pinnae of the ears and other body parts
(e.g., shoulders, nose, etc.). ILD acts primarily at
frequencies below 1,500Hz, ITD acts primarily at
frequencies above 1,000Hz, and comb filtering
especially from the pinnae occurs at frequencies
above 5,000Hz.


Limited high frequency response of the ear will prevent full realization of the spatial information as described above.

As far as the response of the audio engineer who heard BACCH at Grover's, I can only guess that the "electronic signature" he describes with BACCH is due to the elimination of comb filtering from centered images when cross talk is cancelled by BACCH. This was explained in the 1986 AES paper given by D. B. Keele, the reference to which is in my article. BTW, Don worked at among other places, Electro Voice and Harmon. He has patents on the constant directivity horn and the bi-radial constant directivity horn. He also received a Technical Oscar for his work in theater sound. I'm including a PDF showing the effects of cross talk on centered images he measured when using two speakers. That damage to the frequency response is minimized when crosstalk is minimized. If you have a highly reflective room with early reflections, they will reduce the comb filtering effects but also substantially interfere with transients and room sounds. You don't need BACCH to reduce the comb filtering of centered images. An alternate is to redirect centered images to one center channel speaker. Having one centered speaker will also give better timbre results with mono recordings, even though two speakers can produce a phantom centered image. Could his description of "electronic signature" be related to a cleaner, more transient presentation of the sound?



Also remember that there is no overarching single method to get "good" sound. It depends on your needs which can also vary with your mood and type of music being reproduced. All of this and more is described in detail in the October 2026 issue of audioXpress magazine.

Tom,

Reading more on the subject, I gather the speaker placement plays a critical role in the crosstalk. I asked ChatGPT to calculate the ILD and ITD for 20, 30 and 40 degrees speaker placement from the center. At 40 degrees --compared to 20 degrees, crosstalk ILD is increased by about 6 dB at 4kHz due to head shadowing whereas the ITD increases from 175us to 350us. As the ILD increases, ITD becomes less relevant.

So, crosstalk reduces as the distance between the speakers increase. But then, we have to worry about side wall reflections.

That explains why I love my horns placed wide apart.

"Could his description of "electronic signature" be related to a cleaner, more transient presentation of the sound?"

No, it sounded like some processing had been added. It wasn't a natural as the original signal.

Edgar from BACCH suggests dipoles, horns, or else if using omnis, substantial room treatments to control early reflections. They not only interfere with BACCH but also regular two channel playback.