BACCH 3D system at CAF

I had the pleasure of hearing the BACCH system at CAF today which simulates 3d sound. https://invention.princeton.edu/news/edgar-choueiri-bacchtm-3d-sound . This was a night and day effect on the audio that is hard to describe without saying 3d. The sound stage and positioning of sound seemed incredibly accurate and real. Very cool stuff.

 

This confuses me a little bit, reading how it works. So they're saying crosstalk between speakers is bad? If so, why are headphone and IEM people saying those can't stage well because they're missing the crosstalk?

 

There is a certain amount of crosstalk you need in order for something to sound natural because a sound for a single source will diffract around your head in a frequency dependent manner to reach both of your ears.

If I'm reading their website correctly, BACCH seems to use crosstalk cancellation as a first step to make other DSP magic possible.

 

Thats how I understood the basic approach except its dynamic as it tracks an individuals head. It seems like its capable of doing more. For instance he talked about making headphones have the sound quality of a martin logan for instance and also having a changing sound perspective based on your head movement.

 

They're doing both crosstalk cancellation with head tracking (if you're curious, you can try recursive crosstalk cancellation for free without the head tracking with ambiophonics -- http://www.ambiophonics.org/ ).

The purpose of crosstalk cancellation is to eliminate the fact that the sound from each speaker strikes both of your ears. The brain measures the interaural time difference and uses it to help calculate the angle of the speaker. In practice, this limits the width of the soundstage to the region between your speakers, e.g., the standard 120 degree stereo spread. (When systems have a soundstage wider than that, it's because the brain is hearing first reflections off the side walls, creating artificial ambiance.) Whereas a stereo recording naturally has a 180 degree spread. Crosstalk cancellation also reduces the midrange response error that results from interference between the two stereo speakers.

When you kick in crosstalk cancellation, you hear the soundstage open up and become wider and more convincingly three dimensional.

You can actually hear some of the effects of crosstalk cancellation just by holding your hands in front of your nose and making a barrier. You won't get the full effect but you'll definitely hear a difference.

I've played with ambiophonics and physical barriers some, and the effect can be impressive. But I've never had a chance to hear the BAACH system and ambio wouldn't be practical in my setup (the speakers have to be closer together than the standard stereo spread, and my room does double duty as a home theater).