So Many Channels, So Few Ears.

By John Strohbeen • • Tuesday, October 28, 2014


In the beginning there was one, and it was good! In fact, for close to half the life of consumer audio, one channel was all you got. Then came stereo – and later, the flood of multi-channel formats. Quad in the 1970s was pretty much a commercial failure; but, it started people thinking and doing research. Home Theater changed that. Dolby and DTS succeeded with the digital versions of surround in the ’90s with 5.1 and later 7.1 systems.

Dolby Atmos is expected to be strong in 2015 with systems of up to 32 discrete channels of sound. Atmos is the simplified home version of the movie theater sound being used in many blockbuster movies of the past couple years. I believe Dolby Atmos was designed to give a more dramatic audio experience in the theater than in the very best home theater, and it worked. Now, they want to bring that experience to the much larger home market.

Can the benefits of multiple channels and sound sources be extended from movie and home theaters to pure music listening? I believe so.

Music reproduction can be enhanced with additional channels. Early in the first years of home theater, Yamaha strongly supported two extra front high/wide channels to expand the soundscape beyond the left and right main speakers and add height to the image – in effect, a 7.1 system using a 5.1 base. Yamaha utilized that format in its Digital Soundfield Processing receivers for music as well as for movies. It helped.

Although Dolby Digital won the standards war without these channels, they are now added to Dolby Atmos. They can help bring the listener to the concert hall. Many movie effects had things flying overhead. The rear speakers create this effect and ceiling speakers can give further improvements. It is an effect rarely used in acoustical music; but, the hall ambience can be added. Additionally, the depth of the front soundscape can be increase with rear and over-head speakers.

In my experience, most of these effects are outside the front soundscape and ideally should be immersive rather than pinpoints. To create an immersive field with direct-firing speakers is quite difficult. This is probably why THX initially specified dipole speakers for the effects channels. (Dipoles were not a big commercial success because in the showrooms, it was easier to demonstrate the extra channels with direct firing speakers; and thus justify the extra cost of home theater setups.) To get immersive effects, you need many more direct firing speakers in the effects channels than you need speakers with great dispersion. Dolby Atmos supports up to ten ceiling speakers. An easy demonstration: when used in effects channels, laying forward firing speakers on their backs usually makes a dramatic improvement.

Even though we have only two ears, to create a complete holographic soundscape and eliminate the “sound” of the room, you need a very large number of discrete channels in an anechoic chamber. That’s interesting; in the real world, we make compromises and our compromises are providing ever more realistic, dramatic, and enjoyable sound.

Of course, the human factor (the performance and engineering) will dominate the quality of the effects. The rubric “Garbage In/Garbage Out” is as applicable to the world of audio as it is to the world of data.

Nonetheless, I expect that as the number of channels increases, so will our enjoyment of sound – whether it is from a movie or a single instrument. The world of sound is a beautiful environment.

Enjoy & Good Listening!

John

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