October 26, 2021
 by Paul McGowan

There are ghosts in our stereo systems. Phantoms of sound that do not physically exist in the real world.

We call them the center channel.

Think of how much time and effort we put into getting this phantom center channel to sound real.

For most people, the center channel is number one in importance. We typically get it to pop and sound real, then work on the rest of the soundstage until the center begins to degrade and that’s where we stop and call it good.

You can easily tell if you’ve gotten the center channel right. Play a mono recording and if things are properly set up, the music from that monaural recording should be disconnected from the speakers and form a believable image.

And the good news?

Unlike home theater folk with their hardware center channels, ours are but an illusion we never need upgrade.

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17 comments on “Phantoms”

  1. There is no magic in this. It is well known that the ability to image sound arises from the invention of the Blumlein Pair, a recording technique using two microphones of particular design. Alan Blumlein was a top engineering graduate from what is now Imperial College and was working as an EMI research engineer. He published his paper on this in 1931. It took the music industry more than 25 years to adopt this technology. Blumlein’s original motivation was cinema spoken sound, not music, although some early tests were done with orchestral music.

    1. Bear in mind that mono sound for music works perfectly well and some of us still listen to it, quite frequently. Even the Beatles in the 1960s preferred to engineer using mono sound. However, talking movies were produced from the late 1920s and mono sound with several voices at the same time does not work very well at all.

    2. Denon did this with three mics, and then was an early adopter of digital recording. I have several Denon samplers, as I used to sell Denon CD players as well as the whole audio line.

  2. A stereo system also can “generate” phantom images far beyond the left and the right speaker and in some rare cases phantom images from behind the listening seat. This reminds us that our aural perception- as our visual perception – isn’t but an individual neural reconstruction based on more or less limited input data from our ears (or eyes/retina). Concerning headphones an individual HRTF correction should be a must for avoiding in-head-localization.

  3. There are many, many monaural LPs that yield wonderful music. A particular favorite of mine is “Ella and Louis”. Absolutely no need for stereo when these two are singing. Another great one is “Songs for Swinging Lovers” by Sinatra on Capitol.

    1. Sinatra first few albums at Capitol were recorded for mono and stereo using separate microphones, the mono mix being well established using loads of microphones, the stereo using only three. From Come Dance with Me! they all used the same master tape for both mono and stereo. We like a bit of Sinatra and the early stereo mixes are very left-right.

      One of my favourites is a Melodiya issue from the mid-50s of Richter playing the Prokofiev sonatas 6 and 8, using a mono cartridge. Huge sound, huge music.

  4. Disparaging those who’s system include a more robust feature set than simply a 2 channel option isn’t the position to take. If the system includes a multi-channel option or embodies what Paul calls “home theater folk” they can leverage the very same rule set and setup that one would use in a 2 channel system. When someone swears that you’re using a 5.1 configuration and finds that you are actually only using 2, you can also find the same feeling of achievement.

    The assertion you never need upgrade your virtual center channel is lost in the need to forever seek upgrades to the system.

  5. My stereo system produces a great center channel as long as I listen from the center. When I move to the side the soundstage collapses. May be I do need a center channel speaker to maintain the center, or maybe I need some serious adjustment on my setup.

    1. Using the assumption that mono recordings played back over a stereo system feeds essentially identical signals to both channels. You then need to sit dead center for each ear to receive the same sound waves in phase at precisely the same time and let the brain interpret that you a hearing a single sound source directly ahead of you, Paul’s phantom. Or you could turn your balance knob (remember those?) full left or full right so that sound is emanating from only one speaker (assuming that the balance control is 100% either/or at the extreme positions). Voila, instant one channel system.

  6. Sorry for being so late to the discussion here but the current nor’easter has already dumped almost 4 inch of rain on us in about 12 hours and thanks to the new drainage channels that Ida created when it dumped almost 6 inch of rain us I am on leaky basement duty today. For decades I have said give me rain over snow anytime. Thus the saying “Be careful what you wish for”. The winds are now starting to ramp up.

    I really do not like multichannel sound even at movie theaters. Thus I have learned how to setup two channel for good acoustic images including a phantom center channel. I do use a subwoofer in my video system.

    1. Some people like Ford, some like Chevy… However, there is a ton of really great media, concerts and performances on multi-channel. (5.1 or more) Enjoy what you have, even if it’s a handheld transistor from decades long past…

    2. The double edged sword of subsurface structures in places with a shallow and fluctuating water table. Even with a deeper water table, rapidly infiltrating precipitation/melt water will take advantage of any gaps available to it. Water, like electricity, will take the path of least resistance. Good luck and stay dry.

      When Walt Disney World just outside of Orlando, Florida was conceived, the plan was to have an underground infrastructure for the Magic Kingdom so that the behind (below) the scenes workings of the park would be invisible to the guests: the famous (at least to Disney nerds) Utilidor network. It was soon discovered that the depth to the water table was only 1 to 2 ft. Active subsurface drainage/pumping systems is complicated/expensive and not even Disney is 100% reliable. The 2nd Law of Thermodynamics will get you if you don’t watch out and it will still get you even if you do watch out. The solution, build the infrastructure at the original ground level and then build the park on a second level on top of it. This is an oversimplification as there is a lot of clever structural/mechanical/electrical engineering (imagineering in Disney speak) involved, but you get the idea.

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