Three Channel Stereo

Stereo with 3 speakers – is that heresy or maybe a really good idea?

Purists would have you believe that stereo means a recording with 2 channels and played back with 2 speakers.  It turns out that early research done on “stereo” in the 1930s included experiments with both 2 and 3 channel recordings (left, center, right) and with 3 speakers.  Later on, Paul Klipsch (of Klipsch Loudspeaker fame) did experiments and demonstrations with 2 versus 3 speaker playback of a 2 channel stereo recording, and concluded the 3 speaker setup was superior.  Some famous classical recordings were recorded with both a center (mono) and stereo set of microphones, although not released to the public as 3 channel.

In the 1990s, Michael Gerzon wrote and presented a series of papers describing a method for playing the sound from M channels with N loudspeakers, where N>M, and in the simplest case we have 2 channels, 3 speakers.  A commercial implementation of his ideas was the Ambisonics Trifield processor which was implemented by Meridian Audio.

I’ve never heard a Trifield setup, but I’ve read some rave reviews.  More recently, it seems Magnepan is doing experiments and marketing a 3 speaker stereo solution.  Reading about 3 speaker stereo got me thinking and wanting to do some experiments at home.

What might be the advantage of three speakers over two?  With two speakers, sounds that come from the center of the soundstage are present in both the left and the right channels, and our brains create a “phantom” center – if you stand or sit right in the middle between the two speakers, sound mixed equally in both channels will appear to come from the center.

But what if you are not positioned in that perfect sweet spot? And even if you are, there are those who believe there is less listening fatigue with a physical (not phantom) center speaker, as well as a reduction in “intra-aural crosstalk” – the left ear hears sounds from the right speaker, and the right ear hears sounds from the left speaker.  So I thought maybe there’s something to the idea of 3 speakers.

Now the argument for a center channel speaker is well established for movies and surround sound systems for a home theater have become the norm.  Nonetheless, I have resisted the surround sound argument and watch movies with just 2 speakers mainly because of simplicity, effectiveness, and cost.  For example, I reasoned, I would rather have 2 good speakers and a good 2 channel amplifier than (for the same money) 5 speakers and inferior electronics.  In my house, in the setups for movies, I do get to sit in the sweet spot, and for equal quality 2 channel/2 speakers costs less than 3 or 5 or whatever.  But I do my best listening for music in a different room, I don’t get to stay in a sweet spot, and that’s a story for other blog posts.

Some links:

http://www.stereophile.com/reference/407upward/index.html (Keith Howard article)

http://www.audiosignal.co.uk/Gerzon%20archive.html (articles by Michael Gerzon)

http://www.audiosignal.co.uk/Resources/Three_channels_A4.pdf. (3 channel stereo, Michael Gerzon)

http://www.magnepan.com/tri-center

http://www.theaudiobeat.com/blog/magnepan_37_tricenter_system.htm

Two Channel and Stereo

Many people equate stereo and two channel.  In my post about mono, I went to some lengths to explain that mono does not mean one, and similarly stereo does not mean two.  With our eyes we perceive visual depth because each eye sees the world from a different angle.  With our two ears, each ear receives slightly different sounds because the source  will likely be closer to one ear than the other.

I remember when I graduated college and got a gift of a “stereo system” – this was back in the 1980s, and I got a receiver, a turntable, and two speakers.  So the notion that stereo means two is pretty ingrained, but it isn’t necessarily so.

A two channel recording simply means a separate left and right track.  For example, I could create a recording with a singer and a guitar, and record each separately in mono, and place the singer in the left channel and the guitar in the right channel.  Is that stereo?  In fact, many recordings are done this way with the exception that the main interest, say the singer, is “mixed” equally in both channnels.  So you might have the drums in the  right, the guitar in the left, and the singer equally in the right and left.  This is 2 channel, but it’s not stereo.

So what is stereo?  Stereo is short for stereophonic, a word made up to sound like the visual term stereoscopic.  The Greek word stereos means solid, not two, and stereoscopic is a technique to create the illusion of visual depth by having the left and right eyes see different images (like the 3-d movie glasses).

Some people feel adamantly that “true” stereo means two channels and two loudspeakers, for example see: http://www.tnt-audio.com/topics/realstereo_e.html.  A true stereo recording, then, would suggest recording a live musical performance with the acoustics of the performing hall and the position of different voices and instruments captured by at least two microphones.

When a good stereo recording (two channel) is played back with two loudspeakers, and if the two speakers are placed properly in the room (at the same height, and equally distant from room boundaries), and if one is positioned exactly equidistant between the two speakers, one can get a good illusion of the spatial quality of the original performance.  Notice three important caveats – good recording, the positioning of the loudspeakers, and where one is positioned when listening.

I will argue in the next post that since stereo means solid, the best way to create a “solid” aural image may be with more than two speakers.

Vinyl holds actual sound waves and other myths

Vinyl holds actual sound waves whereas digital uses binary code to closely replicate those sound waves.

Do you believe the above statement?  Are you a vinyl fan and unconditionally think vinyl is better?  If so, I have strong disagreements with you.  I’m the son of a teacher, and I like to explain things.  Hope this blog isn’t coming off as too pedantic… Earlier this year I visited a nice audio store in San Francisco, Music Lovers Audio.  I commented on all the turntables in the store to a young and enthusiastic salesperson who explained to me that many customers had an interest in vinyl.  What greatly surprised me was when he also said that many new recordings were being released as vinyl.  Having a turntable to play older recordings, that I understand, but why buy a new recording on vinyl, especially since new recordings are almost always done with a digital recorder?

I started searching on the internet, and came across a number of articles that supported the salesperson’s claim.  Why is vinyl becoming popular?  In quick summation, some reasons include that it can sound better than digital, especially compressed mp3, the retro or nostalgia factor, and the novelty, for a younger generation mostly acquainted with music as digital downloads, of something physical you can touch and look at – vinyl often comes with a large booklet with photos of the artist and the recording and bio information and so on.

I am going on my soapbox here about what is often a lack of critical thinking when people discuss vinyl.  Let’s get some things out of the way.  I grew up before the age of compact disks and mp3 downloads, I have a fair number of vinyl records, and I like vinyl.  If someone wants to say that they enjoy vinyl, no argument from me.  If someone thinks vinyl sounds better than compact disks, I think that’s debatable, but I don’t object to that point of view.  When someone argues complete and total nonsense, examples to follow, I have a problem.

Let’s have a quick oversimplified view of how most vinyl is made.  First, there is a “master tape” – this could be a digital master, or an analog master.  If it is an analog master, it is very precious and fragile, as each time you play the tape or make a copy you cause some wear and tear to the original, and any copy of an analog tape is not a perfect copy and has more noise and distortion than the original.  So, copies of the original analog master are made for use in creating a vinyl record. To make a vinyl record, probably there are at least two or more copies of the original master – a working master, and then a cutting master which has sound equalized and compressed to make a vinyl record.  A vinyl record is produced in a process that I think of as like stamping cookies with a cookie mold, so with this analogy the cutting master tape is used to make the lacquer master from which the “cookie mold” that stamp/press the raw vinyl is made.

Now, if you start with a digital master tape, the process is basically the same except that at some point the digital data needs to become an electrical (analog) signal to “cut” the lacquer master, so either the cutting master itself needs to be converted to analog, or the data on the cutting master needs to be converted to analog.  Said another way – if the master recording is digital, there must be a digital to analog conversion to make the vinyl record, and all the arguments about the inadequacies about digital audio are thus present in the vinyl record that is made from a digital recording.

Consider that today the professional analog tape recorder is nearly an extinct creature in recording studios.  That means new recordings are almost all done using digital recorders, and the true master tape is digital.  Does this mean vinyl cannot sound better than cds or mp3s? No.  There are various reasons vinyl might sound better to some.  Perhaps the digital-to-analog conversion done in the studio, starting with a master tape quality digitial file, is better than the process at home with say a cd or mp3 file.  Perhaps the faults of analog playback from modest equipment are more pleasant than similar faults from modest digital equipment.

Recognizing that new recordings today are done with digital recorders though means that those who make blanket claims about the superiority of vinyl because is it analog and assert that digital is not real music are kidding themselves.  Let me say all this another way: if the source master is digital, then it stands to reason that the very highest fidelity to the master would be a digital file which is a perfect copy of the master.  Now yes, that does not describe mp3s or cds, so if you think vinyl sounds better than those formats, fine with me.

But vinyl cannot inherently be an improvement over the source file which is digital.
To circle back to the statement at the top of the blog, here’s an example quote from my perusing the internet, “When listening to vinyl, one is hearing the closest reproduction of the master recordings, be it digital or analog. Vinyl holds the actual sound waves of those recording session masters whereas digital is using binary code to closely replicate those sound waves.”  How ridiculous is that?  If the master recording is digital, how can the vinyl made by multiple processing steps of the original digital recording hold the actual sound waves?

In summary, if you are buying a new vinyl record today, from a new recording, the recording itself is very likely to be digital.  And, in order to create the vinyl record from the digital recording, there must be a digital to analog conversion.  So, if you are convinced (wrongly in my view) that there is some fundamental flaw with digital audio, then all the putative inadequacies of digital audio are present in the vinyl record that is made from the digital recording.