Geometry and Stereo

In the previous post I explained that the best place to listen to music in my house is in the kitchen.  When I’m in the kitchen, I’m not sitting in some idealized perfect audio sweet spot, I’m moving around.  And, I’m often about 16 feet away from loudspeakers which are 7 feet apart.  The geometry of my listening position relative to the loudspeakers has a lot of implications.

When I got my first stereo system, I was impressed with the imaging – the ability of the two speakers (with a proper recording) to create a visual image where I could “see” the location in space of various instruments or voices.  And when I’m watching a movie, the sense of the location of the sound should match the action on the screen.  But when I’m in my kitchen, it is a different perspective.

Because the speakers are relatively close together compared to how far away I am in the kitchen, most sounds appear to be coming approximately from the center.  And that’s closer to what I usually experience in a live concert in many cases.  Usually I’m relatively far from the stage, and the main interest – perhaps a violinist, or a solo singer, or a piano, is usually near the center of the stage.  And, as discussed in previous posts, most recorded music these days may be available in a 2 channel format, but it’s not a real stereo recording.

So I began to think about adding a center channel speaker, and wondered what would happen.  I bought a fairly high end surround sound processor and used it to create a center channel signal using Dolby Prologic II (or a variation).  At first, I used one of my Spendor Sp2/3 speakers, positioned horizontally, as the center channel, with a pair of inexpensive small bookshelf speakers.  I found a few things; remember these observations are strongly related to the geometry of my listening room and may not apply in other situations:

a) I liked having the physical center channel speaker – the sound coming from the real center was clearer/sharper than the phantom center I was getting from just two speakers.

b) The overall sound coming from a superior center channel speaker with modest left/right speakers was very good – the left/right speakers were important in making the sound more spatious, but as most music has the most important element (solo voice, or solo instrument) mixed to come from the center, it was the center channel that was the most influential determinant of the sound.  In fact, sometimes I would listen to just the center channel speaker, and because of my distance from the center speaker, and perhaps also because of the sound reflections in the large room, just the single speaker alone sounded pretty good, although I preferred the sound of all 3 front speakers.

c) I got a good result with non-matching center and left/right speakers.  Now for movies you want a close match between front speakers, but for music alone the left/right positions of instruments/voices are often fixed for a given music track, and listening as I do from 16 feet away I got an overall blend that didn’t depend on the center exactly matching the left/right speakers.

The experiment with the Spendor (lying on its side, clearly not optimal) as a center channel, lead me to want to find a center channel speaker so that I could use the Spendors as left/right speakers.


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