A high-end retailer writes: Hello again. Part of my work involves home setup. Consequently I pass on hard-won setup tips. I'm going to pass on my experiences re the illusory center image.
What’s the objective? Well … for proper stereo imaging the loudspeakers should ‘disappear’ and the illusory stage is always behind the loudspeakers. I should at this stage point out that personally I'm not that bothered by the phantom; my system appreciation comes from other characteristics. However, some of my customers feel that the image aspect is important and of course my obligation is to serve their needs. Here’s how I go about this.
I position the speakers so they form a perfect equilateral triangle, with their listening position the third point in the triangle. This means if they are 8 feet away from the speakers, then they should be 8 feet apart and slightly angled in towards their listening position (but never closer than 3 feet from each sidewall). I remove spikes or tiptoes at this point. All room correction devices are disabled
I always start with a simple female vocalist of which I have several. I set the volume to the exact level necessary to make sure her voice isn’t too big or too small. What I listen for is a perfect, palpable image placed approximately halfway between the rear wall and the loudspeakers. It should be three dimensional and floating perfectly in space as if it were a holographic image.
If the voice is diffuse or too wide, I toe-in the loudspeakers (point them towards the customer at an angle) a degree at a time until the vocalist pops into focus.
If she is not well behind the loudspeakers, I move the speakers away from the rear wall a bit to increase depth.
If the tonal characteristic of her voice is thin (without lower midbass), I move the left and right speakers closer together until the customer experiences just the right tonal balance (the closer the speakers are together, the better midbass coupling you get from the speakers). I’m careful not to go too close because the size of the soundstage will get too small. Moving the speakers closer to the rear wall will improve bass and weight but decrease stage depth. Finding the perfect balance can take quite a while or it can occur almost immediately. There’s no worthwhile way to predict this.
If she sounds bright, too one-dimensional or too low in height, I tip the loudspeakers back about the same distance as a CD case thickness (hint: use a CD case to slip under the front for now). Add more cases till you get it right.
Once she’s perfect, then move up to more complex music with a good center image. I use a Diana Krall piece that has drums, bass, piano and the singer. Repeat the above tips until the group sounds correct.
I keep moving up to larger pieces, making minor adjustments to balance the presentation, finally going back to the original piece making sure I haven’t lost any ground.
When I get it right, the imaging extends beyond the room and certainly the loudspeakers themselves on the right piece. My final check for everything correct is almost always one of Keith Johnson’s Reference Recordings. They are a perfect reference. Get that right and everything else falls into place.
This setup process is fundamental and I go back to it every single time I setup any system, even an existing system that has gotten out of tune.