Finding the "sweet spot"

By: Gary DeRoy (GTX_SlotCar)                        

After I reread my original article on the BIC speakers a few times, I realized that a further explanation of their imaging was in order. 

My old 3D Acoustic speakers imaged extremely well with a sweet spot that extended way beyond the center listening position. This spoiled me because speaker angle and placement were not that critical. Most speakers, even expensive ones, don't image this well. You have to be in the sweet spot, and when you are the music comes alive. I really noticed this with the BIC DV62 CLR-S speakers. My normal sitting area was outside the sweet spot by about 10 inches. If I leaned my head 10 inches to the left, the music and imaging were great, but the sweet spot was very small, about 6 inches off center on each side.

When I was watching a DVD movie or listening to music on a DVD in DD 5.1 or DTS, there was no problem centering the image, but when I listened to a CD in 2 channel stereo, I often leaned my head a bit. Even when I was off axis, the overall sound was very good and the BIC's still possessed their nice airy quality, but when I was in the sweet spot the imaging was just so much better. 

Over the next year, I tried different speaker angles every 2 or 3 months to see if I could force the sweet spot toward my seat. I was sort of limited to speaker placement  because of the layout and traffic pattern of my listening room. The picture below shows the speaker angle that seemed to work best, but I have no idea why it did.

This was particularly frustrating because the diffraction from the right side of my HDTV was quite evident. Who knows, maybe that's why this configuration worked. I knew that I was sitting closer to the right speaker, but I couldn't move it any more to the right because it would be in a traffic pattern and kids aren't particularly careful all the time. Also, my receiver wouldn't let me change the "distance to listener" on my front speakers independently of each other. I know we're only talking about milliseconds here, but it does make a difference. Turning the volume of the left speaker a bit higher than the right didn't work either. All it did was make the imaging muddier. 

My speaker stands were 31 inches tall. I knew this was too much, so I cut them down to 26 inches. With the tweeters in the DV62 CLR-S's 10 inches from the bottom, it gave me a tweeter height of 36 inches; exactly the height of my ears when I'm sitting. It didn't help the centering problem, but when I was in the sweet spot it did sound better.

I have no idea why it took me so long to try this, but I finally realized that, since I was a few inches closer to the right speaker, maybe if I just moved it back it would fix the timing difference. I set it on the table behind the speaker (actually, my old sub-woofer that will soon be moved to my office). When I listened to the music again, the sound emphasis had clearly shifted to the left speaker. WOW, moving that speaker back 12 inches shifted the sound all the way to the other side! Needless to say, I was excited. I played around with the setback a little and finally came up with moving the left speaker ahead one inch and the right one back two inches.

Not only was the centering fixed, but for some reason I don't yet understand, the sweet spot broadened. It now extends at least 18 inches to each side of the center. Oddly enough, the speaker angle also doesn't seem as critical. I was able to pivot either one a few degrees with almost no difference in where the center imaged on the sound stage.

 Eventually, I brought the old sub-woofer to my office which made room for another DVD rack. I also placed the speakers further apart and staggered them a little more. I'm absolutely delighted with the sound.  I should have done this months ago. The sweet spot extends beyond my normal listening position, the sound is centered even though I'm not, and the imaging is very well focused. If you haven't adjusted the height of your speakers, you might want to try it. And, while you're playing around with speaker placement and angle, don't forget to try different front to back placement. Before I fixed the imaging, sound that should have been centered in the soundstage was clearly heard  in the right speaker as well. It wasn't half way between the center soundstage and the right speaker, it was in both places. That's muddy or vague imaging. Now it comes from the center of the stage as a monaural sound. By the way, it also broadened the sound stage. Before it went to about 4 or 5 feet beyond each speaker. Now it goes all the way out to the walls giving me a 23 foot sound stage. I really like that.