Fine Tunes #4 Page 2

Next on Audio Physic's menu for good sound is room mapping. This is helpful for those without dedicated listening rooms, or with rooms of less than ideal proportions. Measure your room and draw a simple floor plan. Then divide the room into even divisions. According to the plan, the even points on the grid (fig.2) are where the bass will be reinforced.

Fig.2 ABC Grid, Even Divisions

Ideal speaker placements would be at A2 and C2, with the listening chair at B, against the wall. If you prefer the speakers on the short wall, you can get almost the same bass reinforcement by putting the listening chair against the wall at line 2, and the speakers at B1 and B3. This won't give you the advantages of wide speaker placement with maximum distance from reflective surfaces, however. Next best would be speakers at A1 and A3 or C1 and C3. You can also put the listening chair at B2, with the speakers at A1 and A3 or C1 and C3. Or place the chair at A2 and the speakers at C1 and C3.

Tuning the bass and midbass makes use of the same principles to cancel rather than reinforce the low frequencies. Just move the speakers into the odd divisions of the grid. Fig.3 shows a drawing of the same room with odd divisions. The crossing points are the locations with the least bass reinforcement. By overlaying the grids (fig.4), you can see that small movements can have potentially big effects on the sound. According to the paperwork, when you hustle the speakers about the room there's a tendency for lateral movements to affect the midbass, while movements forward and back affect the lower bass. Of course, where to drop the listening chair and speakers has to be determined by room size and furniture layout, not to mention the forbearance of loved ones.

Fig.3 Odd Divisions

Fig.4 Overlay

Round up an audio bud some evening and do the following: After mapping the general placement for deep bass, work out the distance between the speakers. Using material with a strong center image, such as female vocals, listen to the center-fill with the speakers about 6' apart and pointed slightly behind the listener. Move them about a foot farther apart and listen again. When the center image thins out and becomes diffuse, you've reached the point where separation is too great. The Audio Physic method calls for the widest possible soundstage without losing center-fill energy. According to the white paper, blind listening tests have determined that the preferred angle of separation, listener at apex, is 72 degrees.

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