JBL SYN 3 manual Room Reflections

ROOM REFLECTIONS

The most troublesome room reflections are usually the early reflections of the LCR speakers off the floor, ceiling and side walls. These reflections reach the listener’s ears delayed with respect to direct sounds and blur the perceived image. They can also degrade dialog intelligibility, through the same mechanisms.

The design of the THX LCR speakers minimizes the floor and ceiling reflections. As an extra enhancement, it is often a good idea to place a thick, absorptive carpet between the front speakers and the listening position, just to further reduce this primary reflection from floors with hard surfaces. A rug made from wool will generally have more uniform absorption characteristics than one made from synthetic fibers.

The THX LCR speakers have broad dispersion in the horizontal plane in order to ensure a wide usable listening area. This design choice can induce reflections off of the side walls, especially in installations where they are relatively close to the front speakers. These reflections can be reduced simply by angling the left and right speakers inward somewhat.

If giving the speakers some “toe-in” is not enough, the next step is the strategic place- ment of absorptive materials on the side walls. These range from commercially available fiberglass and dense foam to heavy draperies and even large, overstuffed furniture. The optimal position for these materials can be found with a small hand mirror and an assis- tant. Sit at the primary listening position and have the assistant slowly slide the mirror

along the wall. When you can see any of the front speakers reflected in the mirror, mark the wall at the mirror for later placement of absorptive material.

A variation of this method is especially helpful in rooms which are already fairly “dead” acoustically. Rather than using absorptive materi- al in rooms like these, try using diffusion instead.

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