Harman Kardon AVP-1A Owners Manual - Page 25

Fine Tuning Your Audio Systems The procedures outlined in the previous sections should allow proper performance of your system. There are several things you can do to "tweak" the installation even further. In many cases, the concepts contained in this section are not necessary to achieve the kind of impact the AVP1A and a Home THX Audio System can provide. The following ideas and suggestions are for the most demanding installations, or when the room itself presents a special challenge. ACOUSTICAL PROBLEMS IN LISTENING ROOMS The Home THX Audio System addresses many of the problems common to high quality reproduction of music or soundtracks in a home environment. For example, the dispersion pattern of the front LCR speakers minimizes the effects of floor and ceiling reflections. Still, there are many variables which are beyond the control of a manufacturer. Room reflections create spurious false images and "comb filter" interference effects which alter the tonality of the system while degrading the localization of specific sounds. Larger rooms sustain echoes which degrade dialog intelligibility and detail. All rooms have standing waves which emphasize certain frequencies at the expense of others, based on the dimensions of the room. Other concerns include environmental noise, which is often greater than people realize. Although they might become accustomed to its presence and "tune it out," it still reduces the perceived low-level resolution of the system. In addition, the profound bass capabilities of a Home THX Audio System can create distracting rattles which lesser systems might never evoke. It can be tempting to try to solve all of these problems with., the indiscriminate use of sound-absorbing products, but even this technique has its pitfalls. All of these common acoustical problems will be addressed in this section. Once again, these techniques are not necessary for a successful Home THX Audio System installation. Rather, they are provided to solve occasional problems and to provide further enhancement possibilities. ROOM REFLECTIONS The most troublesome room reflections are usually the first reflections of the LCR speakers off the floor, ceiling and side walls, These reflections reach the listeners 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 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 placement 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 assistant. Sit at the primary listening position and have the assistant slowly