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 The Loudspeaker Placement - "How to enhance it ?"
With the arrival of home theater, many listeners have found or at least have come to feel that their choice of speaker positioning is pretty much determined by the realities of trying to squeeze a "theater" into a living room. And there is some truth in that, since you usually begin with a center channel speaker right above a TV monitor and go on from there to fit five other speakers, including a sometimes imposing subwoofer, into a listening/viewing scene. But if others who may be in our household will give you a bit of latitude, you can adjust positioning so that your speakers work sonically with their environment rather than against it. Let's start with positioning front speakers for maximum musical impact. Their sound will put the defining stamp on the way your stereo or home theater system sounds. Main Speakers  The rule-of-thumb with which most listeners begin the positioning of their main speakers is that front speakers should generally be separated from each other by a distance that's a little less than that between the speakers and your seated listening position. You will generally get the best imaging and other spatial qualities if your speakers and your usual seating position form an almost equilateral triangle, with the speakers not quite as far apart from each other as they are from you. If you must sit closer to one speaker than the other, use the Balance control on your electronics (or the individual level controls on home theater channels) to give the more distant speaker a balancing boost in volume. The optimum placement height for main speakers is normally with their tweeters at about the same height as your ears when you are seated. Our tower speakers are designed for optimal listening when seated. For our compact monitors, we offer accessory speaker stands to achieve the right height if you are not using existing shelves or furniture. You may prefer to tilt the speakers towards ear level if the proper height is not possible. The best high-frequency dispersion, producing the widest "sweet spot" in which you and others can sit and enjoy optimum high-frequency definition, will result when your speaker enclosures are positioned vertically rather than horizontally. If you need to place compact monitor enclosures horizontally, the speakers will still perform very well, but the seating area where you will enjoy optimum sound will become more narrow. We suggest you position the tweeters to the outside away from the center line. If you sit equally distant from both speakers, angling the speakers inward ("toeing them in') about 5 to 10 degrees usually produces the best convergence of high frequencies where you listen. Different listening positions may require different toe-in. Now on to the fun stuff: The Speakers in Relation to Room Boundaries  The position of your speakers with respect to the walls, floor, and ceiling of your listening room will often affect their sound in major ways. The closer you place speakers to the boundary surfaces of your room, the greater the proportion of bass in their overall sound. This is due to the enclosing, "focusing" effects of nearby surfaces on longer-wavelength (lower) frequencies. Positioning the speakers near the intersection of two surfaces (wall and wall, wall and floor, or wall and ceiling) will produce more apparent bass than placement near a single surface. The greatest proportion of bass is delivered by placement near three intersecting surfaces in a room corner near the floor or ceiling, where the convergence of the two walls and the floor/ceiling produces an amplifying effect that is a bit like that of a megaphone. And the least bass comes from placing a speaker away from all boundaries. Your own tastes should decide what proportion of bass response seems right in your room. The combination of the three dimensions of your room generally will produce at least three points in the room where the frequency response you experience related to a given position (of either the speaker or you) will either greatly increase or almost disappear. The most obvious effects are on low frequencies, but mid-frequency effects, while usually subtler, are also often present. Keep in mind, then, that very small changes in positioning (of the speakers or you) may produce major or subtle changes. Distances of speakers from the walls can make great differences in the number, strength, and particular frequencies of secondary reflections, changing frequency-balance, sonic spaciousness, and definition. Most listeners prefer their speakers at least a few inches from all walls, but the choice is yours to determine by listening. You in Relation to the Speakers  Where you sit in relation to your speakers obviously makes a difference too. The proportions of the particular triangle formed by your speakers and you matter. (You may need to send more power to the more distant speaker to compensate if you get much further from one speaker than the other.) The overall distances involved also matter. As you get further from the speakers, more sound reflected from your room's surfaces (in contrast to the sound coming directly from the speakers) reaches your ears, and the original spatial relationships in a recording are changed as your room "takes over." Sometimes the result is a mellower, more "integrated" sound. Other times, it's a more strident or annoyingly "echoey.". Once again, the particular dimensions of your room play a part. And depending on what seems more realistic and/or enjoyable to your ears, you may choose to sit at a great distance or have close-up, "near-field" sound. Keep in mind that, as mentioned a moment ago, the proper "toe-in," the right speaker height, and a reasonably symmetrical distance from the speakers all tend to work together to deliver the best high-frequency definition and imaging. You in Relation to Room Boundaries  Changing your own position with respect to a room's boundaries may also bring a big effect and sometimes for only a small change. Getting further from the wall behind you may make sound more precise and localized. Getting closer may make sound more "mellow" and integrated. Coming too close to back wall, side wall, or (especially) a corner may trigger a major peak or cancellation of a certain band of frequencies. It depends on factors we can't cover fully here. Remember too, with respect to your own positioning, that it may or may not be easier to change your own seating location than to move your speakers. As with so much else in life, the one certain rule is that you shouldn't fix, or worry about, what isn't broken (audibly in this case), especially if it means moving heavy furniture. As you consider the three relationships we have outlined, the idea is to manipulate whatever variable is easiest and most productive for improving your listening experience. Be sure to base your judgements on listening to a good variety of recordings of vocals, and acoustic instruments, soloists, different movies and musical instruments to most easily recognize tonal balance shifts. Positioning Surround Speakers  Most surround sound is meant more to create greater depth and overall ambience than to localize effects as coming from a particular spot. This is especially true of Dolby Pro-Logic surround sound, in which both surround channels carry the same (monophonic) information and can't be differentiated from each other. With Dolby Digital and DTS surround sound, there is very definite localization of some surround effects. How much you prefer these localized effects vs. overall sonic depth and diffusion is up to your listening preferences. If you are listening to multi-channel music, you may want the maximum localization of instruments. But if your main concern is the surround effects in movies, they tend to depend more on front-to-back movement than on specific localization. You can locate and aim your surround speakers to produce the effects you prefer, whether precisely pinpointed or pleasantly diffused. Although some people prefer to have their surround speakers behind them on stands at ear height, most find it easiest and best to mount compact monitors on the walls, at least two feet above your ear height when you are seated. We offer matching speaker brackets to make wall-mounting convenient. If your listening room is small, aiming the speakers to diffuse their sound somewhat may produce the best overall surround illusion. They can be mounted, for instance, on the side walls and aimed to bounce sound off the rear walls, or vice versa. If you opt for localization of sound from the surrounds, the speakers should face your listening spot, aimed at or slightly above your seated position. Speakers mounted on the side walls generally will sound best when placed a foot or two behind your seating area. Our illustration shows some typical placement options The Center Channel Speaker  This speaker obviously belongs in the very center of things up front. Most center channel systems, including ours, are designed for placement (preferably) right on top of or (less so) right under your TV monitor. The front surface of a picture tube is very active in determining the way a center channel's sound diffuses, and for this reason most centers are carefully equalized for a position in direct proximity to the tube. If you have a freestanding projection screen, it generally works to put the center channel immediately underneath it, either as high as it can go without intruding on the screen or, in the case of wall-mounted screens, without getting above your seated listening height. With one-piece projection system, the only easy choice in most cases is placement on the wall right above the top of the screen, tilted down (if need be) toward your seated listening position Placing Subwoofers  Most listeners, especially those with Significant Others whose tolerance for audio equipment is already strained by acceptance of a pair of highly visible main speakers, tend to position the solid cubic presence of a subwoofer wherever they can squeeze it in unobtrusively. We at PSB try to make things easier with products such as the SubZeroi Subwoofer and SubSeries 5i Subwoofer, which take up only a very reasonable amount of living space. And even our SubSeries 6i Subwoofer feels less imposing than most subs when oriented vertically. Still, though, a subwoofer is something that's placed "wherever" in most homes. But you can do far better than "wherever," without a lot effort and domestic conflict. And if you are critical about low-frequency response, there's quite a bit of useful experimentation you can do, especially in combination with the crossover, level, and phase controls of our subwoofers. There is no argument among audiophiles that the greatest bass output from a subwoofer comes from corner placement. The natural megaphone-like flaring outward of walls from a room corner focuses low frequencies as we indicate in our discussion of main speakers giving them no place to go but toward you. In the case of subwoofers, there is no automatic penalty in overall balance for this maximal bass, since your main speakers can be located elsewhere. It still may be too much bass for your room or (more particularly) your favorite listening spot in the room, but unless you are seated in a "null" spot, where radiation from the sub is cancelled or diminished by out-of-phase reflections from elsewhere, there should be plenty of bass from corner placement. If you are seated in such a null spot, your only real choices are generally to move either the subwoofer or your listening position until bass returns to the point that satisfies. Cranking up the level control or changing the crossover point almost certainly won't help much. But flipping the phase control 180 degrees sometimes may make a difference, especially if the null is a product of cancellations caused by interaction with low frequencies from your main speakers. If you are in the opposite sort of situation, where direct and reflected bass waves converge in phase and produce a strong peak at your listening location, you can if you like deal with that both with changes in placement or in the position of your sub's level control (or, less likely but possible, the crossover frequency chosen). We say "if you like" because there is no such thing as too much bass for some listeners, and we don't want to be dogmatic. You are definitely the one who has to be pleased, unless your Significant Other chimes in to the contrary. As you go outward from the corner along one wall or another, the general consensus (with which we tend to agree) is that while bass output diminishes somewhat, it also becomes more uniform throughout the room, with fewer of the "standing waves" that produce peaks and nulls at various points. The consensus on this does not include Tom Nousaine, an extremely knowledgeable audio writer who probably has done more listening to subwoofers from an end-user's perspective than anyone else, along with lots of measurement. He finds that corner placement provides the most uniform bass output as well as the strongest bass, but our own experience, while it doesn't directly contradict his, is that away-from-the-corner placement produces better balance in many situations. In any event, the level, crossover, and phase controls give you immediate adjustments for changes as you go outward. And, both with corner and out-the-wall placements, very small changes in positioning can make major differences in apparent balance. This is a fact that makes it very comforting during the setup of a sub to have a partner/friend/who-have-you who will move the sub while you listen. If you are doing this kind of fine-tuning, we strongly recommend using music with steady low frequencies (such as organ music) or steady-state test tones, not movie material. The latter is just too unpredictable and without real standards for comparison. We come now to the inevitable reality for some people that the placement of a sub really comes down to: "Where I can get away with putting it?" A room has only so many places where visual considerations and the need not to fall over a monolith on the floor may allow placing a sub. And in such a case, the idea of "near-field" placement, right near your listening position (and even in an end-table placement with a non-resonant bowl of popcorn on top) can make sense, at least if you can dress the cables going to the sub so that they're not in your way. Because low frequencies below the 150 Hz point are non-directional, you will not (or at least should not) be able to tell that they are not coming from the same general area as the rest of the sound from your speakers even if a sub is very close to you. So there is no theoretical reason not to place the sub nearby except the obvious one that this placement is the complete opposite of corner placement. Bass frequencies, instead of being focused by walls, spread out in all directions toward those walls away from where you are sitting with near-field placement. This is where the controls on the subwoofer can become critically important. You may have to turn up not only the level control but also the crossover control (the latter so that you get satisfying mid-bass as well as low-bass response). And the phase control can make a major difference here. Keep in mind that having to crank up the level of a sub located right next to you may increase the perception of any hum in a recording or piece of audio equipment, or the sub's own background hum from grounding or other anomalies. Since the objective of most people who buy subs is to make sure of plentiful low frequencies, the only situation most of us will run into that makes subwoofer placement really difficult is the factor we all fear the "bad" room, that just won't let you get satisfying amounts or quality of bass. There are rooms with troublesome dimensions, especially as you approach a perfect cube (with a closed door). In such a case, the answer for some people is two subwoofers, placed carefully to work with each other. This can also be true when the problem is too much, or too uneven, bass. For excellent results from this solution, the two subs don't have to be identical. It may be fine, in fact, to use two lesser subs to equal the performance of one with stronger specs. Finally, there are people who feel that the best way to find where to position a subwoofer is to place it temporarily right in your favorite easy chair and then walk around the room, checking how the sub sounds at various points. The idea here is that the point that sounds best as you walk around, poking your head into corners etc, should be the final place for your sub. It's an interesting theory, and it sometimes works. But since the spread of bass from a sub placed at your listening spot may be far different when heard at a distance in a corner than it is when the sub is placed very close to that same corner, this idea is not a reliable rule of thumb. By now, you've noted that we've said almost as much about subwoofer placement as we have about other speaker placements combined. This does NOT mean it's difficult. We get virtually no inquiries about subwoofer placement from customers, which is a good indication that it's not something over which people lose much sleep. A good subwoofer is such a pleasure when used with a good main speaker that enjoyment is definitely the rule.  |
Eddy_THX
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