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TECHNOLOGY Few words ABOUT PLACING THE SPEAKERS
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Unfortunately, and fortunately, the reality is different, and there are rooms with better or worse acoustics, in which are placed better or worse sets for listening to music. Some pay less attention to its quality, others more, but when listening to music and striving to its faithfully reproducing becomes a hobby, and sometimes even a "way of life", then this room, these furniture and these speakers gain a completely different meaning. | MUSIC ROOM Few of us, those with "our" hobby or "our" way of life can afford to have a separate room adapted to listen to music. From life we receive different, in terms of acoustics, rooms, often not rectangles, with alcoves, kitchenette, half-open, long "trams" etc. And in each of these rooms we try to come a little closer to "our" musical ideal. We learned from Newton that every action corresponds to a reaction, meaning "what comes in, must go out" or "what gets out, comes back." It's the same in audio. If the signal from the amplifier comes out, after it is processed by the speaker, some part of this signal returns to the amplifier. The speaker and amplifier become a cooperative system, not separate elements. Going further - if the speaker membrane emits a sound - it will vibrate - it will transmit vibrations to the air molecules close to the diaphragm, they will pass them to the next, and the next. Next ones will transfer the sound to our ears, but also towards the walls, ceiling, floor and furniture in the room. And again some of this energy from the walls and furniture will be given back to the next air molecules and the next and up to those that are again close to the speaker membrane. In turn, they will give some of this energy back to the membrane. This energy, much smaller than that emitted, is, however, high enough to move the diaphragm and speaker coil. Such a loudspeaker works like a microphone and a current is generated in the coil located in the magnetic field, which then goes to the amplifier. And this "unwanted" energy converted into a very small current, read by the amplifier as a distortion caused by the speaker, will actually be caused by sound waves reflected from the walls, ceiling, floor and furniture. 
To prevent these distortions we would have to have a vacuum in the room, but then - neither breathing nor listening to music! We will not eliminate distortions, but we can fight them and minimize them by correctly preparing the room and placing the speakers. Sound waves spread differently in a room - their scattering, reflection, diffraction and interference depend particulary on the room, its dimensions, how suppressed are its flat surfaces, what materials were used for finishing. A lot is written about the room and its suppression in the article Fine-tuning Or how we set up speakers so I will not repeat it. By the way - I have a small request for interior decorators: let the floor tiles stay in the kitchen and the large windows without curtains in Manhattan skyscrapers. | WHAT ARE WE LOOKING FOR? The correct positioning of the speakers in the room should give us - of course, as far as the speakers themselves and the rest of the audio system components allow, as well as recordings - sound as natural as possible, varied, best detached from the speakers, creating space and air, soundstage with instruments with natural colors and internal warmth placed on it. It's a long wish list, in the lower price ranges not quite possible to fulfill, but regardless the price of our set and the quality of the speakers themselves, it is worth looking for the greatest musicality and communication skills in them. Let's try to position the speakers the way that they "disappear" from the room as much as possible and let our room help us a little. When we sit in an armchair that serves as a listening position and look at the speakers, we can define four basic dimensions that determine their location in the room:
|1| Width Many of us know or have heard about the minimum distance of the speakers from the side walls. It must be said, however, that this distance is also, and perhaps above all, determined by the distance between the speakers. Because, if our room is small, it may turn out that when we move the speakers away from the side walls as much as "written in the book" it turns out that there will be too little space between them. The result will be such crowding of instruments on the stage and its complete blurring that it will turn into a wall of sound. However, if we have a very wide room, we can think that you can "go crazy" and place the speakers wide, because the side walls are still far away. The effect of such "madness" can be a wide stage with highlighted sides, where nothing will happen in the middle of it. We will hear the sound coming straight from the speakers, and our favorite artist will be a big levitating spot somewhere in the middle. The width dimension - stereo base - is extremely important for obtaining the correct soundstage. Note, however, that the distance between the speaker and side wall is the distance from both side walls, the one that is closer to the speaker and the opposite. The width of speakers' spacing is therefore a relation between their position relative to both side walls. All these dimensions are just as important. 
It turns out that the width dimension is closely related to the depth dimension, that is the distance of our armchair from the speakers. Some prefer to listen to the speakers widely spaced up close, others listen to the speakers placed closer together from a greater distance. Neither solution is better or worse. When placing speakers in a room, it may turn out that the option with a wider spacing sounds better, while in another room - with a narrower one. Again, it depends on the acoustics of the room itself and the specific speakers. |2| Depth Depth - the distance between ourselves and the speakers - is obviously related to their distance from the wall behind them. This is probably the most widely discussed aspect of setting the speakers. Also in this case, we know the minimum distances and that if the speakers have a bass-reflex outlet led backwards, they must stand a greater distance from the wall, and when the enclosure is closed, they can stand closer. This is a far-reaching simplification, but it works well in many rooms. Why is this distance so important ? 
Each sound is a wave, and each frequency has a wavelength assigned to it. The lower frequency on the scale, the longer the wave. In the range of medium and high tones wavelengths it is a row of centimeters and these waves arrange repeatedly in the listening room without causing such a problem as low-bass frequencies. Already the wavelength of the 80 Hz sound is over 4 meters, which in many cases is a dimension greater than the distance between the walls in our room. The waves then arrange once or less than once before the reflection from the walls and begin the return journey. In one place in the room, reflected waves overlap with the original waves in such a way that they are completely suppressed, and in another place superimposed and excited. In physics, this phenomenon is referred to as interference and the formation of standing waves. That's why we sometimes have a situation that where we sit, you can't hear certain bass frequencies, and already a meter nearby or in the corner of the room booming is so strong that wants to break our head off! In many cases, we try to control this phenomenon by moving the speakers away or closer to the wall behind them. It should be noted that it will not always be the case that pushing closer to the wall will strengthen the bass, and pushing away will reduce its dominance. Again, it depends on the room's acoustics - its dimensions and damping. In many publications, the reviewers point out that the speakers should be moved away from the wall and given them to "breathe". It is nothing but finding the right balance among hundreds of thousands of interference occurring in the room, because moving too close to the wall can cause unwanted wave distribution and bass simply stifle. The distance between the speakers (equally: distance of the left speaker from the right wall and right from the left) will also affect on ubiquitous interference, the frequency distribution in the room, - so setting the width of the stereo base affects not only the organization of the sound stage, but also the bass, its softness / hardness, the filling, dynamics, timbre, etc. For each bass frequency and for each room we would be able to calculate interference, standing wave distribution and find a place for the speaker where it would have the least impact on its work. However, this is a lot of counting and many experienced mathematician would even sweat. Not everyone is an eagle in this field, so let's save ourselves all these formulas and calculations. Instead of counting, each of us can hear it, in which our room will help us again. |3| Height For as long as I can remember, from the beginning of my path in audio, there was a perception that the tweeter should be at ear height and that is how we should position the speakers (adjust the height of the stands). This was explained by the most even tweeter processing characteristics on the main axis. And what about the other speakers? How does this affect the sound? The shape of the sound wave face leaving the membrane is approximately spherical. Just like towards the walls, it also spreads towards the ceiling and floor. Let's forget about gravity for a moment and move the chair over the speakers - close to the ceiling. Then the floor will become a "wall behind the speakers". In a sense, similar distance and propagation relationships occur then, as in the case of the depth dimension - the lowest frequencies are reflected from the ceiling and create further interference and standing waves. And that's why in the best acoustic arrangements distracting systems are also on the ceiling. 
When we have monitors in the listening room, the stands on which they stand determine their height. In the case of floorstanding constructions, the height of the transducers above the floor was decided by their constructor (in my constructions I also take this into account). In most cases, the stands and floorstanding speakers are equipped with spikes with threads - height adjustment. We can also place various types of anti-vibration platforms or just a piece of plywood under the speakers. 
The height of the speaker above the floor is equally important for getting the right amount of bass, timbre, weight, and resolution across the entire band. If the speaker designer has foreseen in the project the location of the drivers at a specific height, we cannot place thick plates or tall stands under the speakers with impunity. For this reason, when I was designing Kepler anti-vibration feet, I fought for every millimeter of their housing so that they were not higher than popular spikes. If there is no up regulation, the recipe is simple, just put something under. However, if there is no down adjustment, you will need to adjust other settings, but we'll talk about that in a moment. |4| Sprain - bend About it briefly. By turning the speakers towards the listening position, we decide on two basic parameters. The first is the rotation of the speakers by a certain angle relative to the main axis of their radiation relative to the listening position. The second is a consequence of the first: it is a change in the ratio of waves directly reaching us from the speakers to the reflected by the side walls. And again - some prefer strong bending of the speakers, others position them almost perpendicular to the walls. It also depends on the specific room conditions and the specific speaker design. |
| RECESSES, "TRAMS" AND ANNEXES Happy those who for listen to music have a rectangular room with wall length ratios conducive to good acoustics! They can keep symmetry in it, set everything down to the nearest centimeter and enjoy great sound. What about the rest of us who hear "differently"? What to do if our room is asymmetrical, has a half-open part, a large door on one side or an open passage to the kitchen, a side window with curtains opposite the bare wall, a recess behind the back, etc.? Let's just try to find ourselves in this asymmetry. Instead of placing the speakers in the middle of the wall, let's move the whole base and the listening chair to the left or right, let's turn the whole thing a small angle, if the room is wide, let's use only a part of it to reduce the stereo base. Let's try to minimize these acoustic imperfections with various settings. 
| Let's set up our speakers! There are certainly many ways to position the speakers and reach the optimal setting. Below I will present my method which I have been using for years and which has already proved itself in many rooms with different acoustic properties. To set the speakers we will need a roll-out meter, adhesive paper tape and several CD'swith music, which we know very well. Let's use CD's with voice, rhythmic, with more instruments, and let them not be well-recorded audiophile records. We intentionally use discs recorded not too bad, but also not very well. Why? 
In most cases, the most audible departure from neutrality in the recording will be underlining hissing sounds. It just so happens that a wrong speaker setting will duplicate and even amplify the distortion. Hissing "s" and too strong "c" often obscures many other sounds and spoils the overall reception of the recording. So the easiest way is to use overly exposed sibilants to set the speakers. I successfully use many discs, such as:
Left - right | At the beginning let's use the well-known minimum setting parameters, i.e. a minimum of 50 cm from the back wall and about 70 cm from the side walls. Let's use a meter, measure all distances so that the left and right sides are set the same in relation to the room. Let's also set a small bending angle towards the listening position. Let this setting be the starting point - stick the pieces of adhesive tape to the floor (carpet) in the corners of the speakers so that you can see where we started. 
Let's listen to music for the moment and pay attention to the voice and soundstage. If the soundstage does not run to the left or right it is already a small success. However, if we can clearly hear that the artist's voice and hissing sounds are "running" to the left or right, the problem should be identified. First, let's see if the error introduces room acoustics or, unfortunately, the speakers themselves. Let's replace the speakers, left to right, right to left, and arrange them according to tapes stuck to the floor. Let's listen and if the soundstage "escapes" still in the same direction, then the room's acoustics will be to blame and we will struggle with it. However, if the stage escaped the other way, meaning towards the same speaker as before, we have, unfortunately, speakers which sound differently. Many manufacturers mount speakers in large numbers and do not pay enough attention to the repeatability of the crossovers. The effect of this is often the "escaping" soundstage. In this case, choose a setting in which the scene "escapes less" and all our subsequent corrections will try to minimize this error. 
Now let's ask our room for a hint. Let's choose one speaker, for example the left one, and move it 5 cm to the left, but keep the same bending angle and the same distance from the rear wall. Before we move the second speaker - let's listen! This is a key moment in our setup method and we will use it many times. Let's not try to move both speakers at once and listen to them, but let's move one of them to determine the change that took place in the sound between the left and right channels. Let's reassess our sound stage and hissing sounds. In the vast majority of cases, after moving one of the speakers, we will notice a shift of the stage towards one of them. We will have the impression that one side starts playing (hissing) louder, and yet we have not changed the volume in the amplifier. This side, which sounds quieter, is better suited to the room - hissing sounds are less accented and thanks to this the amplifier's power is more evenly distributed on the frequency scale. In this channel you can actually hear more sounds, although it seems to us that it is quieter. If we moved the left speaker and after moving the left side sounded quieter, i.e. the sibilants moved to the right, it means that our shift is correct. If not, go back to the previous setting and test the opposite direction. Of course, we listen and evaluate the full range: bass, midrange and treble, but too strong hissing sounds will be the first and easiest to detect distortion. After a positive assessment of the first shift, if our room is symmetrical, we can move the right speaker in the same way as the left and perform a short listening test again before the next change - the hissing sounds should be in the center of the stage again. However, if our room is connected to an open kitchen, has a recess or window on one side, then we set the second speaker independently and after moving we try to set the stage in the middle between the speakers. In the case of asymmetrical rooms, it may turn out that we will move the entire stereo base to the left or right, or one of the speakers only by 5 cm, and the other by up to 20! Let's move the speakers only to the left and right, for now leave other directions alone. Let's move until we reach 1cm shifts and until the next shift does not cause improvement, that is, apparent silencing one side relative to the other. When we set the width of the speakers - their dependence on the side walls - we mark current position of the speakers by tape. Next let's take care of moving them away from the back wall. Similarly, move the left speaker a few centimeters forward, keeping the width and bending angle unchanged. Let's listen again and assess which side is seemingly quieter - this one will work better with the room. Let's check both directions. After making further changes, the sound quality should generally be better and better, the sound should slowly open, and the sound stage should become more real. The fewer the hissing sounds, the more air we hear and bass should be more resolute and varied. The sound should gain fullness and freedom. Let's make changes again until the next change will not cause one of the sides to play "quieter". At this point we should come back to the case of unevenly playing speakers, which I mentioned earlier. The stage setting can be adjusted by moving only one side forward or backward (the louder one) in search of a place where the center of the stage will be as much as possible the physical center of the distance between the speakers. When we have set the distance from the rear wall, we must once again check whether the adjustment of the speaker width settings should not be corrected again by 1-2 cm. Again, we need the adhesive tape. Sprain | It is time to bend. Let's turn one speaker a few degrees inwards. Doing this we will reduce reflections from the side wall, and the speaker itself will radiate to us more directly towards us. Let's listen to the change again and now, apart from paying attention to the sibilants, let's look for a difference in the size of the stage and freedom in giving air in the sound. Again, this side, which will have less sibilants - will be somewhat quieter in this respect - at the same time will better show the space, openness and separation between instruments. The soundstage from this site will be wider and deeper - bigger. When setting the speaker bend, pay attention to the entire soundstage - its continuity. Incorrect bending causes deficiencies in the middle of the stage - a kind of blur and lack of legibility of the artist's voice, a spot/cloud of sound hanging in front of us. At this point, let's also come back to the case of unevenly playing loudspeakers. If at the beginning we found that one side is louder, during our setup we look for one that will place the soundstage as much as possible in the center between the speakers. Our left and right speakers will consequently have different bending angles. The same applies to rooms in which one side is more damped - when on one side we have a recess or a large sofa bed, a transition to another room, a window with curtains, etc. Let's correct the acoustic deficiencies of our room with different bending of the left and right sides. When we find that our angle setting is optimal, we again tape the setting before the next verification test. It is worth going back to setting the stereo base width again. It may turn out that changing the speaker bend will force the correction of the width of their spacing. If we lack embedding sound in space and mass, let's try to position the speakers a little closer together, literally 1-2 cm. If the sound of the speakers still improves, let's test the slight change in the bend again. Height | Time for height adjustment. In both previous cases, we moved the speakers a few centimeters, now the millimeters will have matter (the adjustment available on most speaker spikes is about 1 cm). In well-coordinated and configured systems, the differences will be heard immediately. 
Let's set one speaker 5 mm higher and listen. This time, let's pay attention not only to sibilants, but also to the filling and warmth of medium tones. If the speakers stand too high, we will have the impression of a more light sound, let's place them lower to get more filling. When we overdo it and are set too low, then the midrange will become colorless, the sound will close, as if the amplifier got breathless. Let's listen until we get to 1-2 mm accuracy, it's really worth it! And what about when the speakers sound better standing lower and there are still a few millimeters of adjustment missing? Then try to move them a few centimeters towards the rear wall and try to set the height again. After this correction, you should also check the first parameter - the width of the stereo base. Remember that when changing speaker spikes or adding a platform under, you should consider the change in the height of the speakers. It may turn out that we will not hear the positive impact of the platform, because the loudspeaker simply stands too high on it, or vice versa - we put the loudspeakers on "anything" and sound is immediately better, but not because that "anything", but because that the speaker lacked some height. Let's listen and change the settings until we can't determine if the sound has improved, until we get to the setting that satisfies us and shows the class of our system. Let's get to the accuracy of centimeter. Sometimes it can take many days or even weeks. And finally, when we find that "this is it", it is best to measure and sketch everything again so that in the event of a room renovation or inadvertent rearrangement of the speaker, avoid to repeat the whole procedure again! I hope that at least one of the readers will take advantage of my hints and thanks to them will get even better sound quality in their room. It remains for me to wish you a fruitful setting, and for those who are just buying or building their listening room, I wish acoustic symmetry! ■  | ABOUT THE AUTHOR MSc. Piotr Gałkowski is a graduate of the Faculty of Civil Engineering at the Opole University of Technology (specializing in building and engineering constructions). He designs and participates in the production of steel structures for the industry, but his passion (actually since childhood) is audio technique and utility design. He tries to combine his passions and education in Divine Acoustics projects. Other of this author: Why anti-vibration accessories have effect on sound? DIVINE ACOUSTICS ul. Słowackiego 10B/10 |
f all the rooms in which we listen to music had the same dimensions and were equally furnished, and identical speakers were placed in them, one could count, measure and determine the exact and optimal way of setting them once and for all. Anyone could use this information, set up their set in their room and say that "the matter is done".
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