The app shows some general hints in short form before starting the measurements, a link leads to the detailed version here.
Both loudspeakers must be equally far from the listening position. They must therefore form an isosceles triangle with the listening position.
Our brain locates a sound source mainly by the different intensity and travel time of the sound to the right and left ear. (There are other factors: even unilaterally deaf people can hear directionally.) To reproduce this in music reproduction, no new disruptive factors such as different distances between the two speakers should be added. To compensate for these by adjustments to balance and delay should therefore only be attempted if there is no other way, because the reflections from walls, floor, ceiling and furniture are not taken into account .
The app additionally shows the dimensions in meters suggested in ITU.R 1116-1. However, this is a standard for listening tests, i.e. aim is to make different listening tests as comparable as possible. For the construction of an audio system, it thus provide good guidelines, but no binding regulations.
Usually this triangle is acute-angled, i.e. the distance from the listening position to the loudspeaker is slightly larger than the distance between the loudspeakers, but significantly less than twice as large: Especially if the stage between the loudspeakers tears apart during the first test listening, the loudspeakers are most likely too far apart. Pay attention to natural speech reproduction when the voice comes from the center already during the first test listening.
At live concerts, the edges of the stage also form an acute triangle with the most listeners. A stage set during playback that is too wide does not correspond to the original in most cases. In addition, the stereo image remains more stable when the listener moves the head.
Distances to the walls
The values are determined by the app. However, the distance to front and side walls should be the same (or very large). The side walls should be made of material with equal reflection properties (i.e. not window vs. concrete). Various rules of thumb can be used to place freshly delivered common floorstanding speakers somewhere first:
- Directly in front of the wall (not for speakers with bass reflex channel to the rear)
- Distance from the front and side walls "significantly more than 1 meter".
- "38% rule": speakers at 38% of the room length. (Actually a misunderstanding: This rule was originally recommended by Wes Lachot for the location of listening positions.)
- "1/5 rule": membrane of the loudspeaker to 1/5 of the room length
- In high-end studios (in the million euro range), the speakers are often embedded in the walls, so that the front panel of the loudspeaker and the wall merge seamlessly.
At higher frequencies, perhaps 1 kHz and above, walls can be seen as mirrors for sound. Similar to an optical mirror, this creates effects such as mirror images of the sound sources, which in most cases degrade the sound experience.
. At lower frequencies, amplifications and cancellations occur due to the reflected waves: If, for example, the distance to the wall is 50 cm, i.e. the outward and return paths are 1 m, then an amplification can be expected at 343 Hz (wavelength 1 m), because the sound reflected back from the wall complements the sound emitted directly. At half the frequency (172 Hz), on the other hand, cancellation is to be expected, since direct and reflected sound are in opposite phase. At a distance of 1 m from the wall, the same effect can be expected at 172 and 86 Hz respectively .
The advantage of the short 50 cm distance is therefore that frequencies in the range from 150 to 300 Hz can be treated, which is possible with conventional absorption material behind the loudspeaker. In the 80 Hz range, this is considerably more difficult. In addition, for many loudspeakers, a significant directional dependency also starts at 300 Hz: The sound radiated to the front is often stronger than that radiated to the rear. Typical values for cone loudspeakers without waveguide are 3 dB at 300 Hz and 10 dB at 1 kHz, but there are extreme deviations depending on the design.
Thus, the recommendation arises to either place the loudspeaker directly against the (preferably well damped) wall or at least 1.5 m away. At distances of more than 1-2m, the range slowly begins at which our brain can distinguish the directly arriving and reflected sound by the difference in propagation time.
The behavior of the bass also changes significantly due to the positioning, as the reflections create room modes and standing waves. Detailed version
The listening places should not be too close to the back wall. The center of the room is a good choice. The so-called 38% rule (loudspeakers or listening places at 38% of the room length) also offers a guideline. However, the results of measurement and listening test are the determining factors; they can deviate considerably from both guidelines.
The rules assume that different room modes can resonate, similar to waves in a bathtub. The most important modes are particularly less pronounced in some places, such as in a "shoebox room" at the aforementioned 38%. In practice, however, the room modes depend strongly on the proximity to the sound sources and walls, and their behavior usually deviates considerably from the "shoebox model". Therefore, the center of the room offers itself as a further approach.
Fig. 1. The first spatial modes on a rectangular surface. In practice, the third dimension is added. The loudest modes are audible in the areas where the color concentration changes the most. In contrast, the speed with which the particles move back and forth (velocity) is not perceptible.
How to angle loudspeakers
After the best setup has been found, the speakers should be angled "toeed in". This refers to the orientation of the loudspeakers to the listening position. It is not always the best solution to place the speakers so that they "shine" directly at the listeners from the front. Depending on the design characteristics, the reproduction can improve considerably if the front points a little more inward or outward. If the mids/treble are too weak, you should align the speakers to the listening position. If, on the other hand, the mid/high range dominates, turn the speakers away from the listening position. If your speakers are on spikes, you can also try to adjust the speakers in the vertical axis.
To achieve the best possible listening experience for a single specified space, the speakers should be angled so that you can see their inside. Thus, the speaker axes should cross behind the listening position. Ideally, this creates a deeply staggered stage.
The background is always the physical effect that the higher frequencies have a stronger directional characteristic. The low frequencies, on the other hand, spread rather circularly in the listening room. This orientation causes more higher frequency sound to hit the side walls. In most cases, their reflected sound creates a desirable listener envelopment (LEV) effect. Whether a listening room has the task of "improving" an already finished recording depends on many factors: The program material heard, the demand for analytical audibility, and ultimately personal taste. The reflections should never be so strong that the localization of the instruments suffers, as this can lead to listener fatigue.
To achieve the best possible compromise for several listening places, the loudspeakers should be angled so that you can see their outer sides. The speaker axes should therefore cross in front of the listening position.
This setup causes the left speaker to "radiate" to the right seat and vice versa. Thus, the outer seats come more into the focus of the more distant speaker. Thus the missing volume caused by the greater distance can be compensated, and for the outer seats the sound image is improved.
The specifications for angling are only for initial orientation. The results of measurement and listening test often deviate considerably.
Most often, the speakers are placed side by side in front of the same wall. The installation on two walls, symmetrical to a corner of the room, can be more favorable. An (open) door in this corner can further improve the sound by reducing room resonances.
In this setup, the fronts of the speakers are slightly further away from the walls. Since many constructions emit less sound laterally, reflections on the walls are reduced. Also room modes between the front and rear wall are built up less intensively: since both loudspeakers are not at a similar distance from the same wall, they cannot simultaneously excite the same mode "with combined forces".
Most speakers are designed to sound best when placed at ear height.
Both the individual drivers in common (dynamic) loudspeakers and their interaction create a sound image that can change considerably when the listener moves out of focus. This has nothing to do with the price range of the system - at most perhaps with the intended use. An extreme is the sound reinforcement of a stadium: here individual systems are designed in such a way that only certain areas are specifically "illuminated". Every overlap bears the risk that the signal arrives at some places several times in succession due to differences in propagation time (despite electronic delay).
Floor reflections can significantly degrade the sound, i.e. the setup height of the loudspeakers plays an important role. Special constructions like D'Appolito arrangements (tweeter in the center, two equal woofers symmetrically arranged symmetrically around it) are supposed to reduce this. Center speakers in surround systems often have such a setup. This unfolds however only its effect if the systems are used standing (not lying)! Try both setups and pay attention to natural speech reproduction.
The sound reflected from the floor creates a mirror image of the loudspeaker for the listener (gray in the picture). At certain frequencies, this results in audible amplifications or attenuations that can significantly worsen the sound image. Details
Loudspeakers on a piece of furniture should have a support e.g. made of sound absorbing material like foam.
Transmitted structure-borne sound disturbs the sound image and possibly also people in adjacent rooms. This recommendation also applies to floorstanding speakers. However, these are often decoupled from the floor due to their design and the amplification by the swinging piece of furniture is missing.
Alternatively, spikes, tennis balls, bubble wrap, feet made of rubber or even complex, almost arbitrarily expensive systems for vibration isolation can be used. Large music stores offer many variants online, and you can often find a well-founded assessment by professional musicians there.
To note with spikes: Especially with hard ground, spikes must be well tightened. With four spikes per speaker, all four spikes must have the same ground contact: The speaker must not wobble when you press against it. If the floor is sensitive, coasters should be used.