A few words about subwoofers and why they fit almost everyone.

    Subwoofers have long been firmly established in the life of modern music lovers. But there is a great many prejudices regarding the particular designs of subwoofers, their required number, frequency range and in general the usefulness of this invention for humanity.

    Connoisseurs, experts and simply “very knowledgeable people” often consider it preferable to use or not use these or other technologies, others generally don’t want to use separate low-frequency acoustics, because it’s not kosher that doesn’t correspond to the so-called Tru AU. There are also people who are convinced that there should be 2 subwoofers (or more by the number of playback channels), they even produce corresponding products for them.

    In this article I will try to separate the "flies" from the "cutlets", myths from reality, speculation from existing physical phenomena, to help our readers make the most appropriate choice. I will try to tell in detail about why subwoofers are suitable for almost everyone, and also touch on the questions of acoustic design and frequency range.

    Many channels - one subwoofer

    I often hear that systems equipped with subwoofers are “devices for amateurs” and “these creepy tones,” since the subwoofer is usually one and there are several channels, respectively, channel separation at low frequencies does not occur, which supposedly harms fidelity reproduction. Such people for the most part acquire classical two-way acoustics with low-frequency sections in each column.

    Naturally, channel separation occurs in systems with a 2.1, 5.1, 7.1, etc. configuration, only at medium and high frequencies. At the same time, is there any point in channel separation in the low-frequency spectrum? Supporters of low-frequency multichannel either do not know or are silent.

    The first to whom the bass does not make sense in stereo should be vinyl lovers. The fact is that the recording technology in principle does not imply multi-channel low-frequency sound, all vinyl basses are written in mono, and for vinyl it would be quite natural to use one subwoofer and two satellites. Therefore, it remains unclear to me why some high-end systems, which are positioned as supposedly ideally adapted for vinyl, use 2 powerful subwoofers instead of one.

    In addition, psychoacoustic studies demonstrate extremely low susceptibility to localization of sources at low frequencies. At frequencies below 300 Hz, the sensitivity of hearing to the localization of the source is significantly reduced. The vast majority of people are not able to determine the direction with a frequency below 150 Hz. Consequently, for most stereos, low frequencies are almost useless.

    Dependences of the difference in sound intensity on the angle of its arrival for different frequencies.

    Of course, to meet the few who can distinguish the direction of sound in the low-frequency spectrum, systems with two or more subwoofers (LF sections) have been created, but there are very few such people.

    The question will sound quite logical, and why, with the actual immunity of the person’s hearing to the localization of the low-frequency source 2.0, the systems have not lost their relevance. The fact is that many of them (often shelving) are built according to a two-way scheme and have LF / MF sections that reproduce both low and medium frequencies (in the range much higher than 150 Hz and 300 Hz). In addition, the presence of a second low-frequency driver increases the sound pressure at low frequencies, which may also be useful.

    frequency range

    For classic speakers, the wider the frequency range, the better, but this rule does not apply to subwoofers, it is better for them to use the more specific term “optimal frequency range”. Ideally, this range should start from the so-called. “Deep” 20–30 Hz and end with a threshold frequency, above which we can localize the source, i.e. 150 Hz.

    Not all subwoofers have such characteristics, among the budget samples there are often found subs with a range from 80-90 to 300 Hz and above. A wider range means that the device is designed for a more down-to-earth user who will not listen to the details and bother with the nuances of stereo-panning in the low-frequency spectrum.

    For astronomically expensive high-end techs, sometimes they create subwoofers capable of reproducing frequencies below 20 Hz that are not audible, but can be felt by the skin and internal organs, as pressure wave vibrations (acoustic resonance). Such frequencies are practically not used in music, so I do not know why this is necessary.

    Acoustic design

    From the acoustic design of the subwoofer depends on most of its properties, such as volume, size, frequency response and a number of features in the sound. Today it is customary to use such constructions as a closed box, a phase inverter, a subwoofer with a passive radiator, and an acoustic maze.

    Phase inverter
    This type is the most common, and problems often arise with it. Phase-inverter type manufacturers liked for a relatively high efficiency, which also often attracts users. But technically literate music lovers often write that such subwoofers can introduce significant distortions.

    It is no secret that the low frequencies in the subwoofer are enhanced by acoustic resonance. The sub with PI is just a variation on the theme of the classical Helmholtz resonator. It is quite natural that the resonator has a resonant frequency. In incorrectly calculated, as a rule, budget subwoofers, this frequency can be a big problem, since the notes at the resonance frequency sound much louder than others. There is a rule for a good subwoofer with FI, which states that:

    “The frequency of the resonance of the FI should be no more than 33% lower than the resonance of the speaker in the same case with the closed FI”

    Correctly designed subwoofer with a phase inverter

    Also, some problems with such subwoofers arise in connection with turbulent processes in the phase invert pipe. In high-quality sabah, these problems are solved with the help of special tricks, such as conical dividers from Polk and cutting in a phase-inverter pipe, which eliminates turbulent flows from Monitor Audio.

    As in the other variants of acoustic design for PI-saba, optimal damping is important.

    Thus, the most acceptable areas of application of FI-sabs are cinema and circus games.

    Learn more about common mistakes when creating FI subwoofers in one extremely useful article .

    Closed box
    One of the simplest and most effective types of acoustic design for a subwoofer. It is deprived of almost all the disadvantages of the phase inverter type, as well as its merits. It has a relatively low efficiency, flat frequency response, large size and weight. Does not distort the sound too much. This type is one of the most common among companies specializing in the production of subwoofers. As a rule, closed boxes are popular with critical and demanding audiophiles.

    A relatively rare type of acoustic design of subwoofers, based on the principle of resonance. Efficiency - higher than that of the closed box, and is comparable with the phase inverter type. In this case, the distortion is much less. Due to the fact that the design of such a case is complex in design and production, the cost of labyrinth subwoofers is not low.
    Learn more about the maze here and here .

    Acoustic labyrinth

    Passive radiator
    The original type of acoustic design, where the second unconnected radiator is installed, which works as a passive resonator. This type of design allows you to reduce the overall dimensions compared to a closed box, working with the same frequencies. Also an obvious advantage is the absence of resonant and other parasitic overtones from the bass reflex.

    The operation scheme of a passive radiator.

    The disadvantages include rather large losses, respectively, lower sensitivity, and also the fact that a large mass of a passive radiator adversely affects the transfer characteristic.


    I have nothing against the classic 2.0 stereo speakers, but the use of a subwoofer, to me (as a person with ears not localizing sources in the low-frequency spectrum) seems to be much more rational. I sincerely hope that the material will be useful, will give the necessary ideas about some criteria for choosing a subwoofer. If the topic is of interest to readers, it will be possible to continue the theme of the subs and the features of switching them, power and sensitivity, especially the acoustic design of the rooms where you plan to install powerful low-frequency speakers.

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