In two consecutive phases, the author will conduct a comprehensive discussion on the two parts of the home theater amplifier audio and video, basically complete the basic knowledge of the home theater amplifier, so that many audio and video enthusiasts understand that the home theater amplifier is different from the traditional Hi-Fi two-channel amplifier, which is only used for audio signal processing and amplification, but has both audio and video processing capabilities. This issue will cut into another important part of the home theater audio system - home theater speakers. Among the many home theater audio-visual equipment, home theater speakers are a more complicated part, which is the last link in the audio system responsible for sound reproduction, which determines the style of sound. Therefore, in order to select the right sound and bring shocking audio and video effects, you need to fully understand the home theater speakers. Below, the author will analyze the type and structure of the home theater speakers and the placement of multi-channel surround speakers. I hope that you can find the right home theater speakers and give full play to the hidden performance.
Different types of home theater speakers
Home theater speakers are a fairly complex audio-visual device that is a combination of multiple different types of speakers. Home theater speakers will have different sound styles depending on the height of the high school woofer, the difference in structure, and the connection method. Positioned by traditional regional brands, the sound of the North American family theater speaker system tends to be cinema-like. Under the pressure of large sound pressure, it is still easy to use, and the low-frequency effect is outstanding. The European-style sound style continues the tradition of Hi-Fi speakers, with a focus on music, especially for listening to concerts or music-based sources. If the appearance is different from the internal structure and installation method, the home theater speakers can also be divided into traditional home theater speakers combined with traditional bookshelf boxes and floor-standing boxes, and homes with embedded and wall-mounted speakers. The theater is custom built with speakers. Of course, if the miniaturized fashion music entertainment category consisting of satellite boxes is also included, the entire home theater speaker system can be roughly divided into these three categories.
The home theater speaker system is quite complex and is a combination of many different types of speakers.
Home theater custom installed speakers are an important category for home theater speakers
In the traditional home theater speaker type, the overall structure is not much different from Hi-Fi speakers, but because home theater speakers usually need to be played under loud pressure, there is a certain difference in design. Among these speakers, if they follow the active and passive structure, they can be divided into passive passive speakers and active active speakers. The former requires an external amplifier driver to operate. The latter has an internal electronic crossover and amplifier that can be operated by directly inputting an audio signal from an audio source or a preamplifier. In recent years, the active active speaker series has been well developed. Many audio and video enthusiasts have chosen a more simple AV preamplifier with an active active speaker architecture. In fact, this method has been widely used in professional applications. The field is technically very mature.
Active active speakers can also be used in home theater speaker systems. The difference from conventional speakers is the built-in amplifier module.
Such home theater speakers can be divided into closed speakers, inverted speakers, transmission speakers and other structures according to the different cabinets. As the name suggests, the closed-type speaker is installed in a closed cabinet. The response speed of the unit is greatly improved, and the details of the low-frequency performance are also abundant. The clean and clear sound characteristics are the style of such speakers. Relatively speaking, the overall sensitivity of the speaker is relatively low, which is not conducive to driving. The inverted speaker radiates the back surface of the speaker unit through the inverter tube to reverse the phase, and then superimposes with the front sound wave of the speaker unit, thereby further widening the low frequency lower limit of the speaker, and at the same time obtaining more low frequency energy. The transmission type speaker is a folding reflection pipe with a rectangular cross section behind the speaker unit, which can obtain a deeper and more fuller low frequency from a small box. Welcome to China Home Theater Network!
The classification of home theater speakers can also be determined by the definition of traditional speaker cabinet manufacturing, including closed speakers, inverted speakers and transmission speakers.
At present, in the development of home theater speakers, horn speakers and multi-unit matrix speakers are an important part of the rapid development. In fact, these two technologies are the main technology of professional cinema speaker systems, mainly because they can obtain farther sound transmission distance. And a wider range of sound transmission. The working principle of the horn unit is basically the same as that of the traditional cone unit. Both of them are forced by the intercepting conductor in the magnetic field to promote the sound of the diaphragm. The difference is that the horn speaker adds a horn in front of the diaphragm, which effectively improves conversion efficiency. In general, horn loudspeakers have a higher sensitivity, which means that it is easier to achieve greater sound pressure. Common horn loudspeakers are divided into round horns and rectangular horns. Because rectangular horns have better off-axis response and better sound field performance, they are often used in the structure of home theater speakers. The multi-unit matrix speaker with multiple dome tweeters and cone units in the form of a matrix can also bring greater sound pressure and wider sound field performance, but due to the high manufacturing cost and volume, The development of such speakers in the home field is still in its infancy.
The horn loudspeaker technology itself is derived from professional cinemas and has been widely used in the home theater speaker market in recent years.
Home theater custom-installed speakers are the fastest-growing types of speakers in the past two years. This type of speaker-based speaker can be embedded in the wall, although it is more difficult to install than traditional home theater speakers. But it can get a higher space utilization. In fact, the unit and drive module of this type of speaker are no different from the traditional ones. The difference is that these types of speakers are usually closed. When choosing an embedded speaker, you need to pay attention to whether the speaker has a back box. Try to choose a speaker with a box to simplify the process of installing the whole system, because the back box of an embedded speaker is not easy. thing.
Embedded speakers are the main type of custom-installed speakers in home theaters, which are more complicated to install.
Choose an embedded speaker with a back cabinet for easier installation
The stylish home theater speaker system consisting of miniaturized speakers is another special form of home theater speakers, mainly used in small spaces, which usually consist of a preamplifier plus an active active speaker. The construction is relatively simpler, except that the sound pressure is not large, and the other sound characteristics are not significantly different from the above two types.
The stylish home theater speaker system is suitable for the use of home theater speaker systems in small spaces and the characteristics of each part
The film's post-trial studio is the predecessor of the home theater.
Since the home theater audio system is actually based on the evolution of the professional cinema post-mortem studio, the composition of the home theater speaker system also inherits the characteristics of the film's post-trial studio. In professional cinemas, the speaker system consists mainly of three front speakers, three arrays of surround speakers, and subwoofers in front of the screen. In the movie post-mortem room where the space is much smaller than that of the cinema, the volume and number of speakers used in the speaker system are reduced, but the general structure is basically the same. Welcome to China Home Theater Network!
Home theater speaker system in the film's post-trial studio
7.1-channel home theater speaker system
The overall audio system layout of the home theater speaker system is the same as the same. It also includes the front speakers, surround speakers and subwoofers. However, the signal sources of different channels can be divided into 5.1 channels and 7.1 channels. The audio system, in which ".1 channel" is the LFE channel, specifically restores the low frequency signal below 120 Hz in the movie signal. In the home theater speaker system, the subwoofer is mainly used to express this part of the sound. The difference between 7.1 channel and 5.1 channel is the addition of surround back channel, which improves the surround sound and stereoscopic effect of the sound field.
9.1-channel surround sound system from Dolby Pro Logic IIz
9.1-channel surround sound system from Audyssey DSX
11.1 channel surround sound system from DTS Neo:X
In the last two years, we can see 9.1 or even 11.1 channels of surround sound processing technology in AV amplifiers. This is the multi-channel sound extension technology brought by Dolby, Audyssey and DTS. Dolby Pro Logic IIz, Audyssey DSX and DTS Neo:X, mainly to let the 5.1, 7.1 channel audio signal through real-time sound processing, converted to 9.1 or 11.1 channel output. The 9.1 channel and the 11.1 channel actually add two upper sound fields and two left and right wide sound fields.
The following is an example of a classic 7.1-channel home theater speaker. The entire speaker system is divided into front speakers, side surround speakers, surround speakers and subwoofers.
Front speaker section
The home theater front speakers are mainly responsible for the sound field in front of the movie, including the left and right channel main speakers and the center speaker. They are mainly responsible for sound playback above 80 to 120 Hz. It is important to note that the center speaker is also responsible for the replay of the character dialogue and the front sound details that are very important in movie playback. The quality of the sound will directly affect the performance of the entire sound system. The main speaker section is composed of two speakers with the same structure and consistent performance. When the whole system is output with 2.0 channels, the main speaker is responsible for the playback of Hi-Fi two-channel speakers. The center speaker is a unique part of the home theater speaker system. Because the listening area of ​​the home theater is relatively large, in order to maximize the radiation range of the sound, most of the outstanding THX-certified speakers use a 21â„2 way crossover. Designed to avoid the generation of leaf-shaped radiation in the 2 kHz band when the traditionally designed speakers are placed in the lateral direction, resulting in a substantially consistent listening experience at every location in the listening area.
The front speaker is composed of a center speaker and a main speaker.
For the choice of front speakers, you can also choose according to the size and situation of the home environment. If the home environment is not large, the use of the embedded speaker system with the sound-transmitting screen can not only hide the speaker without damaging the overall design of the home, but also save space and increase the space in the listening area. In addition, in order to simplify the installation of the embedded speaker system, it is recommended to choose the box with the back to avoid the trouble of self-made cabinet.
Surround speakers Partial surround speakers are also unique to home theater speaker systems. Side surround and surround speakers are part of it. Because the placement is usually at the height of the human ear or above the human ear, the volume should not be too large, usually Responsible for sound playback from 80 to 120 Hz. The difference between 5.1-channel, 9.1-channel, and even 11.1-channel and 7.1-channel speaker systems is the difference in the number of surround speakers. The surround speakers are mainly responsible for creating ambient sounds around the movie to create a more realistic surround sound field.
According to the different technical structure of the speaker, it can be divided into three categories, namely, single pole, multipole and dipole. Unipolar is a one-way speaker with only one polarity; multi-pole refers to a speaker with two or more of the same polarity, which has stronger radiation capability and a stronger sense of envelopment; The positive and negative phase speaker unit refracts the inverted audio signal through the rear wall to create a wider sound space.
Dipole surround speakers provide a richer surround feel through the environment
Unipolar surround speakers for greater directivity
Three different surround sound boxes, the most widely used are multi-pole and dipole speakers, of which dipole speakers can also use the environmental space to create a more surround sound field, but in the process of use In particular, pay attention to the phase relationship of the surround speakers. The positive phase sound should be toward the front channel, and the reverse phase should be toward the rear two channels. Otherwise, not only can the surround sound be stronger, but the surround feeling will be weakened.
Subwoofer section
The shocking low-frequency sound is one of the important reasons for attracting a group of audio-visual enthusiasts to enter the home theater field. In the home theater speaker system, the subwoofer is responsible for the low-frequency reproduction below 80-120Hz. It is responsible for the sound playback of the LFE channel in the movie disc. It appears to enhance the bass detail in the movie and reduce the burden of other channels during bass playback.
Subwoofers usually consist of one or more large woofer units
The subwoofer is mainly composed of one or two large-sized woofers of 8 inches or more. For subwoofers with more than two woofers, it can be divided into push-pull and passive radiant. Different types and different types of speakers often have different sound performances in different positions. The specific adjustment needs to be considered in conjunction with the user's actual home environment.
Most subwoofers have phase and level adjustment
Subwoofers usually have built-in amplification modules, which are active subwoofers that everyone is familiar with. When connecting, you only need to connect the LFE output of the AV amplifier to one of the input terminals of the subwoofer. In terms of adjustment, most subwoofers have phase adjustments, including 0-180° or even 0-360°. In addition, there are adjustment knobs for the output level, so that the user can adjust accordingly according to the different positions, and obtain the shocking low-frequency sound with more dive and volume. Welcome to China Home Theater Network!
Home theater speaker system placement recommended
The setting of the home theater speaker is the most difficult place for the enthusiast to have a headache.
The home theater speaker system is a headache for entry-level players, and so many speakers don't know how to position them for the best sound. In fact, there are relevant international standards and recommendations for multi-channel surround speakers such as home theater speakers. Here mainly based on the international standards of ITU-R and the recommendations of the United States THX company, a simple analysis of the main points.
ITU-R on multi-channel speaker placement standards
ITU-R is an organization affiliated with the ITU International Telecommunication Union. The sound field setting methods recommended by Dolby Laboratories and DTS are actually based on the ITU-R standard. Since the ITU-R standard is mainly for multi-channel music appreciation, it emphasizes a more direct connection between the speaker and the listener to obtain a richer musical sense.
The multi-channel speaker system proposed by ITU-R is more inclined to music appreciation.
Taking the classic 5.1 channel as an example, the ITU-R recommended multi-channel speaker placement method is based on the listening position, and the positioning position is the listening position of the center speaker, and the left and right channel main speakers. The angle between the left and right sides is about 30° to the left and right, and the surround speakers are placed at an angle of about 120° slightly behind the listening position. The subwoofer should be placed in the middle of the front left and right channel speakers, close to the middle. In the position of the speaker, the entire 5.1 channel speaker system should be placed in a nearly circular manner. At the height of the placement, the ITU-R requires that all the speakers behave in a consistent manner except for the subwoofer. The tweeter is at the same height as the listener's ear, and the error range should be within ±15°. In addition to the height requirements, it is also required that the orientation of the speakers of each channel should have certain criteria. For example, the tweeter of the center channel should be aimed at the eyebrow of the listener, and the left channel and the left surround channel are aligned. The left ear, while the right channel and right surround are aligned with the right ear, in order to obtain more direct sound and reduce the interference of reflected sound in the room. ITU-R recommends using a unipolar surround speaker for surround speakers for better directivity.
THX's placement recommendation for multi-channel speakers
THX's expertise in home theater audio is very deep. The consideration of multi-channel speaker placement is different from that of ITU-R. It is mainly for movie appreciation, and is more suitable for movie enthusiasts who often watch movies at home. The following is a brief introduction. For those who are interested in more detailed content, you can participate in the relevant home theater training courses to learn more.
THX believes that the way to place multi-channel speakers should be as close as possible from the perspective of movie viewing.
The special feature of THX is that the position of the home theater speakers should be as far as possible to obtain a more surround, clearer and more detailed and layered sound, which should be noted to include the connection with the picture, room boundary reflection, Standing wave, horizontal placement width, height of human ear, etc. Among them, the front speakers should point to the listening area, and the surround sound box should point to the room.
Front speaker placement recommendations
The front speakers should be placed at the height of the human ear as much as possible. At the same time, it should be noted that the front seats will block the rear audience and control the actual height. The height of the front three speakers should be kept as straight as possible. If they cannot be arranged in a straight line, the vertical height difference should be controlled within 60cm (vertical angle <10°). After all, the sensitivity of the human brain to the horizontal position of the sound field should be Higher than the vertical direction.
When the current height of the three speakers cannot be maintained in a straight line, the vertical height difference should be controlled within 60cm (vertical angle <10°). Welcome to China Home Theater Network!
In terms of the projection system, the sound-transmitting screen should be used as much as possible, so that the front speakers can be hidden behind the screen and the horizontal position can be ensured. Unlike the ITU-R regulations, THX believes that the front speakers do not need to be curved, as most AV amplifiers and processors have delay settings. The horizontal angle of the left and right main speakers should be 45o ~ 60o, which can balance the stereo image and multi-channel separation effect. In addition, the position of the front speakers should not be placed directly on the ground or placed in the corners.
Surround speaker placement recommendations
THX recommended standards have different from ITU-R in terms of placement of front speakers, and THX and ITU-R have greater differences in the selection and placement of surround speakers. Taking a 7.1-channel surround sound system as an example, THX believes that the side surround speakers should be mounted on the side wall or behind the viewer's side, above the human ear by more than 60 cm to ensure a large enough surround sound field coverage. The surround back speakers should be placed behind the audience, 2m high from the ground, and 150° from the center speaker.
THX and ITU-R have great differences in the placement of surround speakers. THX is recommended to be installed on the side wall, behind the audience, at least 2m above the ground to avoid being too close to the audience.
In the surround speakers should try to choose the dipole speaker, the null (Null) should face the audience area
THX prefers the dipole surround speaker in the choice of surround speakers, but if the user chooses a monopole speaker, it is recommended to install it on the side wall, behind the audience, at least 2m above the ground, avoiding too much from the audience. near. Unipolar surround speakers should be placed face to face, not towards the audience. In terms of dipole surround speakers, THX believes that it should be installed on the side wall or ceiling as much as possible, leaving the back wall more than 60cm, and the null (Null) towards the audience area. If you want to create a stronger sense of surround, it is recommended to place it in a higher position in the audio-visual room, which is good at about 2m. For listening areas of multiple rows of seats, the position of the zero position and the surround level should be adjusted to ensure uniform sound field coverage. However, it should be noted that if the reverberation time of the room is long, the dipole speaker may fail, so the reverberation time of the room must be controlled.
Subwoofer placement recommendations About the placement of subwoofers, THX also has unique insights. THX believes that the position of the subwoofer should be in the front half of the room. When positioning, it is best to first calculate the corresponding room mode, find out the various areas of low frequency resonance, combined with the listening position, and then based on the calculated results. Find the right location in the room. THX believes that for the position of the subwoofer, the room factor is dominant. It is recommended that the user fix the subwoofer in front of the room when he cannot find the best position, and then gradually move the listening position to avoid the standing wave crests and troughs. To find the best location.
In order to solve the problem of low frequency resonance in the room, THX recommends using multiple subwoofers to solve the problem, but it should be noted that the total sound pressure of the output will be reduced by 12~18dB.
For the problem of low frequency resonance in the room, THX recommends solving the problem by using multiple subwoofers. The four identical subwoofers are placed in the front, rear, left and right sides of the room, which can effectively reduce the standing wave, but the total output sound pressure level will be Reduce 12 to 18dB.
Solving the problem of choosing a home theater speaker system is an important factor in getting the best sound.
In summary, the home theater speaker system is undoubtedly the most complex part of the entire home theater audio-visual equipment. For entry-level players who want to achieve excellent sound performance, in addition to the performance parameters of the home theater speakers, you also need to choose the right one. The type of speaker in the home environment, but also pay attention to every detail of the speaker position, in order to maximize the performance of the entire home theater speaker. In addition, the environment of the audio-visual room is often more important in terms of factors affecting the sound performance of home theaters. When you find that a high-performance speaker system can't show the best sound performance in a home environment, you need to consider whether it is audio-visual. There was a problem with the design of the room space. In the next issue, the author will introduce the video system of the home theater system, so stay tuned.
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