! With it, the restoration of the program source can be made more solid. Without it, it will give people a feeling of lack of power and energy!

The subwoofer reflects the details of the sound!

In principle, subwoofers and speakers work exactly the same way, except that the diameter of the diaphragm is larger, usually 8 to 10 inches, and a speaker for vibration is added. .

In terms of evaluation indicators, the subwoofer is basically the same as the speaker. The specific content will not be introduced in detail here. I will only talk about the numerical requirements. The frequency response is generally below 200 Hz, and the rated impedance is also about 4Ω. , the sensitivity is generally greater than 90 dB/W/m.

At present, subwoofers can be roughly divided into two categories: active subwoofers and passive subwoofers. An active subwoofer refers to a subwoofer that has a built-in power amplifier. It does not require an additional power amplifier when used. It is usually a cylindrical shape. The shortcomings of this kind of subwoofer are that the heat dissipation is not ideal and the power is not very high. The barrel shape usually produces unnecessary vibration, which reduces the controllability of the subwoofer. In contrast, passive subwoofers require an external amplifier to work. The shape and power selection of this kind of subwoofer can be more flexible, and the effect will naturally be more ideal. In addition, active speakers can be further divided into sealed boxes and perforated boxes. The former is more suitable for deep symphony music, and the latter is more suitable for pop music.

"SubWoofer" is often called "subwoofer" in commercial or civilian applications. In fact, the adjective "super" is incorrect. The frequency band it plays back is usually from the upper limit of 150Hz or 100Hz to The lowest is around 25Hz, which is just bass and not sub-bass. Because frequencies below 20Hz are bass that exceed the musical range of human ears, from a scientific or professional interpretation point of view, only frequencies below 20Hz can be called "super" bass. But generally speaking, the subwoofer refers to the bass whose playback frequency is lower than 20Hz. Whether it is replaying dynamic music or movie sound effects, subwoofers are even more important than traditional floor-standing stereo speakers. This is because the special sound effects included in many pieces of music (symphony or harp and drum music) and many movies are extremely majestic and dynamic bass. This sound effect is not just for the listener to "hear", but It is even more important to let them "feel" the atmosphere of this situation.

However, friends who play Hi-Fi have many different reactions to subwoofers. Some people feel that it is difficult to control; some people think that these are for audiophiles who are particularly experienced in playing Hi-Fi. Toy; some people think that this is a device used to solve the shortcomings of small bookshelf boxes, and you don't need to pay too much attention to its placement when adding it to the entire system; some people think that playing with this kind of equipment is thankless and the success rate is too low; and some people think that playing with this device is thankless and the success rate is too low; I feel that an ideal system does not require the addition of a Subwoofer; some people even think that the 3ubwoofer is only suitable for use in very large rooms... Although there are different opinions, the subwoofer is the least talked about and least understood item among audiophiles. Very important equipment. Through this article, I believe it can change some audiophiles’ views on subwoofer equipment. At the same time, I hope to gain some debate and jointly improve the level of fever.

1. Types of subwoofers

Subwoofers are mainly divided into two categories, they are passive (PASSIVE) and active (ACTIVE). There are currently many three-piece "3D" satellite systems (Subwoofer/Satellite System) with subwoofers and two small main speakers on the market. In this system, only one subwoofer is used, so the subwoofer is mono. Channel (L+R) signal has a stereo effect only above the dividing point. This kind of system uses the volume control knob of the front stage to determine the volume of all speakers. If the sensitivity or volume of the subwoofer is not equal to that of the main speakers, it will cause confusion in the sound field, uneven frequency response, and inability to localize the sound image. , and at this time, when the placement of the subwoofer cannot solve this problem, these problems will be difficult to improve. This kind of Subwoofer usually only appears in low-level low-Fi systems.

There is also a passive subwoofer. The left and right main speakers are full-range, and the subwoofer only sounds when the bass below its upper frequency cutoff point appears.

This kind of system is called a connected subwoofer system. For example, the playback frequency of the main speaker is attenuated below 65Hz, and the subwoofer's dividing point is around 65Hz. Its purpose is to connect the main speaker smoothly. The problem with this system is that although the main speaker attenuates below 65Hz, it does not mean that its low frequency begins to decrease below 65Hz. The degree of these decreases depends on the design requirements of each speaker, so Replaying with a subwoofer at 65Hz will still conflict with the main speaker. The important reason is that the subwoofer unit and the main speaker unit are different products. When two different speaker units receive signals, For example, the vibration quality of the large-diameter subwoofer unit is definitely greater than the speaker unit of the main speaker, so the sound speed must be slower, and they will definitely not sound at the same time.

So many audiophiles who play this kind of subwoofer feel that after adding a subwoofer, the effect is messier than without it. Designers of this kind of subwoofer usually try to calibrate the subwoofer's partial point to the lowest possible level to avoid conflict with the main speakers. The subwoofer crossover point of this system should only be designed for a certain pair of main speakers. When the left and right main speakers are replaced, the subwoofer crossover point must be recalibrated. Although some main speakers attenuate below 65Hz, there is still sound at 20Hz. When these speakers are coupled with a docking subwoofer, the effect may be worse. The bass is not strong enough and has no texture, and you may also feel that the bass is low. Very messy. Manufacturers that produce this type of subwoofer usually design the main speakers together. Otherwise, there will be problems with the attenuation (dB/octave) at the crossover points and their frequency cutoff points, which are also the stuff of low-price systems.

In the active ACTIVE (dual amplifier) ??subwoofer system, the signal goes directly into the preamp with active crossover. Frequencies below 100Hz are amplified by the bass amplifier and sent to the subwoofer speaker for broadcast. Frequencies above 100Hz are sent to the rear stage of the main speaker after frequency division, and are amplified and played out by the main speaker. At this time, there must be a volume control to control the ratio of the subwoofer volume to the volume of the main speakers. In addition, there must be a phase adjustment knob that can adjust the phase of the bass amplifier from 0-180. school. Because the power amplifier of the subwoofer amplifier and the main speaker may be of different designs, they are not in the same phase in most cases. The listening effects of different phases will make the listener feel different. This phase adjustment knob is used To achieve the same phase effect as the subwoofer and the main speakers. When adjusting from different phases to the same phase, the volume will feel louder and the bass will be more solid (rich). When the phase is reversed to 180 degrees, the sound effect will be slightly slower.

To use the subwoofer correctly, the author believes that the subwoofer system must have the following five properties: 1. The subwoofer must have its own power amplifier; 2. There must be independent volume control; 3. There must be phase control; 4. The subwoofer must be placed in an independent position; 5. The main speakers must work above the crossover frequency of the subwoofer (for example, above 100Hz or 120Hz).

2. Reasons to use subwoofer Why use subwoofer?

Most readers who play subwoofer think that subwoofer is used because the bass of small speakers is not enough. As for the large speaker floor-standing box, there is no need to use a subwoofer. In fact, playing with a subwoofer is not as simple as using it to assist the bass. There are only a handful of traditional speakers on the market that can faithfully reproduce the bass sound found in movie sounds, and most even mid- to high-priced AV surround amplifiers do not have enough power to drive subwoofers. If active subwoofers are used, the above two problems can be easily solved.

The so-called "active active" means that the subwoofer itself has a specially designed power amplifier, so the signal source it requires only needs to come from the general level of the AV surround amplifier. Signal. Active active subwoofers are easy to match with other audio equipment. No matter what the sensitivity or low-frequency response of the speakers they are paired with is designed, it can handle it by adjusting itself. In addition, no matter whether it is facing the sound field from the front or facing away from the sound field, there is no need to move its position, just adjust the phase. The subwoofers discussed below are all active subwoofer systems.

The advantages are:

1. The main speakers do not need to work below 100Hz. Therefore, the distortion of this speaker above 100Hz will be reduced. Usually the distortion played back by the speaker is due to the frequency distortion above 100Hz due to the need to reproduce the bass. If there is no need to push signals below 100Hz, this unit's ability to reproduce sounds above 100Hz will be enhanced and the distortion will be lower.

2． Because the subwoofer has its own power amplifier, the power amplifiers of the left and right main speakers do not need to push frequencies below 100Hz, but only need to work above 100Hz. Just because there is no need to push these basses, the "power" of this amplifier above 100Hz will be two to four times greater than before. At this point, a little more explanation is needed in this regard. If the power of the power amplifier is 50W, that is to say, when the amplifier operates within the operating range of 20-20000Hz, its driving power is 50W (the manufacturer will never say in advertisements that if their power amplifier is There are sayings such as 200w when working above 70Hz), and when we talk about the power output capability of a power amplifier, it only means that when the amplifier works between 20 and 20000Hz, it can have an output of 50w and so on. But when a 50W power amplifier only works above 100Hz, its power (above 100Hz) is the same sound level capability as a 100W to 200w amplifier that reproduces frequencies of 20-20000Hz! But if this originally It is 50W. Now, if the amplifier that has been upgraded to 100-200W due to reproducing frequencies above 100Hz operates in the full frequency band, its power will return to its original form and become the original 50W. When working above 100Hz, it will become double or quadruple, depending on the frequency of the replayed music. If most of the music is high-pitched, it will be four times; if most of the music is mid-bass, it will be double. . The power amplifier has not changed, but when it works within different frequencies, its driving capabilities will be different, because the energy in the entire frequency band is mostly concentrated in the mid-low frequency and low frequency bands. If a power amplifier only works below 10000Hz, its "power" will not change much. It will only affect its "power" when there is no need to push the bass;

3. Because The subwoofer can be separated from the main speakers and placed elsewhere. The bass we hear in the room is mainly due to the response of these bass in the room, so the placement of the subwoofer in the room has a great impact on the bass effect. Some speaker designers place the left and right main speakers on top of the subwoofer. This design does not take into account the advantages of separate subwoofer and main speakers. Some people may think that one-piece speakers look better, but if they are one-piece speakers, why bother with a subwoofer? In terms of speaker placement, most of the positions that are suitable for high-midrange speakers will not be suitable for bass speakers. The subwoofer should usually be placed behind the left and right main speakers. Because the subwoofer can be separated, the sound field and positioning created by this playback system are incomparable to a pair of left and right main speakers (no matter what level your speakers are). Many people also feel that the bass is not enough when playing with large floor-standing speakers. They feel that there is no bass or that the bass is too heavy and muddy. The subwoofer system discussed in this article has an independent bass adjustment, which can be used to adjust the volume ratio between the bass and the main speaker. , In addition, it can have an independent position, so this subwoofer will never have the problem of too heavy or insufficient bass.

The above are the three major advantages of playing with subwoofer speakers.

Answer: lyzqc - Trial Period Level 6-14 22:13

Audio enthusiasts all know that in order to achieve sound reproduction in the audible audio range (20Hz-20KHz) , many speakers use multiple speaker units to simultaneously complete the sound reproduction of the entire frequency band. Commonly used are two-way crossover and three-way crossover speaker systems. The former uses a tweeter and a mid-bass speaker, and the latter Then use one speaker to output the high, middle and bass respectively. These speakers cannot work normally by simply connecting in parallel or in series. A resistor-capacitor network called a frequency divider must be used to distribute different frequencies so that different speaker units can work normally. Work at the appropriate frequency and achieve a flat connection, so that the entire speaker system can complete sound reproduction in the full frequency band with as little distortion as possible. Therefore, the role of the crossover is not only to enable the speaker unit to work safely, but also to It also determines the performance and style of the entire speaker system.

Some of the excellent speakers we are familiar with, such as the British Rogers LS3/5A BBC monitor speakers (Figure 1), have a crossover design in order to make the response

flat within the full frequency band. It is quite complex, so that the efficiency is very low (82.5dB), and the impedance is as high as 11 ohms, making it difficult for the amplifier to drive it. An improperly matched amplifier cannot produce its actual sound effect. I often see some audio magazines discussing the design of speaker crossovers and their impact on amplifiers. Whenever I see these articles, I always wonder if there is a speaker that can be like the eardrum of the human ear without the use of crossovers. It would be nice if the amplifier achieves a flat response across the entire frequency band. On the one hand, it can avoid the loss caused by the crossover, and on the other hand, it can avoid the timbre distortion and phase changes caused by the crossover device. In theory, it is possible to design such a speaker, such as some high-quality headphones, but it would take finding a material that has the extremely light weight and transient response of a headphone diaphragm and being able to make one of regular size and sensitivity. Speakers are unrealistic at this stage. Even if there were such speakers, the cost would be unimaginably expensive. It seems that for me, a working-class person, this idea can only be regarded as a dream.

By chance, when I came into contact with a small speaker with a special structure, I felt that the distance between dreams and reality seemed to be much closer. I remember it was an early autumn afternoon, the weather was refreshing, and a friend I hadn’t seen for a long time called and said that he had moved to a new house and wanted to put a set of speakers in his small study. I had a pair of unused small speakers in my hand. I wonder if they can be used. I hope I can give them some help. After asking for advice, I happened to be fine, so I immediately agreed. When I came to his small study room, I saw that the room was not big, about ten square meters, in Japanese tatami style. The decoration was not high-end and luxurious, but it was exceptionally elegant and warm. Holding a pair of small speakers, I took a closer look and said, "Hey! Not bad, it's the famous British speaker TANNOY CPA-5 (picture 2)!" My friend quickly said, "This box was originally used for an AC-3 system. Because the living room is too small, the rear speakers have been removed, so I don’t know if it’s suitable for listening to music.” I suggested, so I brought the Denon AV amplifier from the living room. AVC-2800G, the CD player is a SONY CDP-497 that I purchased before, and the signal cable is randomly wired. Because the CPA-5 uses a spring bayonet type speaker terminal, it is impossible to use a speaker cable that is too thick, so I just found it. A Huamin surround was connected with a speaker cable (about 1.5 square meters). The CPA-5 placed on the floor was too short, so I took two square stools to cushion it underneath. When people sit on the tatami, their ears are just right. It's on the same level as the speaker. Okay, I can finally turn on the sound. The first thing to play is the theme song "MY HEART WILL GO ON" from "TITANIC". What's surprising is that this little speaker CPA-5 can play it almost easily. A broad sound field opened up in front of us. Although the vocals broadcast were thin, the focus was very good, and the details of the music were also very rich. However, it was disappointing in terms of low frequencies. Many deep and powerful low-frequency signals seemed to It was filtered out, and then I listened to some music discs. Only a few violin collections with less low frequencies felt good, and the sound was transparent, smooth, and exceptionally melodious.

A few hours passed quickly, and it was almost late at night, so I made a summary: "Although the width and height of the entire sound field are good with this usage, the depth is very shallow. There is a feeling of floating in mid-air, which makes people feel restless after listening to it for a long time. Dry; although the mid-frequency is loud, it is not smooth enough; it is really difficult to force this small 5-inch speaker to produce deep low frequencies, not to mention that Denon's amplifier has a cold sound, which is obviously not suitable for such a small speaker, so The key to making good use of this pair of speakers is how to make up for the lack of low frequency, which is not easy!” After hearing what I said, the friend was a little discouraged: “How about buying another pair of speakers?”, “ Don’t be too busy, I’ll give you a reply in a few days!”

I hurriedly said goodbye and went home, looking through Tianlang’s information late at night and found the detailed specifications of CPA-5 as follows:

CPA-5 CPA-5SBII

Speaker unit 5-inch ICT coaxial 4 pieces 5-inch low frequency

Withstand power 100Watts 100Watts

Frequency response 80Hz-22KHz 45Hz-210Hz

Sensitivity (1W/m) 90dB 90dB

Volume (height × width × depth) 220× 155× 130mm 200× 550× 300mm

Weight (kg) 2.85 12

It turns out that when the Tianlang factory launched the CPA-5, it also launched a passive subwoofer (Figure 3). From the frequency response of the CPA-5 It can be seen that its lower limit of low frequency is relatively high. No wonder the low frequency is not satisfactory. However, the 5-inch speaker CPA-5 is very distinctive. It is a real full-band coaxial speaker without a crossover and adopts the technology of Tannoy Company. Unique patented technology ICT (InductionCoupled Technology); using the principle of magnetic induction and the natural frequency dividing characteristics of high and low frequency diaphragms, it cleverly eliminates the need for frequency dividers and reduces the quality of the treble diaphragm to a new low, getting closer to the theoretical level. the state of perfection. Moreover, the sensitivity of CPA-5 is as high as 90dB, and the power it can withstand is not inferior to that of large-diameter bookshelf boxes. The high-end frequency response exceeds the hearing limit of the human ear. CPA-5 also adopts Tannoy's signature Single Point Source design, which has an excellent sense of sound positioning and can best reflect the true personality and connotation of music. The placement of the speakers is not like ordinary speakers. Speakers are so demanding and difficult to handle.

Since the manufacturer has equipped the CPA-5 with a subwoofer, it seems that there is a solution to the bass problem. However, the original subwoofer has a passive structure and has the problem of matching the driver amplifier, which is quite troublesome. , if you have a suitable active subwoofer, you can save a lot of energy! And debugging is also very convenient.

After rummaging through relevant information about active subwoofers, I found that there are many brands. Some European and American brand-name subwoofers are bulky and the price is ridiculously high, which is unacceptable. Even if the price is not an issue, they are as big as a small coffee table. It’s too exaggerated in my friend’s small study room. Finally, my eyes fell on several Japanese YAMAHA home theater subwoofers. They have exquisite appearance, simple and elegant shape, the price is about 2,000 yuan, which is easy to accept, and the size is not large. Due to the use of YAMAHA's AST technology, Its low-frequency lower limit is actually comparable to those of European and American big guys. Based on the size of my friend's study room, I finally decided to choose between YST-SW40 and YST-SW80.

In home theater equipment, YAMAHA’s products can be said to be at their peak. Its AV amplifiers, DSP decoders and AV speakers all occupy a considerable market share. The subwoofer is also one of its strengths. Taken together, YAMAHA's subwoofer speakers are indispensable in many typical home theater configurations abroad, and the effect when used in HI-FI systems is unquestionable.

Dachang Audio, which happens to be in the local electrical appliance market, is an agent of Tannoy and YAMAHA, so I went to the store with my friends on a weekend morning for a trial listening. At that time, it was also equipped with TANNOY's CPA-5. After repeated listening and comparison, Taking into account various factors such as price, appearance, power, and cost-effectiveness of the entire system, we selected YST-SW40, which is less than 2,000 yuan and is the smallest in size. As shown in Figure 4, this subwoofer has a built-in 20cm full-band woofer unit. The 50W power amplifier adopts YAMAHA's AST (Active Servo Technology) patented technology. Although it is small in size, it can still play ultra-low frequencies as low as 30Hz, and has continuously adjustable high-frequency cutoff in the range of 50-170Hz. The filter can easily achieve perfect frequency connection with various small speakers.

In order to give full play to the effect of Tannoy CPA-5, I also bought a famous domestic machine Bada DC-211AK (Picture 5) on the market, which is famous for its beautiful and delicate mid- and high-frequency. An affordable monster signal cable and speaker cable, with a thick and powerful mid-low frequency, so that the CPA-5 can have a more balanced sound performance. In addition to equipment, a speaker tripod is also a must. Considering that the CPA-5 is relatively compact and light in weight, you can choose a domestic retractable high-quality surround speaker stand (Figure 6), which is easy to debug, high quality and low price.

I went back to the small study room and connected the equipment without turning on the subwoofer. It was still the song "My Heart Will Go On", wow!

The vocals coming from the CPA-5 are so pure and beautiful, the mid and high frequencies have spotless transparency, the thickness of the mid frequencies is obviously better than when driven by the Denon AV amplifier, and there is no sense of coldness and fineness anymore. If you think about it carefully, on the one hand, Bada DC-211AK's mid- and high-frequency performance is indeed well-deserved; on the other hand, it also fully reflects the advantages of crossover-less speakers: it can restore the amplifier's mid-frequency signal without loss. Then put the SW40 subwoofer on the ground between the two small speakers (the layout of the speakers in the study is shown in Figure 7), turn on the power, and select the frequency connection point near 80Hz. After careful fine-tuning and maintaining an appropriate volume, the sound can be heard It’s most natural to go up.

With the help of the subwoofer, the sound field displayed in front of us no longer has the feeling of floating in the air. The height, width and depth are incomparable with before. The sound is flesh and blood and the sound field is solid. The steady and obvious sense of depth makes people feel that the small study has become a big stage; when playing the "TITANIC" CD, the continuous low frequency and ultra-low frequency roll in like thick fog, as if there are a pair of invisible hands. While massaging the skin, it is comfortable and allows people to truly appreciate the low-frequency charm of 20-bit digital recording. In the next few hours, I listened to discs including "Tsai Chin's Old Songs", "Going to Have My Own Way", "Sutra's List", "Starka Cello Collection" and other discs. What I felt most deeply was the smooth low frequency. Performance, I really can’t believe that there are so many low-frequency components that have not been discovered in these discs that I have heard so well before. It’s so shameful! Looking back at that man's smiling face is enough to know how satisfied he is. Let him be intoxicated by himself!