The tweeter reflects the details of the sound!
The working principle of subwoofer and loudspeaker is exactly the same, except that the diameter of diaphragm is larger, generally 8 ~ 10 inch, and a * * * vibrating loudspeaker box is added.
From the evaluation index, subwoofer and speaker are basically the same, so I won't introduce the specific content here, just say the numerical requirements. The frequency response is generally below 200 Hz, the rated impedance is about 4 Ω, and the sensitivity is generally greater than 90 dB/w/m..
At present, subwoofers can be roughly divided into active subwoofers and passive subwoofers. An active subwoofer refers to a subwoofer with a built-in power amplifier, which is usually cylindrical and has no additional power amplifier. The disadvantage of this subwoofer is that the heat dissipation is not ideal and the power is not very large. But the barrel shape usually produces unnecessary vibration, which makes the subwoofer controllable. In contrast, the passive subwoofer needs an external power amplifier when it works. The shape and power selection of this 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, while the latter is more suitable for pop music.
"Subwoofer" is usually called "Subwoofer" in business or civil occasions. In fact, the adjective "super" is wrong. The frequency band it reproduces is usually from the upper limit of 150Hz or 100Hz to the lowest of about 25Hz, which is only bass, not subwoofer. Because frequencies below 20Hz are bass outside the range of music people listen to, from the perspective of scientific or professional explanation, only frequencies below 20Hz can be called "super" bass. Generally speaking, however, a subwoofer refers to a low-frequency bass above 20Hz. Whether it is replaying big dynamic music or movie sound effects, the importance of subwoofer is even more important than traditional floor-standing stereo speakers. This is because many music (symphonies or stringed instruments and drums) and many movies contain special sound effects that are extremely majestic and dynamic bass. This kind of sound effect is not only for listeners to "hear", but also for them to "feel" the atmosphere of this scene.
But friends who play Hi-Fi have many different reactions to the subwoofer, and some people find it difficult to control it. Some people think that these are toys for enthusiasts who are particularly experienced in playing Hi-Fi. Some people think that this kind of equipment is used to solve the shortcomings of small bookcases, and it is not necessary to pay too much attention to its placement when joining the whole system; Some people think that playing this kind of equipment is thankless and the success rate is too low; Some people think that the ideal system does not need a subwoofer; Some people think that 3ubwoofr is only suitable for use in oversized rooms ... Although opinions vary, the subwoofer is an extremely important device that enthusiasts talk about the least and know the least. Through this article, I believe that some enthusiasts can change their views on the subwoofer, and also hope to refute it and improve the level of fever.
First, the types of subwoofers
Subwoofers are mainly divided into two types, passive and active. At present, there are many three-piece "3D" satellite systems on the market, including subwoofers and two small main speakers. This system only uses an ultra-low speaker, so the subwoofer is a mono (L+R) signal, and the stereo effect is only available above the sound separation point. In this system, the volume of all speakers is determined by the volume control knob at the front stage. If the sensitivity or volume of the subwoofer is not equal to that of the main speaker, the sound field will be chaotic, the frequency response will be unbalanced, and it will be difficult to locate the sound image. But when the subwoofer can't solve this problem, these problems will be difficult to improve. This kind of subwoofer usually only appears in low-priced systems.
And a passive subwoofer. The left and right main speakers have a full range, and the subwoofer only sounds when there is bass below the cut-off point of the upper frequency limit. This system is called connected subwoofer system. For example, the playing frequency of the main speaker is attenuated below 65Hz, and the sound separation point of the subwoofer is around 65Hz. Its purpose is to connect the main speakers smoothly. The problem with this system is that although the main speaker attenuates below 65Hz, it does not. It is said that its low frequency begins to cut off and decrease below 65Hz, and the degree of these decreases depends on the design requirements of each speaker. So if you replay it with a subwoofer below 65Hz, it will still collide with the main speaker. The important reason is that the subwoofer speaker unit and the main speaker unit are different products. When two different speaker units receive signals, for example, the vibration quality of the large-caliber unit of the subwoofer is definitely greater than that of the main speaker unit, so the sound speed is slower, and they must be.
Therefore, many enthusiasts who play this kind of subwoofer feel that the effect after adding the subwoofer is more chaotic than when it is not added. Designers of this kind of subwoofer usually try to reduce the sound separation point of the subwoofer as much as possible, that is, to avoid conflict with the main speaker. The subwoofer point of this system can only be used for a pair of main speakers. When replacing the left and right main speakers, the subwoofer points must be calibrated again. Although some main speakers are attenuated below 65Hz, there is still sound at 20Hz. These speakers are connected to a docking subwoofer, the effect may be worse, the bass is not strong enough, there is no texture, and the bass may be messy. Manufacturers of this kind of subwoofer usually design the main speakers together. Otherwise, there will be problems in the attenuation of partials (db/ octave) and its cut-off frequency, which is also a gadget of low-cost system and low-fi system.
Active active (double power amplifier) subwoofer system, the signal directly enters the front stage through source frequency division, and the frequency below 100Hz is amplified by the subwoofer and sent to the subwoofer for broadcasting. The frequencies above 100Hz are divided and sent to the back stage of the main speaker, and then amplified and played by the main speaker. At this time, there should be a volume control to control the ratio of the subwoofer volume to the main speaker volume. In addition, there should be a phase adjustment button, which can adjust the phase of the bass amplifier at will within the range of 0- 180. Because the amplifiers of the subwoofer and the main speaker may be designed differently, they will not be in the same phase in most cases, and the listening effects of different phases will make the listener feel different. This phase adjustment button is used to make the subwoofer and the main speaker achieve the same phase effect. When tuning from different phases to the same phase, the volume will be louder and the bass will be more solid. When the phase is reversed to 180 degrees, the sound effect will be slightly slower.
In order to use the subwoofer correctly, the author thinks 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 speaker must work above the crossover frequency of the subwoofer (for example, higher than 100Hz or 120Hz).
Second, why use a subwoofer?
Most readers who play subwoofer think that the subwoofer is used because the bass of the small speaker is not enough. As for the speaker floor box, there is no need to use a subwoofer. Actually, playing subwoofer is not as simple as assisting bass. In the market, only a few traditional speakers can faithfully reproduce the bass sound effect in movie sound, and most of them, even the AV surround amplifiers with medium and high price, do not have enough power and energy to drive the subwoofer. If the active subwoofer is used, both of the above problems can be easily solved.
The so-called "active" means that the subwoofer itself has a specially designed power amplifier, so the signal source it needs only needs the general level signal of AV surround power amplifier. The active subwoofer can be easily used with other audio equipment. No matter how the sensitivity or low frequency response of the matching speaker is designed, it can adjust itself to deal with it. In addition, no matter whether the front is facing sound stage or the back is facing sound stage, it is not necessary to move its position, just adjust the phase. The subwoofers mentioned below are all active subwoofer systems.
Its advantages are:
1. The main speaker does not need to work below 100Hz. Therefore, the distortion of this speaker above 100Hz will be reduced. Usually, the distortion of speaker playback is due to the frequency distortion above 100Hz considering bass playback. If there is no need to push the signal below 100Hz, the playback ability of this unit for the sound above 100Hz will be enhanced and the distortion will be lower.
2. Because the woofer has its own power amplifier, the power amplifiers of the left and right main speakers do not need to be pushed to the frequency below 100Hz, but only need to work above 100Hz. Because there is no need to push these bass, the "power" of this amplifier above 100Hz will be two to four times larger than before. At this point, it needs to be explained in this regard. If the power of a power amplifier is 50w, that is to say, when the power amplifier works in the working range of 20-20000Hz, its driving power is 50W (manufacturers will never say in advertisements that their power amplifier works above 70Hz with 200w and so on). ), but when we say the power output capacity of the power amplifier, we only mean that it can have 50W output when it works at 20-20000 Hz. However, when the power amplifier of 50W only works above 100Hz, its power (above 100Hz) and the power amplifier of 100W to 200w are the same when reproducing the frequency of 20-20-20—20000Hz! However, if this amplifier, which was originally 50W, is upgraded to 100-200W due to the frequency above 100Hz, and works in the whole frequency band, its power will return to its original shape and become 50W. Working above 100Hz will double or quadruple, depending on the frequency of playing back music, and if most of them are high notes, it will quadruple; If it is mainly bass, it is twice as much. The power amplifier is unchanged, but its driving ability will be different when it works at different frequencies, because most of the energy in the whole frequency band is concentrated in the middle and low frequency bands. If a power amplifier only works below 10000Hz, its "skill" will not change much, and it will only affect its "skill" when it is not necessary to push the bass;
3. Because the subwoofer can be separated from the main speaker, it can be placed in other places. The bass we hear in the room is mainly the response effect of these bass in the room, so the position of the bass speaker in the room has a great influence on the bass effect. Some speaker designers put the left and right main speakers on the subwoofer. This design does not take into account the advantages of separating the subwoofer from the main speaker. Some people may think that two-in-one looks better, but if it is conjoined, why play bass? In terms of speaker placement, it is suitable for the position of high school speakers, and most of them will not be suitable for bass speakers. Subwoofers should usually be placed behind the left and right main speakers. Because the subwoofer can be disassembled, the sound stage and positioning made by this playback system can't be compared with a pair of left and right main speakers (no matter what level your speakers are). Many people think that it is not enough to play the bass with a large landing box, and it is okay to think that the bass is too heavy or too turbid. The subwoofer system discussed in this paper has independent bass adjustment function, which can be used to adjust the volume ratio of bass to main speaker. In addition, it can have an independent position, so this subwoofer will never have the problem of heavy or insufficient bass.
These are the three advantages of playing subwoofer.
Respondent: lyzqc- probationary period level 1 6- 14 22: 13.
Audio lovers all know that in order to reproduce the sound in the audible audio frequency range (20Hz-20KHz), many speakers use multiple speaker units to reproduce the sound in the whole frequency band. There are two-way crossover speaker system and three-way crossover speaker system. The former uses tweeters and woofers, while the latter uses loudspeakers to output high, medium and bass respectively. These speakers cannot simply work in parallel or in series. It is necessary to use a resistance-capacitance network called frequency divider to allocate different frequencies, so that different horn units can work at appropriate frequencies, realize smooth connection, and make the whole horn system complete full-band sound reproduction with as little distortion as possible. Therefore, the function of frequency divider is not only to make the horn unit work safely, but also to determine the performance and style of the whole horn system.
Some excellent speakers that we are familiar with, such as the British Rogers LS3/5A BBC monitor (Figure 1), are designed to make the sound in the whole band.
It should be flat, and its frequency divider design is quite complicated, so that the efficiency is very low (82.5dB) and the impedance is as high as 1 1 ohm, which makes it difficult for the power amplifier to drive it, and the improperly matched power amplifier can't play its actual sound effect. I often see some audio magazines discussing the design of speaker frequency divider and its influence on power amplifier. Whenever I read these articles, I always think, if there is a kind of speaker, it would be great if it can achieve a flat response in all frequency bands without using a frequency divider like the eardrum of the human ear. On the one hand, the loss caused by the frequency divider can be avoided, and on the other hand, the timbre distortion and phase change caused by the frequency divider device can be avoided. Theoretically, it is possible to design such a speaker, such as some high-quality headphones, but it is not realistic at this stage to find a material with extremely light weight and transient response like headphones to manufacture a speaker with conventional size and sensitivity. Even if there is such a speaker, its cost is unimaginable. It seems that my thoughts about the working class can only be attributed to my dreams.
By chance, when I came into contact with a small horn with a special structure, I felt that the distance between dream and reality seemed much closer. I remember it was an early autumn afternoon and the weather was cool. A friend whom I haven't seen for a long time called and said that he had moved to a new house. He wants to set up a set of speakers in the small study, and he has a pair of idle small speakers in his hand. I don't know if I can use them. I hope to give it to the staff. I happened to be fine, so I readily agreed. When I came to his small study, I saw that the room was very small, about ten square meters. The decoration is not luxurious, but it is particularly elegant and warm. There are a pair of small speakers on the low platform against the wall. I looked intently, "Hey! Not bad, or the famous British speaker Tianlang CPA-5 (Figure 2)! " My friend said quickly, "This box was originally used as a surround speaker for the AC-3 system. Because the living room is too small, the rear speaker is cancelled, so it is idle. I wonder if it is suitable for listening to music? " "Listen first!" I suggested it, so I brought Tianlong's AV amplifier AVC-2800G from the living room. The CD player is Sony CDP-497 purchased before, and the signal lines are randomly wired. Because CPA-5 uses a spring bayonet horn terminal, it is impossible to use a thick horn wire, so I randomly found a Hua Min surround horn wire (about 1.5 square meter) to connect it. CPA-5 on the floor is too short. There are two square stools below, and the ear of the person sitting on the collapsed rice is just at a horizontal level with the speaker. Well, we can finally turn on the sound. First of all, play the theme song "My heart is eternal" from Titanic. Surprisingly, CPA-5, a small speaker, almost easily opened a wide sound field in front of us, with a fine voice broadcast but a good sense of concentration. The details of the music are also rich, but it is disappointing at low frequencies. Many low-frequency signals seemed to be filtered out, and then I listened to some music discs. Only a few low-frequency violin collections feel good, and the sound is transparent and smooth, especially melodious. A few hours passed quickly, and it was nearly late at night, so I made a summary: "Although the width and height of the whole sound stage are good, the depth is very shallow, and there is a feeling of floating in mid-air. Listening for a long time will make people feel uneasy; Although the intermediate frequency is large, it is not flexible enough; It is really difficult to force this 5-inch small speaker to emit a low-pitched low frequency. And Tianlong's power amplifier is originally from Leng Yan, which is obviously not suitable for pushing this small speaker. Therefore, it is not easy to make good use of this pair of speakers. Let's see how to make up for the lack of low frequency! " After listening to my words, that friend gave up a little: "Why don't you buy another speaker?" , "don't be busy, wait for me to do something! I'll give you an answer in a few days. "
Leave home quickly, regardless of the night, open the Tianlang data to find the detailed specifications of CPA-5 in the following table:
CPA-5 CPA-5SBII
Speaker unit 5 inch ICT coaxial 4 5 inch low frequency
Bearing power100W100W
The frequency response is 80Hz-22KHz 45Hz-2 10Hz.
Sensitivity (1W/m) 90dB 90dB.
Volume (height× width× depth) 220×155×130mm 200× 550× 300mm.
Weight (kg) 2.85 12
It turns out that Tianlang Factory also launched a passive subwoofer when it launched CPA-5 (Figure 3). As can be seen from the frequency response of CPA-5, its lower limit of low frequency is relatively high, so it is no wonder that the low frequency is not satisfactory. However, the 5-inch speaker CPA-5 is very distinctive. It is a true full-band coaxial speaker, without frequency divider, and adopts the unique patented technology ICT (inductive coupling technology) of Tianlang Company. Using the principle of magnetic induction and the natural frequency division characteristics of high and low frequency diaphragm, the frequency divider is skillfully omitted, and the quality of high frequency diaphragm drops to a new low point, which is closer to theoretical perfection. Moreover, the sensitivity of CPA-5 is as high as 90dB, the bearing capacity is not inferior to that of large-caliber bookcases, and the high-end frequency response exceeds the hearing limit of human ears. CPA-5 also adopts Tianlang's famous single-point source design, which has an excellent sense of sound positioning and can fully reflect the true personality and connotation of music, and the placement of speakers is not as harsh and difficult as ordinary speakers.
Since the manufacturer has equipped CPA-5 with a subwoofer, there seems to be a solution to the bass problem. However, the original subwoofer is passive and has the problem of matching with the driving power amplifier, which is more troublesome. If you have a suitable active subwoofer, you can save a lot of spirit! And debugging is also very convenient.
I searched the information about the active subwoofer and found many brands. Some famous subwoofers in Europe and America are huge in size and outrageous in price, which is unacceptable. Even if the price is not a problem, in my friend's small study, the size like a small coffee table is really exaggerated. Finally, I took a fancy to several home theater subwoofers in Yamaha, Japan. They are exquisite in appearance, simple and generous in shape, easy to accept at a price of around 2,000 yuan, and small in size. Because of the AST technology of Yamaha, their lower frequency limit can be comparable to that of the big guys in Europe and America. According to my friends' research areas, I finally decided to choose between YST-SW40 and YST-SW80.
Among the home theater equipment, Yamaha's products can be said to be in full swing. His AV amplifier, DSP decoder and AV speaker all occupy a considerable market share, and the subwoofer is also one of his strengths. Looking at many typical home theater configurations abroad, Yamaha's ultra-low frequency speakers have contributed greatly, and the effect of using them in Hi-Fi system is beyond doubt. Dachang Audio happened to be the agent of Tianlang and Yamaha in the local electrical appliance market, so I went to the bank for an audition with my friends one weekend morning. It was also Tianlang's CPA-5 at that time. After repeated audition and comparison, I integrated the price, appearance, power, cost performance and other factors of the whole system, and chose YST-SW40, which is less than 2,000 yuan and has the smallest volume, as shown in Figure 4. This subwoofer has a 20cm full-band bass unit and a 50W power amplifier. The AST (Active Servo Technology) technology patented by Yamaha Company is adopted. Although small in size, it can still play ultra-low frequency as low as 30Hz, and it has a continuously adjustable high-frequency cut-off filter in the range of 50- 170Hz, which can easily and perfectly connect various small speakers.
In order to give full play to the effect of Tianlang CPA-5, I bought a famous domestic machine Badadc-211AK (Figure 5), and equipped it with cheap monster signal line and speaker line, in which the low frequency is heavy and powerful, so that CPA-5 can have a more balanced sound performance. In addition to the equipment, the speaker bracket is also essential. Considering the small size and light weight of CPA-5, we can choose the domestic telescopic high-quality surround horn bracket (Figure 6), which is convenient to debug and cheap.
Back in the small study, too many chefs picked up the equipment without turning on the subwoofer first, or the song "My heart is eternal". Wow!
The sound made by CPA-5 is so beautiful and moving. The medium-high frequency has a spotless sense of transparency. The thickness of the medium frequency is obviously better than that of Tianlong AV amplifier, and there is no cold and hard feeling. On the one hand, Bada DC-2 1 1AK's mid-high frequency performance really deserves its reputation; On the other hand, it fully embodies the advantages of the speaker without frequency divider: it can restore the intermediate frequency signal of the power amplifier without loss. Then put the SW40 subwoofer on the ground between two small speakers (the layout of 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 keeping the appropriate volume, the sound will sound the most natural.
With the help of the subwoofer, the sound field in front of us no longer has the feeling of floating in the air. Whether it is high, wide or deep, it can't be compared with before. The sound is flesh and blood, the sound stage is solid and steady, and the obvious sense of depth makes people feel that the small study has become a big stage. When playing "Titanium" CD, the continuous low frequency and ultra-low frequency rolled in like a dense fog, as if an invisible hand was massaging the skin, which made people really appreciate the low frequency charm of 20bit digital recording. In the next few hours, I listened to CDs, including Cai Qin's old songs, Go Your Own Way, Sutera's list, and stucky's cello collection. What impressed me most was the performance of low frequency. I didn't expect that there were so many low-frequency ingredients in these dishes that I had heard very well before. What a pity! Look back at that guy's smiling face, enough to know his satisfaction, waiting for him to be intoxicated alone!