Discussion on Speaker Design

The role of the speaker is to cooperate with the speaker to produce better sound. An excellent cabinet design can maximize the performance of the speaker unit. The original speaker design is to reduce or eliminate the sound short circuit phenomenon of the speaker unit, due to the opposite phase of the sound wave interference, in particular, will have a strong ability to bypass the low-frequency sound wave due to interference caused by the sound pressure is greatly reduced, so that the low-frequency performance of the speaker will be weakened, so that the sense of hearing is reduced. So people think of using the baffle to hinder the interference of sound waves, but in order to achieve a certain low-frequency response, the baffle must be made very large, at least greater than the 1/2 wavelength of the lower limit frequency of the low frequency. Later, people improved on this basis and developed the speaker system we are familiar.

01. Open speaker:

The idea of open speaker is to fold up the baffle to form an open box with the back. The principle is the same as that of the baffle. However, this method makes the placement of the speaker easier. However, due to the limitation of space, the box cannot be made very large. There will still be some low frequencies bypassing the box to reach the front to produce sound short circuit. The low frequency limit of this speaker will also be relatively high, and the location of the unit can not be opened in the center of the panel.

02. Sealed speaker:

On the basis of opening the sound box, people seal the rear of the sound box, which completely blocks the interference of the sound wave on the front of the back. However, the efficiency of the sound box is greatly reduced by only using the radiation in front of the speaker unit, and the air pressure generated by the air pressure difference during the movement inside and outside of the speaker reduces the antegrade of the speaker, thus increasing the resonance frequency and raising the lower limit of the low frequency.

From the perspective of thermodynamic pressure, when the internal volume of the box is larger, the air pressure will hinder the vibration of the speaker, and the lower the frequency will be deeper, which needs to be within the frequency range of the speaker to be effective, but at the same time, the transient performance of the speaker is also declining, which will make the business become muddy. Usually, the Q value of the speaker system is designed between 0.7 and 1.2, which can better take into account the transient and low frequency response.

After the volume of the box is determined, the specific size and shape of the box will also affect the standing wave resonance problem of the box. Choosing the ratio of irrational numbers and eliminating parallel surfaces can effectively prevent the generation of adverse energy interference. It is worth mentioning that the use of sound-absorbing cotton is introduced in the design of sealed speakers. In theory, a good sound-absorbing cotton material can expand the volume of the box by 40%, and at the same time increase the damping of the box. This is also the use of thermodynamic principles.

If the low-frequency feeling of the sealed speaker at home is almost and the transient performance is good, you can choose to increase the sound-absorbing cotton material appropriately to improve it. Conversely reduce sound-absorbing cotton or fill rigid materials. The resonance of the box can also be improved by attaching sound-absorbing cotton to the inner wall and weighting the box.

03. Inverted speaker:

Inverted speaker is one of the most common speakers, it has the advantages of small size, low frequency deep, large radiation energy and so on.

He is a box structure made by using the principle of Helmholtz resonant cavity, which radiates the sound wave on the back 180 degrees in reverse direction. However, in fact, it is not simply reflection, but a new sound wave formed by the air movement in the inverted tube caused by the vibration of the speaker. However, the inverted tube is like a new speaker unit, and the sound wave interferes with the forward sound wave of the woofer to enhance the bass effect. Inverted speakers with the same frequency response are much smaller than sealed boxes, but the transient response is generally less than sealed speakers.

Its volume and inverted tube have to be strictly designed, and the requirements for speakers are relatively high. For the inverted standing wave, the way of low frequency scattering and high frequency absorption should be adopted. Therefore, it is suggested to assign an independent absorption wall to the high frequency unit and make some articles on the inner surface of the low frequency cavity.

When designing, the volume should be as accurate as possible. If too much sound-absorbing cotton is added to the inverted speaker, considering the principle of resonant cavity, the inverted phase seems a bit nondescript. Inverted phase speakers are also divided into front phase inversion, back phase inversion and side phase inversion. If the difference of effect caused by placement position is excluded, the interference results are different due to the different opening of the inverter and the different frequencies emitted by the inverter tube. The front phase inversion is almost the full range interference of the inverter frequency, while the other phases will have the difference of distance from the front of the speaker and hinder some high-frequency interference, that is to say, the rear inverter opening is larger, and when the distance from the wall is about 30cm, there will be a choice to interfere with a lower frequency. If you want to improve the inverter speaker, you can adjust the length of the inverter tube according to the actual situation, or add a damping plug to the inverter tube to improve.

04. meandering (maze) speaker:

This kind of speaker can be said to be the most simple use of acoustic interference box, usually a reasonable design will make the lower limit of low frequency and then extend 1.33 times the resonant frequency of the speaker, has a more excellent low frequency response. The reality is to change the distance traveled by the sound wave behind to make it change phase.

Although this kind of sound box dives deeper at low frequency, its design is complicated, and it is easy to make bass hypertrophy if it is not done well. It is also difficult to master the decreasing law of pipe diameter. The volume of the box is very large. During the design, it is necessary to cooperate with the use of sound-absorbing materials to reduce high-frequency conduction interference. If you do full frequency, listening to elegant slow songs should be, the other may be too much to say a design gimmick. This kind of box in the design if not reserved change space basically can only from the size of the pipe outlet is to do some article.

05. with cylinder speaker:

This kind of speaker is designed for the performance of frequencies below 200Hz designed ultra-low frequency speaker, is made using the physical frequency division principle of the box, the advantage is that you can use a smaller speaker to get better low-frequency effect, and the truth is smaller, but the requirements of the unit is relatively high, sensitivity is his biggest weakness.

It can be used with other sound boxes as low-frequency compensation. Since the audio below 180Hz almost loses its direction, it does not need to be used more. One is enough. Of course, for the sake of sensitivity, the tuning port of both 4th and 6th order box should be opened larger. Usually, the volume of the two cavities of this speaker determines its bandwidth. The wider the bandwidth, the lower the sensitivity. The narrower the bandwidth, the higher the sensitivity. On the basis of the finished box, we can use sound-absorbing cotton and rigid body filling to further adjust.

It is not recommended to use damping plugs here, because the sensitivity of the original box will be relatively low. Common on the market this kind of box, perhaps some unreasonable design caused by the problem of inconsistent sound, we can increase or improve the frequency divider circuit to reduce its frequency response to improve.