Small size speaker but generate higher sound pressure level?

In order to increase sound pressure level, we need to vibrate more air molecule by more power under unit time.
For the two sizes speakers, the area of diaphragms of the 15mm speakers are around 176mm square (7.5*7.5*3.14),
and the 20mm size speakers are around 314mm square(10*10*3.14). The 20mm speakers are only bigger by
5 mm/ 25%, however, the diaphragm are bigger by 78%. Therefore when we input the same power, the 20mm
speakers can vibrate more air at the same time, and it result in higher sound pressure level.
Generally, the speaker in bigger size can provide lower frequency response which is better for human’s
audition. On the other side, we can also provide the smaller speakers more power to make higher sound
pressure level, but it is limited by,
1. Acceptability of the diaphragms2. Thermolysis of the speakers3. After increasing the power, frequency response will change too(because thicker diaphragm, heavier coil..etc)
Therefore, what we can do is reform the material and the structure of the speakers to increase sound pressure level,
but if it is possible to choose the bigger size, the problem of the lower sound pressure level will be improved immediately.
想要有大的音壓,就必需在單位時間之內,以更多的能量來推動更多的空氣分子,
以二種尺寸來說,15mm的喇叭,振膜的面積大約是(7.5*7.5*3.14=176mm平方),
而20mm為(10*10*3.14=314mm平方), 直徑20mm的喇叭雖然在尺寸上只大了5mm / 25%,
但在振膜的表面積卻大了78%,在我們給予這二個喇叭一樣的功率時,
所聽到的聲音大小,就會有很大的不同,就是因為20mm的喇叭可以在同一時間內,
推動更多的空氣分子.
而且更大的尺寸,通常低頻響應也會比較好,人耳所感受的的聲音也會比較好聽些,

當然我們也可以給小喇叭更大的功率,使之發出更高的音壓,但受限於
1. 振膜的承受能力,
2. 喇叭散熱能力,
3. 功率加大後頻率響應特性的改變( 膜片需加厚,音圈變重....)
所以我們只好從材料,喇叭的結構來做改善,盡量將小尺寸的喇叭,聲音做大,
但如果尺寸容許的話,換大一號的喇叭,就可以馬上改善聲音不足的問題囉.

The buzzer has noise 蜂鳴器有雜音

When the sound which the buzzer generates is not a clear beep sound, we call it noise or broken sound. There are two possible ways to cause the noise.
Improperly used If the voltage we input is too high, the diaphragm will easily touch other components, which causes the noise. When we set the wrong frequency instead of the rated frequency is easy to have noise. For example, if the rated frequency is 2730Hz, but the user input 2400Hz, the noise appears easily, especially within the range 10% ahead of the rated frequency.
Disqualified A diaphragm of the buzzer is just set on the braces not firmly attached. Therefore the external force will move the diaphragm and result in the noise. When we assemble the buzzer, or in the process of user’s production line, if there are some iron chippings invade into the buzzer, the noise will also be caused.

當蜂鳴器發出的聲音,不是清脆且單純的嗶聲時,我們會稱為是雜音,或是破音,
蜂鳴器雜音的成因,可分為二種可能,
使用不當:
給予蜂鳴器的電壓過高: 使膜片敲打到內部的其他零件,產生零件撞擊的聲音,
使用的頻率不對: 未將頻率設訂在額定頻率上 , 例如規格是 2730Hz , 使用者卻給 2400Hz 就很容易有異音 , 尤其在額定頻率前10% 範圍最會產生異音.品質不良:
膜片異位: 電磁式蜂鳴器的膜片是"放"而非黏在支架上,故有可能因為激烈的外力使膜片跑出該在的定點,而造成雜音.
有異物侵入: 在組裝蜂鳴器,或是使用者的產線加工時,若有小鐵粉,鐵屑進入蜂鳴器內部,也會造成雜音的發生.

About waterproof speaker 防水喇叭

Generally speaking, a paper diaphragm speaker is easily to have the problem of molding or distortion in a humid environment, and is certainly damaged in the water. On the other hand, the mylar diaphragm speaker is normally waterproof that it can work with drip, fog, or even slightly in the water if we use the rubber ring to fix the diaphragm instead of paper ring.
Another important thing is that all the diaphragms of the speakers are very thin, and the pressure of water might distort even break the diaphragm if it is too deep.
In conclusion, the mechanism design is also very important, especially the joint should be completely sealed in order to reach waterproof function.
一般而言,,紙盆的喇叭在潮濕的使用環境下,比較容易有發霉或是變形的問題,泡水更是會立即的損壞,
而採用塑膠振膜的喇叭大致上都有撥水的能力,亦即水滴,水霧並不會損壞喇叭,
若配上橡膠的墊圈取代紙墊圈,則輕微的泡水也不會有問題,
要注意的是,喇叭的振動膜片都很薄,若水深過深,強大的水壓有可能使膜片變形,甚至破裂!!
當然機構設計上也要注意,喇叭與機構的間隙都必須要密封好,才能泡水的喔!!

The difference between the self drive and external drive buzzers

The difference between the self drive and external drive buzzersDepend on the driving signal, the buzzer divide into self drive and external drive. However inner circuit/ no circuit, DC/ AC, and active/ passive are all mean the same.
The design of the self drive buzzer is to set the circuit inside the buzzer and just offer the direct current to work. The inner circuit has the designed frequency and voltage for the buzzer to generate sound, therefore the frequency of the self drive buzzer is fixed. However the frequency is still different from each buzzer, normally is 2300Hz, the acceptable range is +/-300Hz.
However, the external drive buzzer needs to be drove by the signal of 1/2 square wave V 0-p (magnetic type), or square wave V p-p (piezo buzzer)
It is convenient to use a self drive buzzer, but the disadvantages are the higher cost, the higher defective rate and the unchangeable frequency.

依照驅動信號的不同,蜂鳴器分為自激式及他激式二類,有很多不同說法,但指的都是這二種分類,
如:內含(不含)線路,直流DC/交流AC Type, 有源(無源),
自激式的蜂鳴器是將驅動線路直接設計到蜂鳴器中,故只需給予直流電壓,
內含的驅動線路,就會產生設計好的頻率及電壓給蜂鳴器發聲,所以自激式的頻率是固定的.
但每顆蜂鳴器間的頻率仍會有些差異,一般常見的是2300Hz, 頻率上下300Hz都算可接受的範圍,
而他激的蜂鳴器,需由外部線路給予1/2方波V 0-p(電磁式),或方波Vp-p(壓電式)的信號,才會發聲,
在使用上用自激式的蜂鳴器有其方便的地方,但因為成本及不良率較高,且頻率不可調整,

Introducing the enclosure of speaker 喇叭音箱介紹

Reflex Enclosure 反射式音箱：
It is the most popular design. When the diaphragm of the speaker generates sound, the sound waves which are reflexed from the rear board will be sent out by the reflex pipes. The size and length of the reflex holes and pipes all affect the extension of low frequency, therefore according to the character of the speaker, we should design proper holes and pipes in order to get the best speed and the extension of low frequency.
為最多的設計方式。當單體振膜發聲時，其聲音打到後板所反彈的聲波，藉由反射導管將反相的聲波傳遞出來。其反射孔的大小與導管的長度皆會影響低頻的延伸，因此必須根據單體的特性，設計出適合的孔徑與導管的長度，以取得最佳的速度感與良好的低頻延伸。
Closed Enclosure 密閉式音箱：
The enclosure is entirely sealed. This design will decrease the operating efficiency even though the low frequent voice is good. Therefore in order to get better control, we must give high power to operate it or the speed of the low frequency will be delayed.
其音箱完全採密閉式，雖然能獲得不錯的低頻音色 設計方式會大大降低喇叭的效率，若要獲得良好的控制力，就必須採用超大功率來推用，否則其低頻的速度感會有遲頓的現象。
Passive Radiator Enclosure 背輻式音箱：
A kind of closed enclosure, mainly adds another low frequent speaker. When it vibrates to generate sound, the passive radiator diaphragm is pushed by air. The disadvantage is low efficiency and speed.
屬於密閉式音箱，主要多增加一支只有振膜的單體(低音單體，當低音振動發聲時，其藉由空氣來推動背輻式振膜的延伸。但有效率低及速度慢的缺點。
Isobaric Type Enclosure 等壓式音箱：
It is able to increase the low frequent energy, but the closed design causes the low efficiency. When the two speakers work at the same time, if the sound is out of phase, it affects the results as well.
能增加低頻的能量，但密閉式的設計會造成效率較低,兩支單體同時發聲時，若聲音有不同步的問題產生，也會影響喇叭的暫態反應。
Transmission Line Enclosure 傳輸式音箱：
The transmission line enclosure extends the low frequency by a long wave guide; however the over-length of the wave guide may lower the speed of the low frequency.
藉由較長的傳輸管道來增加低頻的延伸，但過長的管道會導致低頻速度慢。

The structure of specialized enclosure 專業用音箱結構：
Reflex Enclosure 反射式音箱：
The design principle is the same as household reflex enclosure.
其設計原理同家用的反射式音箱。
Horn type Enclosure 號角式音箱：
Because of the good diffusivity characteristic of the horn type enclosure, the low-pitched sound is extruded first then sent by the horn to the far place. At the outdoor concert, it is difficult to send the normal low frequency, therefore, we need to use the horn type enclosure to extrude the low frequency and send it. The disadvantage is the worse low frequency extend.
利用號角擴散性佳的特色，先將低音予以擠壓，再經由號角的擺盪，能將聲音傳送較遠處。在戶外大型的演唱會上，一般的低頻並無法傳送較遠處，因此必須藉由號角的擠壓將低頻傳送出去低音。 缺點為低頻延伸較差。
The enclosures we introduced above can not be completely applied in all the electronic products, it is for consultation; we need to face and solve more problems in reality.但是,以上介紹卻無法完全應用在現在電子產品上,只能參考與活用,原因已經在上述說明,且小speaker參數必須用實際搭配來試,現實問題較多.