Analysis of the characteristics of various speaker cabinets

We will see all kinds of boxes, large and small, with holes, with slits, some with open backs, and various unusual names. What are they like and what are their characteristics?

1. The most classic airtight box,
It evolved from the concept of an infinite panel, and changed the disadvantage of energy waste behind the cone of the speaker caused by the infinite panel, so that the speaker can work in a relatively small volume, but it is still inefficient. The advantages of this box are small size, minimal sound staining, slow low-frequency roll-off, and low distortion! Usually this kind of box is equipped with a soft cone horn (basically equal to high Q). The main point of making this box is to pay attention to the tightness of the box!

2. Bass reflex type (domestic habitually called phase inversion type)
This is the most commonly seen box. The advantages are moderate volume, medium efficiency, and good sound quality in a wide frequency band. The disadvantage is that the low frequency is turbid, and the roll-off is too fast! (Not suitable for low-frequency hifi playback) The secondary phase inversion is a form of enhancing the bass reflex effect. The enhancement effect of the low frequency is improved, but it also causes a deep valley in front of the low frequency peak and the effect of turbidity and distortion of the low frequency Also enlarged! It is difficult to make adjustments.

3. Open back type (abbreviated as OB type, open back or open baffle)
Most electric guitars use this box. It requires a harder cone speaker. The advantage is simple and easy to make, but the disadvantage is that the low-frequency money is not paid. Be careful not to deepen the side panel when making the box, otherwise there will be resonance.

4. Transmission Line and Acoustic Labyrinth
This type of box often has a huge volume, and the sound waves behind the speakers are fed back into a pipe of several meters long. The pipes are often folded, and a lot of sound-absorbing materials are used inside to absorb all sounds except low frequencies and reduce distortion. The low frequency comes out of the duct opening and is in phase with the front sound of the horn. The characteristic is that while the low frequency is strengthened, the quality is quite good.

5. Rear Loaded Folded Horn
4. Transmission Line and Acoustic Labyrinth

This type of box often has a huge volume, and the sound waves behind the speakers are fed back into a pipe of several meters long. The pipes are often folded, and a lot of sound-absorbing materials are used inside to absorb all sounds except low frequencies and reduce distortion. The low frequency comes out of the duct opening and is in phase with the front sound of the horn. The characteristic is that while the low frequency is strengthened, the quality is quite good.

5. Rear Loaded Folded Horn
In the horn box, the sound passes through a cavity whose cross-sectional area is continuously enlarged, and the energy is amplified and the direction is strengthened. The difficulty in making a horn is at the junction of the unit and the horn, and it is necessary to prevent the reverberation from being distorted. Sound dyeing is also a problem. The low-frequency horn is huge, and the right-angle folding horn has the advantage of being compact enough. The disadvantage is that it suppresses high frequency and causes its distortion. The box still uses the front sound of the speaker to directly output. Although the efficiency is higher than the inverted box, it is still the lowest efficient low-frequency horn box!
6. Front Loaded Straight Horn
This kind of box has extremely high efficiency and directionality! Common in large occasions such as stadiums. But it is not suitable for lower frequency, because it will require huge volume and length. In addition to the previous two points, there are also the advantages of low sound dyeing, good sound transients, and high resolution. On hifi, it is often used in medium and high frequency, requiring compression driver.

7. Front Loaded Folded Horn
The classic W-Bin horn box is of this kind, with the advantages of high efficiency and compact structure! The disadvantage is that the bandwidth is narrow and the sound is large. Although efficient, some people think that the bass quality is not even as good as the inverter box.

8. Band Pass
Box designs that have only become popular in recent years, generally there are 4th-order and 6th-order designs. The sound quality of this type of box is very bad, and it is generally not used for hifi purposes! But because it can boost the low frequency and has its own low-pass filtering effect, it is very suitable for AV subwoofer design.
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