Features of the bass reflex
A bass reflex is a musical device that is a slot or pipe . The auxiliary element is located in the inside of the sound system housing. The task of the bass reflex is to convert one input signal into two. The acoustic resonator inverts, that is, gradually turns over the sound waves generated on the back of the diffuser. The inverted ringing wave connects with the sounds of the front surface of the diffuser structure. This increases the sound pressure level. A low-frequency sound is produced.
The size and type of port of the product determines the resonance frequency and air volume. Specialists produce ring and slot-shaped devices. The ring view is a classic version of the bass reflex tunnel. Slot channels are made to increase the internal area of the bass reflex port. There are no cylindrical tunnels available for sale. The cylindrical port reduces noise and significantly reduces its length. In this case, the presented device will not be able to efficiently cope with the task.
The choice of professionals and music lovers in favor of a bass reflex is explained by the following advantages of the available equipment:
- High efficiency of the housing.
- Wide use. 90% of modern speaker systems operate successfully thanks to such devices.
- Equal values between the efficiency and the lower frequency limit significantly reduce the dimensions of the system used.
- Using a modern FI, you can set the required audio frequency.
At the same time, the arsenal of the musical unit has its own weaknesses. Among them are the low level of sound quality , as well as low transient characteristics . The duration of the rise and fall of the signal depends entirely on the state of health of the bass reflex. Certain difficulties may arise in the process of coordinating the interaction of the amplifier with the speaker system.
The disadvantages of a bass reflex system encourage beginners and experienced music lovers to use closed boxes.
Bass reflex (FI) – vented box
A bass reflex is the next most common type of acoustic design. In a bass reflex, part of the energy that is “put against the wall” in a closed box is used for peaceful purposes. To do this, the internal volume of the box communicates with the surrounding space through a tunnel containing a certain mass of air. The size of this mass is chosen in such a way that, in combination with the elasticity of the air inside the box, it creates a second oscillatory system that receives energy from the back side of the diffuser and radiates it where needed and in phase with the radiation of the diffuser. This effect is achieved in a not very wide frequency range, from one to two octaves, but the efficiency is within its limits. increases significantly.
All about the closed box
A closed box is one of the popular types of acoustic design. A simple subwoofer looks like a sealed box . A device with relatively flat amplitude-frequency characteristics interacts well with different types of music. ZYa is intended for instrumental, jazz, club and classical music. A great find for fans of smooth bass.
Still, a closed box is not suitable for all types of music speakers. The Thiel-Smol parameters specified in the special documentation included with the audio device will help determine compatibility. If there are no recommendations from the manufacturer, you can check compatibility yourself using some calculations. The value of the resonant frequency of the dynamic head must be divided by the value of the dense quality factor, that is, Fs/Qts . If the resulting figure as a result of mathematical operations is below 80 Hz , then the purchased closed box is suitable for the selected speaker. Otherwise, you should look for another acoustic design.
The main advantages of a closed box are the small dimensions of the design , as well as high-quality sound . The volume of the body of such a subwoofer is ideal for different types of low-frequency speakers. This easy-to-use music device has a smooth frequency response. The closed box will appeal to fans of different musical genres.
However, in the course of the research, experts identified the weaknesses of the ZY. The sound assistant has a low efficiency level. Sometimes, to soften the sound, it is necessary to place a special filler in the box. For example, wool or padding polyester.
Practice with the SL or “the simplest corpus.”
As you all know, the calculation of any ZY is directly dependent on the speaker parameters, Fs and Qts. The influence of the volume of the GZ on the growth of this pair to Fc and Qtc is determined through Vas. And it’s all really simple, you can calculate the PO in your head, without any special programs - in a volume of PO equal to Vas, Fs and Qts grow 1.41 times to Fc and Qtc.
We usually demand little from the radio - decent sound quality with somewhat reasonable efficiency and from a reasonable volume.
This means that we are looking for a GZ setting in the region of 55-75Hz and a final quality factor of 0.5-1.5. Accordingly, we know the ratio of Fs to Qts of a suitable speaker - from 50/1.5=30 to 75/0.5=150 with an ideal of 65/0.7=93+-10%. If you have already read about EBP and that’s all, then already at this stage you see some discrepancies with real practice.
If Fs and Qts can only increase, then, accordingly, Fs of a suitable speaker should not be higher than 50Hz, and Qts should not be higher than 0.5 at any Vas.
Because We still want a reasonable volume of ZY, then we either look for a large Vas relatively low Fs and Qts in the right combination, or a small Vas relatively high Fs and Qts, and also in the right combination. It sounds different, but from the point of view of sound quality, we are more interested in the first than the second, because it is much more interesting to listen to air that does not distort the sound than to listen to a suspension.
However, low Fs with low Qts almost always mean that the movement is not super-easy relative to the motor, and the suspension in the sane volume required for decent efficiency will not keep its speed normally, the speaker will work effectively in the ground cell only at relatively low power. That is, with any speaker, we will never get maximum sound quality at a decent volume from the radio - we are always forced to either choose a compromise option, or lose something.
Almost everything written is related to the operation of the interior transfer function. That is, it implies the operation of the PV in a closed, conditionally sealed space much larger than the speaker Vas, where there is a rise, similar in steepness to the decline, which makes the PV lower than the setting.
They opened the windows, opened the doors, opened the trunk - everything, there was no bottom. And in order for the bottom to be in these conditions, then the SG is not your help at all, because without a transfer function it is not capable of a flat frequency response - only the dynamics have to make such an frequency response, and only above the SG setting, that is, with an increased % of distortion.
Thus, significantly higher than the settings, we do not want to listen to the radio at all, neither in the cabin nor outside. Because subwoofers designed for installation in an enclosure perform poorly in all respects without acoustic load, and those designed for use outside an enclosure perform poorly in an enclosure. That is, for listening in the cabin, we also don’t want to set the VZ to the usual FI low.
Now directly to the setup. In many places you will see some “general recommendations for the volume of the PO,” but there cannot be uniform such recommendations, all dynamics are different. That is, to make a normal ZY, you can’t just stick any 12″ into 25-30 liters and expect everything to work. It won't work. If only because the volume of the cell does not directly depend on the diameter of the speaker. If you need a normal, tuned and predictable voice, then you will always count. Either you will keep the necessary software at hand, or you will keep all the formulas in your head. But it’s not a problem, it can be solved.
To calculate FI, you can not know the parameters of the subwoofer at all and still get into the settings and get some kind of sound. When calculating the ZY, the trick will not work; you will have to find out the parameters. If the speaker is new (fresh), then the factory parameters may be suitable, but if not, then you will have to learn to measure them yourself. And it can be measured quite accurately, since an error in measuring Fs of a couple of hertz, trivial for a FI, will result in a shift in the GZ setting by almost 4 Hz. With an accuracy of around 10%, which is typical for household measurements, the tuning of your signal cell will fluctuate within as much as 15Hz, and this is serious.
So, the “simplest case” has not at all the simplest, contradictory requirements for the speaker and for the organization of space. The landfill is absolutely not without its advantages, but if you approach its design and construction without the proper knowledge, then the landfill turns into a lottery, in which not many people are lucky.
Well, building a ZY is really simple, yes. 6 walls with a hole for the speaker and you're done.
Good luck!
Comparison of musical devices and application features
A bass reflex and a closed box are similar and at the same time very different musical assistants. The presented types of acoustic design have a single purpose of existence - increasing the sound pressure level and improving the quality of low-frequency sound . Both types of subwoofer attract music lovers with their small dimensions. Both the closed box and the bass reflex can be assembled yourself or purchased in special stores (even via the Internet).
And yet, the presented acoustic design options differ from each other in many ways. Buying a bass reflex will cost less than purchasing a sealed box. At the same time, making a closed box with your own hands is much easier than creating a FI. The first type of subwoofer is famous for its high level of efficiency, while the second speaker system interacts better with different musical genres. The designs discussed are distinguished by their level of sound quality. The closed box has better sound quality than its opponent.
The choice and use of a subwoofer depends on the financial capabilities and personal preferences of the music lover. To emphasize and set a certain frequency, it is better to purchase a bass reflex, since similar capabilities are available in its settings. In pursuit of high-quality sound, it is recommended to choose ZYa. Those who want to make their own speaker system will like the closed box. With the help of this subwoofer, music lovers can enjoy the melodies of different musical genres.
Electronics and technologyComment
What types of subwoofers are there?
Types of structures
- Closed box. ...
- Bass reflex (vented box). ...
- Passive radiator (passive radiator). ...
- Bandpass (bandpass) A bass reflex box divided in the middle by an additional wall into chambers of different volumes. ...
Horn loaded subwoofer .
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