There are thousands of horn speakers, and the appearance of a kind of horn speaker is very interesting. The speaker looks like a speaker unit, but a horn like a bell opening. This strange speaker is called a "horn speaker." Why do you want to put this horn on the outside of the unit? What effect did the sound have on the sound after the horn? Is it better to be louder? Why do some people always remember speaker horn? Under the numerous question marks, let me lead everyone into the mysterious world of the horn loudspeaker .
Why is there a horn?
I remember an interesting natural experiment when I was in high school. I rolled it into a cone with cardboard and then leaned my mouth against the cone of the paper tube. The result was a very interesting phenomenon. That is, in the straight position facing the paper tube, the volume of the speech is getting louder and clearer. Everyone is accustomed to this phenomenon, and it is naturally regarded as part of common sense and is actually used in ordinary life. For example, if I want to call people across the street, I will naturally put my hands together and lean on my mouth, because this will make people on the street more clearly. It is because of this simple principle that not only can the sound be transmitted farther, but also the sound of the area where the horn is projected is more concentrated and the volume is louder. This is the advantage of the horn.
The ancients had long known the benefits of the horn, and invented the great king Edison, he took the Edison phonograph he produced, and picked up the sound signal from the carving of the wax cylinder with bamboo needles, and passed it to the small sounding diaphragm, without adding the horn. Underneath, you can only lean your ear against the diaphragm to hear the tiny sound of sputum. At this time, if a horn is placed on the outside of the sounding diaphragm, the volume suddenly increases by several tens of times, which not only enlarges the response bandwidth, but also fills the entire room with music.
Reason for the horn to use the horn
PaulKlipsch is arguably the pioneer of the research on horn loudspeakers . He found in the laboratory that after the unit diaphragm plus the horn, the impedance of the air pressure is well matched, so that the efficiency of sound generation can be greatly improved by a factor of ten or even fifty. ! This means that to achieve the same sound pressure, the horn technology can greatly reduce the output of the unit, and the unit can achieve lower loss and more linear performance in small amplitude motion. In terms of one-sided acoustic characteristics, the use of the horn is to increase the upper limit of the maximum sound pressure, reduce distortion, increase the dynamic range and control the diffusion angle of the sound. For users using low-power single-ended tube machines, due to the efficiency of the horn speaker They are all very high, so you only need to use the 300B tube machine with only seven or eight watts, you can enjoy the thrilling listening experience. This is the biggest advantage of the horn speaker .
Paul Klipsch is an acoustic scientist who works hard on horn research and will of course use scientific experimental data to prove the benefits of the horn. His experiment is like this: take a unit in the no-sound room, and use the amplifier to input two different frequency sine waves to the unit, and then use the spectrum analyzer to test the unit at the same volume. Add the difference between the horn and the horn. The results of this experiment were published in the journal AES (Audio Engineering Society) in the United States. Because of the high efficiency after the installation of the horn, when the same volume is emitted, the output with the horn is only required to be tens of a power of the horn. Therefore, the proportion of various harmonic distortions is greatly reduced. The principle of using a unit to operate at low power to reduce distortion is like the large-scale speaker system, which prefers to use a plurality of units in parallel to obtain a lower output of each unit, which is exactly the same. The use of horns does not require multiple units to be connected in parallel, only one unit is required, which greatly reduces the manufacturing cost, which is the goal of Paul Klipsch's efforts.
Problems encountered with the bass horn
Although it is known that the horn has the advantage of increasing efficiency and reducing distortion, the length of the horn and the size of the opening are closely related to the acoustic characteristics of the horn. It is very difficult and difficult to elaborate on the mathematical equations when the horn is expanded, because a large number of exponential operations need to be applied. For my general users, you only need to understand the principle of horn calculation.
First, the size of the horn opening affects the lowest frequency cutoff point that the horn can produce. Simply put, the larger the opening area of the horn, the lower the low frequency can be extended. What is the approximate value? The area of the opening extending to 35 Hz 3 dB is about the size of a standard desk; if you want to design a horn that can be extended to 28 Hz? Its opening area is about as large as the front of a Ford heavy-duty truck!
The opening is so big, then I simply increase the angle of the horn to increase it. Of course it is not that simple, because there is a problem involved here, that is, the angle of expansion of the horn is to set the formula. According to the characteristics of different horns, the basic formula is an exponential equation, a parabolic equation or a mixed hyperbolic equation. Different from the mechanical properties of the unit, different coefficients are added to the equation. The data calculated using the formula shows the principle of the expansion of a horn.
In the case of a horn equation capable of generating a spherical wave, starting from the position of the diaphragm in which the unit sounds (this part is called the horn of the horn), the cross-sectional area of the horn increases exponentially every time the unit distance is increased. . The characteristics of the index are such that the rate of increase at the beginning is very slow, but the closer to the back, the faster the value increases, and finally almost straight up to infinity, which is the characteristic of the index. .
Based on this, as the horn increases the unit length, the cross-sectional area of the horn increases exponentially, so the shape of the horn you see is closer to the throat of the unit, and it is slightly elongated and slowly unfolded. The part is bent as fast as the petal petals. So you don't think you are smart enough to add a horn to the unit. Without a rigorously calculated horn, the frequency response, diffused wave pattern, and diffusion angle will be seriously affected.
In this way, the arc of the horn expansion should be set, and the bass horn that extends low enough is so large that it can't be plugged into the home listening room. So the super horn player seen in the "StereoSound" magazine, the bass horn does not come through the wall from the back wall of the listening room; it is like a nautilus or a woofer that rolls up the horn line. If the player has a fever, if The listening room was unable to perform "wall-by-wall". Of course, the whole horn with a length of more than two floors was hoisted and pulled straight down from the third floor to the listening room on the first floor.
Folding bass horn
The place where Paul Klipsch is so powerful is here. Since the opening of the horn is so large that it will sink to a certain degree, the length of the horn will not be short after the opening is large. PaulKlipsch was so troublesome that he couldn't solve this problem. I heard that one day PaulKlipsch had a whim in a nap. Why not fold the horn? Use precise calculations and adjustments to hide the woofer in the innermost layer of the speaker. In space, the clever wood compartment is then used to assemble a calculated passage, which not only damages the area of the horn opening, but also greatly reduces the volume. The scientist has started a series of calculations and experiments, finally Klipschorn, the originator of the folding bass horn (ie Klipsch and Horn) was created.
At the time, Paul Klipsch's idea was this. He set Klipschorn's low-frequency cut-off point at 35Hz-3dB, but even after folding it looks like a big wooden cabinet, so he designed the horn opening on both sides of the horn. However, Klipschorn does not have a side panel. When using it, it must be placed firmly on a hard wall with three sides at right angles, and the contacted wall is considered part of the horn design.
Since Paul Klipsch put the folding horn into practical use, many horn designers later introduced a number of similar designs in accordance with this concept, but most of the designs moved to the difficulty of design calculation. The biggest problem they encountered was that the wooden compartment was a plane-shaped passage, but the expansion of the horn was exponentially increased, so it was inevitable that some compromises would be encountered. The design of the folding horn has a deformed design, that is, the transmission line design, the same place is to use the length of the elongated sound channel to achieve the low frequency extension effect, but the size of the opening and the cross-sectional area of the pipe extension are not The horn loudspeaker is so rigorous, so the acoustic characteristics must of course be compromised.
High-quality horn and woofer efficiency coordination
Most of the horn loudspeakers are subject to volume limitations, and the compromise uses a two-way design. The middle and high notes are designed with a pure horn, and the bass part is replaced by a large-sized high-efficiency conventional unit, because the high- pitched horn is very efficient, and has a high efficiency of 1m and 110dB, compared to the bass. The unit cannot achieve a balance of efficiency with the mid-high range. The solution is to deliberately move the hand on the crossover to force the output of the horn unit to be lowered to achieve the same basic requirements for the efficiency of the middle and high horn units and the woofer.
There are three general practices: the simplest method is to string a low-impedance non-inductive resistor on the horn unit to achieve a reduced unit efficiency by increasing the impedance of the unit. However, it is very unsanitary to reduce the efficiency of the string resistance on the unit. Because the impedance characteristic of the unit is a combination of mechanical and electrical impedance, the resistance on the string can only reduce the efficiency one-sidedly, and the overall performance will be seriously damaged. A more elegant method is to add a horn-specific step-down transformer to the high-pitched output of the crossover to deliberately reduce the efficiency of the horn unit. The most popular way is of course the use of electronic crossover, not only do not have to add additional components, with the active electronic crossover, not only the crossover point can be freely adjusted, the gain of each single is also in control The biggest drawback of course requires multiple expansion machines to serve.
For Klipschorn, it is the full horn design of the three-tone road. The output of the treble and midrange units uses a special self-twisting transformer to reduce the over-efficiency horn unit, so that the sound pressure of the three units is the same. The requirements for the average distribution of high, medium and low frequency sound pressure. Even if you deliberately reduce the efficiency of the mid-high horn, the overall efficiency is still as high as 104dB. By placing the horn on the RCA output of the CD player, you can make a sound. This is the magical place! And its maximum continuous power consumption of 100W, using two pairs of Klipschorn plug in the four corners of the stadium, can be used as a high-quality broadcast system!
