What constitutes a good speaker?
To be precise, we should call "speakers" a speaker system. It is a system composed of some transducers, a frequency divider, a cabinet and some additional parts.
The speaker system designer must understand the complex interactions between the components of the speaker system.
Assembling good parts together does not guarantee a good system. (Note: In the next article, I will refer to the speaker system simply as speaker.)
If one word must be used to describe the speaker design process, I think the term "trade-off" is the most suitable. Because there is a trade-off between the performance of the speaker and the final cost.
This is why it is difficult for us to compare speakers from different manufacturers. If you just look at a certain performance index (such as rated power), a certain speaker may look better. But when we consider the overall performance of the speaker system, it may be slightly inferior.
Why are some speakers so much more expensive? In order to better understand this problem, let's take a look at the speaker components.
The truth about the transducer
The transducer is the heart of the speaker. These transducers convert electrical energy into sound energy. Most of the sound reinforcement transducers are piston transducers.
Compared with the transducers researched and produced at the beginning of the last century, modern design has basically not changed much in the working principle. With the development of technology, better materials have appeared, with light weight and low cost. However, the sound principle of the speaker is basically the vibration of the surrounding air molecules through the movement of the piston.
There is no transducer that can provide the energy needed for listening in the full frequency range. Therefore, most speakers are designed with two-way or three-way frequency, with built-in dedicated low-frequency, mid-frequency and/or high-frequency transducers.
Compared with the two-way design, the three-way design requires more transducers, so the three-way design is more expensive.
Very important part of the basin frame design
The design process of the basin frame is an important factor affecting the price of low-frequency transducers. The speaker basin frame made by the stamping process has a lower cost because of its simple manufacturing process and low consumption of raw materials. The speaker frame made of die-casting process is less likely to be deformed due to cone vibration.
At the same time, compared with the stamping type basin frame, the die-casting type basin frame is larger in quality and weight, and correspondingly, the production cost is also higher. Since most of the electrical energy loaded into the transducer is consumed in the form of heat energy, we can optimize its performance by improving the heat dissipation performance.
The selection of cone material must weigh its quality, strength and cost. Although we have been able to use some special materials (esoteric materials) to make speaker cones, paper materials are still the most commonly used, because it is a good choice after weighing various attributes. The cost of a low frequency transducer is probably between tens of dollars to hundreds of dollars.
The design motivation of speaker system designers determines what cone material they choose. If there are price and cost constraints, they will choose a unit with a lower cost. If it is to pursue higher quality and performance, they will tend to choose higher-priced unit models.
The mid-frequency unit and high-frequency unit of the loudspeaker of the sound reinforcement system usually adopt the horn load design. While the horn load provides high sound pressure levels, it can also control the sound radiation pattern. The horn can be made of many materials, including wood, metal, fiberglass, and plastic.
ABS plastic horn is most commonly used because of its low cost, light weight and simple production. The fiberglass horn is stronger, but because it is difficult to make, the cost increases accordingly. The size of the low-frequency horn is large, so wood materials are often used.
The horn driver (transducer) plays a pivotal role in the speaker system. Piezo drivers with relatively low cost or compression drivers can be used in the design of horn loads. Cone speakers can also be used as horn drivers.
Compression driver is the best choice for re-amplification of intermediate and high frequencies. Compression drivers are superior to low-cost piezoelectric drivers because of their higher efficiency and fidelity.
The magnet structure of the transducer is also an important factor affecting the cost. The large magnet structure can generate a greater magnetic field density (generally equivalent to higher efficiency), which will increase the weight of the magnet accordingly. This kind of magnet structure must have a die-cast basin frame as a support before it can be used. Rare earth elements, such as neodymium, require only a small part of neodymium to generate a stronger magnetic field compared to traditional magnetic materials. Neodymium is also the most expensive of commonly used magnetic materials.
Some speaker manufacturers will produce their own transducers. This allows them to better control the supply chain and optimize the performance of components in a specific speaker system.
Most speaker manufacturers will regard OEM manufacturers as their transducer suppliers. OEMs are very efficient in production, because this is what they are good at. Most OEM manufacturers produce and sell general-purpose transducers for regular customers. At the same time, they also carry out patented designs according to the specifications of the speaker manufacturers.
Vital divider
Although the function of the crossover has not been taken seriously, the crossover is arguably the most difficult part of speaker design. The main task of frequency division is to band-limit the signal transmitted to each transducer, and the transducer only works within the frequency range where it can be converted into sound energy. In principle, the frequency divider is equivalent to the transmission system of a car transmission.
When you smoothly speed up the car from 0 to 60 mph, a good transmission system can make the wheels turn faster (increased frequency). The gear shifting should be natural, smooth and perfect. A good frequency divider design should be the same. It can smoothly transition between low frequency, mid frequency and high frequency.
Passive frequency divider, on the other hand, is a filter network composed of passive electrical devices, such as resistors, capacitors, and inductors. Mass-produced general-purpose prefabs can be used as passive frequency dividers, but in the end, the frequency divider must be optimized according to its corresponding transducer. This work is best done by a design engineer.
Some frequency dividers will be mounted on the printed circuit board (PCB). This installation is not only simple and beautiful, but also easy to mass produce, which will reduce production costs accordingly. This installation method is very suitable for low-power applications, but if the driver is overloaded, the printed circuit board will be damaged due to overheating.
Printed circuit board (PCB) may also bend or break due to excessive inductance. This is why many manufacturers insist on the hard wire design of the frequency divider (Hard Wire). Hard connection design must be completed manually, and the appearance effect after completion is often not very good. But compared to a PCB divider, a hard-wired design divider is more robust (and more expensive).
Some speaker systems do not have a built-in crossover. This type of speaker system is driven by professional electronic processing equipment. After the signal is sent to the power amplifier to complete the signal processing process, we call it an active crossover speaker system.
In theory, such a design should be able to save the production cost of the speaker itself (fewer components), but this type of speaker requires an external processor when the system is built, and even more power amplifier channels, so the final cost tends to be higher. Compared with passive crossover speakers, active crossover speakers can provide higher fidelity and greater sound pressure level (SPL).
Nevertheless, compared to the active crossover design, a high-quality passive crossover design speaker can provide excellent sound quality at a lower total cost, and it is relatively simple to connect and debug.
Box
The speaker cabinet and its structure are also important factors that affect the price of speakers. The cabinet must be very strong and sturdy. The vibrating box itself is a transducer, which will interact with other transducers and reduce the performance of the entire system. A sturdy box requires a lot of quality, a lot of ribs, or both. The price is the heavy weight of the cabinet.
Concrete is a good choice as the box material, but it is only suitable for customized subwoofer system. Medium density fiberboard (MDF) is also a more suitable material for making cabinets. Medium-density fiberboard has high density and low cost, but the material itself is very heavy, and it is easy to bend after being damp.
Boxes made of particle board have low cost, but should be avoided as much as possible. Plywood is lighter and stronger than MDF, but there are gaps between the layers. Baltic birch plywood is the best choice for the cabinet material (more than 11 layers, and there are no gaps between the layers), but it is also the most expensive wood in the production of speakers.
The composite material has high strength and low weight, but the cost is high. Glass fiber has high rigidity and weatherproof, but because it is difficult to manufacture, the cost is higher than wood and plastic.
In recent years, Molded-plastic has gradually become a commonly used speaker cabinet. The molded box has a small weight and can be processed to make it weatherproof. After years of mass production, the original high mold cost can be diluted. This type of cabinet structure is very practical for speakers with smaller cabinets, but speakers with large cabinets require more rigid materials.
The speakers that are hoisted above the auditorium must have special hanging parts (hanging points). And must go through a pull test (Pull test) to ensure the firmness and safety of the box and hanging parts.
There is no big difference in appearance between ceiling-mounted speakers and floor-mounted speakers and pillar-mounted speakers. However, ceiling-mounted speakers have higher requirements for cabinet structure, supporting suspenders and testing, so the cost is often much higher.
