Moving coil cone type loudspeaker design
To order call Many mechanisms for making air move in response to an electrical signal have been tried over the years. Three methods of creating sound work well enough—and are practical enough—to be used in commercially available products. These are the dynamic driver, the ribbon transducer, and the electrostatic panel. A loudspeaker using dynamic drivers is often called a box loudspeaker because the drivers are mounted in a box-like enclosure or cabinet. The Dynamic Driver The most popular loudspeaker technology is without question the dynamic driver.
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Do Bigger Magnets Make For Better Loudspeakers?
The purpose of the acoustic transducer is to convert electrical energy into acoustic energy. Many variations of acoustic transducers exist, although the most common is the moving coil-permanent magnet transducer.
The classic loudspeaker is of the moving coil-permanent magnet type. The main purpose of the Magnet Motor Drive System is to establish a symmetrical magnetic field in which the voice coil will operate. The Magnet Motor Drive System is comprised of a front focusing plate, permanent magnet, back plate, and a pole piece. In figure 2, the assembled drive system is illustrated. In most cases, the back plate and the pole piece are built into one piece called the yoke.
The yoke and the front focusing plate are normally made of a very soft cast iron. Iron is a material that is used in conjunction with magnetic structures because the iron is easily saturated when exposed to a magnetic field.
Notice in figure 2, that an air gap was intentionally left between the front focusing plate and the yoke. The magnetic field is coupled through the air gap. The magnetic field strength B of the air gap is typically optimized for uniformity across the gap. When a coil of wire with a current flowing is placed inside the permanent magnetic field, a force is produced.
The electro-magnetic force is given by the expression of Laplace :. The coil is excited with the AC signal that is intended for sound reproduction, when the changing magnetic field of the coil interacts with the permanent magnetic field then the coil moves back and forth in order to reproduce the input signal.
The coil of a loudspeaker is known as the voice coil. On a typical loudspeaker, the cone serves the purpose of creating a larger radiating area allowing more air to be moved when excited by the voice coil. The cone serves a piston that is excited by the voice coil. The cone then displaces air creating a sound wave. In an ideal environment, the cone should be infinitely rigid and have zero mass, but in reality neither is true.
Cone materials vary from carbon fiber, paper, bamboo, and just about any other material that can be shaped into a stiff conical shape. The loudspeaker cone is a very critical part of the loudspeaker. Since the cone is not infinitely rigid, it tends to have different types of resonance modes form at different frequencies, which in turn alters and colors the reproduction of the sound waves. The shape of the cone directly influences the directivity and frequency response of the loudspeaker.
When the cone is attached to the voice coil, a large gap above the voice coil is left exposed. This could be a problem if foreign particles make their way into the air gap of the voice coil and the permanent magnet structure. The solution to this problem is to place what is known as a dust cap on the cone to cover the air gap. Below a figure of the cone and dust cap are shown. The electrical impedance can be determined as the ratio of the voltage on the current intensity :.
A phenomena of electrical resonance is observable around the frequency of Hz. Besides, the inductance of the coil makes the impedance increase from the frequency of Hz. So the range of frequency where the loudspeaker is used is — Hz.
Most moving coil loudspeakers have a two piece suspension system, also known as a flexure system. The combination of the two flexures allows the voice coil to maintain linear travel as the voice coil is energized and provide a restoring force for the voice coil system. The two piece system consists of large flexible membrane surrounding the outside edge of the cone, called the surround, and an additional flexure connected directly to the voice coil, called the spider.
The surround has another purpose and that is to seal the loudspeaker when mounted in an enclosure. Commonly, the surround is made of a variety of different materials, such as, folded paper, cloth, rubber, and foam. Construction of the spider consists of different woven cloth or synthetic materials that are compressed to form a flexible membrane. The following two figures illustrate where the suspension components are physically at on the loudspeaker and how they function as the loudspeaker operates.
Before implementing a loudspeaker into a specific application, a series of parameters characterizing the loudspeaker must be extracted. The equivalent circuit of the loudspeaker is key when developing enclosures. The circuit models all aspects of the loudspeaker through an equivalent electrical, mechanical, and acoustical circuit. Figure 9 shows how the three equivalent circuits are connected. The mechanical system has electrical components that model different physical parameters of the loudspeaker.
This equivalent circuit allows insight into what parameters change the characteristics of the loudspeaker. Figure 10 shows the electrical input impedance as a function of frequency developed using the equivalent circuit of the loudspeaker. The loudspeaker emits two waves : a front wave and a back wave. With a reflection on a wall, the back wave can be added with the front wave and produces destructive interferences.
As a result, the sound pressure level in the room is not uniform. At certain positions, the interaction is additive, and the sound pressure level is higher. On the contrary, certain positions offer destructive interaction between the waves and the sound pressure level is lower. The solution is to put a baffle round the loudspeaker in order to prevent the back wave from interfering with the front wave. The sound pressure level is uniform in the room and the quality of the loudspeaker is higher.
The external fluid exerts a pressure on the membrane of the loudspeaker cone. This additive force can be evaluate as an additive mass and an additive damping in the equation of vibration of the membrane.
When the fluid is the air, this additive mass and additive damping are negligible. For example, at the frequency of Hz, the additive mass is 3g. The volume of air in the enclosure constitutes an additive stiffness.
This is called the acoustic load. In low frequencies, this additive stiffness can be four times the stiffness of the loudspeaker cone. The internal air stiffness is very high because of the boundary conditions inside the enclosure. The walls impose a condition of zero airspeed that makes the stiffness increase.
The stiffness of the internal air in red is fourth time higher than the stiffness of the loudspeaker cone in blue. That is why the design of the enclosure is relevant in order to improve the quality of the sound and avoid a decrease of the sound pressure level in the room at some frequencies. From Wikibooks, open books for an open world. Category : Book:Acoustics. Namespaces Book Discussion. Views Read Edit Edit source View history. Reading room forum Community portal Bulletin Board Help out!
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How Is A Speaker Constructed? How Does It Produce Sound?
Everybody who listens to audio, whether music, podcasts, movies or other media, depends on speakers. With most speakers being electromagnetic, it begs the question: do bigger magnets make better speakers? Do bigger magnets make for better speakers? However, the overall quality of a loudspeaker depends on more than the size of its magnets. Loudspeakers are transducers that convert audio signals electrical energy into sound waves mechanical wave energy. The transducer units are specifically referred to as speaker drivers.
Speaker Transducer Design
A loudspeaker is a device which converts an electrical signal into sound. The term is used to refer to both the transducer or driver itself, and a complete system consisting of one or several transducers in an enclosure. As an electromechanical device, the speaker is the most variable element in an audio system, the electronic components' designs having been standardized long ago so that the differences between them are minimal, compared to those between speaker systems. Further complicating things is the interaction of the speaker with the listening environment, which is, of course, widely variant. Furthermore, this interaction affects the speaker's electromechanical behavior and thus the load it represents to the amplifier, making it even more difficult to predict the sound a given system will produce in its intended environment without actual listening tests. It is often theorized by those who are skeptical of at least some of the audiophile world that the perceived differences between amplifiers are in fact only differences in their ability to control a given speaker-room interaction in a pleasing manner, rather than absolute differences in sound quality; and similarly, that any perceived differences in speaker cables, past a minimum set of specifications regarding resistance, inductance, capacitance, etc. The traditional design is in two parts, a fibrous semi-rigid cone and attached to the apex of the cone is a coil of fine wire usually copper , called the voice coil or moving coil. The coil is oriented coaxially with a permanent magnet where one pole is outside the coil, whilst the other is within the axis of the coil. During the early days of loudspeaker-equipped radios, permanent magnets with sufficient strength were a rarity, and an electromagnet was often used to provide the stationary magnetic field.
Moving Coil Transducer
Johann Philipp Reis installed an electric loudspeaker in his telephone in ; it was capable of reproducing clear tones, but also could reproduce muffled speech after a few revisions. Alexander Graham Bell patented his first electric loudspeaker capable of reproducing intelligible speech as part of his telephone in , which was followed in by an improved version from Ernst Siemens. During this time, Thomas Edison was issued a British patent for a system using compressed air as an amplifying mechanism for his early cylinder phonographs, but he ultimately settled for the familiar metal horn driven by a membrane attached to the stylus. In , Horace Short patented a design for a loudspeaker driven by compressed air; he then sold the rights to Charles Parsons , who was issued several additional British patents before However, these designs were significantly limited by their poor sound quality and their inability to reproduce sound at low volume.
Moving-Coil Loudspeakers
Loudspeakers are special types of speakers designed to convert electrical signals into sound. Loudspeakers are often used as part of public address systems. They are ideal for delivering loud sound that can fill a large room or an outdoor venue. The actual performance of a loudspeaker depends on the design and build of the speaker itself. Horn loudspeakers are designed from the basic idea of a real animal horn. During historical times, animal horns were used to amplify sound.
CN104219606A - Ultra-long magnetic field moving-coil speaker - Google Patents
A loudspeaker or speaker driver , or most frequently just speaker is an electroacoustic transducer , [1] that is, a device that converts an electrical audio signal into a corresponding sound. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone , and indeed the dynamic speaker driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such a motor in reverse, as a generator. The dynamic speaker was invented in by Edward W.
Granted publication date : Termination date : The utility model discloses a moving-coil type loudspeaker, comprising a conical cone frame, a piece of U iron, a diaphragm and a spider.
Most types of loudspeakers transform electrical current or the voltage of sound frequencies into sound vibrations of the surrounding air medium with the aid of a mechanical movable system diffuser. There are different types of loudspeakers. In the past pneumatic loudspeakers were also used. The direction in which a loudspeaker operates is determined by a horn in moving-coil and pneumatic loudspeakers and by the use of sound columns. The most frequently used devices in broadcast receivers and sound amplification systems are moving-coil loudspeakers with a rated capacity of 0. It consists essentially of a thin flexible sheet called a diaphragm that is made to vibrate by an electric signal from an amplifier amplifier, device that accepts a varying input signal and produces an output signal that varies in the same way as the input but has a larger amplitude.
Address after : Zhejiang province Ningbo Yinzhou investment and entrepreneurship center integrity Road. Applicant after : Audio Limited by Share Ltd. Address before : Yinzhou investment and entrepreneurship center, Ningbo, road, No. Applicant before : Ningbo Soundking Electronic Co. Application publication date : The invention discloses an ultra-long magnetic field moving-coil speaker comprising a frame, a magnetic circuit system and a vibrating system.
This is a work in progress and will be updated as the project progresses. A transducer is a device that converts one form of energy into another. In the case of a loudspeaker transducer an electrical waveform is converted into a pressure wave, transforming electrical energy into acoustic energy.
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