Loudspeaker Design
Introduction
Speakers are a representation of the fantastic advancement of technology that has a profound impact on societal cultures. A loudspeaker is an electric sound-making machine that converts electrical signals into audio sound waves. Speakers are of different range and their overall quality, which is dependent on cost, size, and other various factors. Loudspeakers have different frequency ranges, such as woofer, subwoofer, squawker, and tweeter. The loudspeaker is enclosed in a cabinet to prevent damage and enhance the performance of the sound (Komiyama et al., 2003). The quality of a speaker is usually the ultimate factor that affects its output. Speakers, therefore, come in all shapes and sizes and enhance listening of music in all devices and environments such as iPods, phones, or film in cinemas.
Understanding the electronic working of speakers requires the translation of the electrical signal into an audible sound. Sound is an essential aspect of a loudspeaker. The sound occurs after rapid changes in air pressure, which causes vibrations. Knowledge of sound production by a speaker can be best understood by understanding the basics of sound, such as how a human ear intercepts sound produce. Scientifically, objects can produce sound in all mediums, including solids, liquids, and gases. However, the air is the best medium of transmission for sound. Sound is delivered through the vibration of the air by disturbing the air particles. The disturbed particles disturb the next set of air particles continuing the cycle, and the sound produced is dependent on the strength of the original sound. Disturbed air particles reach the ear by striking the eardrum, a thin layer of skin that vibrates and sends the particular signals to the brain, which interprets the vibrations as sound.
Loudspeaker Characteristics
A loudspeaker consists of drivers, a speaker, and a driver. The speaker produces sound while the driver is involved in the creation of the original sound through pressure waves.
Illustration of The Components of The Electronic System of a Loudspeaker
Figure 1. (Swagatam, 2019)
The Basics of The Speaker
A speaker will consist of a cone /diaphragm, coil, and a magnet, as shown in the above figure. The cone will be located at the front of the loudspeaker. Though it occurs in various forms such as fabric, plastic, paper, or lightweight metal. The project will incorporate a paper cone. The outer part of the cone will be attached to the outer part of the loudspeaker circular metal rim. The inner part is fixed to the coil, which is usually made of iron, which is placed in front of a permanent magnet. The workings of the speaker can be explained as follows. When the speaker is connected to a sound system, the electrical signals flow through the speaker cables into the coil (Swagatam, 2019). The coil is transformed into an electromagnet. The flow of electricity back and forth in the wires causes the electromagnetic to either attract or repel the permanent magnet in the speaker. As a result of the movement, the coil is pushed back and forth, which pushes and pulls the loudspeaker cone. The moving cone is responsible for pumping the sound into the air. Therefore, the diaphragm and the voice coil work on the principle of an electromagnet (Komiyama et al., 2003). The magnetic field is produced as the electric current is passed through the two output wires of the speaker to complete the circuit.
Woofer and Tweeter Drivers
Loudspeakers use drivers to help in the translation of electrical signals into physical vibrations to enable the hearing of the recorded sounds. A woofer is a significant driver that creates low-frequency sounds. A tweeter, on the other hand, is a type of driver whose function is the production of the highest range of frequency. It is smaller in size but has high-frequency sounds.
The Outer Structure of a Speaker
Figure 2. (Swagatam, 2019)
Pictorial Representation of a Woofer
Figure 3. (Swagatam, 2019)
Pictorial Representation of a Tweeter
Figure 4. (Swagatam, 2019)
Model and Specific Parameters
Woofer – TRUVOX 1225
- Nominal diameter (‘’) 12
- Power rating (W) 250
- X Max (mm) 2.35
- f/pl (mm) 8
- coil (mm) 12.7
- Nominal impedance (O) 8
- Sensitivity (dB) 97
- Voice coil diameter (‘’) 2½
- Surround Material Cloth – Sealed
- Magnet type Ceramic
- Magnet assembly flux (T) 1.2
- Magnet Weight (oz.) 42
- Chassis type Pressed Steel
- Cone material Kevlar loaded paper
Working of the Woofer and Tweeter
The woofer driver will reproduce low frequencies. It works in the enclosure to produce suitable low frequencies and is closely linked to serving their purposes well. The design used will use a woofer with low frequencies to eliminate the need for a subwoofer (Mascolo et al. 2016). The woofer will also be used to handle middle frequencies, as will also eliminate the need for a mid-range driver. Combined with the tweeter, the woofer will work low enough, and the tweeter will respond high enough so that the two drivers will effectively produce the middle frequencies.
Overall Circuit of a Loudspeaker Using A Woofer and A Tweeter
Figure 5. (Anderson & Bocko, 2016)
The diagram shows a crossover, which is an electronic circuit that works in assigning the appropriate frequency range to different speakers. The above is a 2-way speaker where the crossover has been set at a specific frequency point. As a result, any frequencies above that point are sent to the tweeter, while the remainder is sent to the woofer. In this case, the 2-way crossover point is a 3 kHz, which means that anything above will go to the tweeter, and anything below goes to the woofer (Mascolo et al. 2016). The diagram also displays the circuit wiring with two wires for the positive and negative. The cables enter the terminals and connect to the crossover unit. Both the positive and negative terminals leave the crossover unit and connect to the woofer and similarly leave the crossover unit and connect to the tweeter (Komiyama et al., 2003).
The tweeter operates in phase with the woofer (Mascolo et al. 2016). The speaker has a high pass filter (HPF) that filters out low frequencies and lets high frequencies pass through, and a low pass filter (LPF) that filters out high frequencies and lets low frequencies pass through.
Functional Circuit of a Woofer and A Twitter
Figure 7. (Anderson & Bocko, 2016)
A Two- Way Connection of Tweeter and Woofer
Figure 8. (Anderson & Bocko, 2016)
The diagram shows the use of a capacitor, inductors, and resistors. The functionality can be discussed as follows. The positive side of the tweeter goes into the capacitor and is transmitted to the inductor, which connects to the tweeter (Sendek & Plummer, 2019). The negative side connects to the ground. The woofer function when the positive goes to the inductor then to the capacitor, which connects to the positive side of the woofer while the negative connects at the ground. The specific components of both the woofer and the tweeter have been discussed.
Electronic Components
Electronic and circuit diagrams
Woofer and Tweeter Crossover
Figure 9. (Anderson & Bocko, 2016)
Principle for Working Woofer and Tweeter of a Speaker
Loudspeaker System
Figure 10. (Anderson & Bocko, 2020)
Components
Loudspeaker drive units – they convert electric currents into sound waves. The loudspeaker will have speaker drivers with different ranges.
Cross over the unit- the loudspeaker will use two drivers hence the need for a cross over the unit. The unit will help in acquiring the required frequencies by connecting them to the relevant speakers (Anderson & Bocko, 2020). The crossover unit consists of inductors and capacitors to control the low end and high-end speakers
Cabinet- the loudspeaker is contained in the cabinet, which is rigid and airtight to ensure that vibrations are generated by the speakers only.
Internal sound absorbent material- the loudspeaker cabinet has an absorbent material which prevents resonances from being set up inside the loudspeaker.
Electronic system and functions
Cone/Diaphragm – it is made up of made of a flexible material such as paper or plastic. It is used to amplify the vibrations and, in turn, pumps sound waves into the surrounding air enabling a person to hear it cones also transfer the vibrations from the coil to the air to offer a large surface area (Mascolo et al. 2016). The cones used can be of different sizes as they are dedicated to high medium and low frequencies. The frequency of the vibrations is dependent on the sound produced.
Magnet- it is a significant electronic component of the loudspeaker, which provides a fixed magnetic field against which the coil will operate.
Dome – it covers and protects the coil from dust and dirt.
Surround or suspension refers to the rim of flexible material connected to the cone to enhance its movement. It is attached to the driver’s metal frame.
Voice coil- it is an electromagnet or a metal coil is used in the creation of a magnetic field when an electric current flow through it. The electromagnet is mobile, unlike the permanent speaker, which is firmly fixed (Harris et al., 2018) (Decanio & Banka, 2016) (Anderson & Bocko, 2016). The mobile nature enhances movement where the electromagnet is attracted to and repelled from the permanent magnet, vibrating back and forth.
Spider- it is flexible support that holds the coil in place while allowing it to move freely. It ensures that the coil is centered correctly
Function
The loop will be tied over a paper and will be set and mounted over the magnet to allow movement and enabling it to slide over the entire length of the magnet. The input signal will be put to the terminals of the speaker, where they meet connecting the two ends of the coil. The coil, before reaching the output terminals, will be allowed to run over the length of the diaphragm (Ilkorur, 2019). The functionally will be observed when electronic music or speech signals are applied to the coil on the terminals (Sendek & Plummer, 2019). The application will create varying magnetic fields around the coils corresponding to the received signals. The position of the coil, which is mounted over the permanent magnet, will allow the magnetic field created to interact with the magnetic field of the permanent magnet.
In the interaction, the positive end of the electromagnet is attracted to the negative pole of the permanent magnetic field. On the other hand, the negative pole of the electromagnet is repelled by the permanent magnet’s negative pole (Harris et al., 2018) (Decanio & Banka, 2016). Usually, the electromagnet’s polar orientation will switch, and the change will also be reflected in the switch in the direction of repulsion and attraction. In change will occur in such a way that the alternating current will continuously reverse the magnetic forces between the voice coil and the permanent magnet (Mascolo et al. 2016). As a result, the coil will be pushed back and forth rapidly, like a piston. The interaction of the magnetic field will create pressure over the coil and therefore force it to move and slide forward and backward over the magnet. The displacement movement of the coil to and fro is equated to the various pitches of the input.
The link between the coil, the cone, and the diaphragm enables the action of the coil and the pressure to be applied to the diaphragm, which in turn will vibrate. The process will force the air volume surrounding the cone to start its vibrations and create audible sound waves ((Decanio & Banka, 2016) (Anderson & Bocko, 2016). (Keele et al., 2017). The electrical audio signal is interpreted as a wave, and thus the frequency and amplitude of this wave represent the original sound wave. Thus, the rate and distance that the frequency and amplitude determine the voice coil moves.
Working Characteristics
Both the diaphragm and the voice coil work on the principle of an electromagnet such that a magnetic field is produced when an electric current passed through the wire(Anderson & Bocko, 2020). The voice coil works as an electromagnet to produce a magnetic field with polar alignment. The production, therefore, means that the current flow has to be inverted to help in switching the north and south ends of the magnet. To work efficiently, the loudspeaker drivers will require two output wires. The permanent magnet will use its magnetic poles to produce magnetic fields, which will push the coil outwards until all the magnetic fields are lined up together. If the magnetic fields are lined oppositely, the coil will be pushed outwards. As a result, the voice coil will be pushed outwards, and inwards giving to the music and the push-pull movement of the cone will increase-decrease air pressure in the eardrum to create audible music (Swagatam, 2019 (Keele et al., 2017).
Woofer, the big driver, is designed to produce low-frequency sounds. The tweeter is smaller units that will provide the highest frequencies. The working is sensible in that to create a higher frequency where points of high pressure and high pressure are close together requires the diaphragm to vibrate more quickly. Thus, for efficient working of the speaker, each driver is dedicated to a particular frequency range, and the designation of low frequency, high frequency and mid-range frequencies are designated to the cross over.
Advantages of the design
The project embraces a bass-reflex design, which is mainly used for hi-fi speakers and home theatres. The system is made up of a two-resonant system consisting of the driver and the response system) (Hill, 2018). (Harris et al., 2018). The response system works by sucking audio output from the back of the active driver and then entwining that energy back out of the cabinet, either through a tube or an inert radiator. Thus, more bass is produced while all other factors are equal.
Disadvantages of the design
The design may encounter various limitations and issues. Doppler distortion is a challenge encountered when the loudspeaker is reproducing both high and low-frequency notes. It arises when the movement caused by the low-frequency tone is present on the high-frequency tone and is referred to as the Doppler Effect. The design also requires a problematic compromise of the cone, where making it rigid with a low mass presents a challenge (Sendek & Plummer, 2019). The cone cannot be flexible as the flexure will distort the signal. The loss mass enables the minimization of inertia, which allows the loudspeaker to detect and respond accurately to changes in the sound. Therefore, the materials that will enhance the compromise must be used to improve the performance of the loudspeaker.
Cone suspension has also been a challenge as the way it is suspended a direct impact on its operation. The manner of suspension must enhance its free movement in and out and must also ensure that it remains centered (Keele et al., 2017) (Anderson & Bocko, 2020). The efficient management of the position and movement of the cone, therefore, requires a spider, which is additional support to secure the cone and ensure that it never moves out of its specific alignment to enhance its functionality.
Conclusion
The loudspeaker is a two-way driver using a woofer and a tweeter to handle low and high frequencies producing a perfect combination. The combination has tonal characteristics and is custom made with accuracy and simplicity, producing the right audio system enticing to the ears. The describe electronic, and circuit system will, therefore, produce an outstanding loudspeaker
References
Anderson, D. A., & Bocko, M. F. (2020). Systems and methods for controlling plate loudspeakers using modal crossover networks. U.S. Patent 10,560,781.
Anderson, D., & Bocko, M. F. (2016). Modal crossover networks for flat-panel loudspeakers. Journal of the Audio Engineering Society, 64(4), 229-240.
Decanio, W., & Banka, R. (2016, September). Loudspeaker Crossover Network Optimizer for Multiple Amplitude Response Objectives. In Audio Engineering Society Convention 141. Audio Engineering Society.
Harris, L., Newell, P., & Holland, K. (2018). The ‘Bass Transmission Index’: a new concept for evaluating loudspeaker performance.
Hill, G. (2018). Loudspeaker Modelling and Design: A Practical Introduction. Routledge.
Ilkorur, O. (2019). Diaphragm suspension for a loudspeaker. U.S. Patent 10,368,172, issued July 30, 2019.
Keele, Jr, D. B., & Sarvis, H. (2017, October). Design and Implementation of a Constant-Directivity Tw-Way 12” Woofer Wedge Loudspeaker System. Audio Engineering Society Convention 143. Audio Engineering Society.
Komiyama, S., Nakayama, Y., Ono, K., & Koizumi, S. (2003). A loudspeaker-array to control sound image distance. Acoustical science and technology, 24(5), 242-249.
Mascolo, J., Bartolomeo, N., Laprade, A., Gorczynski, E., Wolff, G., Pisani, G., & Turo, D. (2016). Loudspeaker design and analysis. The Journal of the Acoustical Society of America, 139(4), s2034-2034.
Sendek, H., & Plummer, C. (2019). Loudspeaker Research & Design–HSD5.
Swagatam. (2019, May 17). How to make an active loudspeaker circuit. Homemade Circuit Projects. https://www.homemade-circuits.com/how-to-make-your-own-active/