Hybrid hierarchical fuzzy group decision-making based on information axioms and BWM: Prototype design selection

The paper notes the drawbacks of classical loudspeaker motors: the inductance varies with the coil's position, there is a reluctant effect, and eddy currents appear because of the iron in the motor. It then presents ironless structures of loudspeaker motors to eliminate these drawbacks. These structures are studied with the use of Coulomb's model of permanent magnets, which affords analytical calculations. Thus, a design can be optimized to create a uniform, high-level induction in the space where the coil moves.

https://ieeexplore.ieee.org/iel5/20/4277883/04277903.pdf

Ironless Loudspeakers

This invention provides a compensation system capable of compensating for power loss due to the power compression effects of the voice coil as the temperature of the voice coil increases. To compensate for the power compression effect, the invention predicts or estimates the temperature of the voice coil using a thermal-model, and adjusts the estimated temperature according to the cooling effect as the voice coil moves back and forth in the air gap. The thermal-model may be an equivalent electrical circuit that models the thermal circuit of a loudspeaker. With the input signal equating to the voltage delivered to the loudspeaker, the thermal-model estimates a temperature of the voice coil. The estimated temperature is then used to modify equalization parameters. To account for the cooling effect of the moving voice coil, the thermal resistance values may be modified dynamically, but since this cooling effect changes with frequency, a cooling equalization filter may be used to spectrally shape the cooling signal, whose RMS level may be used to modify the thermal resistance values. The invention may include a thermal limiter that determines whether the estimated voice coil temperature is below a predetermined maximum temperature to prevent overheating and possible destruction of the voice coil.

System for using digital signal processing to compensate for power compression of loudspeakers

Graphene is flexible and transparent with one-atom layer thickness, and is a novel building block with potential applications in future portable devices. Herein a flexible, transparent and ultrathin earphone based on single-layer graphene (SLG) is reported. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB at a 1 cm distance. The SPLs emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone, which is packaged with a commercial earphone casing, can play music clearly. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time and frequency domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications.

A flexible, transparent and ultrathin single-layer graphene earphone

https://hal.archives-ouvertes.fr/hal-00368286/document

Time-varying non linear modeling of electrodynamic loudspeakers

Moving-Coil Loudspeaker Topology as an Indicator of Linear Excursion Capability

Dynamic Linearity and Power Compression in Moving-Coil Loudspeakers

While the individual elements used in large loudspeaker arrays may be well documented, the performance characteristics of the complete arrays themselves have not generally been measured in detail. Measurements on limited arrays, in conjunction with array theory and advanced modeling techniques, correlate well with observations made of large arrays and thus from the basis for accurate estimation of the performance of arbitrary arrays in large spaces

Mark R. Gander

Papers

Moving-Coil Loudspeaker Topology as an Indicator of Linear Excursion Capability

Dynamic Linearity and Power Compression in Moving-Coil Loudspeakers

Measurement and Estimation of Large Loudspeaker Array Performance

Ground Plane Acoustic Measurement of Loudspeaker Systems

Historical Perspectives and Technology Overview of Loudspeakers for Sound Reinforcement