Speaker Driver Research Articles

A −91 dB THD+N, Class-D Piezoelectric Speaker Driver Using Dual Voltage/Current Feedback for Resistor-Less LC Resonance Damping

This article presents a Class-D audio amplifier for capacitive piezoelectric speaker loads. Employing a dual voltage feedback (VFB)/current feedback (CFB) topology, the amplifier is capable of damping LC resonance without using an external damping resistor, therefore reducing system power consumption, cost, and size. Additional power savings are achieved by using a push–pull (PP)-modulated output stage. To mitigate linearity degradation due to the mismatch of the feedback resistors, they are dynamically matched by employing choppers. The prototype, taped out in a BCD 180-nm process, can drive up to 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{F}$ </tex-math></inline-formula> load with a peak current of 4.4 A while achieving an idle power consumption of 122 mW and a peak THD+N of −91 dB.

Acoustic characteristics of a miniature dynamic speaker driver unit MT006B for measurement of head-related impulse responses by reciprocal method

Acoustic characteristics of a miniature dynamic speaker driver unit MT006B for measurement of head-related impulse responses by reciprocal method

Design of a MEMS speaker driver

Microelectromechanical systems (MEMS) have already found widespread use in highly integrated audio applications. Currently, they are used for microphones where their small size has enabled the use of multiple microphones in a single device to improve noise cancellation. Nowaday, even loudspeakers realized as MEMS structures are possible, which brings up new challenges in circuit design that are the focus of this paper.Starting with an overview of current research activities of MEMS speakers, their advantages and disadvantages, as well as the peculiarities of the driver design are discussed. Compared to electrodynamic speakers, MEMS speakers have a different physical structure which needs to be accounted for when designing the driving circuitry. Possible driver concepts are presented and compared with special consideration of their efficiency and audio quality. Existing concepts are shown and new concepts are proposed.

The Design and Implementation of the Unmanned Vehicle Fixed-point Tracking System

The detection and continuous tracking of a certain object is the leading direction and hot spot in the field of computer vision. This design is the CamShift algorithm in the OpenCV transplanted to the OpenCL for DE1-SOC. The whole design is divided into five modules: Video module, audio module, Ultrasonic distance measuring module, Bluetooth speaker driver module and algorithm transplantation module. Finally our car can achieve fixed-point tracking fixed target, and then stop in front of the target 10cm and at the same time to pick up the Bluetooth speaker.

A 4Ω 2.65W Class-D Audio Amplifier With Embedded DC-DC Boost Converter, Current Sensing ADC and DSP for Adaptive Speaker Protection

In this paper a class-D smart speaker driver is presented that can deliver 2.65 W at 1% THD into a 4Ω load. Maximal output power is maintained at low battery voltage by supplying the class-D amplifier from a DC-DC boost converter. Speaker damage is avoided by a speaker protection algorithm that runs on an embedded DSP. The protection algorithm estimates the membrane excursion and voice coil temperature using a speaker model that tracks the speaker impedance which is determined by measuring the speaker current with less than 2% relative error. A sample & hold technique is presented that rejects the load current ripple by sampling at the moments where the instantaneous load current equals the average current. At full output power the combined efficiency of the class-D amplifier and DC-DC boost converter is higher than 80%. The complete system is implemented on a single chip that measures 6.6 mm2 and is fabricated in a 0.14 μm CMOS technology with a 5 V gate-oxide option.

Sound-evoked network calcium transients in mouse auditory cortexin vivo

Population calcium signals generated by the action potential activity of local clusters of neurons have been recorded in the auditory cortex of mice using an optical fibre-based approach. These network calcium transients (NCaTs) occurred spontaneously as well as in response to sound stimulation. Two-photon calcium imaging experiments suggest that neurons and neuropil contribute about equally to the NCaT. Sound-evoked calcium signals had two components: an early, fast increase in calcium concentration, which corresponds to the short-latency spiking responses observed in electrophysiological experiments, and a late, slow calcium transient which lasted for at least 1 s. The slow calcium transients evoked by sound were essentially identical to spontaneous NCaTs. Their sizes were dependent on the spontaneous activity level at sound onset, suggesting that spontaneous and sensory-evoked NCaTs excluded each other. When using pure tones as stimulus, the early evoked calcium transients were more narrowly tuned than the slow NCaTs. The slow NCaTs were correlated with global ‘up states' recorded with epidural potentials, and sound presented during an epidural ‘down state' triggered a calcium transient that was associated with an epidural ‘up state'. Essentially indistinguishable calcium transients were evoked by optogenetic activation of local clusters of layer 5 pyramidal neurons in the auditory cortex, indicating that these neurons play an important role in the generation of the calcium signal. Taken together, our results identify sound-evoked slow NCaTs as an integral component of neuronal signalling in the mouse auditory cortex, reflecting the prolonged neuronal activity of local clusters of neurons that can be activated even by brief stimuli.

An innovative low-profile monolithic constant-temperature anemometer

A constant-temperature anemometer has been developed which uses a single high-fidelity speaker driver as a combined signal and power amplifier. Owing to its small size and simplicity of construction, the anemometer is well suited for applications requiring a large number of channels (such as hot-wire rakes) as well as applications requiring the embedding of instrumentation within confined experimental models (such as reduced-scale wind turbine blades). The anemometer is shown to have performance characteristics similar to those of a commercial anemometer when used under its design conditions. An operating bandwidth as high as 10 kHz can be achieved, which is greater than most available time-resolved digital particle-image velocimetry systems and is shown to be sufficient to track large-scale turbulence structures in channel flow.

A speaker driver for a single phase supply class G & I

A speaker driver applied to class G/class I with a single phase power supply is presented. Gain expanding and compressing technology are employed in the signal processing circuit to optimize power dissipation. The circuit is implemented in 0.18 μm N-well CMOS. Experimental results show that the speaker driver has a good audio sound quality and power efficiency. Less than 0.006% THD at a low power range and less than 0.4% at a medium power range can be obtained with a 1 kHz sine wave signal. Maximum output power of 360 mW can be gained at a load of 8 Ω. The power efficiency is about twice that of a traditional class AB driver at the power range of 80 mW and shows more than 18% improvement at the higher output power range.

Constant-Beamwidth Loudspeaker Array

A loudspeaker is provided for receiving an incoming electrical signal and transmitting an acoustical signal that is directional and has a substantially constant beamwidth over a wide frequency range. The loudspeaker may include a curved mounting plate that has curvature over a range of angles. The loudspeaker may include an array of speaker drivers coupled to the mounting plate. Each speaker driver may be driven by an electrical signal having a respective amplitude that is a function of the speaker driver's respective location on the mounting plate. The function may be a Legendre function. Alternatively, the loudspeaker may include a flat mounting plate. In this case, the respective electrical signal driving each speaker may have a phase delay that virtually positions the speaker onto a curved surface.

Speaker With Acoustic Damped Port

Systems, methods, and devices for improving speaker performance with an acoustic damped port are disclosed. In accordance with various embodiments of the present invention, a damping material is placed around a vented frame of a speaker driver, and substantially covers or fills the vents of the frame. In some embodiments, the damping material results in improved impedance matching with acoustic delay, without required dimensional tuning (as with conventional ports). In some embodiments, it also reduces the air velocity gradients minimizing higher order frequency distortion components. In some embodiments, the damping material also acts as an absorber of energy by coupling to the sound wave. In some embodiments, low-frequency performance is improved in a small-scale design.

A 120 dB Dynamic Range 400 mW Class-D Speaker Driver With Fourth-Order PWM Modulator

High efficiency Class-D speaker drivers have become ubiquitous in battery driven mobile audio applications. Analog switching errors and timing jitter are known limitations to the dynamic range in these types of switching audio drivers. To overcome these limitations the Class-D architecture chosen in this paper provides a low 667 kHz pulse rate. This architecture is based on a 4th-order digital modulator with pulse-width modulation (PWM) feedback. The modulator loop processes the PWM signals at a high 24 MHz clock rate, and provides pulse edge timing resolution within a single clock period of the high-rate clock. Timing distortion errors due to uniform sampling of the low-rate PWM signals are reduced with the high forward loop gain of the digital modulator feedback loop. The driver receives a 22-bit digital audio input and combines the functionality of a high-fidelity digital-to-analog converter (DAC) with a speaker driver. It achieves 120 dB dynamic range over a 20 kHz bandwidth, provides 88% power efficiency while driving an 8 Ω speaker load, and consumes a total quiescent current of 2.4 mA.

Speaker cabinet and speaker device

A speaker cabinet includes a cabinet having a side board to which a speaker driver can be fixed, a substantially cylindrical tube which is inserted into the cabinet such that a vertical line passing through the center of gravity of a horizontal plane of the cabinet coincides with the axis of the substantially cylindrical tube and which is in contact with the base board and the top board of the cabinet, and a support rod which is inserted into the substantially cylindrical tube through a through-hole formed in the base board of the cabinet and which supports the top board of the cabinet at the upper end portion of the support rod such that the cabinet undulates so as to move like a see-saw.

Audio speaker with graduated voice coil windings

An audio speaker driver having a voice coil with graduated windings such that different sections of the voice coil have different electrical resistances and/or lengths per unit of height of the voice coil. A center portion of the voice coil gives a greater BL, while outer portions give lower overall electrical resistance, such that the audio speaker driver is highly efficient and linear during low excursion operation, with a smoother transition from the linear region to the grossly non-linear region. The wire of the graduated voice coil can have varying cross-sectional area over its length, can be wound on varying on-center spacing, can be wound in different numbers of layers in the various sections, and/or it can fork into interlaced, parallel windings.

Thermal chimney equipped audio speaker cabinet

A thermally conductive chimney tube extends through a loudspeaker cabinet that encloses a volume of air heated by a speaker driver. The open ends of the chimney are outside the cabinet. A column of air within the chimney is in contact with the external ambient air, but sealed off from the enclosed volume of air. As the speaker driver heats the enclosed volume of air, the material of the chimney transfers the heat to the column of air, which rises and carries the heat away into the external ambient air, cooling the inside of the loudspeaker cabinet and thus cooling the speaker driver.

Audio speaker system employing an axi-symmetrical horn with wide dispersion angle characteristics over an extended frequency range

A speaker system includes a speaker driver loaded by a horn waveguide. The speaker driver reproduces sound within an extended frequency range that includes a high frequency band between 8 kHz and 11 kHz. In the preferred embodiment, the extended frequency range includes a wide frequency band between 2 kHz and 11 kHz (and most preferably including the frequency band between 800 Hz and 11 kHz). The horn waveguide has an axi-symmetrical waveguide surface that provides uniform polar dispersion at dispersion angles greater than 90 degrees for sound within the extended frequency range. The waveguide surface preferably has an annular cross section with a radial dimension that increases curvilinearly from its throat to its mouth, such as a tractroid surface.

Capability measure for asymmetric tolerance non-normal processes applied to speaker driver manufacturing

Process capability indices, Cp(u,v), including Cp, Cpk, Cpm, and Cpmk, have been proposed in the manufacturing industry to provide numerical measures on process potential and performance for normal processes. Earlier studies considered a class of flexible capability indices, called CNp(u,v), for processes with non-normal distributions where the tolerances are symmetric. In this paper we consider an extension of CNp(u,v), called C”Np(u,v), to handle non-normal processes with asymmetric tolerances. The extension takes into account the important property of the asymmetric loss function, which is shown to be more sensitive to process shift and more accurate than CNp(u,v) in measuring process capability, hence provides better manufacturing quality assurance. Comparisons between CNp(u,v) and the extension C”Np(u,v) are provided. We propose a sample percentile estimator, and apply the bootstrap method to find the lower confidence bound for testing manufacturing capability. We also develop an integrated S-PLUS program to calculate the percentile estimator and the corresponding lower confidence bound. As an illustration, the proposed approach is applied to capability testing of home-theater speaker systems.

Voice-operated remote control

This disclosure provides a voice-operated remote control intended to replace multiple entertainment system remotes, and it preferably includes two parts, a base unit and a remote (or table-top) unit. During normal operation, the base unit receives each electronic speaker driver signal from a stereo receiver or other sound source and uses speaker-specific transfer functions to generate an “audio mimic signal” which accounts for room acoustics and circuitry distortions. This signal is then subtracted from detected sound and a residual is used to detect spoken commands. In response to spoken commands, learned IR commands are transmitted by the base unit to the remote unit, which then repeats these commands, directing them toward the appropriate entertainment system. Learning of room acoustics and of IR and spoken commands are each performed in discrete modes. During a speaker learning mode, the base unit causes each speaker in turn to generate a test pattern which is measured via microphone and used to develop a speaker-specific transfer function. During a command learning mode, a user speaks each command (e.g., “TV on,” “Tape Off,” “louder,” etc) several times into the remote unit until that spoken command is “learned” and recognizable.

Tuned elastic loudspeaker enclosure

The enclosure of the invention enables greater response in the base range by converting the rear wave present within the enclosure. The enclosure is flexible and is able to act in a manner analogous to a lens in that below a transition frequency, the back wave is reversed to be in phase with the acoustic wave produced by the speaker outside the enclosure and then passed to the listening environment. Above the transition frequency, the enclosure acts as a baffle to dissipates the back wave and acts as a baffle. The result is greater bass response. The speaker system is able to use an underdamped speaker (driver). In this manner, a smaller magnet is used with the speaker (driver) than would otherwise be conventional. The enclosure itself is a simple construction and the result is a low cost speaker system that delivers greater base response.

Active dipole inlet using drone cone speaker driver

An air induction system comprises an air induction body, a speaker with a first diaphragm disposed about the air induction body, and a second diaphragm spaced from the first diaphragm. A signal is generated from the first diaphragm and transmitted to the second diaphragm. The second diaphragm generates a noise attenuating sound.

Cone reflector/coupler speaker system and method

A speaker system (10) including a cone reflector (14) connected to a speaker driver (12). The cone reflector (14) has at least one included angle used to reflect sound in a desired pattern in the horizontal and vertical planes. Where the sound is dispersed in the vertical plane as a function of the included angles. These angles may be varied or more included angles may be added to achieve certain sound energy distributions. The speaker driver (12) is located above the cone reflector (14) with the narrower end of the cone (14) facing the output of the speaker driver (12). Sound generated by the speaker driver (12) is reflected off the cone reflector (14) and dispersed as a function of the included angles of the cone reflector.