AES New York 2009
Poster Session P3

P3 - Transducers and Amplifiers

Friday, October 9, 10:00 am — 11:30 am
P3-1 Target Modes in Moving Assemblies of Pleated LoudspeakerJose Martínez, Fernando Bolaños, Acustica Beyma S.L. - Moncada, Valencia, Spain; Enrique Gonzalo Segovia Eulogio, Jaime Ramis Soriano, Universidad de Alicante - Alicante, Spain
In this paper we present the process followed for the adjustment of a numerical model in finite elements of the mechanical behavior of a pleated loudspeaker, based on the AMT technology (Air Motion Transformer). In this type of transducer, the diaphragm is formed by longitudinal folds. In the internal face of each one of these folds is printed a conductive ribbon. We have obtained first the participation factors and the generalized mass from the results of a natural vibration modal analysis. Next, an analysis is realized taking into account the loss factors of the materials, followed by a forced vibration modal analysis. Finally, a method is described for the characterization of the materials (Young Modulus and Loss Factor), by using modal analysis techniques.
Convention Paper 7835 (Purchase now)

P3-2 Cone Shape Optimization Based on FE/BE Simulation to Improve the Radiated Sound FieldPatrick Macey, PACSYS Limited - Nottingham, UK
An optimization procedure is used in conjunction with finite/boundary element simulation to adjust the shape of an axisymmetric cone, defined as initially straight, and improve the radiated sound field, while keeping the maximum depth as a constraint. The effect of several different objective functions is considered. The optimization procedure is made more feasible by reducing the effect of local minima by artificially high damping applied to some components within the drive unit.
Convention Paper 7836 (Purchase now)

P3-3 Study and Improvement of DC-Link Perturbations Models for DCI-NPC Power AmplifiersVicent Sala, Luis Romeral, Universitat Politecnica de Catalunya - Terrassa, Spain
This paper presents the most important sources of distortion in high power DCI-NPC amplifiers. These distortions sources are attributed to power supply perturbations due to the DC-Link midpoint voltage oscillations. We have presented a classic model for assessing the magnitude of these disturbances and justified the need to correct the classic model to accommodate the real load impedance variations. A new model is proposed, and this is compared and studied with the classic model by analytical, experimental, and simulation methods. This paper concludes that in control or cancellation applications it is necessary to use models that include the load impedance variations regarding the frequency.
Convention Paper 7837 (Purchase now)

P3-4 Active Control Based on an Estimator for the Bus-Pumping Cancellation in the Half-Bridge Class-D Audio Power AmplifiersVicent Sala, Luis Romeral, Universitat Politecnica de Catalunya - Terrassa, BCN, Spain
This paper presents a new technique to avoid the distortion generated due to midpoint voltage variations on DC-Bus of Class-D Half Bridge audio amplifiers. An usual distortion source on a Class-D amplifier is the Bus-Pumping effect. Bus-Pumping causes characteristic distortion and introduces attenuation on output gain. Due to this effect the amplifier efficiency decreases. By including distortion factors on the Half-Bridge amplifier model a new Hybrid Active Control (HAC) is implemented. The HAC minimizes distortion due to midpoint DC-Bus voltage variations. Simulation and experimental results confirm the theoretical approach of parameter influence on Bus-Pumping and the effectiveness of HAC implemented control. Results show a reduction of general distortion, which allews incremented audio amplifier efficiency.
Convention Paper 7838 (Purchase now)

P3-5 Simple Amplifier for Single Frequency SubwooferVladimir E. Filevski, Audio Expert DOO - Skopje, Macedonia
Frequency mapped amplifier driving single frequency subwoofer is an inexpensive way to add the missing low tones to small satellite loudspeakers. The whole amplifier system consists of a band-pass filter (typically 20–120 Hz), an envelope detector, single frequency (typically 50–60 Hz) constant amplitude generator, mixer (that multiplies output from the envelope detector and single frequency generator), and a conventional power amplifier. The amplifier proposed in this paper unites the functions of the mixer, the generator, and the power amplifier in a single unit and does not need a DC power supply, but it runs on 50/60 Hz AC power supply, without rectifier and without big voltage-smoothing capacitors. With an appropriate MOSFETs the proposed amplifier can run directly on the 120 V/60 Hz mains supply line—without a power transformer; but in that case, it needs a loudspeaker with a sufficiently high impedance on the frequency of 60 Hz in order not to stress output transistors of the amplifier.
Convention Paper 7839 (Purchase now)