2007 Winter Symposium: Training Sessions, Tutorials and Invited Technical Papers

Training Sessions
Peter Larsen presented an extremely popular half-day course on "Practical Aspects of Loudspeaker Design", Lidia Lee presented a half-day course entitled "Fact or Opinion" about opinion versus evidence based research, and Dan Digre presented a half day course entitled ‘Loudspeaker 101 for non-technical professionals’.
Course notes are only available to people who registered for the course. Contact ALMA if you attended ether of these seminars and would like a copy. We’re interested in hearing what subjects you would like to see covered in next years training programs, so drop us a line and let us know.

Invited Technical Papers

(all paper titles will link to a PDF file or downloadable presentation of the paper)

Measurement and Visualization of Loudspeaker Cone Vibration ; Wolfgang Klippel, Klippel GmbH.

Optical measurement of loudspeaker cone vibration (scanning vibrometry) can also be accomplished by using Laser triangulation technique which is a cost effective alternative to Doppler interferometry. Since triangulation sensors provide primarily displacement advanced signal processing is required to measure the break-up modes up to 20 kHz at sufficient signal to noise ratio. In addition to stroboscopic animation of the radiation pattern a new decomposition technique is presented for the visualization of the measured data. Radial and circular modes can be separated and the total vibration can be split into radiating and non-radiating vibration components. This kind of post-processing reveals critical vibration modes, simplifies the interpretation and gives indications for further improvements.

A New Method for Measuring Distortion using a Multitone Stimulus and Non-Coherence; Steve Temme, Listen, Inc.

A new approach for measuring distortion based on dual-channel analysis of noncoherence between a stimulus and response is presented. This method is easy to implement, provides a continuous distortion curve against frequency, and can be used with a multitone stimulus, noise, or even music. Multitone is a desirable test signal for fast frequency response measurements and also for assessing system non-linearities. However, conventional singlechannel multitone measurements are challenging because the number of intermodulation tones grows exponentially with the number of stimulus tones and makes it extremely difficult to separate harmonics from intermodulation products. By using dual-channel measurement techniques, only well-known, standard signal processing techniques are used, resulting in simplicity, accuracy and repeatability.

Sound Quality Improvements in Compression Driver Systems; Earl Geddes, AcousticIntelligence.

Based on recent studies of the subjective effects of diffraction, internal diffraction type modes in a horn are expected to be highly detrimental to sound quality. With the use of modern polyurethane foams and improved waveguide contours these diffractions can be substantially reduced resulting in compression driver/waveguide systems with superior sound quality. The theory and implementation will be reviewed. This technology is Patent Pending.

Diamond cones for high quality loudspeaker drivers; Adrian Bankewitz, Thiel & Partner.

Sonic quality and acoustical performance of midrange and treble loudspeaker drivers can be significantly improved by the use of CVD diamond membranes. Production of such membranes is described herein. Improvements include usable bandwidth, harmonic and nonlinear distortion, thermal compression and overall stability. Furthermore we demonstrate that by using the right parameters, finite analysis simulations correspond well with measurement results.

Tutorial Sessions

(all tutorial titles will link to a PDF file or downloadable presentation of the tutorial)

An interesting selection of tutorial sessions and technical papers on a variety of manufacturing topics was presented. Click on the paper title for a downloadable PDF version of the presentation.

Anadigm's Sonic Woofer Family - Simon Dickinson, Anadigm

An  introduction to Anadigm’s SonicMaster family - an advanced subwoofer signal processing module solution for quickly upgrading existing subwoofer plate amplifier designs with an enhanced feature set that allows for state-of-the art subwoofers with minimal cost and negligible product development.

Rub & Buzz Measurement - Ib Rasmussen, K&K International

Ib Rasmussen discussed Rub & Buzz measurement using the P630 test system. He introduced the types of Rub & Buzz and how they are generated, and explain why it causes problems in a production environment.

Objective and Perceptual Method of Assessment of Nonlinearity in Loudspeakers - Alex Voishvillo, JBL Professional
This tutorial discusses recent perceptual models created specifically for the assessment of nonlinearity in transducers. These new methods are compared with other methods and the prospects for future developments discussed.

A CD containing all papers and tutorials can be purchased from ALMA by Members Only for $25. Email management@almainternational.org for details.

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