1999 January/February, VOLUME 47 NUMBER 1/2

CONTENT

PAPERS

The Acoustic Lever Loudspeaker Enclosure
Earl R. Geddes 3
A new system for substantially improving loudspeaker system efficiency is presented. The loudspeaker driver's output is coupled to resonant chambers that effectively raise the acoustical efficiency. A further increase in the efficiency is achieved by mechanically coupling the compliant members of the coupled chambers. The trade-off for the improved efficiency is a limiting of the overall acoustical bandwidth.

Comparison of Loudspeaker Equalization Methods Based on DSP Techniques
Matti Karjalainen, Esa Piirilä, Antti Järvinen, and Jyri Huopaniemi 15
Digital filters to equalize loudspeaker response are used in this study. A new equalization principle which employs warped filters is described. The warped filter designs have the advantage over traditional designs of a reduced filter order with improved numerical robustness. The disadvantage is the higher computational complexity of the warped structure, depending in which hardware or software environment the warped filter is used.

Evaluation of Artificial Heads in Listening Tests
Henrik Møller, Clemen Boje Jensen, Dorte Hammershøi, and Michael Friis Sørensen 32
The subjects in this presentation listened to and compared real sound fields to artificial-head recordings of the same sound field. This study was designed to evaluate comparative localization performances of artificial heads. The results of listeners' localization performance tests, when comparing artificial-head recordings to those of the real sound fields, resulted in an increased number of errors. The results obtained when using some of the artificial heads in this study also showed an increase in confusion of directionality perception outside the median plane. The overall conclusion indicated the need for an improved artificial-head design.

COMMUNICATIONS

Electronic Damping for Dynamic Drivers in Vented Enclosures
T. S. Hsu and K. A. Poornima 47
Loudspeaker voice coils when driven at high power levels experience considerable heating which results in elevated voice coil resistance and subsequent damping loss. The authors have restored the damping loss by introducing velocity feedback to the electromechanical system. The loudspeaker driver system damping can then be maintained at a constant value, independent of the changes in the voice coil's dc resistance, by employing current drive.

STANDARDS AND INFORMATION DOCUMENTS

AES Standards Committee News 55
Patch panel connectors; audio in 1394; acoustical diffusion

FEATURES

16th Conference Preview, Rovaniemi, Finland 58
Calendar 60
Program 62
Registration Form 69

DEPARTMENTS

News of the Sections 70
Upcoming Meetings 76
Sound Track 76
New Products and Developments 78
Available Literature 80
Membership Information 81
AES Special Publications 85
Sections Contacts Directory 90
AES Conventions and Conferences 96