The agenda and the report of the previous meeting on 2004-10-30 in San Francisco, US., were agreed as written.
A. Voishvillo asked about rotation of driver on plain wave tube. M. Buck commented that averaging is required and noted that any asymmetry could also show in off-axis horn measurements if a driver is rotated. He commented that it would be necessary to measure things two or three ways in order to fully understand them.
AES 5id R: Review of AES-5id-1997 (r2003): Frequency and angular resolution for measuring, presenting and predicting loudspeaker polar data
No action was required or proposed.
AES2-R: Review of AES2-1984 (r2003): Specification of loudspeaker components used in professional audio and sound reinforcement
M. Buck reviewed progress: It is planned to reinstate the pink noise test, but with a high pass filter of 24db per octave.
D. Keele demonstrated software for a candidate "AES Standard Pink Noise Generator", designed to provide test signals for loudspeaker power testing. It included a noise generator with an optional sine-wave envelope modulator. He raised a question: the software currently uses a 1 Hz sine wave, which results in a half-second repeat rate. Should this be changed to a 0.5 Hz sine wave (i.e a 1 second repeat rate) to conform with IEC 60268-? Further, should the crest factor be measured at the loudspeaker or at the system?
W. Ahnert still wants a full loudspeaker testing standard - fill in missing targets & all very clear instructions & procedures. It was suggested that two documents are required: the full blown AES2, and a companion paper specifying what needs to appear on a specification sheet.
The group reviewed Buck's draft. Anhert will work with Buck to shape it as a companion document to AES2. Full comments should be sent to Buck in preparation for the meeting in New York, 2005-10.
AES-X103: Large Signal Parameters of Low-Frequency Loudspeaker Drivers
W. Klippel re-capped ALMA discussions of 2005-01 on X(max) and various related measurements and criteria.
Klippel proposes closing the project for a period and re-estabishlishing the focus within the context of a revision of AES2.
AES X129: Loudspeaker Distortion Perception and Measurement
This project is being developed by task group SC-04-03-D. S. Temme provided an update on behalf of J. Stewart and reviewed the notes of a March task-group meeting.
A proposal will be available at the end of June to establish a concensus for a hypothesis and for work to begin.
The next meeting will be held in conjunction with the AES 119th Convention in New York, NY., US., 2005-10.