SC-04-03 meeting, San Francisco, 2004-10

Report of the SC-04-03 Working Group on Loudspeaker Measurement and Modeling of the SC-04 Subcommittee on Acoustics held in San Francisco, CA., US., 2004-10-30

The meeting was convened by chair D. Prince.

The agenda and the report of the previous meeting on 2004-05-09 in Berlin, Germany, were agreed as written.

Open Projects

AES-1ID-R, Review of AES-1id-1991 (r2003): Plane-Wave Tubes: Design and Practice
M. Buck has presented the latest document revision to the working group on the reflector. The chair requests any final comments to the revisions before this draft is moved forward to a call for comment. The call for comment is targeted for 2005-02.

AES-5ID-R, Review of AES-5id-1997 (r2003): Frequency and angular resolution for measuring, presenting and predicting loudspeaker polar data.
The chairman noted some coordination issues with the AES-X072 project but the two will remain independent. An AES-5id revision will be produced simultaneously with the report or information document generated in AES-X072.

AES2-R, Review of AES2-1984 (r2003): Specification of loudspeaker components used in professional audio and sound reinforcement
Buck was not present at the meeting. Task group SC-04-03-A that is handling this revision met earlier during the convention and finalized the brief format introducing the alignment with IEC documents and the release of three major additions for maximum excursion measurement, polar resolution, and power testing. The power test signals is expected to be defined by standardized signal creation software.

Development Projects

AES-X072, Acoustic Center of Loudspeakers
A report was issued to the working group which will be further developed into an information doc and coordinated with definitions in AES-5id-R.

AES-X103, Large Signal Parameters of Low-Frequency Loudspeaker Drivers
Prince reviewed incorporation of reports from AES-X102 into AES2-R. W. Klippel reviewed the background of the measurement technique and his imminent proposal to IEC. He will provide terminology based on AES documents. ALMA provided a report and will confirm and update any recommendations.

AES-X129, Loudspeaker Distortion Perception and Measurement
This project is being developed by task group SC-04-03-D. J. Stewart reported that the group has been using experts to help coordinate testing. It was hoped to repeat the Berlin meeting tests in San Francisco but this was not possible. PEAK testing and G. Soulodre did agree to try to get a new test to compare listening vs. objective measurements. Along with the work of N. Zacharov there are now 5 tests that did not exist when the group started. Soulodre will meet with Klippel to review the relevant hardware and software. Stewart read a mission statement to solicit feedback to confirm the group's direction with general approval from the meeting which will be posted in due course.

Liaisons

ALMA - The International Loudspeaker Association (see above)

ASA. The chair noted that a termination of the liaison to ANSI via ASA would be proposed to the AESSC by ballot. A high financial cost compared with poor returns to AESSC was noted as the reason.

New Projects

Loudspeaker data format
Prince noted some recent issues with standardizing loudspeaker data format. As one example, it was noted that an informal group (see www.clfgroup.org) is developing a common file format for delivering loudspeaker measurement data.

W. Anhert would prefer such data presented as an impulse response in binary format and then have the freedom to use converter programs. M. Dodd observed that there are some CAD formats that might be valuable. D. Gunness requested that the data table should not be derived from just a point. Anhert keeps all measurements & analysis in binary.

Prince noted that liaison will be required with SC-04-01 and will open the subject on the email reflector. Since the SC-04-01 meeting had not yet occurred, further discussion was deferred. At this point there is no new project but discussion will continue on the reflector.

New Business

Chair D. Prince noted that his committments severely limited the time he is able to devote to individual projects and invited others to consider how they might wish to contribute.

The next meeting is scheduled to take place in conjunction with the AES 118th Convention in Barcelona, Spain, 2005-05.

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