SC-04-03 meeting, Vienna 2007-05

Report of the meeting of the SC-04-03 Working Group on Loudspeaker Modeling and Measurement of the SC-04 Subcommittee on Acoustics, held in Vienna, Austria, 2007-05-05

The meeting was convened by chair J. Stewart

The agenda and the report of the previous meeting, 2006-10-05, were accepted as written.

Open projects

AES-1id-R: Review of AES-1id-1991 (r2003): Plane-Wave Tubes: Design and Practice
Project scope: to establish, expand, and improve the practice for the design and use of plane-wave tube measurement techniques, as recommended in section 2.2.1 of AES2-1984, "Recommended Practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement."

Status: Amendments awaited from M. Buck prior to secretariat-formatting

AES-5id-R: Review of AES-5id-1997 (r2003): AES information document for Room acoustics and sound-reinforcement systems - Loudspeaker modeling and measurement - Frequency and angular resolution for measuring, presenting and predicting loudspeaker polar data

Status: No action requested or required. Activity in AES-X083 to be monitored.

AES2-R: Review of AES2-1984 (r2003): AES Recommended Practice - Specification of loudspeaker components used in professional audio and sound reinforcement

Secretariat-formatted draft is awaited ASAP, accepting latest revisions.

The changes suggested in San Francisco were discussed and in that discussion it became apparent that the 2000 revision of the AES2 scope had been used and that that scope did not match the intent of a simplified version of AES2.

The following scope is proposed for a new simplified document, separate from AES2:

Title: Characterization of loudspeaker systems

Intent: short document under a new project [AES-X168]

Scope: This document defines a minimum set of characteristics of loudspeaker systems for inclusion in manufacturers' specification documents, and identifies the relevant methods of measurement.

The document considers both passive and active loudspeaker systems for professional applications. It does not consider components of such systems such as loudspeaker drivers or crossover filters. It is intended for system specifiers, system installers and end users.

This new scope then prompted a revised scope for revision of the existing the AES2:
Title: Characterization of loudspeaker drivers

Intent: comprehensive document updating AES2

Scope: This document defines a complete set of characteristics of loudspeaker drivers for inclusion in manufacturers' specification documents, and identifies the relevant methods of measurement.

The document considers loudspeaker drivers for professional applications. It does not consider sub-components such as spiders or cones. It is intended for loudspeaker system designers and drive unit manufacturers.

These two new scope statements were developed with a fair amount of discussion regarding nomenclature, target audience, and the neccessary separation between standards for parts like spiders and coils, assembled loudspeaker drivers, enclosure assemblies, clusters and line arrays, crossovers and amplifiers.

Both of these documents may be released as standards, not recommended practices, requiring new numbers to be assigned. It was pointed out that the AES2 standard is still a popular download from the website.

J. Woodgate volunteered to lead the proposed new project - provisionally identified as AES-X168.

Stewart will contact Buck to seek his opinion on proceeding with AES2-R with the above scope. All members are invited to comment on this direction.

Development projects

AES-X129: Loudspeaker Distortion Perception and Measurement
Project scope: to research the correlation of loudspeaker distortion perception with old and new distortion measures.

Status: Continuing work in task group

Discussion: A request was made for possible authors of the listening test portion of the document. A.B. Belcher offered to join the committee and offered a distortion technique that has been used to evaluate semiconductor analogue-to-digital and digital-to-analogue convertors. This information has been made available on the SC-04-03 documents site.

Liaisons:

There were no other liaison issues.

New Projects:

The five project proposals that resulted from the group's earlier email reflector activity were reviewed (A to E, below). The project that generated the most discussion was the compression-limited project. One concept discussed was that this standard may not necessarily define a voltage, but that it may be used to characterize thermal or other non-linear model parameters.
  • A:
    PROJECT TITLE: Maximum (compression-limited) Input Voltage of a Professional Loudspeaker

    PROJECT RATIONALE: As an addtional clarification to power ratings as defined in IEC 60268-5, Sect 17 and 18, the maximum input voltage is to be defined by a measure of sound pressure level (SPL) compression. Using only a broad band noise signal is inadequate.

    Scope: For sound-generating electro-acoustic transducers, with or without an active input stage, in situations with an SPL target

    Output Intent: AES standard to be submitted as a proposed Addendum to IEC 20628-5, Loudspeakers

    Who Benefits? The Audio industry, consultants, manufacturers, designers, end users, and contractors

    Why it belongs in AES: We have the expertise

  • B:
    PROJECT TITLE: Maximum (damage-limited) Input Voltage of a Professional Loudspeaker

    PROJECT RATIONALE: As opposed to power ratings as defined in IEC 60268-5, Sect 17 and 18, the maximum input voltage is defined by the signal that produces an irreversible change in performance. Using only a broad band noise signal is inadequate.

  • C:
    PROJECT TITLE: Maximum (SPL quality-limited) Input Voltage of a Professional Loudspeaker

    PROJECT RATIONALE: As opposed to power ratings as defined in IEC 60268-5, Sect 17 and 18, the maximum input voltage is defined by the signal that produces an audible change in performance. Using only a broad band noise signal is inadequate.

  • D:
    PROJECT TITLE: Update AES2 for powered/active Professional Loudspeaker Systems

    PROJECT RATIONALE: There are no provisons in AES2 for these systems

    Scope: For sound-generating electro-acoustic transducers separate from the signal source by an active electrical device

    Output Intent: Addendum to AES2

    Who Benefits? The Audio industry, consultants, manufacturers, designers, end users, and contractors

    Why it belongs in AES: We have the expertise

  • E:
    PROJECT TITLE: Amplifier Selection Criteria for Voltage-Specified Professional Loudspeaker

    PROJECT RATIONALE: Input voltage and relative phase to the current do not correlate with the general practice of amplifier selection. Amplifier power ratings do not take various source material crest factors.

    Scope: For sound-generating electro-acoustic transducers

    Output Intent: Addendum proposed to IEC 20628-5, Loudspeakers

    Who Benefits? The Audio industry, consultants, manufacturers, designers, end users, and contractors

    Why it belongs in AES: We have the expertise

Stewart will initiate more email correspondence to refine the project scope and gain acceptance on both continents.

New business:

There was no new business.

The next meeting will be scheduled in conjunction with the AES 123rd Convention in New York, NY., US, 2007-10.

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