SC-04-03 meeting, New York, 2007-10

Report of the SC-04-03 Working Group on Loudspeaker Modeling and Measurement of the SC-04 Subcommittee on Acoustics, held in New York, NY, US, 2007-10-05

The meeting was convened by chair J. Stewart.

The agenda and the report of the previous meeting, 2007-05-05, 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."

Assigned to: SC-04-03, Initiated: 2003
Intent: Revision, Target: 2008
Current goal: PTD, Goal date: 2007-10
Status: Amendments awaited from M. Buck prior to secretariat-formatting

Discussion: J. Stewart to contact M. Buck.

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

Project scope: This document provides guidelines for measuring, presenting, and predicting polar data from a single acoustic source or from an array of acoustic sources. It describes and quantifies possible errors, defined as differences in numeric values, associated with measurement resolution, presentation resolution, prediction techniques and measurement environments.

Assigned to: SC-04-03, Initiated: 2003-03
Intent: Review, Target: 2008
Current goal: Status report, Goal date: Continuing
Status: No action requested or required

Discussion: Invitation to attend SC-04-01 and/or review minutes.

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

Project scope: This Recommended Practice establishes a set of primary specifications to be followed by manufacturers in describing loudspeaker components used in professional audio and sound-reinforcement system design.

Assigned to: SC-04-03-A, Initiated: 2003
Intent: Revision, Target: 2007
Current goal: PTD, Goal date: 2007-07
Status: Secretariat-formatted draft ASAP, accepting latest revisions. Concentrate on the simple doc with clarified scope - potentially a new project for clarity and to avoid confusion with intent of existing AES2 publication.

Discussion: The modified scope proposed in Vienna was reviewed. R. Sauro re-iterated his "elegant" reflector proposal to create four sections:

  1. Drivers - Direct Radiators, Compression Drivers, and Driver-Waveguide combinations
  2. Systems - Passive
  3. Systems - Active (Passive systems with external, powered, electronic components)
  4. Systems - Powered (Systems with internal, powered, electronic components)
A modified working document, "SC0403A-AES2R-Buck001-070714.doc" could be released as an initial, interim version of part 1 and the proposed project X-168 could be split into parts 2, 3, and 4.

A further part 5 was suggested to cover array systems.

A further part 6 was suggested for system evaluation within a room, such as a hall, or a car.

Future work might separate product-design parameters and product-evaluation data from data required for digital signal processor (dsp) designers and room system design. An example of this multi-part approach are shown in AES31.

We reviewed a first draft proposal of X-168 before we realized what it was and shelved the discussion for a later date, possibly within task group SC-04-03-A

It was proposed that AES2 will be kept as an active Recommended Practice until such time that the new versions have completely replaced its functionality.

Continued work on part 1 would remain in the SC-04-03-A task group, but new project approval will be required to develop the other sections. These projects will be reviewed over the reflector WITH SPECIFIC ATTENTION TO THE WORDING AND INTENT OF THE SCOPE STATEMENTS, and the final versions submitted for project approval. Only the projects that have a task group leader will be submitted for approval.

Draft, "SC0403A-AES2R-Buck001-070714.doc" was reviewed with the following proposals:
  • Adopt the new scope proposed in Vienna
  • In Section 3, add reference to the definitions in IEC-60268-5, Annex C.
  • In Sec. 4.3.2, clarify the requirements of a meter with sufficient bandwidth by giving recommendations relating meter bandwidth to measured signal bandwidth and for frequency-related time constant requirements. (D. Blore and S. Orth will post suggestions to the reflector.)
  • Eliminate all systems references including boxed woofer
  • Section 3 definition modifications recorded by Mark Yonge
  • Analog electrical input and acoustic output
  • Add a definition for "component" (Steve Hutt?)
Group consensus may be easier to gain via reflector. John Stewart will run a trial by sending sections of the document to the reflector for comments. Another suggestion is for more teleconferencing or web conferencing.

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.

Assigned to: SC-04-03-D, Initiated: 2001-05
Intent: Information document, Target: 2008
Current goal: Status report, Goal date: 2007-10
Status: Continuing work in task group

Discussion: The AES-X129 task group met later in the conference and will attempt to begin a summary document via reflector discussions.


Many missed the ALMA liaison meeting. An ad-hoc IEC meeting was held regarding power testing of powered loudspeaker systems.

New Projects

The five project proposals that resulted from the group's email reflector activity will be re-reviewed for applicability to the proposed sections of AES2

New business

A new project request to better define filter Q was delegated to the Technical Committee on Signal Processing

The next meeting wil be scheduled to be held in conjunction with the 124th AES convention in Amsterdam, Netherlands, 2008-05.

AES - Audio Engineering Society