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 Los Angeles, CA., US., 2016-09-30
The meeting was convened by chair S. Hutt.
The agenda and the report of the previous meeting, held in New York, 2015-10-19, were approved as written.
Projects assigned to this group but not mentioned here had no action requested or required - see www.aes.org/standards/meetings/project-status.cfm for details.
Open projects
AES2 Review of AES2-2012: AES standard for acoustics - Methods of measuring and specifying the performance of loudspeakers for professional applications – Drive units
Review is required in 2017. Since some users continue to utilize some aspects of AES2-1984 we should review the current standard carefully and amend AES2-2012 as necessary to improve it. Comments welcome.
AES-1id-R
This document is due for formal review in 2017, with reaffirmation the most obvious outcome. David Murphy offered to review some analysis work that he has done on plane wave tube termination and explore if it might be added to AES-1id as an addendum. Comments welcome.
AES-X168 Characterization of loudspeaker systems;
Background: A long time ago, we expected that SC-04-03 would update AES2 in two parts; part 1 for loudspeaker drive units, part 2 for systems. But, after much consideration it was decided that what became AES2-2012 should be a loudspeaker drive units standard and a new standard would be develop for passive and active loudspeaker systems with the working project title designated as AES-X168. In the meantime, IEC and CEA have been developing their own standards for loudspeaker systems and we agreed that SC-04-03 should hold back development pending these documents and standards that we might defer to. The current status is:
IEC PT 60268-21, Sound system equipment - Loudspeakers - Acoustical (Output Based) Measurements
This IEC standards project comprises two parts.
Part A will use a black box approach and only address what comes out of the box for a specified input. It will define a rated maximum input value (Umax); this may be a may be low level input to an integrated amplifier, for example. It will define a rated maximum output SPL. The input will be a multitone signal calibrated to the rms value of the stimulus. It was noted that a multitone signal can be used to measure distortion as well as to generate all properties of pink noise, but is completely reproducible. Wolfgang Klippel observed that this multitone stimulus could actually be a form of pseudo random noise.
Part B will use a 'grey' box approach. It will relate a transducer in terms useful for a system integrator. It will specify digital signal processing (DSP) as necessary. All parameters are for driver units
Discussion ensued around areas of interest that SC-04-03 will engage in. It was proposed to initiate AES-X168 - [this will require a PIR to define the scope and rationale for the work]. This includes defining goals with explanation of differences to ‘other’ standards. In the draft, references will be made to IEC for related information with a focus on systems for professional applications. An example specification might recommend amplifier minimum and maximum capacities.
A first draft Abstract and Scope will be proposed in the coming weeks by the chair.
Development Projects
X223: Loudspeaker Driver Correlation Chamber: Information Document:
Background: Replicating non-anechoic loudspeaker driver measurements in different locations is a well-known and challenging endeavor due to numerous influences and degrees of freedom. Geoff Hill and Ed Simon have contributed concepts. A generic draft will be presented to the reflector before AES 140.
Discussions: A draft abstract & scope was distributed through the reflector in September 2016 and after some edits is now acceptable to the group. The chair will begin sending edits of the ID sections through the reflector for comment and update. Target – wrap & complete before AES 142 in Berlin.
AES-X194 Report on loudspeaker terminology
scope: [To be revised]
status: To be terminated.
This project has languished and it was agreed at the meeting that other sources cover the interest. It could of course, be resurrected if a champion volunteers
Liaisons:
ALMA International Dan Foley informed the group that ALMA is exploring expanding beyond focus on
loudspeakers to the complete audio chain.
New Projects
End-of-Line Loudspeaker Driver Testing
A proposal for an Information Document or possibly a standard has been submitted by TC Automotive Audio via TC Loudspeakers & Headphones. This proposal includes a first concept draft from Dr. Angelo Farina with pertinence to the automobile manufacturers. An AES document could prove valuable to the industry to quantify pertinent characteristics that validate that production transducers meet design and performance goals.
Numerous attendees in the meeting have expressed interest in participating on a task group for this project. Richard Stroud has volunteered to contact Dr. Farina to discuss if he would like to lead such a task group, if not Mr. Stroud has agreed to lead.
The chair will initiate an active project request. At this stage it is not clear whether the output should be in the form of a standard or an information document. Completion is expected within eighteen months.
New Business
There was no new business.
The next meeting will be scheduled in conjunction with the AES 142nd Convention in Berlin, Germany, 2017-05.
