SC-04-03 meeting report, Milan, 2018-05

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 Milan, Italy, 2018-05-24

The meeting was convened by chair S. Hutt.

Present were S Hutt, B Olson, A Svobodnik, R Yamane, K Nagy, A Klingelnberg, P Vicente, J Serrano, M Cobianchi, K Kleijro, H Suzuki, G Hill, C Bellmann, K Mick, H Alavi, D Murphy, E Esposito, P Massini, R Cabot, T Nizzoli, P Peace, A Voishvillo, J Bosnes.

Richard Cabot, the AES Standards Manager, read the AES patent policy statement.

The agenda and the report of the previous meeting, held in New York, were approved as written.

The chair re-ordered the order of discussion for open projects.

Projects assigned to this group but not mentioned here had no action requested or required - see for details.

Open projects

AES-X223: Loudspeaker Driver Correlation Chamber: Information Document:
Information document explaining factors affecting the interchangeability of measurement data from simple loudspeaker comparison chambers.

The draft is being edited.

The draft was updated to reflect absorption requirements & benefits though the reflector picked up some comments.
David Murphy will help Geoff Hill in writing the standard deviation requirements.
We need more rigor to support the expected repeatability tolerances.
Geoff Hill has data to support the repeatability stated in 5.1.3.
We need to make adjustments before we can achieve consensus.
There was a suggestion that x223 include guidance on "Measurement System Analysis" and that we should reference one of Peter John Chapman���s papers (Quantifying Acoustic Measurement Tolerances and Their Importance in the Loudspeaker Supply Chain preprint 9056)

Draft November 2018.
Release 2019.

AES-X241 AES Standard for Acoustics - End of Line Testing for Production Loudspeaker Drivers
Scope: This standard specifies parameters and methods of measurement required for end-of-line quality control tests performed on loudspeaker drivers manufactured for automotive, consumer and professional applications. It includes requirements for mechanical setup. It does not consider measurements of loudspeaker systems or multi-driver arrangements.

Status: Gathering comments on draft by R Stroud

The chair gave an overview of relation between x223 and x241.

H Alavi raised the question of definitions & semantics: semantics will be reviewed & cross correlated with IEC before the document is complete, possibly a last action. A loudspeaker driver is referred to as loudspeaker, an enclosure should be called a loudspeaker system. Loudspeaker driver + something that turns it into a loudspeaker system. Maybe loudspeaker drivers should be called transducers. He offered to help with the definitions.

The next stage of the draft is to consider tolerances. P Massini is working on a template. It is 80-90% done.

Intent Target: First draft before next meeting.

AES2-R Review of AES2-2012: AES standard for acoustics - Methods of measuring and specifying the performance of loudspeakers for professional applications - Drive units
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.

Status: Reaffirmed in 2017

The next revision is starting from a blank page, there is much work to do.
The chair reminded everyone that we will focus on quantifiable scientific & engineering terms only.
MIV will move to x168.
Life test benchmarking needs a term to replace "power" test.
We must define some kind of benchmark test signals recognizing that the life test is a benchmark for accelerated testing only.
Inputs are to be rated in voltage only. A discussion of "Power" (eg. V^2/?) can be included in the appendix.
Burst signals are under consideration and can be a benchmark, much work is needed.
B Olson noted that AES2-r2012 did not state that it supersedes 1984 in the earlier version standard. A statement to this effect can be add to the forward.
We will make define a format for people to use to say that their spec refers to AES2 xxxx.
We will not delete AES2-r1984, so it is available for reference.

AES-X168 Characterization of loudspeaker systems;
Scope: This document defines a set of characteristics of loudspeaker systems for inclusion in manufacturers��� specification documents, and identifies the relevant methods of measurement. It considers loudspeaker *systems* for professional applications. They may be combinations of active and passive sub-systems. It is intended for users and designers of loudspeaker system installations.

Status: Scope updated, writing has begun, first draft by David Murphy is posted to the repository.

Discussion: Nothing of consequence.

Target: Draft fall 2019

AES-1id-R Review of AES-1id-2012: AES Information Document for Acoustics - Plane-Wave Tubes - Design and Practice
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: Reaffirmation required

Discussion: David Murphy has additional data to add to the appendix, formatting is required.
Interesting side discussion is that 'some' use the Holland horn, scaled for different compression driver throats, as the driver test device noting that there are consistent results regardless of axisymmetric orientation.


C Bellmann gave an overview of new work in IEC 60268-21 on loudspeaker drivers, IEC 60268-22 on loudspeaker systems, and IEC 63034 on micro-speakers.

New Projects

There were no new projects.

New Business

There was no new business.

The next meeting will be scheduled in conjunction with the AES 145th Convention, to be held 17 to 20 October 2018 in New York, NY, US.

AES - Audio Engineering Society