IEC

International Electrotechnical Commission — the standards body whose IEC 60268-5 (1972–, withdrawn) defined how loudspeaker parameters are measured, and whose TC 100/TA 20 committees wrote the three standards replacing it: 60268-21, 60268-22 and 63034 (iec-60268-5-replacement). Discovered while ingesting that source.

Every T/S figure this wiki reads from a datasheet was produced under one of its documents, which is why it is paged rather than mentioned.