The opening at the narrow end of a horn, where it is attached to a compression driver. Also, the small diameter opening of a compression driver, where it is attached to a horn.
"I would like to thank you for the superb work for the 16" Transcription. We are especially thankful for the faster turnaround time you provided, which was above and beyond the fastest selected option that we chose. Our 92 year old cousin was able to hear it before her serious decline. Also, I wanted to let you know that the History Center in ..."