I found an old thread regarding the input impedance for the LS-3
military speaker. I didn't see any article with the correct answer.

According to TM 11-487, "Electrical Communications Systems Equipment,"
2 October 1944, paragraph 317, page 49, it is 8000 ohms, with internal
6" permnanent magnet speaker, intended to be used with a BC-312 on a
CD-267 cord.

Steve.