Greetings to all from the NW Left Coast.

I have recently scored Several Altec 300H HF units. I've been told they are very good and were even used by the Boeing Co. for ultra sonic research. My questions are: Is anyone familiar with these units, and how flat are they? Has anybody seen a response curve on these things? An inquiring mind (what little is left after the '60's ) want's to know.

Best regards to all