Sound FX filters

Hi all

Having browsed through the forum I know it is mainly focused on amplification and speakers, but I am hoping somebody can help me find out a bit more about the Altec Sound Effects filters.

I am researching radio sound design from a technical perspective and I am looking for any info about the 9067b and any other hi-pass and low-pass filters. The Urei 565 and the Krohn-Hite laboratory filters are both of interest, and I believe there was also a Langevin FX filter that was possibly related to the Altec.

Any info, circuit diagrams, promotional material etc. would help give me some perspective on who was using these filters and for what, and of course, how they might have sounded. I'm very interested to know if they were primarily sold as studio tools, Sound System/PA tools, cinema tools or domestic hi-fi add-ons.

Of course, if anyone still uses them it would be excellent to hear from you.

atb
sean