I just purchase an Altec 291-16A driver that will have to go to GPA for a new diaphram and remagnetizing .What is wanted out of the driver is maximum sensitivity , it is to be used with a crystal radio with no amplification .Right now a Trim horn with a 12" bell is mated to a sound powered elementand it produces sound levels on a loud station that can be heard clearly for twenty feet .
Vintage Altec Lansing 291 16A Driver, Western Electric - eBay (item 120510217173 end time Jan-04-10 01:00:16 PST)
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I will be using two UTC-LS 12's as matching transformers and will have an input impedance of 240,000 ohm and an output impeadance of 24 ohms into the driver.

What would be the best horn to mate with this to get maximum volume .

Mark