I thought H 1505 is the earliest version of altec's 15-cell horns
filled with tar and covered with smooth sheet metal. 1505B is a later
version of 15-cell horns made lighter and with each cell not covered
and with unsmooth surface exposed. I never heard of 1505A before.
My question is 1)if there is H1505 without sheet metal cover and with
the exposed uneven surface like 1505B 2)if there is 1505A at all and
if so, what the difference there is between H1505 and 1505A.
Any knowlegeable expert is requested to enlighten me on these
questions.