Great Plains Audio 604-8H-II
The
Great Plains Audio 604-8H-II is a much improved version of the vintage ferrite magnet Altec 604 family, and is currently in
production. Compared to the early production ferrite Altec 604-16X discussed elsewhere in these pages, the GPA 604 exhibits
very smooth and extended response.
I
was given the opportunity to measure these drivers some time ago, and came to the conclusion that a Butterworth 2nd
order filter centered at 1500Hz with the crossover points spread 30% would both accomplish the necessary phase correction
and also yield reasonably flat SPL magnitude throughout the crossover region. The drivers’ owner, and subsequent first
DIY builder of this filter, reported “The sound using your crossover design is exceptionally transparent and clear with
smooth response top to bottom”.
Follow
the link below to download a copy of the schematic in PDF format.
