frank wrote:

I've been given an old Hammarlund SPR-210. It needs a good amount of
restoration but appears complete inside and outside. I've seen on the
manual that it has 600 ohm speaker output and I was wondering where to
find such a spekear with this impedance. Probably there's need for an
external audio transformer to use any low impedance (I have many
in the 16-4 ohm range) speaker?
Any hint is welcome.

If you wound a 600 ohm voice coil on a speaker, it would be so heavy
you'd have no high end at all.

SO, what we do is to put a 600-8 ohm transformer behind the speaker; lots
of communications speakers have mounting points on the back so you can bolt
the transformer right there.

A 1W transformer for a 70V PA system has about a 600 ohm to 8 ohm ratio,
and will cost less than $5 at an electronics supply house. Or ask a guy
who installs 70V PA systems for piped-in music in supermarkets for an old
one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."