On Mon, 20 Jun 2005 14:57:10 GMT, Steve Urbach
wrote:

On Mon, 20 Jun 2005 06:37:41 GMT, spudrick
wrote:

From an old Magnavox tube stereo. It used two cabinets, each with 3

What were the output tubes like? 50C5 and a small transformer for
each channel (class A, about two watts MAX)? or two output tubes and a
slightly larger transformer for each channel (now we're talking Class
AB power, maybe 5 to 10 watts)?

speakers. The largest is 15" but it only has a 1 inch or so magnet.
This is to save money or is there another reason? The other two
speakers had similar sized magnets on 6" and 2" speakers. It looks
like they had a capacitor across each speaker to divide the signal
into bass, mid, treble sections.
I salvaged the speakers to make a bass amp but they look kind of
anemic now that they're out of the cabs. What say all of you?

My offhand guess is they won't last ten seconds as speakers for a
bass guitar amp. You need decent woofers with large excursion, good
power handling, etc.

For good speakers, check out the outfits listed he
http://www.audioxpress.com/resource/...lace/index.htm
and also http://www.madisound.com which is inexplicably not listed in
the other link.

Some tube sets had 12-15" speakers with electro magnets (extra leads
to a coil near the typical magnet position) wired in series with the
B+ supply. IIRC these speakers also had a 3.2 ohm VC

Those are really old models (1940's, maybe?), where the
electromagnet or "field coil" was used instead of a permanent magnet.
This saved money, as the power supply generally had smallish value
electrolytic capacitors which were by themselves inadequate, and the
field coil was actually a large-inductance choke coil in the plate
supply that helped filter out the rectified plate voltage. If a
permanent-magnet loudspeaker were used, it would have still needed a
choke coil, so it was cheaper to have the coil in the speaker to
provide the field, and save the cost of the magnet.


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