Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.

:Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.
:

::Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.
::
:
:I think most were 4 ohm impedance

Thanks Peter
:

Some will have 3.2, 3.5, or 4 ohms stamped on the inside of the voice coil. This was a common impedance for the voice coils that will fit around your pinky or index finger.

As Peter suggested, most were this impedance, but there were, of course, many variations from this, especially with larger or much older speakers.

T.

:Some will have 3.2, 3.5, or 4 ohms stamped on the inside of the voice coil. This was a common impedance for the voice coils that will fit around your pinky or index finger.
:
:As Peter suggested, most were this impedance, but there were, of course, many variations from this, especially with larger or much older speakers.

Thanks Thomas

:
:T.
:

::Some will have 3.2, 3.5, or 4 ohms stamped on the inside of the voice coil. This was a common impedance for the voice coils that will fit around your pinky or index finger.
::
::As Peter suggested, most were this impedance, but there were, of course, many variations from this, especially with larger or much older speakers.
:
:Thanks Thomas
:
::
::T.
::
:
I just got a Crosley that has some kind of "split" voice coil. There's a coil in the dotted area for the speaker, and another winding in series next to the field coil. It must be a Crosley thing. Humm, weird.

Most radios with electrodynamic speakers have this extra coil. It's called a hum bucking coil, and is wired to pick up magnetic fluctuations from the field coil, and feed those fluctuations out of phase into the voice coil. It's called a 'hum bucking coil,' and removes the hmmmmmmmmmmmm from your radio. The wire gauge is rather large, and affects the voice coil impedance little. Plus, it doesn't move, so no mechanical energy is wasted, and any magnetic fields it does create (from being fed an audio signal) also react against the voice coil, so, theoretically, there are no losses.

T.

:Most radios with electrodynamic speakers have this extra coil. It's called a hum bucking coil, and is wired to pick up magnetic fluctuations from the field coil, and feed those fluctuations out of phase into the voice coil. It's called a 'hum bucking coil,' and removes the hmmmmmmmmmmmm from your radio. The wire gauge is rather large, and affects the voice coil impedance little. Plus, it doesn't move, so no mechanical energy is wasted, and any magnetic fields it does create (from being fed an audio signal) also react against the voice coil, so, theoretically, there are no losses.
:
:T.
:
I haven't had a chance to get into it yet-
dealing with more medical problems, (what else is new). I'm going to try and pull the chassis tonight and at least do some work on the cabinet.
I may have to have the speaker re-coned, (it is VERY stiff), because I doubt if I'll find another like it. I've got some jealous comments on ARF about it. I LOVE that!
Terry

Speaker impedance varies with frequency, but it's customary to quote the impedance at 400 Hz. An ohmmeter will give you a lower number than the impedance at 400 Hz.

With a signal generator, it should be possible to inject a 400-Hz voltage and measure the current with a series resistor.

Matching the original speaker impedance isn't real critical. Selection of the original speaker impedance was always a compromise between audio power output and distortion. And, the most important thing is the load impedance seen by the final audio amplifier stage - which depends both on the speaker impedance and the turns ratio of the output transformer.

When in doubt, try a 4 ohm speaker. It only makes a real big difference in "battery" operated sets when the audio output is really small. There, a 16 ohm speaker may be barely audible, but a 3.2 or 4 ohm speaker will be just fine. Like the gentlemen said, in real old sets, try to get the specs, and match them up. Can't do much harm so long as there is a load attached to the set.

:Speaker impedance varies with frequency, but it's customary to quote the impedance at 400 Hz. An ohmmeter will give you a lower number than the impedance at 400 Hz.
:
:With a signal generator, it should be possible to inject a 400-Hz voltage and measure the current with a series resistor.
:
:Matching the original speaker impedance isn't real critical. Selection of the original speaker impedance was always a compromise between audio power output and distortion. And, the most important thing is the load impedance seen by the final audio amplifier stage - which depends both on the speaker impedance and the turns ratio of the output transformer.
:

:When in doubt, try a 4 ohm speaker. It only makes a real big difference in "battery" operated sets when the audio output is really small. There, a 16 ohm speaker may be barely audible, but a 3.2 or 4 ohm speaker will be just fine. Like the gentlemen said, in real old sets, try to get the specs, and match them up. Can't do much harm so long as there is a load attached to the set.
:
::Speaker impedance varies with frequency, but it's customary to quote the impedance at 400 Hz. An ohmmeter will give you a lower number than the impedance at 400 Hz.
::
::With a signal generator, it should be possible to inject a 400-Hz voltage and measure the current with a series resistor.
::
::Matching the original speaker impedance isn't real critical. Selection of the original speaker impedance was always a compromise between audio power output and distortion. And, the most important thing is the load impedance seen by the final audio amplifier stage - which depends both on the speaker impedance and the turns ratio of the output transformer.
::
:
Terry

You can almost short out the output of most low power radios with no trouble. I'd suspect otherwise with big consoles and guitar amplifiers. Definitely a no-no with transistor amps.

T.

For tube-type audio output stages, check the tube data for the plate resistance. Then maybe add 50%, and that might be a decent guess at the optimum impedance seen by the output tube (at the primary of the output xfmr).

The impedance at the primary of the output xfmr is the speaker impedance mulitplied by the square of the turns ratio. The speaker impedance is inmaterial, as is the xfmr ratio. It's the two combined that is important. With a multi-tap (universal) xfmr, you can mix and match speakers of various impedances - experiment and see what you like.

:Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.
:

:Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.
:

:Hi all, This my show my ignorance but what impedance were most of the radio speakers in the 1930's? Most modern speakers a clearly labeled 4Ù, 8Ù etc.
:
:Some of the early Philcos had a VC impedance of 1.1 ohm and some even less than one ohm. Steve