As Meade so graciously pointed out, I need a 8 to 10 ohm speaker with a choke in series to provide the correct load for the 1958 Delco car radio with a 15 Watt germanium output transistor.
My question is simple - Why? :>)

The choke I need is 26 milliHenrys and 1.5 ohms. It connects across the speaker terminals, so it provides a 1.5 ohm load in parallel with the 10 ohm speaker coil.
Why was it needed then and how was it eliminated in the later models?
I have a few odd chokes in my junk box. Is it going to be risky to bench test the radio without the correct choke?

:As Meade so graciously pointed out, I need a 8 to 10 ohm speaker with a choke in parallel to provide the correct load for the 1958 Delco car radio with a 15 Watt germanium output transistor.
:My question is simple - Why? :>)
:
:The choke I need is 26 milliHenrys and 1.5 ohms. It connects across the speaker terminals, so it provides a 1.5 ohm load in parallel with the 10 ohm speaker coil.
:Why was it needed then and how was it eliminated in the later models?
:I have a few odd chokes in my junk box. Is it going to be risky to bench test the radio without the correct choke?
The choke is in parallel, not series as I wrote in the first post.
:

:As Meade so graciously pointed out, I need a 8 to 10 ohm speaker with a choke in parallel to provide the correct load for the 1958 Delco car radio with a 15 Watt germanium output transistor.
:My question is simple - Why? :>)
:
:The choke I need is 26 milliHenrys and 1.5 ohms. It connects across the speaker terminals, so it provides a 1.5 ohm load in parallel with the 10 ohm speaker coil.
:Why was it needed then and how was it eliminated in the later models?
:I have a few odd chokes in my junk box. Is it going to be risky to bench test the radio without the correct choke?
The choke is in parallel, not series as I wrote in the first post.
:

Not having a schematic of the set, I can only guess that the single output transistor is DC-coupled to the speaker (no impedance-matching transformer) and operates with fairly high quiescent current. So an inductor in parallel with the speaker would absorb most of the DC while allowing the AC component to transfer into the speaker. Without the inductor, all of the output transistor's DC current would have to flow through the speaker voice coil, either overheating it/burning it out, or current-starving the output stage due to the higher DC resistance of just the speaker alone. I would guess that the second scenario is more likely, which wouldn't result in permanent damage to either radio or speaker, but the set would probably sound very bad if it worked at all.

Of course, continuous high current doesn't do the transistor any favors, either- it makes the output transistor run very hot at all times, even at low volume settings.

Presumably, later car radio designs used dual complementary transistors in the output stage which essentially gave zero DC output current, so the set could drive a low-ohms speaker directly with no shunt inductor needed.

The single-transistor output stage was inefficient but cheap, and closely-matched complementary transistors were probably not yet available at that time.

Thanks CV. That makes it perfectly clear. And yes there is a DC component in the output. The schematic is in Bietman's, the radio is a Delco 987727.

I found I have to downoad the whole book from this site but was then able to print the schemo.

http://makearadio.com/beitmans/