Speaker Identification

[Jim Bradt]

I have a 15 inch, non pedestal, speaker. The Scott label shows the part# 925 and the model# L5E30I6.

Could someone identify what model this speaker goes to?

I would like to use this speaker on a Phantom (non FM). If this is possible, how would the speaker wires be hooked up to the octal socket on the power supply?

[David C. Poland]

A 15 inch flange mount Scott speaker with field coil would likely date from about 1938 to 1942. The standard Phantom speaker was the 12 inch Scott by Magnavox model 302. But there were an optional arrangements that used an external crossover with a 15 inch and a tweeter.

To start, Go to the Scott document site. Compare Phantom, Laureate and Phantom speaker values and field coil arrangements of the diagrams with the observed values of your speaker. This may identify your speaker. And then study the the Phantom diagram to see its requirements. Not advisable to depart from the specs of your Phantom because alterations are problematic. The AM Phantom amp needs a speaker with properly tapped field coil of specific ratings and a suitable output transformer for the 6V6 output tubes.

[Jim Bradt]

Thanks Dave for the reply. I have done as much research as I can. The schematics on the internet are scanned and I am having trouble reading values. The schematics in Hobbs' book are much clearer but not complete. The schematic for the speaker used on the Phantom Deluxe appears to match my speaker. However, my speaker has a ten pin Jones plug which goes to the power supply. The only model I could find that uses a Jones plug is the Laureate. Both speakers seem to match each other. Both models use 6L6 output tubes, my radio uses 6V6 tubes.

My speaker has seven wires. My power supply has an octal plug with eight wires. The power transformer primary is 175 ohms. The field coil measures 947 ohms. From one side to center tap is 413 and the other side to center is 532 ohms.

My question is, if my conclusions are correct, can the speaker be modified to work with 19 tube Phantom?

[David C. Poland]

Jim,

Let's be sure of what model Phantom you have. The 6 tube 6V6 amp goes with the receiver having 13 tubes including the magic eye, for a set total of 19 tubes - and the amp has an octal socket for the speaker. The Phantom Deluxe uses 6L6's in the 6 tube amp and the receiver uses 14 tubes, for a set total of 20 tubes and the amp has a 7 pin plug.

The 19 tube Phantom uses the same model 302 Scott/Magnavox 12 inch flange mount speaker as the Model Sixteen and the 14 tube Scott Masterpiece. Scott offered optional 15 inch speaker or the optional tweeter combo with crossover. The Riders 10/21/38 diagram for the 19 tube Phantom shows the standard speaker arrangement and values. Wiring for the octal plug: pins 4&5 for the 680 ohm field. The other field coil is tapped - pin 3 (also ground and connects to the voice coil) is 125 ohms to the pin 7 tap then at 65 ohms to pin 6. Pin 1 feeds B+ to the center tap of the output transformer, and 2 & 8 from the output transformer back the 6V6 plates.

I advise against altering the amp or the speaker. To use your speaker, you will need to use power resistors to substitute for the field coil sections needed. I suggest you leave the 15 inch speaker Jones plug "as is" and get a female Jones plug. Rig a separate little outboard chassis for the resistor network you need to build, and incorporate the speaker field because the speaker needs the field energized in order to operate. Mount the female jones plug on the outboard chassis. Then make up an 8 wire cable with octal plug for your outboard chassis to connect to the amp. If and when you find the correct speaker, then you have an unaltered 15 inch Scott speaker to sell ,or to use someday on another Scott model.

Good luck.

[Jim Bradt]

Thanks again David.

Yes, I have the 19 tube model. Your explanation and suggestions are what I needed. Now I need to design the circuit.
 
David C. Poland said:

Jim,

Let's be sure of what model Phantom you have. The 6 tube 6V6 amp goes with the receiver having 13 tubes including the magic eye, for a set total of 19 tubes - and the amp has an octal socket for the speaker. The Phantom Deluxe uses 6L6's in the 6 tube amp and the receiver uses 14 tubes, for a set total of 20 tubes and the amp has a 7 pin plug.

The 19 tube Phantom uses the same model 302 Scott/Magnavox 12 inch flange mount speaker as the Model Sixteen and the 14 tube Scott Masterpiece. Scott offered optional 15 inch speaker or the optional tweeter combo with crossover. The Riders 10/21/38 diagram for the 19 tube Phantom shows the standard speaker arrangement and values. Wiring for the octal plug: pins 4&5 for the 680 ohm field. The other field coil is tapped - pin 3 (also ground and connects to the voice coil) is 125 ohms to the pin 7 tap then at 65 ohms to pin 6. Pin 1 feeds B+ to the center tap of the output transformer, and 2 & 8 from the output transformer back the 6V6 plates.

I advise against altering the amp or the speaker. To use your speaker, you will need to use power resistors to substitute for the field coil sections needed. I suggest you leave the 15 inch speaker Jones plug "as is" and get a female Jones plug. Rig a separate little outboard chassis for the resistor network you need to build, and incorporate the speaker field because the speaker needs the field energized in order to operate. Mount the female jones plug on the outboard chassis. Then make up an 8 wire cable with octal plug for your outboard chassis to connect to the amp. If and when you find the correct speaker, then you have an unaltered 15 inch Scott speaker to sell ,or to use someday on another Scott model.

Good luck.