RadioTechnica Field Coil 12"

Misho Myronov writes:  "I dug out some interesting things from my collection. Stored for years, but I realized that I will not use it (well, too many projects....) so I put it for sale in a well-known place. It's a pair of Field Coil 12" wide rage speakers, made in 1946 at the RadioTechnica plant in Riga, former (prior soviet invasion) Siemens/Telefunken collaborators."

"It was used in the Riga T-689 radio set, which was ready for production in 1945, with all Siemens and Telefunken technologies, tooling, and professionals.

A few details from the history of this radio set, for a better understanding of its roots of it.

RadioTechnica plant was established in Riga right after WWII, and it was completely based on experience, tooling, technologies, and of course people of Mr. A.Apsītis radio factory:

It was started back in 1933 when he founded his radio production company “A. Apsītis un F. Žukovskis”. With help from Siemens company that gave rights for use of Telefunken-made radio lamps and Siemens schematics Apsītis again produced new radio receivers...

In 1940 there were 70 people employed in the factory. There were many other private radio companies. However, after Latvia was occupied and annexed by the Soviet Union, everything was nationalized including the Apsītis company. The company was renamed “Radiotechnika” (Radio Technics). Soviets trusted Apsītis and made him the executive director of the Radiotehnika company. After the German invasion in 1941, Radiotehnika was united with Radio Pionieris and called “Telefunken Geratewerk Riga”. It was run by Baltic German Blauberg. Apsītis took the technical operator's office. The company only fulfilled the orders of the German military and made no new radio receivers for civilians.

In 1944 as the Soviets were approaching Germans issued an order to evacuate all the equipment. Apsītis and his co-workers fooled the Germans by placing rocks and metal stuff into packs while digging the equipment in the basement rooms. With this, the work of the factory was soon restarted.

Soviets took over the German unified Apsītis-Leibovics company and called it Radiotehnika. Apsītis was placed as the director of the new company. In 1945 it was ready to produce the first radios. The first radio receiver produced was Riga T-689 with LW, MW, and 3 Shortwave bands.

So, no doubt it's NO surprise at all that speakers from T-689 are brothers of famous Klangfilm / Telefunken field coils speakers from the 30s."

The data :
  • Voice coil - 2 layers, total 92 turns of PEL-1 0,15 mm, DCR=11,5 Ohm
  • Field coil - 9000 turns of PEL-1 0,25 mm, DCR=520 Ohm
  • the central pole piece of the magnetic system made of brass (according to the description and look)
  • field coil was used as a choke in the power supply of the radio set.