Speaker field coil resistances in two-speaker Allwave Deluxe XII

[Jiri Placek]

Does anyone please know the values?

Thanks, Regards, Jiri

[David C. Poland]

Yes. I have a set. Note the two speaker's voice coils are in series. But the field coils are in separate circuits.

The smaller 8 inch speaker field is 900 ohms - in the bias circuit for the output tube filaments.

The larger 9 1/2 inch speaker is 2500 ohms - in the B+ high voltage circuit

FYI - those two brown painted speakers were made by Rola and normally have Scott decales

[Jiri Placek]

Thank you very much, David.  I have an 8" Rola speaker with 900 Ohm field coil from a Silvertone radio so that would be a good fit.  The schematics in Rider's page Scott 3-2 shows both voice coils in a parallel circuit - it the Rider's drawing incorrect?

Regards, Jiri

David C. Poland said:

Yes. I have a set. Note the two speaker's voice coils are in series. But the field coils are in separate circuits.

The smaller 8 inch speaker field is 900 ohms - in the bias circuit for the output tube filaments.

The larger 9 1/2 inch speaker is 2500 ohms - in the B+ high voltage circuit

FYI - those two brown painted speakers were made by Rola and normally have Scott decales

[David C. Poland]

Hummm.  For the first time, I took a really close look at my twin speaker set and the harness, and made continuity checks.  The diagram is correct - the voice coils are in parallel, not series. 

FYI -  the output transformer is mounted on the smaller of the two speakers.  So, you will need to determine what output transformer to use/buy  to match  your speaker's voice coil impedance to the impedance load required for P-P type 45 output tubes.

Also, you will need to substitute a 2500 ohm power resistor for the 2500 ohm field coil in the B+ circuit, assuming you will use the field coil in your speaker for the negative bias circuit for the output tube filaments. Rather than modify the amp, I suggest you mount that power resistor as an outboard item, perhaps on a terminal strip on the speaker frame. A 6 pin tube base from a dud tube should fit the amp speaker socket and serve to make up a speaker cable for your speaker.

And with today's higher voltage AC, do toggle  the amp's hi-lo switch to "hi" to reduce the radios working voltages (ie, dim the filaments a bit).

[Jiri Placek]

Thanks, David.  The Allwave XII Deluxe I have is actually a kludge as there is a clearly non-original sound board with only one - apparently original - Rola 10 inch (9 1/2?) speaker.  I speculate that, in the past, someone removed both the smaller, 8 inch speaker and the V-shaped sound board.  Then a new, flat sound board was made and the 10" Rola was re-installed.  Now I have both speakers, (a) the original 10" Rola, and, (b) the 8 inch Rola with correct filed coil so I would like to convert the radio back into the apparently original two-speaker arrangement.  

I wonder whether I could please ask you for the following questions regarding your radio:  (1) what is the angle between two sound boards in the V-arrangement, (2) is the V symmetric or offset from the center of symmetry, and, (3) how far inside the cabinet does the V protrude?  The radio I have is in the Lido cabinet.

Thanks, Regards,

Jiri

[David C. Poland]

For an image of the twin speakers in a cabinet, look at page 6 of the Instruction Booklet in the archive section above, in the set folder for the DELUXE model.

Both sound boards are 11 1/2  x 11 1/2  of 3/4 inch of solid wood (pine?). 

The two boards at set at a 50 degree angle, so the adjoining edges are cut at 25 degrees each. They are joined by 4 pocket screws - 2 on each board. The other 3 edges are square cut.  The edges opposite the beveled cut have a nailed on screen door cap - 1/4 inch thick and appear original - and have two angled holes drilled for securing the sound boards to the cabinet. Speaker holes are 7" and 8 1/4 inch diameter.

I will add some photos of my twin speaker set which previously had been removed from an unknown Scott cabinet.   Your installation will depend on the shelf configuration in your LEDO cabinet. Although I have seen a couple cabinets with the twin speakers, I do not recall speaker mounting details, nor whether the the top and/or bottom area of the assembled speaker boards were open to the internal cabinet. I will soon face the same issue putting these speakers in an early 1930's TASMAN lowboy.  My inclination is to set the speaker set on the cabinet floor, and consider installing  a cap piece 21 x  4 1/2 screwed to the top of the speaker boards for sealing the the speakers front from the back.

 

[Jiri Placek]

Thank you David, your advise has been extremely helpful.  I appreciate your willingness to help.

Kind regards,  Jiri

[David C. Poland]

Photos attached show the Twin Speaker set used by Scott starting mid 1932 for the 12 tube DELUXE  ALLWAVE and continuing in December 1932 with the revised DELUXE with AVC into Spring 1933.  Each speaker has a field coil.

The smaller speaker has the original cone with spider screwed to the pole piece, The larger speaker has a new cone. The output transformer is on a bracket mounted on the smaller speaker.  The speaker cable has a 6 pin plug. Note the positions of the 4 screws attaching the two speaker boards together.