Speaker technologies

[Mark Schroeder]

Looking for technical info all about speaker technologies from the 20’s through the 50’s. Looking for that “rare” detail about dynamic vs non-dynamic, power handling, load, inductance, etc? Can anyone point me references that can give me these? Almost none of the technical schematics of these eras provide this, nor do the various parts catalogs. These just show a “speaker” and of it is a electrodynamic or not. And what the specifications are for these? Did Jensen ever put together a catalog that would help take any mystery out of what the best speakers are for various radio brands? Did Scott ever provide specs for the speakers they sold or recommended for their radios? If so, where would that be found?  Thanks. 

[Mark Schroeder]

By the way, just to add, your archives of information that you all have collected are amazing! I was a little concerned digging into this project once I got the radio, but now have a huge amount downloaded that provides excellent details about the radio design and more. So much better than just having one schematic in an EH Scott book from years ago. The internet and all these resources have really spoiled us by bring research just a couple of clicks away, thanks to the work everyone has done over many,many, years!

[David C. Poland]

Mark - re speakers:

The AW-12 Wunderlich model was upgraded December 1932 with 58's in the IF amp  and the new Wunderluch tube 2nd detector adding AVC - but continued the pair of Scott badged ROLA field coil speakers (7.5 inch and 9 inch). One field coil is in the B+circuit, the other in the bias circuit for the output tubes. Mounted on angled baffle boards.

After a few months, Scott upgraded to the 12 inch pedestal speaker, a Scott badged special version Jensen with 2 field coils that was backwards compatible, so electrically the same as the earlier twin speakers.

IMG_0197%202.JPG

IMG_0197.JPG

Note the casting details to avoid confusion with the similar AW-15 pedestal. 6 pin plug. Output transformer is in side the pedestal. Speaker model number 3569 ink stamped on the side of the pedestal.

,IMG_0197%202.JPG

[David C. Poland]

The AW-23 uses a special 12 inch Scott branded Magnavox field coil pedestal speaker - and an optional pair of Jensen Q series tweeters to extend the audio frequency range. The pedestal speaker has two 5 pin sockets on the base. There are 2 versions of the AW-23 speaker (and of the tweeters) - and they are hard to distinguish visually. The early 5 knob 1935 version has a 38 ohm voice coil. The later 7 knob 1936-7 version has a 19 ohm voice coil. Either version will be satisfactory on any AW-23 amp. Riders diagrams show the terminal board variation inside the respective pedestal. The appropriate output transformer is inside the pedestal along with a large tapped ceramic resister. Late version speaker set shown below.

IMG_1148.jpeg

IMG_1149.jpeg

The short cable from the speaker is plugged into one or the other base socket, depending on whether the tweeter set is used. The tweeter field coils substitute for the big resistor  inside the speaker pedestal. Refer to an owner manual for short cable information. Note that the big speaker has a curvilinear cone.

The circuit diagrams available in the various set folders in the Info Archive usually shows the resistance of the speaker field coils and voice coils.

CAUTION - Never power up a Scott without the proper speaker because the field coils and subsequent circuit load prevent a large voltage spike that can blow the first filter cap and other damage.

[David C. Poland]

Here are the intended photos for the AW-12. (sorry for dups - in a hurry to go to dinner)

2nd photo of twin ROLA speakers: IMG_0198.JPG

and 12 inch Jensen pedestal:  Allwave%2012%20-speaker%20rear%20view.jpg