G.E. Flat tweeters. What are they?

[Pano]

Does anyone know what these odd flat tweeters are? They are from an old General Electric speaker with a 20x9 inch woofers. An online friend bought a pair, I've never seen them before. I call them "Cheese Graters"

At first glance they look electrostatic, but there is no high voltage supply.
Anyone know?

 

[turk 182]

i would think they're a long flat piezo element.

 

[turk 182]

look at the "Blue Line" on this link
http://www.sonitron.be/useruploads/files/SonitronPiezoelectricSpeakerTechnology.pdf

 

[Pano]

Thanks. They look like piezo to me, but piezo that shape are unfamiliar to me.
Since there is no crossover with these, it's hard to say.

 

[kevinkr]

I believe they're actually electrostatic tweeters, look very similar to others I have seen.

Generally connected to the output tube plate through a tiny cap and polarization voltage applied through a large resistance to HV.

 

[turk 182]

Pano did you look at that link i posted?

 

[Pano]

Briefly, yes. Will look again later. Super busy at work.

 

[Pano]

Turns out the are electrostatic. And driven as Kevin says. G.E. used them in stereos and TVs in 1959 and a little later. Amazing.

 

[turk 182]

interesting any info or reference i can look up?

 

[Pano]

There is this as documentation, that clinches it. Found by a someone quick and posted on Facebook. Amazing what's out there. The speakers look like the ones on the Danish modern TV.

 

[turk 182]

way cool... i guess tv sound was a concern back in the day.

 

[WrineX]

Single ended esl funny

 

[tyu]

Single ended esl funny

Martin logan in the 1990s thay set up most of there ESL panels Single Ended....thay said it was for the off shore sales.... were the front of there panels had to be gounded....not in the nom push pull tranfourmer setup..
this setup drove me nuts at frist....till like with most things ESL....Bolserst helpet me-us get our head a round the setup....
thanks you Bolserst for years of help on all thing esl...
here the one CLS setup...an yes any esl panels can be setup Single endedly...an work an sound great!

 

[ondesx]

Pathe Marconi produced a similar unit 29x16 cm in the sixties !

The tweeter was en ESL.

 

[mckaymckaymckay]

Ive got something similar in my Graetz Comedia 4R/416

 

[WrineX]

Still push pull would be beter but he it is a fun setup

 

[tyu]

Would push pull be better??...Bolserst.... I think said there were no real diff?....
but seeing how the CLSz was the last.... an gave-got the most output out of the panel...ezer to drive if you well...I have setup Acoustat an ML panels Single Ended...it works well.

 

[bolserst]

Turns out the are electrostatic. And driven as Kevin says. G.E. used them in stereos and TVs in 1959 and a little later. Amazing.

Philco and Zenith are probably better know for their use of ESL tweeters in their late 50s early 60s radios and hi-fi consoles than GE. Attached pic and circuit for a typical Zenith. With bias voltages not much higher than the audio signal, most of the single-ended ESL tweeters I have measured of this vintage have significant THD(>5%), but since they cross over so high, they still tend to sound much better than their dynamic driver counter parts of that vintage.

Front view of Zenith ESL tweeters posted here: http://www.diyaudio.com/forums/plan...o-stereo-phone-electrostatic.html#post4109102
Example Philco ESL tweeter pic posted here: http://www.diyaudio.com/forums/plan...o-stereo-phone-electrostatic.html#post4109100

 

[bolserst]

Would push pull be better??...Bolserst.... I think said there were no real diff?...

If you have a push-pull ESL, (ie two stators with diaphragm in between) there really isn't any difference if you move the ground reference from center tap of the step-up transformer to one of the stators. Some people call this single-ended drive of a push-pull ESL. The diaphragm only responds to the static electric field generated in the air gap between the stators, so moving the ground reference point won't make a difference to the ESL although it might change the HF response slightly due to changes in the transformer parasitics.

But, if you have a single-ended ESL, (ie one stator and diaphragm) distortion is much higher. If I recall correctly, the Janzen/Hunt analysis and experiments showed that the bias voltage needed to by 5x higher than the audio signal voltage to keep THD < 5%.

 

[lcsaszar]

"Capacitor" tweeter in an old Orion radio:

http://www.garai.hu/radiok/csoves/Pacsirta/Pacsirta-04e.JPG