High Voltage tweeter question one??

I guess that if they are ceramic tweeters rather than coil types, there is no particular reason that they should not be driven straight from the plate circuit, as DC wise, they are an open circuit, so a simple resistive divider to arrive at any drive level you wanted, would be appropriate.

Arfa

Electrostatic tweeters seem to have been more popular way back. They are still regarded as some of the finest, but todays dynamic tweeters are much better than they used to be. Electrostatic needs a high voltage DC bias plus signal. I'm sure the plates can accomplish this.

greg

Yup - piezo. Very high input impedance. Very high distortion too. ;-)

Ha ! Piezo ! That's the word I was struggling for ... It's 'orrible getting old and addled

Arfa

Piezos do not like HV. They will snap or arc. Common Piezo tweeters are rated at roughly 35 volts RMS.

greg

I should say there are some that will withstand more. I built a system using about 300 volts driving a mechanical wand.

greg

I had a valve radio where the (it said) piezo tweeter was wired across the output transformer primary.

Back in the late 60's I can remember making a "flame speaker" for an engineering open house in college. Propane torch, wick supplying saline solution into the flame, couple of electrodes in the flame connected to an amplified audio signal with a high DC bias, couple of hundred volts IIRC. Astonishingly clear sound for a kludged-up lab setup.

Years later, was surprised to see "plasma speakers" at an amazingly high price.

Jerry

There are a few technologies that were around in valve days and could have done it.

Rochelle salt crystal tweeters - probably the most likely here Electrostatic - not likely on a low cost single ended EL84 output High R moving coil - unlikely, as they never went high enough R for a pentode output, 600R was about the limit iirc Moving iron - again probably not, but possible as a low cost tweeter. Lots of distortion.

NT

EL84s single ended suggest a pretty basic amp and electrostatics are rather more expensive than piezo. Besides, I've seen just this arrangement on a mid priced European radio.

More likely electrostatic.

Chris

I would not rule out electrostatic speakers for the reason of cost. There is nothing inherently expensive required to make an electrostatic tweeter. I have made electrostatic headphones myself. All you really need is a bit of plastic film and some metal with holes in it. Normally the high-voltage transformer or amplifier is the hard part, but if you start with a valve amplifier then using the anode voltage directly is a simple and cheap solution.

Chris

Electrostatic tweeters. Ceramic tweeters would have a capacitor for safety and DC isolation where electrostatics do need the DC bias to work well.

I've encountered exactly one in my time repairing consumer electronics. There were some articles on building your own electrostatic speakers back in the 60's, and at least one high end audio company that was making a large 4' X 6' electrostatic speaker system.

Some info on the web on building and repairing them.

More than likely electrostatic. I encountered one in a table stereo radio. Some doctor picked it up in Europe and couldn't find anyone else to service it so I got a chance to play with it. Low cost? not relative to the toob type table radios of the 50's, but not high end either.

Mylar tape can be used as an electrostatic tweeter. You need two plates, and the Mylar tape has a permanant charge in it to make the sticky stuff stay on. trouble is, the sticky is too heavy to get good efficiency. I took the sticky off, but alas, no charge. Electrostatic tweeters were all over the place in the 50's and 60's. I once picked up a mono record player that used one.

greg

I fondly remember a pair of martin logan SL3s i had to fix a while ago. 4' panels of carbon impregnated mylar film sandwiched between 2 metal meshes. H.V. was fed to the conductive tracks on the mylar film, while the metal meshes were driven in push-pull by a stepped up audio source. A 12" woofer in a sealed enclosure provided low end. A unique listening experience . As you rose from seated to standing position, the sound perceived changed, totally justifying recommendations for a single point source. I still loved them, the high end was soooooo crisp though low mids tended to distort a bit. Jango

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$12,000 speakers from the original quad co .. mains energised as well .. indoor use only ?