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High Voltage tweeter question one??

B

bob

Jan 1, 1970
0
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer?
I was given some an old METZ 1720 German stereo and I've been disassembling
it for parts and while it has a conventional woofer/tweeter speaker
complement it also has a pair of small tweeters that are driven through a
voltage divider from the plates of the output tubes which are a pair of
EL84's running single single ended .

thanks
Bob
 
A

Arfa Daily

Jan 1, 1970
0
bob said:
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer?
I was given some an old METZ 1720 German stereo and I've been
disassembling it for parts and while it has a conventional woofer/tweeter
speaker complement it also has a pair of small tweeters that are driven
through a voltage divider from the plates of the output tubes which are a
pair of EL84's running single single ended .

thanks
Bob
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
 
G

GregS

Jan 1, 1970
0
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer?
I was given some an old METZ 1720 German stereo and I've been disassembling
it for parts and while it has a conventional woofer/tweeter speaker
complement it also has a pair of small tweeters that are driven through a
voltage divider from the plates of the output tubes which are a pair of
EL84's running single single ended .


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
 
D

Dave Plowman (News)

Jan 1, 1970
0
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer? I was given some an old
METZ 1720 German stereo and I've been disassembling it for parts and
while it has a conventional woofer/tweeter speaker complement it also
has a pair of small tweeters that are driven through a voltage divider
from the plates of the output tubes which are a pair of EL84's running
single single ended .

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

Arfa Daily

Jan 1, 1970
0
Dave Plowman (News) said:
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
 
G

GregS

Jan 1, 1970
0
Yup - piezo. Very high input impedance. Very high distortion too. ;-)

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

greg
 
G

GregS

Jan 1, 1970
0
Piezos do not like HV. They will snap or arc. Common Piezo tweeters are
rated at roughly 35 volts RMS.

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

greg
 
D

Dave Plowman (News)

Jan 1, 1970
0
Piezos do not like HV. They will snap or arc. Common Piezo tweeters are
rated at roughly 35 volts RMS.

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

Jerry

Jan 1, 1970
0
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

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
 
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer?
I was given some an old METZ 1720 German stereo and I've been disassembling
it for parts and while it has a conventional woofer/tweeter speaker
complement it also has a pair of small tweeters that are driven through a
voltage divider from the plates of the output tubes which are a pair of
EL84's running single single ended .

thanks
Bob

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
 
D

Dave Plowman (News)

Jan 1, 1970
0
More likely electrostatic.

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.
 
C

Chris Jones

Jan 1, 1970
0
Dave said:
Yup - piezo. Very high input impedance. Very high distortion too. ;-)

More likely electrostatic.

Chris
 
C

Chris Jones

Jan 1, 1970
0
Dave said:
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.

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
 
D

default

Jan 1, 1970
0
Has anyone ever seen or heard of a Tweeter that runs off the plate of an
output tube rather that through a transformer?
I was given some an old METZ 1720 German stereo and I've been disassembling
it for parts and while it has a conventional woofer/tweeter speaker
complement it also has a pair of small tweeters that are driven through a
voltage divider from the plates of the output tubes which are a pair of
EL84's running single single ended .

thanks
Bob
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.
 
D

default

Jan 1, 1970
0
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
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.
 
G

GregS

Jan 1, 1970
0
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.

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
 
J

jango2

Jan 1, 1970
0
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.
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
 
G

Graham

Jan 1, 1970
0
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.

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

http://www.hi-fi-insight.com/44/quad_esl-2905_electrostatic_loudspeaker.htm
 
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