JMB99 <mb@nospam.net> wrote:

On 26/10/2023 11:54, Max Demian wrote:

I think I've seen them for an extension loudspeaker connection for a
radio, like the old Hacker valve FM radios.

I have seen them used in various places but no idea what they are called.

They were also used as voltage selectors, with a larger hole in the
middle of a paxolin panel and a semi-circle of smaller holes around it.
The smaller holes were connected to tappings on the mains transformer or dropper resistor, the large hole was connected to the incoming live
supply. The large pin of the plug always went in the central hole and
the other pin could be put in whichever of the smaller holes was
labelled to correspond to the mains voltage.

There was nothing to stop you touching the pins of the half-withdrawn
plug, so you very quickly learned to switch off before adjusting it.
(There was also nothing to stop you plugging the loudspeaker in series
with the mains transformer, but I never heard of anyone doing that.)

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <1qj7sa7.x2rz8tnpkyk2N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

JMB99 <mb@nospam.net> wrote:

On 26/10/2023 11:54, Max Demian wrote:

I think I've seen them for an extension loudspeaker connection for a radio, like the old Hacker valve FM radios.

I have seen them used in various places but no idea what they are called.

They were also used as voltage selectors, with a larger hole in the
middle of a paxolin panel and a semi-circle of smaller holes around it.
The smaller holes were connected to tappings on the mains transformer or dropper resistor, the large hole was connected to the incoming live
supply. The large pin of the plug always went in the central hole and
the other pin could be put in whichever of the smaller holes was
labelled to correspond to the mains voltage.

There was nothing to stop you touching the pins of the half-withdrawn
plug, so you very quickly learned to switch off before adjusting it.
(There was also nothing to stop you plugging the loudspeaker in series
with the mains transformer, but I never heard of anyone doing that.)

not to be confused with a "mains energised" loudspeaker.

--
from KT24 in Surrey, England - sent from my RISC OS 4té²
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thu, 26 Oct 23 16:45:03 UTC, charles <charles@candehope.me.uk>
wrote:

In article <1qj7sa7.x2rz8tnpkyk2N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

JMB99 <mb@nospam.net> wrote:

On 26/10/2023 11:54, Max Demian wrote:

I think I've seen them for an extension loudspeaker connection for a
radio, like the old Hacker valve FM radios.

I have seen them used in various places but no idea what they are called.

They were also used as voltage selectors, with a larger hole in the
middle of a paxolin panel and a semi-circle of smaller holes around it.
The smaller holes were connected to tappings on the mains transformer or
dropper resistor, the large hole was connected to the incoming live
supply. The large pin of the plug always went in the central hole and
the other pin could be put in whichever of the smaller holes was
labelled to correspond to the mains voltage.

There was nothing to stop you touching the pins of the half-withdrawn
plug, so you very quickly learned to switch off before adjusting it.
(There was also nothing to stop you plugging the loudspeaker in series
with the mains transformer, but I never heard of anyone doing that.)

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thu, 26 Oct 2023 18:21:17 +0100, Max Demian
<max_demian@bigfoot.com> wrote:

On 26/10/2023 18:03, Scott wrote:

On Thu, 26 Oct 23 16:45:03 UTC, charles <charles@candehope.me.uk>
wrote:

In article <1qj7sa7.x2rz8tnpkyk2N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

JMB99 <mb@nospam.net> wrote:

On 26/10/2023 11:54, Max Demian wrote:

I think I've seen them for an extension loudspeaker connection for a >>>>>> radio, like the old Hacker valve FM radios.

I have seen them used in various places but no idea what they are called. >>>

They were also used as voltage selectors, with a larger hole in the
middle of a paxolin panel and a semi-circle of smaller holes around it. >>>> The smaller holes were connected to tappings on the mains transformer or >>>> dropper resistor, the large hole was connected to the incoming live
supply. The large pin of the plug always went in the central hole and >>>> the other pin could be put in whichever of the smaller holes was
labelled to correspond to the mains voltage.

There was nothing to stop you touching the pins of the half-withdrawn
plug, so you very quickly learned to switch off before adjusting it.
(There was also nothing to stop you plugging the loudspeaker in series >>>> with the mains transformer, but I never heard of anyone doing that.)

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

No, they were the speakers fitted to (mostly pre WW2) radios that used
an electromagnet instead of a permanent magnet when it was (relatively)
hard to make ones that kept their magnetism. They were used as the choke
for smoothing the HT. I don't know why they were ever called "mains >energised".

Silly question - why would it be harder to make a magnet in 1933 than
it is in 2023?

Second question - what were the speakers I am trying to describe?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/10/2023 18:03, Scott wrote:

On Thu, 26 Oct 23 16:45:03 UTC, charles <charles@candehope.me.uk>
wrote:

In article <1qj7sa7.x2rz8tnpkyk2N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

JMB99 <mb@nospam.net> wrote:

On 26/10/2023 11:54, Max Demian wrote:

I think I've seen them for an extension loudspeaker connection for a >>>>> radio, like the old Hacker valve FM radios.

I have seen them used in various places but no idea what they are called. >>

They were also used as voltage selectors, with a larger hole in the
middle of a paxolin panel and a semi-circle of smaller holes around it.
The smaller holes were connected to tappings on the mains transformer or >>> dropper resistor, the large hole was connected to the incoming live
supply. The large pin of the plug always went in the central hole and
the other pin could be put in whichever of the smaller holes was
labelled to correspond to the mains voltage.

There was nothing to stop you touching the pins of the half-withdrawn
plug, so you very quickly learned to switch off before adjusting it.
(There was also nothing to stop you plugging the loudspeaker in series
with the mains transformer, but I never heard of anyone doing that.)

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

No, they were the speakers fitted to (mostly pre WW2) radios that used
an electromagnet instead of a permanent magnet when it was (relatively)
hard to make ones that kept their magnetism. They were used as the choke
for smoothing the HT. I don't know why they were ever called "mains
energised".

--
Max Demian

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In message <6t6ljidbp7p2am4u4a5mka78tf3a4dtq59@4ax.com> at Thu, 26 Oct
2023 18:03:49, Scott <newsgroups@gefion.myzen.co.uk> writes
[]

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

I don't think so. Electrostatic speakers use an electrostatic field to
move the diaphragm, rather than magnetic force; I don't think they
appeared until, I think the 1970s; the first widespread model was the
Quad (I think) 65, claimed to be named for the year they started to
design them.

I'm not sure what "mains energised" meant: at a guess, the magnetic
field against which the voice coil reacts being generated by a coil
(presumably driven by rectified and smoothed mains!), rather than a
permanent magnet - before the rare earth magnets we're used to these
days, _strong_ permanent magnets were hard to make. Am I right, Liz? (Or
was it just an early name for speakers with their own amplifier, as
became common initially with computer speakers?)
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

"Purgamentum init, exit purgamentum." Translation: "Garbage in, garbage out."

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In message <248lji135rinbm8q7s81v816n1nido5nv1@4ax.com> at Thu, 26 Oct
2023 18:24:15, Scott <newsgroups@gefion.myzen.co.uk> writes

On Thu, 26 Oct 2023 18:21:17 +0100, Max Demian
<max_demian@bigfoot.com> wrote:

[]

No, they were the speakers fitted to (mostly pre WW2) radios that used
an electromagnet instead of a permanent magnet when it was (relatively) >>hard to make ones that kept their magnetism. They were used as the choke >>for smoothing the HT. I don't know why they were ever called "mains >>energised".

Silly question - why would it be harder to make a magnet in 1933 than
it is in 2023?

Materials. I didn't know about them losing their magnetism, but
certainly the strength in the first place - usually just magnetised
metal - wasn't great, so acoustic power out for electric power in was
less. Modern (well, probably about 1970s?) developments using cobalt and
other materials, and in a sort of sintered ceramic rather than just
metal, has made much stronger/smaller magnets than was earlier possible.

Second question - what were the speakers I am trying to describe?

Electrostatic, which didn't use magnetism at all. They were renowned for excellent treble, but struggled with base, hence the size. (That's a
gross simplification.)
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

"Purgamentum init, exit purgamentum." Translation: "Garbage in, garbage out."

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Scott <newsgroups@gefion.myzen.co.uk> wrote:
[...]

Silly question - why would it be harder to make a magnet in 1933 than
it is in 2023?

Not a silly question at all. The answer is yes, very much so. A lot of
the transducers we have nowadays wouldn't have been pssible then because everything depended on the strength of the magnets. There is a huge
amount of information on this, and the development of ferrites, in the
earlier issues of Philips Technical Review

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <vrNO4mF2KqOlFw5o@255soft.uk>,
J. P. Gilliver <G6JPG@255soft.uk> wrote:

In message <6t6ljidbp7p2am4u4a5mka78tf3a4dtq59@4ax.com> at Thu, 26 Oct
2023 18:03:49, Scott <newsgroups@gefion.myzen.co.uk> writes
[]

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

I don't think so. Electrostatic speakers use an electrostatic field to
move the diaphragm, rather than magnetic force; I don't think they
appeared until, I think the 1970s; the first widespread model was the
Quad (I think) 65, claimed to be named for the year they started to
design them.

At boarding school until 1958. My housemaster had a a pair.

I'm not sure what "mains energised" meant: at a guess, the magnetic
field against which the voice coil reacts being generated by a coil (presumably driven by rectified and smoothed mains!), rather than a
permanent magnet - before the rare earth magnets we're used to these
days, _strong_ permanent magnets were hard to make. Am I right, Liz? (Or
was it just an early name for speakers with their own amplifier, as
became common initially with computer speakers?)

The speaker acted as a choke in the secondary (rectified) part of the
power supply.

--
from KT24 in Surrey, England - sent from my RISC OS 4té²
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/10/2023 18:32, J. P. Gilliver wrote:

In message <6t6ljidbp7p2am4u4a5mka78tf3a4dtq59@4ax.com> at Thu, 26 Oct
2023 18:03:49, Scott <newsgroups@gefion.myzen.co.uk> writes
[]

not to be confused with a "mains energised" loudspeaker.

Were they also called electrostatic speakers or something like that? I
knew a guy who worked for the BBC and had speakers that were about 5
feet tall in his (mother's) living room.

I don't think so. Electrostatic speakers use an electrostatic field to
move the diaphragm, rather than magnetic force; I don't think they
appeared until, I think the 1970s; the first widespread model was the
Quad (I think) 65, claimed to be named for the year they started to
design them.

The first model came to be known as the Quad ESL 57.

--
Robin
reply-to address is (intended to be) valid

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

J. P. Gilliver <G6JPG@255soft.uk> wrote:

[...]

I'm not sure what "mains energised" meant: at a guess, the magnetic
field against which the voice coil reacts being generated by a coil (presumably driven by rectified and smoothed mains!), rather than a
permanent magnet -

There were two variants.

The commonest one was in wireless sets where the field coil for the
loudspeaker also acted as the H.T. smoothing choke. Usually this was in
the +ve line between the first and second smoothing capacitors, but some
sets put it in the -ve line. This meant that one of the aluminium-cased smoothing capacitors would need to have its casing, which was also its
negative terminal, isolated from the chassis. The advantage of this
placing was a lower voltage between the coil and the loudspeaker frame,
which meant less chance of a breakdown which could electrocute the
unwary serviceman. The voltage drop across the coil would seem to be a
useful source of negative bias for some of the valves, but I don't
recall seeing any set that took advantage of this.

The second variant had a much higher resistance coil which was powered
by its own rectified supply unit, completely independently of the
wireless set or amplifier that supplied the audio signal. Some of
Voigt's corner horns were energised this way - and the term 'Mains
energised' was used to distinguish speakers like this from permanent
magnet speakers, so the purchaser knew they would have to energise the
speaker separately.

The efficiency and damping of the loudspeaker depended to a large extent
on the strength of the field magnet. Permanent magnets could not
approach the strength of a good mains energised magnet, so a lot of
public address, cinema and high quality domestic speakers used mains energisation even though a permanent magnet type would have been more convenient.

In the early 1930s, A.D. Blumlein's recording cutterhead had energised
magnets with graded layers of windings to obtain the maximum number of
ampere turns without fouling the recording wax with the end of the
windings. In the early 1940s, the Decca FFRR cutterhead used a gigantic energised magnet to give a strong enough field to permit recording up to
much higher frequencies than before. The magnet was so heavy it had to
be suspended by a rope and pulley from the ceiling, with a
counterweight. The power supply occupied a fair bit of a 19" rack.

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/10/2023 18:37, J. P. Gilliver wrote:

Materials. I didn't know about them losing their magnetism, but
certainly the strength in the first place - usually just magnetised
metal - wasn't great, so acoustic power out for electric power in was
less. Modern (well, probably about 1970s?) developments using cobalt and other materials, and in a sort of sintered ceramic rather than just
metal, has made much stronger/smaller magnets than was earlier possible.

I think some modern ones use quite exotic materials to enable them to
make small but very powerful magnets.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/10/2023 20:45, charles wrote:

In article <vrNO4mF2KqOlFw5o@255soft.uk>,

I don't think so. Electrostatic speakers use an electrostatic field to
move the diaphragm, rather than magnetic force; I don't think they
appeared until, I think the 1970s; the first widespread model was the
Quad (I think) 65, claimed to be named for the year they started to
design them.

At boarding school until 1958. My housemaster had a pair.

I too thought that electrostatic speakers were first available in the 1970s.

I can imagine my old music teacher having some if they were the dog's
bollocks. He used to *try* to teach me to play the piano in his
apartment at school (it was a boarding school, so some masters lived in)
and I became adept at playing looking over my right shoulder while
eyeing-up his very expensive hifi system ;-)

As a music teacher he was too highbrow for boys who were into 1970s pop.
If he'd started us on Classic FM classical music - short preludes and
excerpts of the most tuneful parts of symphonies - he might have enticed
some of us to listen to classic music, but he jumped straight into the
really heavy Wagner's Ring Cycle etc so music lessons were boring and over-our-heads. A great wasted opportunity.

He had built his own pipe organ in the loft of his apartment - I've seen
photos of boys from 10-15 years earlier helping him to arrange the pipes
on the lawn outside so he took them inside in the correct order.

He told us that it was a great curse that he was blessed with perfect
pitch, because almost all music that he heard in TV films was
out-of-tune because of the 4% speed-up when showing 24 fps films at 25
fps on UK TV. This was in the days before pitch-shifting was possible to correct for that.


When I knew him, it was before the days of CDs. I wonder where he would
have stood on the vinyl versus CD and valve versus transistor debates. I
think I can guess. He was the sort that probably believed in gold-plated
mains leads and other snake-oil from a certain expensive hifi shop...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 26/10/2023 20:45, charles wrote:

In article <vrNO4mF2KqOlFw5o@255soft.uk>,
J. P. Gilliver <G6JPG@255soft.uk> wrote:

In message <6t6ljidbp7p2am4u4a5mka78tf3a4dtq59@4ax.com> at Thu, 26 Oct
2023 18:03:49, Scott <newsgroups@gefion.myzen.co.uk> writes
[]

not to be confused with a "mains energised" loudspeaker.

I'm not sure what "mains energised" meant: at a guess, the magnetic
field against which the voice coil reacts being generated by a coil
(presumably driven by rectified and smoothed mains!), rather than a
permanent magnet - before the rare earth magnets we're used to these
days, _strong_ permanent magnets were hard to make. Am I right, Liz? (Or
was it just an early name for speakers with their own amplifier, as
became common initially with computer speakers?)

The speaker acted as a choke in the secondary (rectified) part of the
power supply.

That was the usual arrangement. Because the HT wasn't completely
smoothed at this point, there was a "hum bucking coil"; a small coil
next to the field coil wired in series to the speech coil in such a way
that any AC currents induced in the speech coil would be neutralised,
whereas the audio currents would be reinforced.

--
Max Demian

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)