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Sensitivity of 2000-ohm Headphones

R

Reg Edwards

Jan 1, 1970
0
I am writing a program involving an antenna plus two coupled tuned circuits
plus a matched simple receiver.

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker
broadcast radio receiver.

Such headphones are more sensitive than modern 8-ohm varieties. I have a
pair of 2000-ohm headphones but unfortunately no means of measuring power or
voltage input.

Just the number of micro-watts please. At what low power input level does
speech or music just BEGIN to fade out to a person of normal hearing? Any
ideas? I could take the average of a few replies.
 
J

John Jardine

Jan 1, 1970
0
Reg Edwards said:
I am writing a program involving an antenna plus two coupled tuned circuits
plus a matched simple receiver.

I would like to know, crudely, the audio power input level to 2000-ohm, iron
diaphragm headphones for a nice, comfortable, not too difficult listening
level. Such as when the phones are used on a crystal and cat's whisker
broadcast radio receiver.

Such headphones are more sensitive than modern 8-ohm varieties. I have a
pair of 2000-ohm headphones but unfortunately no means of measuring power or
voltage input.

Just the number of micro-watts please. At what low power input level does
speech or music just BEGIN to fade out to a person of normal hearing? Any
ideas? I could take the average of a few replies.
A pair of to hand, WW2, S.G.Brown's D1's, (only 1015 ohms DC resistance
though) gave a just detectable signal with a 10uV (true rms, 2kHz measuring
bandwidth) input, (50ohms source). Similar levels for both music and a 1KHz
sine. I.e about 100 femto-watts!.
My hearings crap. Good ears would do better.
 
J

John Larkin

Jan 1, 1970
0
A pair of to hand, WW2, S.G.Brown's D1's, (only 1015 ohms DC resistance
though) gave a just detectable signal with a 10uV (true rms, 2kHz measuring
bandwidth) input, (50ohms source). Similar levels for both music and a 1KHz
sine. I.e about 100 femto-watts!.
My hearings crap. Good ears would do better.

I was just thinking about that the other day. Stray thought trains
arrived at the question, how can a spark-gap transmitter send a signal
across the ocean to a crystal receiver, which seems incredible given
how big the universe is compared to the receiving antenna. But 10 KW
to 100 fw is a ratio of 1e17:1, which explains a lot. Actually, the
crystal needs a lot more voltage to rectify, but the whole thing is
still impressive.

The 100 fw level is amazing.

John
 
R

Reg Edwards

Jan 1, 1970
0
John Jardine said:
power
A pair of to hand, WW2, S.G.Brown's D1's, (only 1015 ohms DC resistance
though) gave a just detectable signal with a 10uV (true rms, 2kHz measuring
bandwidth) input, (50ohms source). Similar levels for both music and a 1KHz
sine. I.e about 100 femto-watts!.
My hearings crap. Good ears would do better.

==============================

John, just the info I was looking for. Thanks very much indeed.

I first wore a pair of S.G.Brown's phones around 1932 when my father clapped
them around my head to hear the BBC's Birmingham transmitter on a crystal
set he had just completed. About 40 years later Mother gave them away to
the weekly rag and bone man along with a load of father's other old "Junk".
She didn't even collect the traditional gold fish because she hadn't an
empty jam jar to keep it in. But I still love her memory.

I heard prime minister Neville Chamberlain's declaration of war on 3rd
September 1939 on a pair of S.G.Brown's phones plus a PM1LF 1-valve
receiver. Five years later I was in the RAF working with the newly-invented
3000 Megacycle cavity magnetron, the device which led thousands of Lancaster
bombers to German cities to incinerate their populations. Now every kitchen
has one. After the war I still used father's phones on incomplete home made
receivers. I seldom got round to building the loudspeaker output stages.

Thanks again for your trouble.
--
............................................................
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
............................................................
 
T

Tam/WB2TT

Jan 1, 1970
0
John Jardine said:
A pair of to hand, WW2, S.G.Brown's D1's, (only 1015 ohms DC resistance
though) gave a just detectable signal with a 10uV (true rms, 2kHz measuring
bandwidth) input, (50ohms source). Similar levels for both music and a 1KHz
sine. I.e about 100 femto-watts!.
My hearings crap. Good ears would do better.
John,
Your 1015 Ohms seems right. I am 99% sure that the 2000 Ohm spec is for the
two phones in series, which is how they were wired.

Tam
 
T

Tim Wescott

Jan 1, 1970
0
John said:
A pair of to hand, WW2, S.G.Brown's D1's, (only 1015 ohms DC resistance
though) gave a just detectable signal with a 10uV (true rms, 2kHz measuring
bandwidth) input, (50ohms source). Similar levels for both music and a 1KHz
sine. I.e about 100 femto-watts!.
My hearings crap. Good ears would do better.
Does anybody know if the ones that Antique Electronic Supply sells are
as good, or do I have to dig for an original pair?
 
J

John Jardine

Jan 1, 1970
0
John Larkin said:
I was just thinking about that the other day. Stray thought trains
arrived at the question, how can a spark-gap transmitter send a signal
across the ocean to a crystal receiver, which seems incredible given
how big the universe is compared to the receiving antenna. But 10 KW
to 100 fw is a ratio of 1e17:1, which explains a lot. Actually, the
crystal needs a lot more voltage to rectify, but the whole thing is
still impressive.

The 100 fw level is amazing.

John

(I'm always suitably impressed by the wild numbers attached to space-probes
received signal powers).
The spark gap people would also seem to have had the support a much, much
cleaner aether.
If a long wire aerial, installed many years ago when I had a radio interest,
is anything to go by, then the grass on the spectrum analyser baseline
(0-120megs) is growing at an astonishing (to me!) 2-3dB a year.
I occasionally wonder where the limits lie. Surely we can't go on pumping
nearly logrithmically escalating Gwatts of what is essentially 'noise-power'
into the aetheric void, without some tangible physical or even physiological
effects turning up. (Maybe we'll find that empty space is non linear :).
regards
john
 
J

John Jardine

Jan 1, 1970
0
[clip]
for both music and a
1KHz

==============================

John, just the info I was looking for. Thanks very much indeed.

I first wore a pair of S.G.Brown's phones around 1932 when my father clapped
them around my head to hear the BBC's Birmingham transmitter on a crystal
set he had just completed. About 40 years later Mother gave them away to
the weekly rag and bone man along with a load of father's other old "Junk".
She didn't even collect the traditional gold fish because she hadn't an
empty jam jar to keep it in. But I still love her memory.

I heard prime minister Neville Chamberlain's declaration of war on 3rd
September 1939 on a pair of S.G.Brown's phones plus a PM1LF 1-valve
receiver. Five years later I was in the RAF working with the newly-invented
3000 Megacycle cavity magnetron, the device which led thousands of Lancaster
bombers to German cities to incinerate their populations. Now every kitchen
has one. After the war I still used father's phones on incomplete home made
receivers. I seldom got round to building the loudspeaker output stages.

Thanks again for your trouble.
--
...........................................................
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
...........................................................
No trouble at all Reg. The question piqued my own curiosity. I built up a
military radio collection. Hence to hand, drawers full of classic headsets,
mic's etc.
Your'e going back some there!. Came across a PM1LF article in a volume of
pre war 'Practical and amateur Wireless'. Often wondered what it would have
been like to be around at a time when large sections of the population
enthusiastically pursued technical hobbies and interests, self improvement
seemed to be the order of the day and people innovated rather than consumed.
My radio collection tops out at 500MHz with a 'R1359' receiver, believed
used in the home chain defence network. I/p signal onto a couple of tuning
rods and straight into a silicon cartridge diode for prompt down conversion
to some manageable frequency.
The cavity magnetron invention must have brought tears of joy to the eyes of
designers doing their damndest to squeeze out just a couple of watts at the
low UHF frequencies. I'll look at this particular #1359 grey painted Rx,
ugly, heavy, markedly insensitive and yet know that it has it's own
(pre-magnetron)particular exact time and place in history.
I'm eulogising, must move on. Time I found a museum etc, maybe in the
Yorkshire area that can take the collection. Let other enthusiasts enjoy the
kit.
regrds
john
 
J

John Larkin

Jan 1, 1970
0
(I'm always suitably impressed by the wild numbers attached to space-probes
received signal powers).
The spark gap people would also seem to have had the support a much, much
cleaner aether.
If a long wire aerial, installed many years ago when I had a radio interest,
is anything to go by, then the grass on the spectrum analyser baseline
(0-120megs) is growing at an astonishing (to me!) 2-3dB a year.
I occasionally wonder where the limits lie. Surely we can't go on pumping
nearly logrithmically escalating Gwatts of what is essentially 'noise-power'
into the aetheric void, without some tangible physical or even physiological
effects turning up. (Maybe we'll find that empty space is non linear :).
regards
john

I saw a calculation that shows that, extrapolating our present rate of
energy consumption growth, the surface of the earth will reach
incandescence about the year 2100.

John
 
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