Some 25 years ago I built a couple of Radford Monitor 180 with drivers
left over from a pair of Radford Studio 360, where one of the speakers
was burned out. I remember there was some difficulty with the
crossovers. For impedance reasons, I could not use the same ones as in
the Studio 360. However, I never got neither hardware nor schematics
from Radford, so I ended up building my own, with next to no knowledge
in the area. The speakers sounded good to my ears, however, and I still

love them and see no reason to stop using them.


Now I have to do some repair work on them, and started thinking about
the possibility (with Internet and all) to find the info necessary to
build the right kind of crossovers. So far, I have found a schematic
for the FN12A crossover, which was what Radford used in the Monitor
180.


You can look at this at
http://goto.glocalnet.net/bring/pics/FN11FN12Xover.gif.


This schematic has no coil values, however, so I am stuck on that
point. And there is another question.


The Studio and the Monitor were both three-way systems, but the Studios

had twice as many drivers as the Monitors (ten per unit against five).
What I don't know now is if they used the same impedance drivers or
compensated for the number by using 4 ohms in the studio and 8 ohms in
the Monitor. In the last case, I could not use the schematic for FN12A
unmodified, even if I had the coil details. And I certainly don't have
the know-how to do the necessary calculations.


Can anyone of you gurus out there help me in any way with these
questions?


Sven

"sbring" wrote in message
oups.com...
Some 25 years ago I built a couple of Radford Monitor 180 with drivers
left over from a pair of Radford Studio 360, where one of the speakers
was burned out. I remember there was some difficulty with the
crossovers. For impedance reasons, I could not use the same ones as in
the Studio 360. However, I never got neither hardware nor schematics
from Radford, so I ended up building my own, with next to no knowledge
in the area. The speakers sounded good to my ears, however, and I still

love them and see no reason to stop using them.


Now I have to do some repair work on them, and started thinking about
the possibility (with Internet and all) to find the info necessary to
build the right kind of crossovers. So far, I have found a schematic
for the FN12A crossover, which was what Radford used in the Monitor
180.


You can look at this at
http://goto.glocalnet.net/bring/pics/FN11FN12Xover.gif.


This schematic has no coil values, however, so I am stuck on that
point. And there is another question.


The Studio and the Monitor were both three-way systems, but the Studios

had twice as many drivers as the Monitors (ten per unit against five).
What I don't know now is if they used the same impedance drivers or
compensated for the number by using 4 ohms in the studio and 8 ohms in
the Monitor. In the last case, I could not use the schematic for FN12A
unmodified, even if I had the coil details. And I certainly don't have
the know-how to do the necessary calculations.


Can anyone of you gurus out there help me in any way with these
questions?


Sven
Sven
Have you had a look at the Wilmslow and Falcon audio site? These guys are
well up on crossovers and may be able to help you or suggest alternatitives.

Happy listening, Mike

"sbring" wrote in message
oups.com...
Some 25 years ago I built a couple of Radford Monitor 180 with drivers
left over from a pair of Radford Studio 360, where one of the speakers
was burned out. I remember there was some difficulty with the
crossovers. For impedance reasons, I could not use the same ones as in
the Studio 360. However, I never got neither hardware nor schematics
from Radford, so I ended up building my own, with next to no knowledge
in the area. The speakers sounded good to my ears, however, and I still

love them and see no reason to stop using them.


Now I have to do some repair work on them, and started thinking about
the possibility (with Internet and all) to find the info necessary to
build the right kind of crossovers. So far, I have found a schematic
for the FN12A crossover, which was what Radford used in the Monitor
180.


You can look at this at
http://goto.glocalnet.net/bring/pics/FN11FN12Xover.gif.


This schematic has no coil values, however, so I am stuck on that
point. And there is another question.


The Studio and the Monitor were both three-way systems, but the Studios

had twice as many drivers as the Monitors (ten per unit against five).
What I don't know now is if they used the same impedance drivers or
compensated for the number by using 4 ohms in the studio and 8 ohms in
the Monitor. In the last case, I could not use the schematic for FN12A
unmodified, even if I had the coil details. And I certainly don't have
the know-how to do the necessary calculations.


Can anyone of you gurus out there help me in any way with these
questions?


Sven


Hello Sven. After the death of Arthur Radford, and the demise of the
company, his senior designer John Widgery set up Woodside Electronics,
and carried on with his own designs. He also wound transformers to
the original Radford design. John has himself retired, and Mike Davis
now runs the firm. He may be able to help you.

.

Regards.
Iain Churches

Why not bi-wire direct thus by-passing the crossovers altogether?

--
John the West Ham fan


"sbring" wrote in message
oups.com...
Some 25 years ago I built a couple of Radford Monitor 180 with drivers
left over from a pair of Radford Studio 360, where one of the speakers
was burned out. I remember there was some difficulty with the
crossovers. For impedance reasons, I could not use the same ones as in
the Studio 360. However, I never got neither hardware nor schematics
from Radford, so I ended up building my own, with next to no knowledge
in the area. The speakers sounded good to my ears, however, and I still

love them and see no reason to stop using them.


Now I have to do some repair work on them, and started thinking about
the possibility (with Internet and all) to find the info necessary to
build the right kind of crossovers. So far, I have found a schematic
for the FN12A crossover, which was what Radford used in the Monitor
180.


You can look at this at
http://goto.glocalnet.net/bring/pics/FN11FN12Xover.gif.


This schematic has no coil values, however, so I am stuck on that
point. And there is another question.


The Studio and the Monitor were both three-way systems, but the Studios

had twice as many drivers as the Monitors (ten per unit against five).
What I don't know now is if they used the same impedance drivers or
compensated for the number by using 4 ohms in the studio and 8 ohms in
the Monitor. In the last case, I could not use the schematic for FN12A
unmodified, even if I had the coil details. And I certainly don't have
the know-how to do the necessary calculations.


Can anyone of you gurus out there help me in any way with these
questions?


Sven

housetrained wrote:
Why not bi-wire direct thus by-passing the crossovers altogether?


Could you explain this a little? I don't understand.

Sven

In article , housetrained
wrote:
Why not bi-wire direct thus by-passing the crossovers altogether?

To do this you would need to ensure that:

A) the crossover point and order were correct. (Fairly easy)

B) That any effects due to impedance interactions between the drivers and
original crossover were taken into account. (Harder without detailed
knowledge of the original crossovers.)

C) That any use of the original crossovers to alter the in-band response
was also taken into account (inc B). (Also hard without the required
details.)

Thus you may need all the details of the original crossover in order to
arrange for a suitable active crossover as a replacement.

For obvious reasons, simply bi-wiring with no crossover or filters at any
point would probably be unsatisfactory.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"sbring" wrote in message
oups.com...

housetrained wrote:
Why not bi-wire direct thus by-passing the crossovers altogether?


Could you explain this a little? I don't understand.

Sven


Actually he means bi-amp, that is apply the LF/HF filtration at
signal/line rather than loudspeaker/power level. Such filters are
small, you can even build them yourself if you can use a soldering
iron. The only downside is that you need one power amp per speaker per
frequency range, albeit they don't need anything like as much power as
there is no crossover loss. I.e. if you have a two-way speaker, a
woofer and a tweeter, then you will need two amps: if you have a
squaker as well in a three-way system, then you will need three amps.
However if you have two drivers per frequency range (i.e. six speakers
in the cabinet in pairs) then you still only need three amps. The same
quantity is needed again for the other speaker box.

Bi-wiring is when you feed seperate cables from the amp to the
speaker, but you still need some form of crossover to feed the correct
frequencies to each loudspeaker driver.


--
Woody

harrogate2 at ntlworld dot com

WRONG I don't mean bi-amp ( which requires an amp for each cone.) Bi-wire
means you allocate a wire for each cone - from the same amp output. Seems
strange but it works. The separate wires stop interference.

--
John the West Ham fan


"harrogate2" wrote in message
...

"sbring" wrote in message
oups.com...

housetrained wrote:
Why not bi-wire direct thus by-passing the crossovers altogether?


Could you explain this a little? I don't understand.

Sven


Actually he means bi-amp, that is apply the LF/HF filtration at
signal/line rather than loudspeaker/power level. Such filters are
small, you can even build them yourself if you can use a soldering
iron. The only downside is that you need one power amp per speaker per
frequency range, albeit they don't need anything like as much power as
there is no crossover loss. I.e. if you have a two-way speaker, a
woofer and a tweeter, then you will need two amps: if you have a
squaker as well in a three-way system, then you will need three amps.
However if you have two drivers per frequency range (i.e. six speakers
in the cabinet in pairs) then you still only need three amps. The same
quantity is needed again for the other speaker box.

Bi-wiring is when you feed seperate cables from the amp to the
speaker, but you still need some form of crossover to feed the correct
frequencies to each loudspeaker driver.


--
Woody

harrogate2 at ntlworld dot com

On Sat, 12 Nov 2005 20:53:44 GMT, "housetrained"
wrote:

WRONG I don't mean bi-amp ( which requires an amp for each cone.) Bi-wire
means you allocate a wire for each cone - from the same amp output. Seems
strange but it works. The separate wires stop interference.

Nonsense. And how does this bypass the crossovers?

Kal

"Kalman Rubinson" wrote in message
...
On Sat, 12 Nov 2005 20:53:44 GMT, "housetrained"
wrote:

WRONG I don't mean bi-amp ( which requires an amp for each cone.)
Bi-wire
means you allocate a wire for each cone - from the same amp output.
Seems
strange but it works. The separate wires stop interference.

Nonsense. And how does this bypass the crossovers?

Kal


Exactly.


--
Woody

harrogate2 at ntlworld dot com