Microphone re-ribboning
John Cafarella
I've got an old Philips ribbon mic that had an obviously stretched ribbon
when I picked it up.
Due to $ constraints I can't send it off for professional repair just now.
Yesterday, I decided that I would have a go at retensioning it myself, as I
didn't have anything to lose by it. Before I started the corrugations were
at an angle of about 40-45 deg. After pulling the ribbon a bit tighter they
are now at about 60-70 deg.
What I hear now is quite a prominent peak that spectrum analysis shows to be
centred at about 4-5k. Will playing with the tension of the ribbon affect
this peak? If so, should I be able to pretty much eliminate the peak when I
get the tension right?
Another concern that I have is that the corrugations in the ribbon are not
regular, some are at a more acute angle than others. Do you think it would
be worthwile for me to attempt to construct a new ribbon using domestic
kitchen foil?
There's also a fairly steep rollof below about 120hz. Is this a ribbon
artifact, or just a crappy transformer?
Thanks for any help; I'm totally in the dark on this, and very much making
it up as I go along. Fun isn't it!
--
John Cafarella
End Of the Road Studio
Melbourne, Australia
Scott Dorsey
>I've got an old Philips ribbon mic that had an obviously stretched ribbon
>when I picked it up.
>
>Due to $ constraints I can't send it off for professional repair just now.
>
>Yesterday, I decided that I would have a go at retensioning it myself, as I
>didn't have anything to lose by it. Before I started the corrugations were
>at an angle of about 40-45 deg. After pulling the ribbon a bit tighter they
>are now at about 60-70 deg.
>
>What I hear now is quite a prominent peak that spectrum analysis shows to be
>centred at about 4-5k. Will playing with the tension of the ribbon affect
>this peak? If so, should I be able to pretty much eliminate the peak when I
>get the tension right?
Yes, but if the ribbon itself is stretched, you won't be able to get the
tension right.
If you have access to a rolling mill, take some of the aluminum from a
Wrigley's gum wrapper, roll it against itself thirty times or so, folding
each time. Then roll it down until it's about the same thickness (gauged
with calipers) as the original ribbon. Then, get a pair of gears with
pitch about that of the original corrugations, and run it through them
to corrugate it.
The microphone has an inherent body resonance. The ribbon itself has a
couple resonant points, the primary resonance being broken up by the
corrugations so it is very wide. Summed together they should all give
you a pretty flat response.
>Another concern that I have is that the corrugations in the ribbon are not
>regular, some are at a more acute angle than others. Do you think it would
>be worthwile for me to attempt to construct a new ribbon using domestic
>kitchen foil?
Try Wrigley's wrappers and a rolling mill rather than kitchen foil and
a rolling mill. You'll get better results with the Wrigley's gum foil
alloy than with Reynolds Wrap, and since it starts out much thinner, it
will take a lot less rolling to thin it down.
>There's also a fairly steep rollof below about 120hz. Is this a ribbon
>artifact, or just a crappy transformer?
That is the result of the ribbon being stretched.
>Thanks for any help; I'm totally in the dark on this, and very much making
>it up as I go along. Fun isn't it!
You can try asking local suppliers for duralumin alloy foils. Easier to
make your own if you have access to a shop with a brake and a rolling mill.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
John Cafarella
"Scott Dorsey" <klu...@panix.com> wrote in message
news:aniurk$7p2$1...@panix2.panix.com...
>
> If you have access to a rolling mill, take some of the aluminum from a
> Wrigley's gum wrapper, roll it against itself thirty times or so, folding
> each time. Then roll it down until it's about the same thickness (gauged
> with calipers) as the original ribbon. Then, get a pair of gears with
> pitch about that of the original corrugations, and run it through them
> to corrugate it.
> "C'est un Nagra. C'est suisse, et tres, tres precis."
Thanks for the wealth of info Scott. IIRC, the foild in Wrigley's gum is
the stuff that's backed with paper that can be removed right?
If this isn't available, I want the thinnest foil I can find, yes?
Byron G Jacquot
> the stuff that's backed with paper that can be removed right?
That's the stuff. Gently boil the wrapper in hot water for a minute or
so and the paper peels right off...at least if your gums is packaged
similarly to that in the states
You can guess how I learned that...
Byron Jacquot
Steve
I have a copy of the UK "Tape Recorder" magazine (July 1963 vol5 no6)
It includes an article on a diy ribbon mic. It suggests extracting the
foil from
an old style waxed paper capacitor. They were commonly used in old
tube equipment. I am not suggesting you wreck your Fairchild for this
but vintage radio collectors may be able to help. If you wish I may be
able to scan the article for you.
Steve Lane
Scott Dorsey
John Cafarella <cafa...@powertel.com.au> wrote:
>
>"Scott Dorsey" <klu...@panix.com> wrote in message
>news:aniurk$7p2$1...@panix2.panix.com...
>>
>> If you have access to a rolling mill, take some of the aluminum from a
>> Wrigley's gum wrapper, roll it against itself thirty times or so, folding
>> each time. Then roll it down until it's about the same thickness (gauged
>> with calipers) as the original ribbon. Then, get a pair of gears with
>> pitch about that of the original corrugations, and run it through them
>> to corrugate it.
>
>the stuff that's backed with paper that can be removed right?
Right.
>If this isn't available, I want the thinnest foil I can find, yes?
Yes. I don't recall how thick the original foil, is, but Mr. Sank will
know. Just measure the one you've got and roll it down that far.
It's not just a matter of being thin, though, it has to be the right
alloy (and the Wrigley's stuff is pretty close to the original duralumin
alloy from what I can tell) and it has to be rolled and worked properly
to get it to the right level of hardness.
--scott
--
Scott Dorsey
>
>I have a copy of the UK "Tape Recorder" magazine (July 1963 vol5 no6)
>It includes an article on a diy ribbon mic. It suggests extracting the
>foil from
>an old style waxed paper capacitor. They were commonly used in old
>tube equipment. I am not suggesting you wreck your Fairchild for this
>but vintage radio collectors may be able to help. If you wish I may be
>able to scan the article for you.
I'd love to see that article! I have an article from QST magazine in
the thirties on making homebrew ribbon mikes.
You can also get capacitor foil by taking apart film-and-foil type capacitors
or some types of aluminum electrolytics. Most modern film capacitors use
a plastic film with a thin layer of aluminum vacuum-sputtered on it, rather
than film and foil wrapped together, but some capacitor suppliers still make
the older film and foil types for high voltage applications (and for the
audiophile market).
Don't forget that the neodymium magnet assemblies from failed hard drives
make great ribbon mike magnets!
--scott
Richard
If you eventually give up, I couldn't reccomend more that you ship
your microphone to Stephen Sank, who often monitors RAP. If he
doesn't post any hints to this thread, you may want to send him an
email at bk...@thuntek.net. He's a really nice guy and would certainly
be willing to point you in the right direction to fix it yourself or
help explain why you can't get it exactly back to original specs.
I've seen his workshop, and he has the proper tools to do make the
corrugations. They're really precise, and you will probably be able
to come close at best. He's told me some neat stories about things
people have done to try to re-create ribbons, and most of them don't
work!
I don't work for Stephen, but I am a very satisfied customer. He's
one of the most genuine, nicest guys you can ever hope to deal with.
If you ever need [ribbon] microphone re-ribboning or even a full
restoration job, he's your man.
Regards,
Richard
"John Cafarella" <cafa...@powertel.com.au> wrote in message news:<anii49$ecu50$1...@ID-137430.news.dfncis.de>...
Dodger
>John,
>
>If you eventually give up, I couldn't reccomend more that you ship
>your microphone to Stephen Sank, who often monitors RAP. If he
>doesn't post any hints to this thread, you may want to send him an
>email at bk...@thuntek.net. He's a really nice guy and would certainly
>be willing to point you in the right direction to fix it yourself or
>help explain why you can't get it exactly back to original specs.
>
>I've seen his workshop, and he has the proper tools to do make the
>corrugations. They're really precise, and you will probably be able
>to come close at best. He's told me some neat stories about things
>people have done to try to re-create ribbons, and most of them don't
>work!
>
>I don't work for Stephen, but I am a very satisfied customer. He's
>one of the most genuine, nicest guys you can ever hope to deal with.
>If you ever need [ribbon] microphone re-ribboning or even a full
>restoration job, he's your man.
>
>Regards,
>Richard
Absolutely secondend on Stephen Sank. He's the authority on ribbons
of all types, and is indeed a great guy. He reribboned an odd mic I
have that he had never seen before, and went so far as to come up with
a nifty mod that he charged me a pittance for, just because he was
excited to do the mod.
Carey Carlan
>
> John,
>
> If you eventually give up, I couldn't reccomend more that you ship
> your microphone to Stephen Sank, who often monitors RAP. If he
> doesn't post any hints to this thread, you may want to send him an
> email at bk...@thuntek.net.
I second the recommendation of Stephen Sank. How much of an expert is he? His
father designed several ribbon microphones for RCA, including the BK-11.
John Cafarella
>
> It's not just a matter of being thin, though, it has to be the right
> alloy (and the Wrigley's stuff is pretty close to the original duralumin
> alloy from what I can tell) and it has to be rolled and worked properly
> to get it to the right level of hardness.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."
Thanks again for the info. The Wrigleys gum in Australia does have the foil
in it, I checked over the weekend.
I have a friend who has a decent workshop who should be able to roll it for
me. The only thing I have for rolling is a pasta maker <g>.
John Cafarella
"Richard" <ces...@att.net> wrote in message
news:6ef23a74.0210...@posting.google.com...
> John,
>
> If you eventually give up, I couldn't reccomend more that you ship
> your microphone to Stephen Sank, who often monitors RAP. If he
> doesn't post any hints to this thread, you may want to send him an
> email at bk...@thuntek.net. He's a really nice guy and would certainly
> be willing to point you in the right direction to fix it yourself or
> help explain why you can't get it exactly back to original specs.
>
> I've seen his workshop, and he has the proper tools to do make the
> corrugations. They're really precise, and you will probably be able
> to come close at best. He's told me some neat stories about things
> people have done to try to re-create ribbons, and most of them don't
> work!
>
> I don't work for Stephen, but I am a very satisfied customer. He's
> one of the most genuine, nicest guys you can ever hope to deal with.
> If you ever need [ribbon] microphone re-ribboning or even a full
> restoration job, he's your man.
>
> Regards,
> Richard
>
I've already been in contact with Stephen, and he has pictures of this
unusual mic. He says there should be no problems with reconditioning it. It
will go to him eventually. Freight is a killer though, it about doubles the
cost of the repair.
It's just that I'm temporarily unfinancial, with a few fairly hefty expenses
coming up.
I just got sick of looking at this damn mic sitting on my desk that had
never even been plugged in since I got it off Ebay gambling that that it was
a ribbon mic.
I thought what the hell, I haven't got anything to lose, and I'll likely
learn a bunch having a play with it. And I have.
A suggestion I have had by email for putting the corrugations into the foild
comes from a ham, VK6FT, who suggested the following (paraphrased by me):
In a piece of perspex about 30mm wide, at about 2mm intervals, score across
with a hacksaw blade. on each score point, file a groove with a fine
triangular file.
After all the filing is done cut the piece of perspex lengthways into two
pieces. Gently heat one and bend it into a curve. Place the foil onto the
flat piece, and roll the curved piece over the foil.