D
DJL
Self Banned
Is this your example of how you want me to bless this forum with grace like you do?c7sus said:
Anyone know how to make a high-quality mic like the well-known brands?
Marik
Pro Microphone Design
First—price list:
Huge (50mmx20mmx10mm) neodymium magnets off Ebay--$20. Lundahl LL2911 1:40 transformer--$44. Misc hardware from ACE- $12. Mesh pencil holder, as a body, from OfficeMax- $7. XLR connector- $5. Old paper in oil capacitor as a ribbon donor came from junk box. Total $88 US.
The pictures show the stereo version, which I made a couple years ago for MS recording. The upper (Mid) mic is omni, and the lower (Side) is fig 8. As I said before, it was my first design and some things I did not do right then. Basically, the weakest point is arrangement of the huge magnets, around which I built the faceplate, so the baffle is too big, which is good for low end, and not good for HF. The smaller magnets will be still very efficient, but will improve the HF response.
My current version has completely different arrangement, and also has symmetrical signal path from the front and rear, which is important for the Side in MS. It is not finished, so I don’t have pictures yet.
Here is the description of the old one, if you are interested. Please refer to the drawings on the bottom of my webpage.
On the aluminum faceplate mount iron pole pieces, leaving 5mm slot between them--later there you mount the ribbon. The distance between outer edge of the pole and the faceplate will be about 1mm. To the faceplate glue the long ribbon clamp made out of PCB. Align the short ribbon clamp on the top of the long ones, and drill two holes through the whole construction. Make sure to take off some copper around the holes, so later the screws won’t short the circuit. On the top of the pole pieces glue magnets. Make sure that the magnets overlap top, bottom and outer edges of the pole pieces about 1mm, to focus the magnetic field. The distance between inner edges of the magnets will be about 20mm. On the top of the magnets glue return circuit, made out of long and short 1/8” square rods.
The omni version is similar, except of return circuit is made out of solid piece of iron, and then, the cavity is filled with stuffing to tune the response with acoustical resistance. In fact, here I am thinking of combining fig 8 ribbon and condenser omni to get a cardioid pattern, and making up for HF roll off. Another idea is to cross them over, and get exellent low and mid response of ribbons, and extended HF of condenser.
Huge (50mmx20mmx10mm) neodymium magnets off Ebay--$20. Lundahl LL2911 1:40 transformer--$44. Misc hardware from ACE- $12. Mesh pencil holder, as a body, from OfficeMax- $7. XLR connector- $5. Old paper in oil capacitor as a ribbon donor came from junk box. Total $88 US.
The pictures show the stereo version, which I made a couple years ago for MS recording. The upper (Mid) mic is omni, and the lower (Side) is fig 8. As I said before, it was my first design and some things I did not do right then. Basically, the weakest point is arrangement of the huge magnets, around which I built the faceplate, so the baffle is too big, which is good for low end, and not good for HF. The smaller magnets will be still very efficient, but will improve the HF response.
My current version has completely different arrangement, and also has symmetrical signal path from the front and rear, which is important for the Side in MS. It is not finished, so I don’t have pictures yet.
Here is the description of the old one, if you are interested. Please refer to the drawings on the bottom of my webpage.
On the aluminum faceplate mount iron pole pieces, leaving 5mm slot between them--later there you mount the ribbon. The distance between outer edge of the pole and the faceplate will be about 1mm. To the faceplate glue the long ribbon clamp made out of PCB. Align the short ribbon clamp on the top of the long ones, and drill two holes through the whole construction. Make sure to take off some copper around the holes, so later the screws won’t short the circuit. On the top of the pole pieces glue magnets. Make sure that the magnets overlap top, bottom and outer edges of the pole pieces about 1mm, to focus the magnetic field. The distance between inner edges of the magnets will be about 20mm. On the top of the magnets glue return circuit, made out of long and short 1/8” square rods.
The omni version is similar, except of return circuit is made out of solid piece of iron, and then, the cavity is filled with stuffing to tune the response with acoustical resistance. In fact, here I am thinking of combining fig 8 ribbon and condenser omni to get a cardioid pattern, and making up for HF roll off. Another idea is to cross them over, and get exellent low and mid response of ribbons, and extended HF of condenser.
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crazydoc
Master Baiter
Thanks, Marik. This is much appreciated. It's going to take me awhile to digest it, as I know nothing about ribbon mics. When you get pics of the new mics, please post and give us a heads up.
H
Harvey Gerst
New member
Ribbon mics are pretty straight forward, especially when they're a pure velocity design (i.e., figure 8, or bi-polar).
Like a speaker, they consist of a voice coil suspended in a magnetic field, except the "voice coil" in a ribbon mic is simply a corregated strip of aluminum, exposed to sound from both sides.
Now obviously, a 2" or so piece of VERY THIN aluminum ribbon ain't gonna have much impedance or output. So you need a fairly high turns ratio transformer to get it up to where most preamps will see anything but a dead short.
A velocity mic doesn't respond to the air pressure in the room, it responds to blasts of air that make the diaphragm move enough to generate a small amount of electricity. Since that air blast can come from the front or the back, the response is identical from either direction. And since there's no trapped air behind the element, the resonance can be made very low, and the response becomes very smooth, without big peaks or dips.
Big air blasts can distort the ribbon permanently, causing it to sag or rub.
Any sound coming from either side is not heard since both sides of the ribbon "hear" the sound equally, and therefore, no movement occurs. Off axis response of velocity mics can be among the very best, as long as it's not exactly 90 degrees. Figure 8 velocity mics also have the largest amount of proximity effect.
Some ribbon mics (like the RCA 77DX) have a series of movable vanes and open and closable acoustic chambers that can make the mic into a multipattern mic by strictly mechanical means. Seal the back side and it's an omni; open the back side partially and it's a cardioid.
It's about as simple and elegant design as you can have: a piece of ribbon, a big hunk of magnet, and a transformer.
Like a speaker, they consist of a voice coil suspended in a magnetic field, except the "voice coil" in a ribbon mic is simply a corregated strip of aluminum, exposed to sound from both sides.
Now obviously, a 2" or so piece of VERY THIN aluminum ribbon ain't gonna have much impedance or output. So you need a fairly high turns ratio transformer to get it up to where most preamps will see anything but a dead short.
A velocity mic doesn't respond to the air pressure in the room, it responds to blasts of air that make the diaphragm move enough to generate a small amount of electricity. Since that air blast can come from the front or the back, the response is identical from either direction. And since there's no trapped air behind the element, the resonance can be made very low, and the response becomes very smooth, without big peaks or dips.
Big air blasts can distort the ribbon permanently, causing it to sag or rub.
Any sound coming from either side is not heard since both sides of the ribbon "hear" the sound equally, and therefore, no movement occurs. Off axis response of velocity mics can be among the very best, as long as it's not exactly 90 degrees. Figure 8 velocity mics also have the largest amount of proximity effect.
Some ribbon mics (like the RCA 77DX) have a series of movable vanes and open and closable acoustic chambers that can make the mic into a multipattern mic by strictly mechanical means. Seal the back side and it's an omni; open the back side partially and it's a cardioid.
It's about as simple and elegant design as you can have: a piece of ribbon, a big hunk of magnet, and a transformer.
D
DJL
Self Banned
Wow, good thread... thanks.
Marik
Pro Microphone Design
Yes, as Harvey has said the ribbons are probably the simplest and most elegant mic design. What fascinates me the most with them is that with all their simplicity of construction, they are in fact, probably the most difficult to design. The whole thing is full of compromises, and trade offs. Let’s face it—almost none of them have the HF response even close to average condenser—that’s why everybody describes them as “dark sounding”—whatever it means.
Theoretically, because of low mass of the ribbon, they are capable to go at least to 50Khz(!), but in reality, it is at the best…. well, depending on the design.
In velocity type you want to get them go higher, so the baffle (the “wings” around the magnet) should be smaller, as the force on diaphragm will be canceled at frequencies when the wavelength is equal to the length of the signal path between front and rear of the ribbon. In other words--the smaller the path—the shorter the wavelength—the higher the frequency. At the same time, the smaller baffle means that pressure difference built up between front and rear is much smaller at low frequencies, so we get loss on low end, since the ribbon becomes more resistance rather than mass controlled. At the same time, the smaller baffle means smaller magnets, or pole pieces, which reduces the magnetic flux, and thus sensitivity of the mic.
There is number of designs to overcome some of these—for example Coles, which uses smaller pole pieces, and additional baffle, made out of porous gauze with low acoustical resistance to compensate lows. Also, there were other designs, which are still full of different kinds of compromises. WE and Altec, with their dual—velocity ribbon, and dynamic omni capsule, which then were electrically combined for different patterns. Some designs with horns, tuned to high frequencies. Unidirectional RCA 77A, where one half of the ribbon is velocity, and another—pressure type, with closed chamber behind, and sofisticated acoustical labyrinth—actually I like this one a lot. In addition, they have quite uniform directional pattern. Ooooops, just got an idea... Huh, enough for today.
BTW, did I mention their output? OK, time to go to sleep.
Oh, and I almost forgot—I just love ribbons!!! Aren’t they wonderful?
Theoretically, because of low mass of the ribbon, they are capable to go at least to 50Khz(!), but in reality, it is at the best…. well, depending on the design.
In velocity type you want to get them go higher, so the baffle (the “wings” around the magnet) should be smaller, as the force on diaphragm will be canceled at frequencies when the wavelength is equal to the length of the signal path between front and rear of the ribbon. In other words--the smaller the path—the shorter the wavelength—the higher the frequency. At the same time, the smaller baffle means that pressure difference built up between front and rear is much smaller at low frequencies, so we get loss on low end, since the ribbon becomes more resistance rather than mass controlled. At the same time, the smaller baffle means smaller magnets, or pole pieces, which reduces the magnetic flux, and thus sensitivity of the mic.
There is number of designs to overcome some of these—for example Coles, which uses smaller pole pieces, and additional baffle, made out of porous gauze with low acoustical resistance to compensate lows. Also, there were other designs, which are still full of different kinds of compromises. WE and Altec, with their dual—velocity ribbon, and dynamic omni capsule, which then were electrically combined for different patterns. Some designs with horns, tuned to high frequencies. Unidirectional RCA 77A, where one half of the ribbon is velocity, and another—pressure type, with closed chamber behind, and sofisticated acoustical labyrinth—actually I like this one a lot. In addition, they have quite uniform directional pattern. Ooooops, just got an idea... Huh, enough for today.
BTW, did I mention their output? OK, time to go to sleep.
Oh, and I almost forgot—I just love ribbons!!! Aren’t they wonderful?
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H
Harvey Gerst
New member
Marik said:
Yup, I have a Coles 4038, a Sank modified Beyer M260, a beautiful RCA 77DX and an equally gorgeous RCA 44BX, and a pair of the new AEA R84s. I love ribbons too.
Marik
Pro Microphone Design
Harvey,
I am wondering if you know something about these beauties:
http://www.sequerra.com/prosound/data/ribbon-mic.html
Huh--the price tag...
Also, have you ever heard Fostex printed ribbons, and if yes, what are your impressions?
I am wondering if you know something about these beauties:
http://www.sequerra.com/prosound/data/ribbon-mic.html
Huh--the price tag...
Also, have you ever heard Fostex printed ribbons, and if yes, what are your impressions?
H
Harvey Gerst
New member
Marik said:
No, I never had the pleasure of hearing them, although it looked like a cool idea.
crazydoc
Master Baiter
Marik and Harvey
Thanks for the infomative posts. So much better than "I think that mic sucks."
I'm trying to digest the ribbon stuff still to incorporate into my new laser mic design.
Thanks for the infomative posts. So much better than "I think that mic sucks."
I'm trying to digest the ribbon stuff still to incorporate into my new laser mic design.
Marik
Pro Microphone Design
<I'm trying to digest the ribbon stuff still to incorporate into my new laser mic design. >
Hey Crazydoc,
You are laughing... You will laugh even more, if I tell you that in fact I am working on this idea--instead of the magnets to use optopair, with a laser led as a light source.
Meantime have a look at:
http://www.k-bay106.com/doc.htm
A lot of info on RCA ribbons.
Also take a Royer tours:
http://www.royerlabs.com/Royertour/Tour_R-121p0.html
and
http://www.royerlabs.com/Royertour/Tour_SFp0.html
And finally, look at pictures of internal structure of some RCA ribbons, among some other cool stuff:
http://www.coutant.org/contents.html
Hey Crazydoc,
You are laughing... You will laugh even more, if I tell you that in fact I am working on this idea--instead of the magnets to use optopair, with a laser led as a light source.
Meantime have a look at:
http://www.k-bay106.com/doc.htm
A lot of info on RCA ribbons.
Also take a Royer tours:
http://www.royerlabs.com/Royertour/Tour_R-121p0.html
and
http://www.royerlabs.com/Royertour/Tour_SFp0.html
And finally, look at pictures of internal structure of some RCA ribbons, among some other cool stuff:
http://www.coutant.org/contents.html
F
Flatpicker
...
I bet the Stephen Paul mic works something like this.Marik said:
ausrock
Well-known member
I may be wrong but I doubt it, however, Stephen did make mention of developing a diaphramless mic which used light........whether he got far enough with it for it to eventually become a reality who knows.
D
DJL
Self Banned
This is turning into one of the best threads on this board... keep the info and links comming. Thanks
crazydoc
Master Baiter
I'm laughing, but I'm thinking about it seriously too. However, given my limited knowledge and intelligence, chances of success are small.Marik said:
Thanks for the links.
Marik
Pro Microphone Design
<I may be wrong but I doubt it, however, Stephen did make mention of developing a diaphramless mic which used light........whether he got far enough with it for it to eventually become a reality who knows.>
I heard of three diaphragmless designs: 1) Integrated circuit mic by Sank, where silicon chip was directly actuated by deposited strain-gauge bridge. 2) Using ionized cloud--don't ask me--I don't know what's this and how it works. The last, third one, is even more obscure. I remember reading about it a few years ago on internet, but since then never could find where... It might be even a proposal. Do you know something about plasma speakers? Yeah, these beasts are the best known tweeters-- trust me--I heard them--once I made a prototype. Audio signal modulates high voltage RF oscillator in MHz range, the size of the flame (plasma) changes, producing the audio signal. Think of it as a "singing" Tesla coil. The upper frequency limit about 250Khz (!!!), no Dopler distortions, and all this stuff. So, as a mic this system supposed to work "in reverse". Needless to say, it wouldn't be a perfect vocal mic, 'cauze it is little bit....hot.
Wait a second, are the ##2 and 3 the same? Probably Harvey knows.
I cannot tell if Stephen was talking about diaphragmless mic, but as I wrote in another thread, I read his post on RO, which was about digital optical mic, with a light pipe as a transmission line.
<keep the info and links comming.>
DJL, which ones are you interested in?
Ribbons? Then have a look at Royer's patent:
http://l2.espacenet.com/espacenet/viewer?PN=US6434252&CY=gb&LG=en&DB=EPD
I heard of three diaphragmless designs: 1) Integrated circuit mic by Sank, where silicon chip was directly actuated by deposited strain-gauge bridge. 2) Using ionized cloud--don't ask me--I don't know what's this and how it works. The last, third one, is even more obscure. I remember reading about it a few years ago on internet, but since then never could find where... It might be even a proposal. Do you know something about plasma speakers? Yeah, these beasts are the best known tweeters-- trust me--I heard them--once I made a prototype. Audio signal modulates high voltage RF oscillator in MHz range, the size of the flame (plasma) changes, producing the audio signal. Think of it as a "singing" Tesla coil. The upper frequency limit about 250Khz (!!!), no Dopler distortions, and all this stuff. So, as a mic this system supposed to work "in reverse". Needless to say, it wouldn't be a perfect vocal mic, 'cauze it is little bit....hot.
Wait a second, are the ##2 and 3 the same? Probably Harvey knows.
I cannot tell if Stephen was talking about diaphragmless mic, but as I wrote in another thread, I read his post on RO, which was about digital optical mic, with a light pipe as a transmission line.
<keep the info and links comming.>
DJL, which ones are you interested in?
Ribbons? Then have a look at Royer's patent:
http://l2.espacenet.com/espacenet/viewer?PN=US6434252&CY=gb&LG=en&DB=EPD
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