The True Story of the RM1 Microphone
By Cliff Henricksen
This story really starts in the 1970’s when I was a recording artist and on-call studio musician living in the Philadelphia area. One of the studios I worked in was Veritable Recording in Ardmore PA, owned by one Douglas W Fearn. Doug was (and is) a real purist and lover of The Beautiful Sound. I got to know him well, working often in his studio and inevitably engaging in “the endless discussion” of high-fidelity in recording and playback (often waiting around for a producer to make up his mind about a mix or take). One real non-equipment lesson I learned early on was that the player often had the greatest impact on the perceived fidelity, sound quality and excitement of recorded sound. I remember a session I did (actually recording a few of my own songs for a local artist, Frank Mancano) with studio legend Bernard Purdy playing drums. I was actually intimidated to play with this monster drummer, but Doug made a clear point that Bernard made it easy for everyone. First of all, Bernard relaxed everyone with a great attitude and sense of humor. But he set it all up so easy for the players, like a good point guard in basketball, and did the same for a recording engineer to get a good sound because of how he played; how he actually hit the drums. It was with this lesson that I began to appreciate how important the artist is to what many believe to be a purely technical field (making a beautiful and artistic recording).
In 1974, to the relief of my wife and growing family, I left my “career” (ha!) as a fulltime professional musician and started a long and successful career in professional audio, starting with the founding of a small applied-research group at Altec-Lansing in Anaheim California. But I stayed in touch with Doug over the years as we both followed our paths of work and personal life. Around 1993, Doug introduced his now-famous all-tube, handwired VT2 preamplifier. About the same time, I came into possession of an RCA44 ribbon microphone with some equipment trades. I did some recording with it and even with its problems (needed tons of noise-inducing gain, needed a lot of HF boost and was really sensitive to P-pop on close vocal), it had a very special and unique combination of sound qualities to my ears. It sounded human, especially when you made it sound right with gain and eq. Talking with Doug about it, I came to learn that he too was a long-time lover of ribbon microphones, having a collection of RCA and Coles units in his regular-use rotation. He sent me a VT2 preamp to try with the 44 and we had endless conversations about how great it was to record with; sound qualities (especially vocals) that transcended the microphone’s deficiencies. I still have (and treasure) (and use extensively) his now-famous preamp.
Now Doug and I are both inventors and, by nature, fascinated and intently-curious about most things, especially those associated with musical sound. And we both love all kinds of technical and intellectual challenges. In our conversations, we shortly decided that it should be possible to design a ribbon-format microphone that had all the qualities we loved about the 44 but improved on the qualities we didn’t like. Personally, I sure wanted one. And of course, we decided we would, simply, do it. You know; swords in the air shouting "code duelo" and all that. "Charge"!! The mic would be a fully-integrated system design with Doug’s electronics and my electroacoustics, coupled with Doug’s full knowledge of what a professional recording engineer or studio owner really wanted in a microphone.
The first step for me was to take the 44 apart and see what made it work. It appeared pretty simple to me, with a case not unlike a sheet-metal chassis for a piece of period electronics. When I opened it up, I noticed that the ribbon diaphragm was stretched way out of shape, bulging out of its intended position. So I undid some clamp mechanism and stretched it tighter, not realizing how fragile the thing was and how lucky I was to have accomplished this task. I also made a bunch of mechanical measurements of the magnetic circuit and ribbon itself. It had a couple of sandcast horshoe-shaped Alnico magnets top and bottom, delivering magnetic flux-energy in the central airgap. It was basically the same as any loudspeaker magnetic circuit, right in my happy space. The ribbon, vibrating in the magnetically-charged air, generated a voltage you could record. It obeyed classic laws of physics. Piece of cake.
When I reported all this to Doug and we all started talking like lead guitar players (“I could have done that”), we began speculating on how we would make an improved version. We quickly went down the “back to the future” path, deciding it would be oh-so-retro-hip to make a microphone with genuine field coils instead of permanent magnets and connected by a big rubber multiconductor cable (with mil-spec nuclear submarine-type connectors on it) that went to a metal chassis full of giant glowing vacuum tubes, like right out of Menlo Park labs. The chassis would house a Genuine DW Fearn preamplifier of course. But it would also house a bunch of those milk-bottle-sized rectifier and regulator tubes to power the field coils in the microphone, all radiating purple, orange and red light and emanating the hidden life of electrons flowing in vacuums. And big, fist-sized polished black Bakelite knobs with a white-strip on its pointer. Oh boy. It was a grand vision that would clearly outdo Captain Nemo’s sonar rig and be a delight to a small but dedicated army of recording purists. Like us. So we decided to build a couple of them. With the Alnico magnets as a guide, I designed, wound and epoxied a bunch of big red-wire coils in my shop at home. Cyclotron. Doug calls the whole technology “RetroDymium™.
…That is until we found that it was technically flawed, and it really could not generate enough flux to replicate the Alnico magnets (unless the power supply could be wired up to 220v) and probably had a world market of 27 potential customers, given the expense required to build such a thing much less a sort-of construction crane to install it. Make that 25 if you exclude the inventors.
That was probably in 1998-9 or so. And so we both kind of sunk into a sort-of numbed-out ennui/funk on the project. So we continued with our own “other” lives and careers, either ignoring or being in denial of the fabulous Captain Nemo microphone. “Unacceptable” was Doug’s recent recollection. Cowards. He’s probably right, but we did it anyway; walked away from it.
The subconscious is a mighty and mysterious thing. Ideas go in and continue to process and percolate, even while you’re raising a family, moving them all over America, helping deliver babies, soldering wires, running an all-tube electronics company or designing loudspeaker systems. You’re not aware, but it’s happening anyway.
In 2009, I decided to have another look at what I fondly-remembered as a really juicy project. I decided that more flux, like in a loudspeaker, would probably be a fundamental benefit to the mic, not yet knowing exactly how. In a loudspeaker, the more money you throw at it in terms of magnetic energy, the more you get in gain/bandwidth. The magnet assures quality of performance, especially if you are good at “magnetic husbandry” and can design an efficient magnetic circuit. I assumed the same was true for a magnetic microphone. So, always looking for ultimate performance (and ignoring price and other practical matters), I looked for the best way to cram as many “gallons of magnetism” as possible into the RCA44-sized airgap. Forget Alnico; The world-champion at this, by far, was Neodymium-Boron-Iron, packing more magnetic energy per cubic inch that anything the world had ever seen. This is the equivalent of nuclear power in permanent magnetics or dropping a Viper engine into a Yugo. So I convinced Doug to have his machinist make some simple pieces that would allow me to fit a pair of high-capacity Neodymium magnets to one of our previous electromagnet microphones. This took a long time, apparently due to the machinist’s other priorities, independent of Doug’s urgings to him.
“After a fashion”, I finally put this first prototype together, with a real blacksmith-level series of wood tools and assembly fixtures, and it worked. It looked dumb though and didn’t really have the sensitivity or high end I had hoped for, never realizing I would need more than two orders of magnitude thinner (and more fragile) aluminum for the diaphragm than what I was using.
So I redesigned it, turning the magnet 90 degrees, resulting in a much better design in many ways; aesthetically, acoustically as well as magnetically-efficient. Short story: I sent drawings to Doug, who sent it to his machinist. They needed different format drawings for their n/c machines. They would have to convert my 2d drawings. I tried some file conversions, which didn’t work for miniscule reasons. I got a 3d program, sent them 3d dxf files. These did not work, but were not really specific as to why. It went back and forth for months, Doug being careful not to interrupt the same company making his own products. It got interminable and frustrating and maddening and numbing. Vendors. Plus Doug was, as always, mostly distracted by the normal workings of his studio-equipment business. He often was apologetic about this. Frustrating.
I finally decided I really should do this myself. On January 8, 2012, after a (typically) kind and friendly conversation, Doug formally separated himself from the project. I wanted to press forward. Doug basically could not get his machinist to do anything on this either. And he had a company to run. Everyone has only so much time in their lives and this really did not fit into Doug’s. So from this point on, it was my baby, with Doug being open to some kind of collaboration possibly later on. He encouraged me to press on.
And so, I did.
As I turned my attention to the microphone for the first time alone, I realized that this would be the very first time in my life when I would be creating a product and a means of making and selling it (creating a company). This would be my very first solo effort.
So I set these goals for the microphone, mostly as if I was making the thing for my own use:
- I wanted to create a microphone that was as simple to use as a hammer: set it up and be confident the recording will be what you put into it. Period. No noise, no p-pop, not twiddling knobs. Just a solid baseline signal that satisfies and needs no special preparation. Commercial studios as well as the growing army of artist-operated studios all need this.
- I wanted a microphone that was genuinely “Made in America”, like a really good handcrafted tool for professional use. I wanted something special for a professional user. Doug also said this was a big issue today. Customer support of a product made by vendors in an unknown building in, say, Shenzhen China, is impossible. And just about everything is made there today. Recording professionals in America, at least, would be very attracted to being able to get support and advice directly from the maker of such a professional tool. Doug thought this would also be very true in South America, Europe/UK and Japan.
- I wanted to achieve maximum possible flux density for a 2” long 0.190” wide magnetic air gap. It looked like 1 Tesla would be a lofty and probably hard-to-approach goal. I would do it with big potent slugs of Neodymium and mild steel to conduct the flux to the airgap, damn the expense. This would be the microphone equivalent of Carroll Shelby dropping a 427 Ford NASCAR engine in a polite little 2000-pound English sports car.
- I wanted a compact-as-possible package design.
- I wanted a system that simply worked. This would include anything needed to amplify the ribbon’s voltage so that a useful signal resulted. Doing and I did some market research and found this level to be around -45dB for 1Pa (94dB) acoustic input. Good for loud and good for soft.
- It should have sturdy, integral P-pop rejection when used as a close-vocal microphone.
- Above all, I wanted to make a microphone that created a simple “plug-and-play” user experience, giving a treasured sound recording of anything. And I wanted to make a physical hand-crafted product that inspired pride of ownership. I personally wanted, including for my own use in recording, a microphone that could be put in front of any voice or instrument and produce a signal that the performer really did not have much, if any, post-processing to do. Set it up and love the sound. Full confidence in a microphone is a very practical quality. If you don’t have to worry about how it’s going to sound; you know – futz around with the knobs and placement; you can save a lot of time and get things done quickly for any artist, especially when the juices are flowing from inspiration. An engineer that can capture such moments, like overdubbing, works with an artist as a team with often staggering results. In contrast, the worst case is stopping such action because of some technical flaw. A great microphone is a very valuable artistic tool.
So, I proceeded on my own. I found a local machinist here in the Boston area and by February 2012 I had a completed working prototype, using a Jensen transformer loaned to me by Doug. I started experimenting with different configurations and thicknesses of ribbons and quickly found out how important it was to get really thin aluminum. I also found how difficult it was to work with this stuff, once I got a sheet of it. Actually, I quickly found how difficult it was to even get very thin foil, because it needed to be less than a tenth of a thousandth of an inch thick. A strip of this stuff, let go in free air, is almost buoyant, floating lazily in any small thermal air current. That and the creation of a mini-blizzard of the things, sitting on my workbench as I sneezed. So I spent hours and months playing with this stuff, finally figuring out how to cut it, form it and install it accurately. Not obvious.
I finally knew I could make one of these, and make others in production. And so, drawing on my engineering expertise, I set about getting analytical, developing equations of output v/s frequency and getting the most out of my (expensive) slugs of Neodymium using modern finite element analysis (FEA). Optimizing my original back-of-the-envelope calculation, I found that all I had to do was improve the design I had in the area of the airgap. To my amazement, the FEA investigation showed a theoretical gap flux in the neighborhood of 1 Tesla, maintained over almost 2 tenths of an inch of air. Later, I checked this with a calibrated “Hall Effect Probe” and it was right on the money. This is monster-level magnetic energy. I was pumped.
By the way, you don’t want to buy these magnets and let your kids play with them. They come fully charged, because unlike normal (barium ferrite and Alnico) speaker mag-circuits, no one can really charge these as assemblies. Unless you’re General Motors. My magnets (pretty big for NeO) are simply insane handgrenade-level force-generators. I think you could lift a SmartCar™ with one. Get two of them close to each other and the attraction is simply crazy-strong. You need discipline and smart assembly fixtures to put them together in a magnetic circuit. They will, if you’re not careful, pull together and lacerate your hands. I can show you photographs. They are very dangerous in a way that is far beyond normal experience.
I mentioned what I was doing to my long-time buddy Lloyd Baggs, his company being famous for guitar pickups and very low-noise, high-quality phantom-powered amplification. Lloyd, a devout "listener" (as opposed to a data-slave), is a big fan of ribbon mics and before our conversation ended, he had volunteered to develop a preamp for the microphone. This solved a major problem for me (yo, I can't even spell "E equals I R") and his engineering department came up with The Silver Bullet preamp. A little circuit board fits neatly into soffits in the magnetic circuit, shaped for magnetic efficiency but a perfect place to put the microphone’s brain. The Baggs preamp is a quiet little high-fidelity jewel that makes the whole thing sound like it should.
On good advice, I came up with a nice short name for the microphone (RM1) and for my fledgling company (Cliff Mics). Through some networking, I found some machine shops and finishers in New Hampshire (a really nice drive from Framingham MA) that could make parts for my microphone and we all joined together to create a team of businesses to make the mic. Made in America; my dream.
So, that's it...it's the end of one story and the start of yet another.