Ribbon Microphones

If you have listened to this podcast for any length of time, you probably know that I am a big fan of ribbon microphones.

In this episode, I talk about my introduction to ribbon mics while I was in high school, and how over the years I tried to make them work for me. Eventually, ribbon mics became my favorite, and now I often do sessions that use only ribbon mics.

I explain the characteristics of ribbon mics, good and bad, and suggest ways to get the most from this type of microphone. I compare the sound and pickup pattern characteristics with condenser mics, and suggest techniques for several common recording situations.

I mention a video showing how we mic a grand piano with a stereo ribbon mic. Here is the link to that video:  https://www.youtube.com/watch?v=4mzVne64ItQ

As always, thanks for listening, commenting, and subscribing. Your feedback is valuable to me, so let me know what you think of this episode or any other. I can be reached by email at dwfearn@dwfearn.com

And please help this podcast grow by suggesting it to your friends and sharing it on social media. Thanks.

email: dwfearn@dwfearn.com
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Transcript

71    Ribbon Microphones                                            6 October 2022

I’m Doug Fearn and this is My Take On Music Recording

If you have listened to this podcast for any length of time, you probably know that I am a big fan of ribbon microphones.

My first encounter with ribbon mics was at my high school FM broadcast station. They were not in use, and not in very good condition, but I pulled them out of a cabinet and hooked them up to see what they sounded like.

At that time, the station used a Shure 55S Unidyne in the studio as the main announce mic. It looked cool, although it was old-fashioned looking even in 1965. It did not sound very good, but it was a great match for announcers with no mic experience since it was pretty indestructible and difficult to pop. Most of the other mics we had were Electro-Voice omni dynamics, which were used primarily for sports remotes and shows with guests.

I quickly discovered why the ribbon mics were not well-suited for the high school station. For one thing, they were easy to pop, and sounded really bad if you got too close to them.

We had several RCA KB-2 “Paintbrush” mics, which were very small. They sounded OK but not great. There was an RCA 74B, which was a smaller version of the 44B. It sounded really good, but the acoustics of our radio station studios were pretty awful, and the bi-directional characteristic of these mics made the rooms sound even worse. The announce booth was small, and the mic was only inches away from the window, so a bi-directional mic would not work in that situation.

Working the Shure very closely was the best solution we had. By the way, that Shure dynamic element eventually was used for the ubiquitous SM57.

In my senior year, I started working weekends at WPEN AM/FM in Philadelphia. They used mostly E-V dynamics, too. But I discovered quite a collection of RCA ribbon mics in various locations around the station. Most were on stands, out in the open. Who knows how long they had been stored like that.

I bought a pair of 44s and a 77 from the station. The 44 is the classic mic from 1930 that has a diamond-shaped profile, while the 77 is peanut shaped. Everybody knows those two mics, even if you are completely removed from anything in recording or broadcast. They are icons, often used to represent a generic microphone.

When I opened my own studio, I had in my mic collection a Neumann U87, plus a pair of KM84s. Those were two of the first solid-state condenser mics that Neumann made. They sounded dramatically different from the ribbon mics, and I valued their presence peak and in-your-face character. I had other mics, from E-V, Altec, Beyer-Dynamic, Sennheiser, Schoeps, a Neumann M49, and others I cannot remember now.

I brought out the 44s and the 77 for horn sections, but otherwise did not use them much.

Soon I acquired a pair of RCA BK-5s, which were unidirectional ribbon mics. I think of the BK-5 as the “Eric Severeid” mic. He was a newscaster and commentator on the CBS TV network, and always had a BK-5 on the desk, about two feet from his mouth. It sounded great. A perfect match for his voice. It looked good on TV, too. Much more modern-looking than the RCA 77 or 44.

I was not working with anyone who had a voice like Eric Severeid, and the BK-5 did not sound good on any of the vocalists I was working with at the time.

However, I learned that some studios were using a BK-5 as a kick drum mic, so I gave it a try. It was not very close to the drum, but it lasted exactly two hits before the ribbon blew out. I sent it back to RCA to be re-ribboned, and never used it on kick ever again. Finally, after not using the BK-5s for a long time, I sold them to get more condenser mics.

Despite trying to educate my engineers about how to use ribbon mics, they did not like them on anything. I warned them about the powerful magnets in those mics, and the dangers to tape reels. Despite that, one day I walked into the control room to see a 44 sitting on top of album master tape. After admonishing the miscreant who did that, we put the reel up to check it, only to find about a 20dB increase in noise on each revolution of the tape reel.

After that, I took the ribbon mics out of the mic locker, and eventually sold them all.

I did not think about ribbon mics for many years after that, except for a Beyer-Dynamic M160 which was my go-to high-hat mic. I had a pair of Coles 4038s from the 1980s, which I used as a Blumlein stereo pair for orchestral recording, but that was it. It wasn’t until around 1990 when I became friends with Wes Dooley of Audio Engineering Associates that I thought maybe I should revisit the world of ribbon mics.

You can hear Wes talking about how he got into the ribbon mic business in episodes 5 and 10.

Wes was generous in letting me borrow some of his mics to try out on recording projects. His line of mics was much smaller than it is now. I think the first ones I tried were R84s, which I thought sounded very good, but not exactly what I was looking for.

By the way, I, and other people, suggested to Wes that he make a stereo version of the R84, which he did. That became the R88, although it is significantly different from the R84. The R88 has become one of my favorite mics, which I use almost always on piano and on drums, or sometimes as a single-mic stereo pickup with the performers arrayed around the front and back of the mic.

Although inspired by the 44, AEA’s mic line did not include a real recreation of the 44 for quite some time. Part of AEA’s business was refurbishing RCA 44s, and after a while Wes decided he had the parts and expertise to exactly duplicate the original RCA design.

When he sent me a pair of 44s to try out, I was sold on the ribbon sound. Why it took me all those decades to appreciate that sound I will never know.

I have done sessions entirely with 44s, and they sounded great on everything. But more on that in a minute.

So, what exactly is the “ribbon sound?” Well, I could make an analogy:

Ribbon mics are to microphones what vacuum tubes are to electronics.

To my ear, tubes sound like the music. Ribbon mics sound like the music. Maybe I needed to pair those two technologies up to fully appreciate the difference from the condenser sound.

To be clear, these are not mics for everyone. I think they could be, but for people who get the sound they want with condenser mics, I think they should stick with what works for them. I still have many condenser mics, and use them when needed. But I think I have moved beyond that sound, into something that better fits my style.

Certainly, not everyone will agree, but it works for me.

No microphone type is perfect for every situation, and many people find ribbon mics awkward to use.

Not every sound is a good match for ribbon mics, either. Nor every situation. Most ribbon mics are big, heavy, and fragile, so they are not well-suited for stage use. There are ribbon mics designed for live performance. In this discussion, I am focusing on studio use.

The output level of a ribbon mic is very low, compared to a condenser mic. That is usually not a problem for most mic preamps, but in some situations, like distant mic’ing of relatively quiet instruments, the low level, and maybe preamp noise, will become a problem. Perhaps a condenser mic is a better choice for that application in many situations.

Some ribbon mics are sensitive to electrical noise, usually heard as a low-level hum or buzz. This has become particularly troublesome with the proliferation of noise-generating electronics, like cell phones, LED lights, SCR light dimmers, HVAC units with variable speed motors, and switching power supplies. During a recent session, we had a problem with noise in one of the ribbon mics. It was traced to one of the LED video lights we had set up for video recording of the session. This is also a problem with many dynamic mics. Condenser mics are much less likely to pick up that electrical noise.

Because of the low output level of ribbon mics, there has become a market for “pre” preamplifiers, which raise the level of a ribbon mic about 15 to 20dB so that they are more in line with condenser mics. Those work pretty well, although I prefer to avoid the solid-state stage.

And many modern ribbon mics now contain active electronics, which boosts the level. Some of those “active” mics also insert a presence peak boost to make the ribbon sound more like a condenser. Not a bad option for some people, but I think if you want a condenser sound, use a condenser mic.

To studio people accustomed to hearing nothing but condenser mics, a ribbon mic initially sounds dull. But if you look at the frequency response of a good ribbon mic, they are generally fairly flat through the range that is most important. True, they tend to roll off at the very high end, often down quite a few dB at 20kHz, but that might not have as much impact on the final product as you might think.

I find it remarkable that ribbon mics can usually take a lot of eq without a problem. Basically, you can tailor the frequency response to fit the need of the music and your recording style. All the frequencies are there, and you can boost or attenuate any frequency range easily to get the sound you want.

It may take a while to adjust your ears to the sound of ribbon mics, but once you do, you may find your condenser mics sound too harsh and shrill for a lot of things.

Generally, I do not use any eq on my ribbon mics, except for some low-end roll-off when needed.

That low-end problem is caused by proximity effect. That simply means that the mic sounds bassier the closer it is to the sound source. Sometimes that is desirable, but most of the time, I find that some gentle roll-off of the lows, starting around 150Hz, restores flat low-end to the ribbon sound.

For me, a 2 to 6dB shelving rolloff at 40Hz on a D.W. Fearn VT-4 or VT-5 equalizer allows me to make the lows much more natural. Other equalizers will probably need different settings.

Proximity effect is not unique to ribbon mics. Just about all directional mics have some degree of bass boost. It is a physics. Some mics even have a bass roll-off filter you can switch in to compensate.

Wes Dooley tells me that the 44 does not exhibit flat bass response until it is 9 feet from the sound source! That’s not possible for most of our recording sessions, so some eq may be necessary.

You could think of the increased bass response as some built-in low frequency boost eq. Where you might reach for an equalizer to achieve that with other mics, the ribbon mic might do just what you want without any eq.

As an example, lately I have been using a  cello part for bass, either plucked or bowed. A ribbon mic a foot or so away adds a lot of body to the cello sound and works well in the acoustic music I tend to record.

Proximity effect can also be a useful dynamic tool for singers who understand how to use it. Singers in the 1930s and 40s were great at this. When you need more intimacy in the vocal, have the singer move a bit closer to the mic. The bass response will go up, as well as the sense of presence.

There is a danger of too much of a good thing. If you get too close, a ribbon mic can suddenly change character and become something that is not a complement to the sound. It’s difficult to describe, but a couple of minutes of experimenting will tell you where that point is on any given sound.

With an experienced vocalist, moving just a bit closer and farther during the performance can be very effective at enhancing the message.

Some of these drawbacks of a ribbon mic can be seen as a defect or a useful tool. This often applies to  your other mics, too, but usually not to the extent it does with ribbons.

Also in the “feature or bug” category is the native bi-directional pickup pattern of a ribbon mic. To me, that’s where a lot of the magic comes from. There is something about that figure-8 pattern that has always appealed to me. I believe it is a function of the pattern, not the microphone type, because multi-pattern condenser mics in the bi-directional setting also have some of this characteristic.

To my ear, the sound suddenly becomes more focused in bi-directional. I discovered this back in the 1970s when I tried one of my large-diaphragm condenser mics in figure-8. Suddenly it sounded like the singer was half the distance from the mic as they sounded with the mic in cardioid. There was also a pleasant warmth to the sound that appealed to me. The room sound improved, too.

I prefer that sound, and unless circumstances make it impractical, I always have my condenser mics set to the figure-8 pattern.

The downside of the bidirectional pattern is that it is, well, bi-directional. Sound is picked up equally on the front and back of the mic. If we want good isolation between sounds in the same room, or to minimize room sound, it would seem that a figure-8 pattern would be counterproductive. And that might be true except for one thing.

The bi-directional mic is almost entirely insensitive to sounds arriving from the “side” of the mic. And that “side” is really a disc all the way around the mic. That null in sensitivity is profoundly deep, as illustrated in a short demonstration I did in episode 64, “Studio Technology for Musicians, Part 1.”

Sound arriving from the side is attenuated by a huge amount, theoretically infinitely at the point directly off the sides. In reality, what you will hear of sounds from the sides is entirely room sound when recording a single source. Whether that is good or bad depends on your room and what your intentions are, but I find it very useful in a couple of scenarios.

If you want room mics, for drums or an electric guitar, for example, you can place the bi-directional mic as far away as you like. Aim the null, the side of the mic, toward the drum kit or guitar amp. What you will get is almost entirely room sound with very little of the direct sound.

Isolation between instruments in the studio is often necessary for replacing parts later, or for special processing of just one instrument. Often, a uni-directional mic would work well in this case. But I find that a bi-directional mic can be oriented so that the null faces the sound or sounds in the room you want to minimize, and you end up with much better isolation than you would with a cardioid mic.

Another interesting characteristic of a bi-directional mic Is that the frequency response of the mic varies very little as you move around the mic. Only the level changes. This is not the case with most directional mics, where the nature of the sound can change dramatically off-axis. Try it and see for yourself. What bleed there is with a bi-directional mic is much more natural sounding than it is with a cardioid mic. Some directional mics are better at maintaining the off-axis frequency response than others, but nothing sounds better off-axis than a bi-directional ribbon mic.

Since the RCA 77 in the 1930s, microphone manufacturers have tried to make a directional ribbon mic. Some early designs used a combination of a ribbon and dynamic element, combined in a way to focus the pickup on sound arriving at the front of the mic. The Western Electric 639 is an example of this approach. It works, but I was never impressed with that sound.

Another approach is to create an elaborate path to the back side of the ribbon, in order to cancel out sound arriving from that direction. That’s how most directional ribbon mics work. It is effective, but it is challenging to make the frequency response completely flat using that technique. That tends to give the directional ribbon mic a distinctive sound, which may or may not work for a given situation. The resulting pattern is similar to most other cardioid mics.

There is another thing to like about ribbon mics: they have very little distortion. Condenser mics have a built-in level of distortion that designers try to minimize, but it is always there. It puts a hard edge on the sound, which some people like. It all depends on what you are recording. If that distortion fits the music, by all means use that as a tool. But if you want to eliminate those irritants to the listener, the ribbon mic will always be cleaner sounding. That’s important to me, since most of what I record these days is acoustic music, which reveals any defect in the equipment much more readily than, say, an electric guitar through pedals. There, distortion is part of the sound. That’s fine, and there won’t be much to be gained by eliminating the condenser mic distortion,

But why are ribbon mics so popular on guitar amps? There must be more to it than just reduced distortion.

My theory is that the ribbon mic principle is the purest form of a microphone. The ribbon itself is not only the diaphragm that picks up the sound, but also the device that changes the mechanical energy of the sound to the electrical energy we need for recording. There is nothing in the way. No electronics, at least in passive ribbon mics. It picks up the essence of the sound better than anything else, at least to my ear.

There is concern about ribbon mics and phantom power, used for many condenser mics. The fear is that the 48 Volts that many condenser mics require could damage the ribbon.

Any voltage that is placed on a ribbon mic can be translated into movement of the ribbon itself. That could damage it, since it is a vanishingly thin strip of aluminum foil.

Like many transducers, the ribbon mic principle can work both ways: as a microphone or as a speaker. Ribbon tweeters are used in some speaker systems.

A passive loudspeaker can also work both ways, too, such as when a speaker is used as a kick drum mic.

The engineers at WPEN told me stories of how on late night shows they would temporarily feed a low-level audio signal into the announcer’s ribbon microphone and make it “talk” to them. They had great fun freaking out the announcers who were unaware of this trick. I do not recommend trying this because it is far too easy to damage the mic that way.

The 48 volts powering condenser mics is called “phantom power” because the DC voltage is undetectable by the microphone audio path. The 48V is provided by the mic preamp through carefully matched resistors connected to pins 2 and 3 of the XLR connector – the balanced audio signal pins. Pin 1 is for the shield. Since the voltage is exactly equal on both sides of the balanced line, the microphone never sees it. It is a phantom.

Special circuits extract this 48V between the signal pins and ground, pin 1, to power the microphone’s internal electronics.

The system works great. It allows us to power our solid-state condenser mics through ordinary mic cables – unlike tube condenser mics which require a separate power supply and a special cable with more conductors.

A problem can arise when there is a fault in the wiring. If for any reason the balanced audio connection becomes unbalanced, by connected either pin 2 or 3 to ground, for example, then the 48V can go right into the microphone element. This applies to both ribbon and dynamic mics.

The faulty connection does not have to be a direct short circuit. Anything that upsets the careful balance between pins 2 and 3 can result in the phantom voltage appearing on the audio lines.

That DC voltage will make the ribbon react, driving it either in or out, depending on the polarity of the voltage. Unfortunately, that excursion can be severe, permanently damaging the ribbon in the mic.

That situation can occur when you have a defective mic cable. If the shield comes in contact with pin 2 or 3, then destructive voltage can imperil the ribbon mic.

By the way, a mic cable with that defect will not power your condenser mics. That cable will have other problems, too, like increased noise pickup.

Well-constructed and well-treated cables are unlikely to ever have this problem, but the potential is always there, especially with cheap mic cables or those subjected to abuse. Rolling a piano over a cable might be enough to cause a defect like that.

However, the real danger with ribbon mics is caused by TRS patch panels. If you have mic lines and preamp inputs on your patch bay, every time you insert or remove a patch cord, the 48V phantom power is shorted to ground for an instant. That puts a pulse of DC into your microphones. You can see tiny sparks on your patch plugs when you do this.

Condenser mics can usually handle this without damage. It will create a huge spike of noise, however. I’ll bet you have experienced this when the fader was up while you were patching. It can take the condenser mic a second or two to settle down, during which a lot of extremely low-frequency energy could damage your monitor speakers, or maybe blow a fuse in the speaker.

Patching a ribbon mic line with phantom power turned on can instantly damage your mic.

There are a couple of solutions to this. One is to make sure the +48 switch is always off except for condenser mics that require it.

The other solution is to eliminate any TRS patching of mic lines. Many big studios use an XLR patch panel for all mic lines. The way an XLR connector works, the ground connection, pin 1, always makes contact first, and then pins 2 and 3 make contact simultaneously. There is no way the audio line can get a pulse of DC like it can in a TRS patch panel. XLR connectors for mic patching are a good safety feature.

In my studio, all the patching is done with XLR connectors. It takes up a lot of rack space, but my studio is relatively simple, so I can get away with it. TRS patch panels are fine for line-level signals, although I believe those patch bays are a source of a lot of noise and distortion. I don’t have to worry about that with my XLR patch panel. Nor do I have to worry if I accidently patch a ribbon mic line with the 48V power turned on.

The first two consoles I had in my studio had 48V on all the mic inputs all the time. You could not turn it off. I used ribbon mics all the time with those consoles, and never had a problem. But it requires good cables and no patching of mic lines.

It’s best to get in the habit of checking the position of the 48-volt switch every time before you connect any mics. Some mic preamps have a locking switch that requires an extra step to turn on the 48 volts, just for this reason.

My solution is to turn off all the 48-volt switches at the end of a session. And then I make sure they are all off before setting up for the next session. Once that becomes a habit, you should never to worry about damaging your ribbon mics.

The ribbon mic was the gold standard for recording and broadcast up until the 1950s. Neumann, AKG, and other manufacturers of studio condenser mics started marketing their microphones in the 1950s and they were immediately adopted by most engineers and producers because of their unique and compelling sound. Ribbon mics fell into disuse.

Like most trends, things often swing one way and then another. Ribbon mics have made quite a comeback in the last 20 years, as people discovered their unique qualities. There are now quite a few manufacturers selling ribbon mics at a range of prices. Most of these mics are cheaper than a quality condenser mic.

If you have not used a ribbon mic, I can give you some examples of how I use them that might help you get started.

Let’s start with vocals, since this is often the most critical application for a mic in music recording.

My favorite for vocals is a 44, either a vintage one or a new-production version. It is an amazing microphone, which is even more astounding when you consider that it was the world’s first truly high-fidelity microphone available. After many years of development, it was introduced by RCA in the early 1930s. What are the chances that a mic design that goes back nearly a century would still be one of the best-sounding mics you can buy? I attribute that to Harry Olsen, the scientist at RCA who spent years perfecting the sound.

The 44 is well-suited for vocals, since it was designed for broadcast use. It has a variety of layers of protection for the ribbon that makes it suitable for fairly close mic’ing of a voice. It’s still possible to pop a 44 if you get too close or if the vocalist tends to emphasize “Ps” or other plosive sounds. But no more so than most large-diaphragm condenser mics.

You probably use some sort of wire, cloth, or foam pop filter on your condenser mics to minimize the pops. You may not need that on a 44 for a couple of reasons.

One is the built-in pop filtering, but the other is that you should not work a 44, or any ribbon mic, like you might a SM58 on stage. Some inexperienced singers will try to do this, but it will sound awful and everyone will realize it right away. Give the mic some distance.

How far? It depends on the singer, the room, and the material, of course. But I would say rarely closer than a foot away. Typically, I have singers about 18 to 24 inches away. At that distance, proximity effect is not as pronounced, and the singer is unlikely to pop the mic. Ribbon mics always sound “closer” to the sound than their physical distance would suggest. Eight inches between a vocalist and a ribbon mic is about as close as you would ever want, and it sounds to me like the intimacy you get at that distance is equivalent to a condenser mic at 4 inches or less. Working any mic that close requires really good mic technique from the singer.

How about an electric guitar? Put the mic where you normally put your SM57 or whatever you typically use. Too close can sound bad, so I would avoid putting the mic right up against the grill cloth. But you can safely get pretty close, even to a loud amp. However, if you can feel air movement at the mic distance, it is too close.

Acoustic guitar? Frankly, I use a condenser half the time and a ribbon the other half, depending on the instrument, the player, and the music. Getting a ribbon mic close enough to achieve an intimate guitar sound is sometimes a bit too close for a ribbon.

If the instrument is thin sounding, with more treble than bass, a ribbon can do wonders. On the other hand, a guitar with a lot of low end is going to take a ton of eq to tame, and the ribbon mic’s proximity effect is not going to help.

When I do use a ribbon mic on acoustic, I tend to use a Royer R121, which is small and easy to place and doesn’t get in the way of the player like a larger mic might.

I could do an entire episode on mic’ing drums, but my favorite technique is to use one stereo ribbon mic in front of the kit, maybe 5 feet or more away, aimed horizontally, and positioned vertically to get the desired kick drum balance with the rest of the drums and cymbals.

This technique can be challenging, since it can take some time to find the right placement. I always use two figure-8 ribbon mics at right angles to each other, in the Blumlein configuration. That means that the mics will pick up equally on their back side, so consider what is happening there. It could be a problem of isolation from other instruments, or there might be a reflection off a wall that doesn’t sound good.

This also requires a drummer who plays the various drums and cymbals in a proper balance. You have almost no control over the mix with this approach. I would guess the majority of drummers cannot do this, so you may have to augment the sound with some spot mics. Usually the only spot mic I use on a drummer is a kick drum mic, for those times when you need more control of that sound.

The Hazelrigg Brothers record their jazz trio with two stereo R88 ribbon mics. One is over the piano, and the other is in between the drums and the upright bass. The sound is very cohesive and natural.

A piano mic’d with ribbons sounds great to me. The characteristics of the ribbon mic seems to complement the piano very well. Where to put the mics is a topic in itself. We made a video about how we do it, using a stereo ribbon mic. The link to  that video is in the description.

It can be challenging if you have to record a vocalist who is simultaneously playing acoustic guitar or similar stringed instrument. It is difficult to get good isolation between the two sources, and the arrival time difference between the two mics degrades both the vocal and the guitar. My preference is to record the vocal and guitar separately, perhaps replacing a version recorded simultaneously. But we do not always have that luxury.

There are ways to improve the isolation, and ribbon mics are the best way I have found to make this work. The concept is to utilize that infinite rejection of the sound off the side of a bi-directional ribbon mic. You want to aim the null of each mic at the center of the voice or guitar. Remember that the “side” means all the way around the mic in that plane. It’s pretty easy to get at least 20dB of separation that way, without too much compromise of either sound.

Of course, there are many other variables. How well-balanced is the vocal and guitar to begin with? If they sing too loud while playing too soft, or vice versa, that might make isolation more challenging. But the isolation is usually better than using cardioid mics, and the off-axis pickup does not degrade the sound as much.

There are many more examples I could give you, but I think you get the idea.

For those new to ribbon mics, please try to resist the urge to immediately go back to your condenser mics. Listen for a while, if the session affords that luxury. You may find that the sound becomes much more acceptable to your ears. And when you go back to condenser mics, you may find them shrill and annoying on many instruments and voices.

As always, thanks for listening, commenting, and subscribing. Your feedback is valuable to me, so let me know what you think of this episode or any other. I can be reached by email at dwfearn@dwfearn.com

And please help this podcast grow by suggesting it to your friends and sharing it on social media. Thanks.

This is My Take On Music Recording. I’m Doug Fearn. See you next time.