Ultimate‌ ‌Guide‌ ‌to‌ ‌Ribbon‌ ‌Microphones‌

In a market dominated by Dynamic and Condenser microphones, Ribbon microphones are the most complicated and also, in most cases, the most valued type of microphones for professional use.

The ribbon microphone’s diaphragm is designed like a ribbon which gives it its name. Its thin diaphragm, which acts as a transducer, transforms the sound waves into audio signals.

Ribbon microphone’s working principle is based on electromagnetic induction, making them “dynamic.” 

In this ultimate guide to ribbon microphones, we will walk you through the features, functionality, and pretty much every minor detail there are about ribbon microphones.

This guide is all you need to be well equipped with all the knowledge required for any of your future ribbon microphones-related endeavors.

What Is A Ribbon Microphone?

As complicated as a ribbon microphone may look, the definition can be simplified to be easily understood:

A ribbon microphone is a microphone transducer with an electrically conductive and thin diaphragm designed like a ribbon and suspended within a magnetic structure. These microphones primarily work on the principle of electromagnetic induction.

The mic’s diaphragm moves due to the sound wave, which induces an AC voltage across the ribbon through electromagnetic induction. This AC voltage is the mic signal.

The ribbon diaphragm moves in a back and forth motion within the magnetic field, and therefore a mic signal is induced across it electromagnetically. Ribbon microphones can also be called “dynamic ribbon microphones” because moving coil, dynamic microphones also work on the principle of electromagnetic induction.

The ribbon-like diaphragm is generally made from corrugated aluminum. Aluminum remains not only conductive but also strong in the thin ribbon shape for proper movement within the magnetic field. 

I have mentioned below the two primary reasons why aluminum is considered to be an excellent material for ribbon microphones:

• Aluminum has adequate conductivity for ribbon microphones (3.77×107 Siemens/meter).
• Aluminum is light (2.7 g/cm3), helping the diaphragm to react at lower tensions.

If the working of ribbon microphones or the concept of electromagnetic induction still sounds difficult to you, then don’t worry, as I will explain all the different components of the ribbon microphone along with the principle of electromagnetic induction in great detail. 

But let’s go through its history first.

History Of Ribbon Microphones 

Ribbon microphones may seem like some latest technology, but their origination dates back to 1924. A couple of German scientists named Dr. Erwin Gerlach and Walter Hans Schottky invented the first ribbon microphone.

Originally the idea was that a conductive diaphragm while moving in a magnetic field will create audio signals. The diaphragm is made of thin conductive material and suspended within the magnetic structure creates audio (electric) signals when moved by the sound waves.

But still, the ribbon microphones were made commercially available for audio production in 1931. It became possible because of the availability of strong magnets required for ribbon microphones to work practically.

With the new strong magnets, RCA’s Harry F. Olson became a major manufacturer of ribbon microphones and also enhanced its technology. He designed the first commercial ribbon microphone RCA PB-31 which was released in 1931, and it exceeded condenser mics in clarity, frequency response, and realism. 

Ribbon mics had a limited run of 50 units which served as a major step in microphone advancement during that time. Eventually, PB-31 was replaced by the upgraded RCA 44-A (the predecessor of 44-BX) in early 1932. Since then, most ribbon microphones designs are inspired by the famed RCA 44-A.

Components & Working Of Ribbon Microphones

Till now, we have understood that a ribbon microphone consists of a ribbon-like diaphragm that moves due to sound waves within a magnetic structure inducing AC voltage (mic signal).

It’s time to dive into some details of the functioning of ribbon microphones, but before that, let’s get a better grip on its different elements.

The Ribbon Transducer 

The “ribbon transducer element,” also called the ribbon baffle, indicates the whole transducer element of ribbon microphones. The baffle is the most critical part responsible for transforming the mechanical wave energy (sound) into electrical energy (audio).

The microphone has three essential elements:

• Thin conductive ribbon-shaped diaphragm made from corrugated aluminum. 
• Magnetic structure consisting of magnet and pole pieces.
• Electrical lead wires. 

Let’s understand each of these elements separately.

Ribbon Diaphragm

The ribbon design of the diaphragm is what gives this microphone its name: ribbon microphones which tell how important is this part.

Like we mentioned multiple times earlier that the diaphragm is mostly made of aluminum, and it reacts in accordance to the sound wave and moves back and forth to induce AC voltage.

Aluminum is considered best for ribbon microphones because it’s conductive and powerful when shaped like a ribbon. It’s also lightweight and reacts well to different sound pressure levels.

The diaphragm is designed to be very thin, so it reacts correctly to the incoming sound waves. Fragility and conductivity are compromised for movement and accuracy.

Sound waves cause fluctuation in ambient pressure. The two ends of the diaphragm are exposed. The pressure difference between the two exposed sides makes the diaphragm outward and inward in its resting position.

As we know already, the diaphragm is corrugated, and it improves its strength resulting in looser tensioning without any sagging. The corrugation also improves the frequency response process because the low tension lowers the resonant frequency of the ribbon mic below the audible range.

Magnetic Structure

In electromagnetic induction, you need a magnetic field to induce AC voltage (mic signal in this case) from the moving diaphragm. There are a couple of horseshoe-like magnets at both the ends of the diaphragm’s length to create the magnetic field. The poles line up in a way that the south pole is on the ribbon’s one end and the north pole is on the other.

Nowadays, most manufacturers of Ribbon microphones use magnetic pole pieces, which create a surrounding magnetic structure with ideal polarity and magnetic field. 

The primary purpose of these pole pieces is to extend the poles of the main magnet. Each of them connects the same pole on both sides. One connects the two south poles, while the other connects two north poles.

For main magnets, ferrite or powerful neodymium is usually used because they need to be strong for their small size. But soft iron is used for pole pieces as they need higher magnetic permeability to act as “extenders” of main magnets. There are also better materials for pole pieces like alloys, such as  Hyperco 90 or Permendur.

Due to the opposing magnetic polarity on either end of the ribbon’s length, perfect magnetic flux lines are created, which as a result, provides the electromagnetic induction.

Another interesting thing with the ribbon microphone is that the magnetic structure is very close to the ribbon, allowing adequate space for the diaphragm to move while not letting any sound waves pass through the ribbon and magnets.

Electrical Lead Wires

An electrical lead wire is connected at each side of the diaphragm to take the induced voltage (mic signal) created during the electromagnetic induction across the diaphragm and connect it to a larger circuit that leads to the output of the ribbon microphone.

Working Principle Of Ribbon Microphone 

Now that we got an idea of the significant components of a ribbon microphone, it’s time we understand that how all the components work together to convert sound into audio.

Let’s start from where the ribbon microphone gets its name, the diaphragm. For anyone who doesn’t already know, sound waves cause relative changes in ambient pressure from where it passes. The changes fluctuate the localized pressure at precise points in the medium through it passes (in most cases air).

In the case of ribbon microphones, when sound waves reach the microphone, they vary the pressure on both sides of the diaphragm. The pressure difference between the diaphragm’s front and rear moves it back and forth in its resting position.

Generally, ribbon baffles are designed so that both the sides of the diaphragm are equally exposed to sound pressure. This is why it’s a perfect example of a pressure-gradient microphone. Ribbon microphones are bidirectional as they have a figure-8 polar pattern. If it sounds slightly confusing, don’t worry, as I will explain it in more detail later in the article.

One of the significant differences which makes a ribbon microphone different from a dynamic or condenser microphone is that its diaphragm is fixed at its ends but can move under sound pressure change freely. But condenser or dynamic mic’s diaphragm is fixed at its circumference. We talk about this in detail in our what is a condenser microphone guide.

When the ribbon diaphragm moves by the pressure change due to sound waves, an AC voltage is induced across the diaphragm, and this process is called electromagnetic induction. According to electromagnetic induction, when a conductive material (ribbon diaphragm) moves within a constant magnetic field (magnetic structure), a voltage (mic signal) is created across that conductor.

The voltage induced is AC (Alternating current) voltage as the diaphragm moves in back and forth motion. Electric lead wires then take this AC voltage out of the baffle, which is the ultimate mic signal.

It is how ribbon microphones convert sound energy to microphone signals and act as a transducer.

Ribbon Microphone Design Post-Baffle

A ribbon microphone is just not about the element/baffle we just discussed. Pretty much every ribbon microphone has some kind of baffle, but once the mic signal goes out of the transducer, the circuits can vary a lot.

Ribbon transducers do not need electric power to function, and they are inherently passive. In the same way, most ribbon microphones are also passive with straightforward circuits. But it doesn’t mean there are no active ribbon microphones. There are different circuit topologies in the market, including even tube ribbon microphones.

I will take you through the three primary types of circuit paths used in ribbon microphones.

• Passive ribbon microphones
• Active tube ribbon microphones
• Active solid-state ribbon microphones

The circuit designs can be different from the aforementioned circuit designs as it is difficult to cover every type of circuit, but still, it’s enough to get a general idea.

Passive Ribbon Microphones

Most ribbon microphones out there in the market are ribbon microphones. They are simply made of five components:

• A ribbon baffle/element 
• An output transformer 
• An output connector (mostly an XLR), 
• A physical body with a grille to cover the components in a single microphone unit.

In a passive ribbon microphone, the lead wires from the diaphragm complete a circuit with an output step-up transformer.

Output Transformer 

Before I dive into how the output transformer worker let’s see some of the ways it benefits ribbon microphones:

• It protects the mic from DC voltage.
• Increases the voltage of the induced microphone signal
• Keep a match with the induced microphone signal voltage’s impedance (overall resistance of a circuit to current).
• It helps in separating the mic from other electronic devices.

Now let understand the components of a step-up transformer. It has three major components:

• Primary winding
• Secondary winding
• Magnetic core

Just like the ribbon transducer, this step-up transformer also works on the principle of electromagnetic induction.

The electrical lead wires connect the ribbon diaphragm with the transformer’s primary winding. The primary winding is looped around a magnetic core. This winding is generally made of conductive wire like copper. 

The AC voltage in the primary coil received from the ribbon changes the magnetic core’s magnetic field via electromagnetic induction. The significance of magnetic variation depends on the strength of the microphone signal (AC voltage) and the number of turns on the magnetic core by the primary coil.

If all the other factors remain equal, the winding with more turns will induce more voltage, or we can also say a more significant change in the magnetic field. Therefore a “step up” transformer must have more turns in the secondary coil compared to the primary coil to increase the Ac voltage (mic signal).

To simplify, the signal passed from the ribbon transducer to the primary coil, as a result, varies the magnetic field in the magnetic core. Then this signal (voltage) is magnified further and induced across the secondary winding.

With the help of the step-up transformer, the voltage is increased, and hence a greater audio strength is received.

In fact, boosting the signal strength is not the only way it affects the microphone, but it also increases the impedance of the AC voltage. Usually, the low impedance is considered better for microphones, but the increased impedance is generally not something to worry about with a ribbon mic’s output transformer.

A transformer also effectively protects the microphone from DC voltage like phantom power as it only passes AC voltage. The primary reason behind this is that DC voltage will not cause any variations in the core’s magnetic field.

As already mentioned, ribbon microphone diaphragms are made of aluminum; therefore, they are really fragile. DC voltages such as Phantom power can potentially snap, stretch or damage the ribbon if misapplied. Therefore, transformers become a vital part of ribbon microphones to protect the diaphragm from DC voltage.

At last, transformers help separate the microphones from other electric devices and also block radio frequency interference as the secondary and primary do not physically touch one another.

Active Solid-State/FET Ribbon Microphones

In 2002, Royer Labs introduced R-122, a new concept for ribbon microphones. It was the first active phantom-powered ribbon microphone. There are many differences between passive (old school ribbon microphones) and active microphones that we will cover later in the article. Still, we need first to understand the design of Solid-State/FET Ribbon Microphones and how it works.

A passive ribbon microphone has a very simple signal path. The sound waves cause movement in the ribbon, inducing voltage that is then transferred to a transformer to further increase the mic signal. 

But in active ribbon microphones, the transformers have greater turns ratios. This increases the voltage (signal) of the microphone but also, as a result, enhances the signal impedance.

The output of the AC voltage signals increases even further in the transformer’s secondary winding with also a higher impedance. Active Solid-State/FET Ribbon Microphones use an impedance amplifier to help with signal processing.

FET Impedance Amplifier/Converter

The impedance converter or amplifier of an active ribbon microphone aids in converting the impedance (resistance of the current in the circuit) of the signal to a controllable level. 

These IC mainly uses field-effect transistors and act as pseudo-amplifiers that can boost the audio signal’s voltage. They are the active components in active FET ribbon microphones. 

The transistors have three terminals:

• Gate
• Source
• Drain

When phantom power (the powering source in this case) supplies a voltage towards the drain and source terminals, it causes an electrical current between them.

The mic signal received from the secondary coil of the transformer completes a whole circuit with the source and gate of the IC.

The comparatively high-impedance signal (voltage) at the source and gate modulates the lower-impedance current flow between the source and drain terminals.

In simple words, the source-gate is the input with high-impedance input while the source-drain is the output with converter-impedance. The output usually has a stronger signal which benefits the user.

This impedance converter/amplifier efficiently boosts the voltage and simultaneously enhances the ribbon mic signal’s nominal impedance. So this way, the IC increases the compatibility of the ribbon mic with standard mic preamps and makes sure it works properly even without adequate gain or input impedance to get the best possible outcome from the naturally low-output passive ribbon microphone.

DC Power Source

Unlike passive ribbon microphones, DC power is not a hazard for the active FET/solid-state ribbon mics and won’t be harmed by phantom power. On the other hand, phantom power will actually work to run their impedance converters efficiently.

Transformerless Output

You will find it amusing that many solid-state/FET ribbon microphones work perfectly without transformers because of transformerless output circuits. Transformerless circuits are considered to sound cleaner and also save some bucks for the manufacturers.

Active Tube Ribbon Microphones

Just like the first active FET ribbon microphone, the first tube ribbon microphone was also developed by Royer Labs called the Royer R-122V.

Active tube ribbon microphones use multiple transformers and feature a vacuum tube which works as an impedance converter/amplifier just like the transistors for the FET ribbon microphone

Let’s go deep into each of the components of the Active Tube Ribbon Microphone:

The Transformers

The first thing that makes an active tube ribbon microphone unique right out of the bat is the presence of two transformers. You will find both step-down and step-up transformers in it.

As we already discussed multiple times, the step-up transformer boosts the voltage (strength) of the mic signal before reaching the tube.

On the contrary, a step-down transformer balances the signal and impedance before they reach the microphone’s output connector. Unlike active FET ribbon microphones, which get powered by phantom power, the tube microphones use external power supplies. Therefore it also protects the microphone from DC power.

The Vacuum Tube

The vacuum tube in a tube ribbon microphone performs the same job that transistors perform in the FET ribbon microphone. They work both as impedance converters and pseudo-amplifiers. The vacuum tube has four major components:

• Heater
• Anode (positively charged)
• Cathode (negatively charged)
• Grid

The external power supply unit that we discussed earlier efficiently heats the vacuum tube’s heater. When the negative cathode hets heated, it starts to emit electrons within the sealed vacuum tube.

Note: The tube must be vacuumed; otherwise, the air (mainly oxygen) would burn the elements.

The negatively charged electrons are opposed by the cathode (negatively charged) and are drawn to the anode (positively charged). In the most laymen way, electrons flowing is what we say electrical current, and it’s exactly what’s happening here. In a heated tube, a constant stream of electrons is flowing from the cathode to the anode.

The mic signal controls the grid of the vacuum tube, which can also be stated as the tube’s high-impedance input.

The mic signal very effectively opens & closes a grid in the tube. It increases or lowers electron flow in accordance with the input signal’s strength.

So, in conclusion, the input signal present at the grid modulates another signal between the anode and cathode of the tube. You can also state this new signal as the output of the tube. It has a lower impedance and higher voltage compared to the original mic signal.

This is how the tube functions as an impedance amplifier and converter of the mic signal.

The Power Supply Unit

You might wonder why tube ribbon microphones need an external power source while solid-state ribbon microphones are powered by phantom power. The primary reason is that the tubes are needed to be heated in tube ribbon microphones, and phantom power is not strong enough to provide sufficient heat to heat up the tube. 

Electromagnetic Induction

I have mentioned electromagnetic induction in this article almost as many times as ribbon microphones. Now that we have covered almost every type of ribbon microphone, it’s time to understand the main working principle behind it in detail.

Electromagnetic induction was discovered initially by an English scientist named Michael Faraday in 1831. Since then, this principle is employed in many electrical components such as microphone transformers and ribbon microphone transducer elements.

So what’s electromagnetic induction? In the simplest words, electromagnetic induction creates/induces a voltage across an electrical conductor put in a specific position in a varying magnetic field.

There are mainly three situations in which electromagnetic induction occurs:

•  A moving conductor in a stationary magnetic field: This is what happens in a ribbon microphone baffle.
• A fixed conductor within a changing magnetic field: We see this type of electromagnetic induction in both step-up and step-down microphone transformers.
• Any other condition in which there’s relative movement between a conductor and magnetic field.

In the case of ribbon microphones, the electric conductor (diaphragm) moves within the permanent magnetic field made from the magnetic structure of the microphone. 

The magnetic field around the diaphragm keeps changing relative to the ribbon. In a closed circuit, an electromagnetic current is induced across the magnetic field, which is the mic signal in this instance.

The proper definition of Micheal Faraday’s Law of Induction will be:

According to Faraday’s Law of Induction, the magnitude of the electromotive force (voltage) induced in a closed circuit is directly proportional to the magnetic flux’s rate of change that cuts across the circuit over time.

Three factors affect the magnitude of volage induced/produced across the ribbon through electromagnetic induction: 

• Ribbon Diaphragm Conductivity: The more conductivity the ribbon material has, the more the magnitude of induced voltage will be.
• Ribbon’s Velocity: When the velocity of the ribbon’s diaphragm increases, it moves across the magnetic field even faster and, as a result, causes a quicker rate of change in the magnetic flux.
• The strength of the magnetic field: As the strength of the magnetic field improves, you can observe an increase in magnetic flux whenever field lines get perpendicular to a specific area. The change in magnetic flux can be expected to be more in this case.

Note: The number of coils present in a conductor is also among the significant factors in producing/inducing a voltage. 

Dynamic microphones, the moving-coil counterpart of ribbon microphones, feature conductive coils that can more easily create mic signals in a magnetic field. On the contrary, Ribbon diaphragms find it more challenging to produce electrical signals.

The diaphragm of ribbon microphones have a fixed conductivity, and their magnetic structures provide a steady magnetic field. Therefore, the velocity of the ribbon microphone’s diaphragm manages the voltage change across that moving coil.

In conclusion, faster and stronger fluctuations in sound pressure produce more powerful mic signals.

Comparison Of Active And Passive Ribbon Microphones

Till now, we have a decent knowledge about the different types of ribbon microphones. We discussed both the passive ribbon microphone and active ribbon microphones in detail. I will add that most ribbon microphones in the market are still passive microphones, but active mics are also becoming popular.

In this particular section of the guide, I will go through all the similarities and differences between the three types of ribbon microphones: Passive Ribbon Mics, Active Solid-State (FET) Ribbon Mics, and Active Tube Ribbon Mics.

• Transducer Principle: All the type of ribbon microphones work on the principle of electromagnetic induction.
• Frequency Response: All ribbon microphones have dark/natural frequency response.
• Polar Pattern: The polar patterns are bidirectional by nature for all ribbon microphones.
• Output Transformer: Active Tube Ribbon Mics and Passive Ribbon Mics always feature an output transformer, but FET Ribbon Mics can be transformerless too.
• Impedance Converter: Passive Ribbon Mics do not require an impedance converter. Active Solid-State (FET) Ribbon Mics features a Transistor-Based IC, while Active Tube Ribbon Mics features a Vacuum Tube IC.
• Power Source: Passive Ribbon Mics does not require any power source. Active Solid-State Ribbon Mics uses phantom power, while Active Tube Ribbon Mics uses an external power supply unit.
• Output Impedance: It’s low and leveled for both Active Solid-State Ribbon Mics and Active Tube Ribbon Mics. But for Passive Ribbon Mics, it’s low and frequency dependant.
• Audio Quality: For Passive Ribbon Mics, it’s dependent on the preamp; for Solid-State Ribbon Mics, it’s Relatively Cold, and for Tube Ribbon Mics, it’s Relatively Warm.
• Durability: All three of them have fragile diaphragms.
• Price: Passive Ribbon Mics are the most affordable, while Active Tube Ribbon Mics are the most expensive. The Active Solid-State (FET) Ribbon Mics fall in between the other two mics. We have researched and written an article all about how much microphones cost.

Some Problems With Passive Ribbon Microphones

In a passive ribbon mic, the magnitude of impedance depends a lot on the frequency, and the output is very low voltage (low-level signals).

The regular preamps usually used face a lot of difficulty in recognizing the signals from ribbon microphones. There are primarily two reasons for this:

• Gain: Most regular preamps usually can’t offer enough gain to bring the signal of ribbon mics up to line level. While some preamps provide sufficient gain, they are generally near or at the maximum gain where the gain begins to deteriorate the signal.
• Input impedance: The passive ribbon mic’s output (source) impedance usually increases around the lower frequency range. A regular preamp’s specific nominal input impedance might not accurately represent the frequencies in this range. The characteristics of a passive ribbon microphone will change with change in a regular preamp.

The solution to this problem is generally to go for a high-impedance and high-gain preamp, which brings the best out of a passive ribbon microphone and uses its full potential. These kinds of preamps are often made specifically for ribbon microphones. 

The Active Ribbon Microphone

Active ribbon microphones aids in countering the issues of inconsistent and low-level impedance we find in passive ribbon microphones.

The active ribbon microphones are equipped with internal impedance amplifiers/converters that help level the ribbon microphone’s impedance. The impedance converter can be tube-based or transistor-based. Besides that, they also boost the strength of the signal to make it more compatible with the standard microphone preamps.

Features Of Ribbon Microphones

Considering there are so many different ribbon microphones out there in the market, it is not easy to group together the characteristics of each type of ribbon microphone. But ribbon microphones have some general features that are common amongst all types.

Some of the primary features of ribbon microphones:

• Fragility
• Strong proximity effect
• Bidirectional (Figure-8) polar pattern
• Accurate transient response
• Sensitive roll-off of high frequencies

There are some specific features of passive ribbon microphones that are not really beneficial but worth mentioning in this section:

• Variable frequency-dependent output impedance.
• Low Output Levels.

Let’s cover the features we mentioned earlier in a more detailed way: 

Fragility

Ribbon diaphragms are fragile, and by that, I mean incredibly delicate. In fact, they are generally thinner than even a strand of hair. They are tensioned at both the ends of their length.

Even the slightest blow of air or vocal plosives are enough to snap or stretch the ribbon diaphragm if they are powerful. They can rip apart by fine airborne dust particles too.

Storing a ribbon microphone is also not an easy job, and any mistakes can sag the ribbon, which, as a result, will expose it to more and damage and also decrease its effectiveness. 

As mentioned in the previous sections of this article, DC voltages like phantom power have the ability to harm a ribbon diaphragm. It usually happens when an electrical surge or hot patch sends an unstable DC voltage through the transformer directly to the ribbon diaphragm.

But don’t worry; there are few effective steps you can take to ensure your ribbon microphone’s safety. We will cover it later in the article in a separate section. 

Bidirectional (Figure-8) Polar Pattern

The way ribbon microphones are designed, they are the perfect examples of pressure-gradient microphones. The rear and front of the ribbon microphone’s diaphragms are equally exposed to any variations in the sound pressure. The exposer of both ends ribbon diaphragm to the varying sound pressure is facilitated by the fact that it is kept inside a magnetic structure.

To understand the reason behind the ribbon mics having a bidirectional polar pattern, we need to look at some different situations.

First, we will discuss the bidirectional polar pattern of pressure-gradient ribbon mic when the sound source is in the front:

In this specific situation, the sound waves collide with the ribbon diaphragm’s front, and then after a specific time t, they eventually collide with the ribbon diaphragm’s rear. It implies that one sound wave alone causes both amplitude and phase differences between the two ribbon diaphragm’ sides. 

It is mainly the difference in the pressure of the sound between the two ends that makes the diaphragm move and, as a result, put out a  mic signal.

It should also be noted that when the ribbon diaphragm is pushed toward the rear (inward), the signal achieves a positive polarity.

Now, we will discuss the bidirectional polar pattern of pressure-gradient ribbon mic when the sound source is in the rear:

There’s plenty of the same things that happen in this situation too. The sound waves coming from the rear collide with the ribbon diaphragm’s rear initially, and then after a specific time t, they collide with the front. This, again just like the last scenario, causes amplitude and phase differences between the rear and front of the diaphragm. 

It is mainly the difference in the pressure of the sound between the two ends that makes the diaphragm move and, as a result, put out a  mic signal.

When the ribbon diaphragm is pushed towards the front(outward), the signal creates negative polarity.

Lastly, we will discuss the bidirectional polar pattern of pressure-gradient ribbon mic when the sound source is in the side:

When sound waves collide with the pressure-gradient, bidirectional ribbon microphone from the side, they will simultaneously reach the diaphragm’s rear and front. It will put the same amount of pressure at both the sides of the ribbon diaphragm and cause no movement whatsoever. 

Without movement, there won’t be any mic signal which means that the microphone will have no sensitivity to any sound coming from the sides.

This situation causes the bidirectional or figure-8 polar pattern. As ribbon microphones are originally designed like this, they naturally have figure 8/bidirectional polar patterns.

Note: The bidirectional pattern’s front yields a positive polarity signal while the rear yields a negative polarity signal.

Strong Proximity Effect

All the pressure gradient microphones have a natural tendency to show the proximity effect, which increases the microphone’s bass response as the source of the sound gets closer.

Roll-Off Of Higher Frequencies

As the frequency increases, the ribbon microphones tend to become less sensitive.

Four factors are affecting the high-end roll-off in ribbon microphones:

• The lightweight ribbon.
• The uneven shape of the diaphragm.
• Proximity effect.
• The phase relationship between the back and front of the ribbon diaphragm.

This roll-off of high frequencies pushes the microphones out of favor at a certain point in time. In the early days of analog recording, condenser microphones became practical; they were considered to be a much better option compared to ribbon mics. It is because analog recording used to feature a high-end roll-off too. The condenser microphones’ brightness also aided in mitigating an overly dark recording.

But now that analog recordings are a thing of the past, and digital audio recording has taken over, which are, by the way, are “bright” and “perfect.” 

The ribbon microphones are back now as their inherent darkness helps to mitigate the bright digital audio recordings.

Accurate Transient Response

The low tension and thinness of the ribbon diaphragm give the microphone its ability to be highly reactive to sound waves. The ribbon diaphragm movement represents the transients (peaks in sound pressure variation) perfectly.

Important Safety Measures For Ribbon Microphones

I think it’s almost clear so far that microphones are delicate. Therefore I have made a list of some of the safety measures you can for your ribbon mic and also some of the things you must avoid.

Things To Do For Ribbon Microphone Safety

• Always use a pop filter while recording your vocals. It’s a protection filter for microphones that reduces popping sounds caused by the mechanical impact of plosives during recording.
• While working in a windy environment, always use a windscreen. It also reduces undue pressures on a microphone baffle.
• When recording loud sound pressure level (SPL) sources position the mic off-axis manner.
• Makes sure to use high-quality mic cables with the right type of wiring.
• Always use “mic sock” when taking a ribbon microphone from one place to another.
• While not in use, store the ribbon mic upright and adequately.

Things Not To Do For Ribbon Microphone Safety

• Never put the ribbon mic to blasts of air.
• Never hot patch the ribbon microphones with phantom power (DC power).
• Don’t allow any foreign particles to be subjected to the ribbon microphone.
• Don’t “mic drop” a ribbon microphone.

You will have a higher chance of keeping your microphone safe by following the above safety tips. Just remember that ribbon mics are not made for rough use, especially the diaphragm; they are easy to snap, stretch, snap, or damage. 

Taking the aforementioned steps will increase the longevity of your ribbon mic by at least a few years.

Applications Of Ribbon Microphones

Ribbon microphones are among the most technologically advanced and sophisticated microphones available in the market. They are used in multiple ways by audio engineers in the studio environment. 

In fact, they are used in live stage performances as well sometimes, but in some applications, microphones absolutely excel. So let’s see some of the effective and popular ribbon mic applications:

• Brass
• Vocals
• Drum overheads
• Guitar amplifiers

Vocals

If you ever use ribbon microphones, one of the first things you will notice is that they sound very natural.

But due to the ribbon microphone’s fragility and bidirectional (figure 8) pattern, it is not used a lot in live performances. When it comes to gain-before-feedback in the presence of stage monitors, the bidirectional patterns are disastrous for it. 

Due to the fact that ribbon mics are so delicate, they are not a great choice to use on stage as they are very prone to damage (which is a disaster during a live performance).

But when it comes to studio usage, ribbon mics are great for both voiceover vocals and signing vocals. Still under studio condition, too, It can be damaged while speaking/singing if proper safety measures are not taken.

Some of the best safety tips are using a pop filter or using the mic slightly off-axis.

Brass

When it comes to capturing brass instruments with proper clarity without losing their character, the ribbon mics truly excel. The accuracy combined with the ribbon mics’ slightly dark/natural character emphasizes the brass instruments exceptionally well and adds a whole new life to your recordings.

Drum Overheads

Condenser microphones have always been considered to be the first choice for drum overheads, but ribbon microphones excel in this area too. Ribbon microphones’ neutral sound of a pair of mics has the ability to capture the complete character of a full drum kit within the stereo.

Guitar Amplifiers

It’s not a secret that guitarists just love ribbon microphones. Any guitar amplifier sounds incredibly well via ribbon mics. Any standard ribbon microphone captures the amplifier’s authentic sound easily. It also does a great job of capturing the airiness of a room without being too bright.

Differences Between Dynamic & Ribbon Microphones

Both ribbon microphones and their moving-coil counterparts dynamic microphones work as a transducer to convert sound into audio. Ribbon microphones and dynamic microphones both works on the same principle of electromagnetic induction.

Now, It is probably some of the very few things you will find common between these two microphones (even though it’s a big one). 

The difference between these two microphones is enough to separate them from each other. One of the most obvious differences is the transducer element’s design. 

The moving-coil dynamic microphones feature a conductive moving coil attached to a diaphragm which is non-conductive. On the contrary, the ribbon microphones have conductive ribbon-shaped diaphragms. Our complete article on what is a dynamic microphone goes into more detail.

I have listed some of the primary factors differentiating between ribbon mics and dynamic mics:

• Conductive Element: The Dynamic Microphones has a coil attached it the diaphragm as its conductive element. For Ribbon Microphones, it’s the diaphragm itself.
  
• Sensitivity Ratings: The sensitivity rating is low for dynamic microphones but even lower for ribbon microphones.
  
• Transient Response: The ribbon microphones have natural Transient Response, while the Moving-Coil Dynamic Microphones have slow Transient Response.
  
• Frequency Response: Moving-Coil Dynamic Microphones give out colored frequency response, but Ribbon Microphones have a natural, high-end roll-off.
  
• Active Or Passive: Moving-Coil Dynamic Microphones are always passive, but Ribbon Microphones can be both active or passive.
  
• Transformer: The moving-coil dynamic microphones can be either with transformer or transformerless. In the case of ribbon microphones, the passive ones always have a transformer, but for active ribbon microphones, the solid-state ones can be transformerless too sometimes.
   
• Polar Patterns: The polar patterns for Dynamic Microphones are either Omnidirectional or unidirectional, but never bidirectional. On the contrary, it’s Bidirectional by default for ribbon microphones, but other patterns can be achieved too. 
  
• Durability: Moving coil dynamic microphones are inherently very durable because of their design; on the other hand, the ribbon microphones are pretty fragile.
  
• Price: When it comes to price, dynamic microphones are slightly more affordable than ribbon microphones.

Differences Between Condenser & Ribbon Microphones

Audio engineers cherish both the ribbon microphones and condenser microphones for different reasons. These two microphones are different from each other in many aspects. Our write up on the differences between condenser and ribbon microphones may come in handy here.

One of the primary differences between these two types of microphones is the transducer principle. Ribbon microphones work on the principle of electromagnetic induction, while condenser microphones use electrostatic principles. 

Besides that, there’s a difference in their element design, too, as ribbons microphones feature conductive ribbon-shaped diaphragms within a magnetic structure. In contrast, condenser microphones use a parallel-plate capacitor-like system.

I have made a list of some of the most significant differences between condenser and ribbon microphones:

• Transducer Principle: Ribbon Microphones work on the Electromagnetic induction principle while the Condenser Microphones apply Electrostatic principles.
  
• Active/Passive: Ribbon Microphones can be both passive and active, but the Condenser Microphones are always active.
  
• Frequency Response: Ribbon Microphones have a natural frequency response. The Condenser Microphones have a Flat/extended frequency response.
  
• Transient Response: Ribbon Microphones are known for their accurate transient response, while Condenser Microphones have a fast transient response.
  
• Polar Patterns: Ribbon Microphones tend to have naturally bidirectional polar patterns, but the Condenser Microphones have All polar patterns, especially with the dual-diaphragm capsule.
  
• Sensitivity: Ribbon microphones usually have really low sensitivity, but the sensitivity can be high too if it’s active. Condenser microphones have high sensitivity.
  
• Self-Noise: Condenser microphones have self-noise. There’s no self-noise in the case of passive ribbon microphones, but in the active ones, there is self-noise. 
  
• Max Sound Pressure Level: The maximum sound pressure level in ribbon microphones is usually too high even to measure. But for condenser microphones, the maximum sound pressure level is generally within the practical limits.
  
• Transformer coupled output: For passive ribbon mics, there is always transformer-coupled output, but for active ribbon mics, it’s not a necessity. In condenser mics, there is a transformer-coupled out in some cases.
  
• Durability: We already know that ribbon mics are fragile, so you can’t expect much durability, but the condenser mics can be somewhat durable.
  
• Price: The ribbon mics are usually moderately priced in comparison to the condenser mics. In fact, condenser mics are available in many price ranges.

Frequently Asked Questions

We have covered all the necessary things you need to know about ribbon microphones and their different types, along with how they work. In the end, I just want to add some related questions to this topic that are frequently asked.

Further reading:

• What is a Cardioid microphone?
• What is a Supercardioid microphone?
• What is a Hypercardioid microphone?
• What is an Omnidirectional microphone?