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Recording, Microphones, Preamps, and Audio Interfaces


Bawu in f made of bamboo with added key

Since the COVID-19 outbreak, many more people are video conferencing. More musicians are also recording from home. Such users are discovering that recording audio is not a point and click activity.

There are a multitude of reasons that recordings turn out poorly. Common ones include:

I will consider some of these points in turn. The places where we live can be quite noisy. There may be traffic outside, people or animals inside, heating systems, air conditioning, refrigerators, all the way down to sounds produced by compact fluorescent and light emitting diode light bulbs. Many of these things we simply cannot control. The best we can do is try to avoid the sounds and insulate ourselves from them. To this end try to record in a room with the door closed, and at an hour when not much else is going on. You can go one step further and try to give the room some home-style soundproofing and acoustic treatments. This can take the form of pillows by the door, and blankets or mattress foam on the walls. This will help decrease the volume of the ambient sound, and reduce unwanted reflections of sound in the room. Having more objects in the room, such as coat racks complete with coats, again helps reduce unwanted reflections. However you should ensure that those objects do not vibrate or make noise when you play music.

Now on to microphone placement. We all have some experience with mics, however, we tend to forget these things when recording. From experiences on speakerphones we know that when the mic is far away from the sound source, the recorded sound is much quieter than when it is close. Instead of putting this knowledge into action, we revert to instincts based on our own hearing, and thus we expect some decrease in volume, but not to the extent that generally occurs. Mics do not necessarily match the sensitivity of our ears, and tend to drop off much faster. Thus, people are still surprised when they try to record music with their phone and place it several feet away and the sound that is recorded is quieter than they expected. The lesson is that when recording acoustic instruments and using a cellphone or laptop mic, is is important that the microphone is close to the instrument. If the instrument is quiet, such as a clavichord, it should not be further away than the distance to your music stand. The exact placement of the microphone can be very important. I am certain that you have seen microphones suspended from the ceiling in concert halls, or on large boom stands. In such situations they can place the mics anywhere they want. They choose those locations, as that is the location that has the sound they are seeking to capture. Recording at home is no different, certain places have the sound you are looking for and others do not. Two good places to record woodwinds are a few inches to the side of the body of the instrument, and a few feet in front of the instrument at about the height of your head pointing downwards towards the instrument. It can be difficult to find a place to put your cellphone or laptop while recording. Putting on the floor can result in unwanted low frequency noises. Tables can be ok, but usually involves you positioning yourself around the table, which is not always possible. If low frequency noises are a problem you can try to place the microphone on top of a soft pillow. (Be careful to ensure that the laptop is still properly vented so that it does not overheat.) This can help absorb some of the vibrations. Large instruments, such as a harpsichord need the microphone placed in such a fashion that the various sounds of the instrument are equally picked up by the mic. This may require more distance from the sound source than a cell phone or laptop mic / preamp can really handle.

If you have taken care of the basic environmental sounds and worked with mic placement, and are still unhappy with the recordings when you play them back on your machine, it is time to start considering a better microphone. (It is important to note that a microphone will not correct issues relating to the encoding and transmission of the data. Voice communication over the telephone has a low frequency cutoff, and thus it sounds high pitched. Video conferencing services such as Zoom and Skype have very much the same issue. The sound is also compressed in various ways. Those audio problems are the result of the services, and not your gear.)

So what kind of microphone should I buy, you may be thinking. Well, there is no single correct answer, just as there is no single correct answer of which instrument you should purchase. On this page I provide some information about microphones that can help you make an informed purchase. I also provide some recommendations to mics to audition. Purchasing a microphone without listening to it, is like purchasing a painting sight unseen. It is simply unthinkable.

Microphones are transducers, that transform kinetic energy (sound waves) into electrical energy. There are four main types of microphones that are used in recording music:

Condenser microphones are the most prevalent type of mic in music recording. Examples of famous condensers include the Neumann U47, Neumann U87, Neumann KM84, AKG C12, and the Schoeps CMC5 with MK4 capsule. The condenser mic was invented in 1916, by E. C. Wente at Western Electric. However, it took until 1928 for the first commercial condenser mic to be produced, the CMV3 by Georg Neumann. The transduction takes place in the capsule of the microphone. It contains two charged plates, one of which functions as a diaphragm. The pressure of a sound wave moves the diaphragm, and thus the two plates move closer or further apart from one another. This change in distance results in a change in voltage across the plates. Plates and voltage may sound familiar to those who have studied electronics. It is the concept of a capacitor, and indeed condenser microphones operate as capacitors. In fact their name comes from the fact that condenser was an early name for a capacitor. The signal produced by the condenser has a high impedance, which may be thought of as the resistance of flow of the AC current. Such signals are more prone to interference and external noise than low impedance signals. In addition, microphone cables have capacitance. When used with high impedance signals they act as low pass filters, eliminating important high frequencies from the signal. Thus, it is desirable to lower the impedance of the signal. In early condensers the electronics used to accomplish this were made from vacuum tubes. In many modern mics the vacuum tubes have been replaced with field effect transistors (FETS). In a tube the negatively charged electrons flow from the cathode to the annode. A triode type tube has a third element, a metal grid which is placed between the cathode and anode. This grid takes the signal from the capsule and modulates the flow of the current between the cathode and anode. Thus it imparts the capsule's signal on the current. FETs operate in a similar fashion. Current flows between a source and a drain. A gate takes the signal from the capsule and modifies the conductivity of the circuit. The resulting signal has lower impedance and usually higher amplitude than the signal from the capsule. Thus, the circuitry acts as a pseudo-amplifier. For this reason condenser microphones are the most sensitive of the four types, they produce the strongest signal based on sounds of equal amplitudes. Thus, they need less external amplification. Condenser microphones need power to run this circuitry. This is typically provided by what is known as 'phantom power' which is sent through the microphone cable. (+48V Phantom power was another Neumann innovation.)

Ribbon mics have gone in and out of fashion. They are currently widely used, but require more care and special equipment than condensers. Examples of famous ribbon microphones are RCA 44BX, Coles 4038, Beyerdynamic M160, Royer 121, and the AEA R84. Ribbon mics were invented at Telefunken by Drs. Walter H. Schottky and Erwin Gerlach in the early 1920's. Dr. Harry F. Olson was designing ribbons mics at RCA Research not long after that. The fruits of his labor were realized in 1931 with the RCA Photophone Type PB-31, the first commercially produced ribbon mic. Ribbon mics have a thin corrugated metal strip which is excited by the sound wave. The ribbon moves through a magnetic field and thus results in a current. Ribbons produce a weak signal. For this reason they need a preamplifier that can produce a lot of gain without imparting a lot of noise. Alternatively you can purchase some of them with circuitry that is similar to the condenser microphones. Microphones that have it are called active microphones, and ones that do not are called passive ribbons. Surprisingly, this is a relatively new invention, and was developed by Royer Labs within the last 20 years. Ribbon mics are much more fragile than the other types of microphones. A breeze can damage the ribbon and render the microphone useless. Even plosive consonants, such as p, can damage the ribbon. Thus care must be taken when being handled, and to protect them from such things as singers being too close to them. In general when used by singers, a pop filter is used to shield the microphone from their breath. They must also be stored in an upright position, or the ribbon will sag. Despite all of this, ribbon mics have a big upside, they create highly musical signals. In general they are warm and dark, with an accentuation of low to mid range frequencies. Some of the fast sharp sounds like esses are smoothed out by ribbons.

Dynamic mics are the ugly stepchild of the mic family. In general they are less sensitive than the other types, and do not quite have the beauty in their sound that ribbons have. However, they are very sturdy and see a lot of use on stage as the type of handling that occurs there would destroy other types of microphones. The Shure SM57, Shure SM7B, Sennheiser E835, Sennheiser MD421 II, and Electrovoice RE20 are some of the best known mics of this type. The first commercial dynamic mic was produced in 1931 by Western Electric, although they were patented by Ernst Siemens back in 1874. (It took from 1874 to the 1930s to develop the necessary technology in manufacturing magnets to make dynamic microphones commercially viable.) Dynamic microphones have a thin flexible diaphragm that is set in motion by the sound wave. A coil of wire is attached to the back of the diaphragm. It is moved through a magnetic field which produces an electric current. The coil is a more efficient transducer than a ribbon, and thus dynamic mics can have a somewhat better signal than ribbon mics. Generally they are able to withstand high sound pressure levels that would damage other types of microphones. This makes them useful for recording drums and other loud instruments. They also do not need an external power source.

Piezoelectric are a specialized type of microphone. They require contact with a surface, such as a wall or the body of an instrument. The particular models are generally not as well known as the other types of mics. The Trance Audio Inducer, Barcus Berry Planar Wave, and Ehrlund EAP are some of the best known piezoelectric mics. These mics contain crystals that produce a voltage when they are subjected to pressure, a phenomena known as the piezoelectric effect. In modern musical settings they are typically used in contact microphones (some cell phones have MEMS peizo mics). Contact microphones are placed on an instrument and pick up the sound from its surface. For example, there are contact microphones for guitars that take the place of the saddle under the strings. Peizoelectric mics have a high impedance. Bog standard preamplifiers do not work well with them, cutting off the low-end frequencies. Thus, like ribbons, a special or high-end preamp is needed.

There are several other types of microphones, but they are not as commonly used in music. These include laser microphones, and liquid microphones.

Microphones are classified in terms of the size of the diaphragm, in addition to the type of transduction discussed above. In general they are grouped into two sizes, small-diaphragm, and large-diaphragm. Small-diaphragm mics produce a more accurate reproduction of the sound, but in general produce more noise in the signal. One reason for this is that the smaller diaphragm is better able to respond to the force of the wave, and thus can capture the high energy short duration sounds known as transients more quickly than large diaphrams. Small-diaphragm mics tend to be noisier than large-diaphragm mics, as they do not produce as large a signal, and noise is created in the amplification process. Typically large-diaphragm microphones are used to record singers. They are generally not as suitable for instruments with fast transients, such as drums. Many recordings of classical music make use of small diaphragm mics. It is important to note that music is an art. The objective not to capture the sound as accurately as possible. It is to capture a sound that is the most musical. Somewhat similarly, in ribbon microphones the length of the ribbon (and the length of the path around the magnets) influences the accuracy of the reproduction. Longer ribbons, which are approximately 60mm, have the greatest ability to capture high frequency sounds. Medium ribbons, which are approximately 45mm, tend to have a low to mid-range boost between 500 and 5000 Hz, and their response then falls off faster than the longer ribbons. The dual ribbon mics are more colored and have an even more exaggerated mid-range boost.

Microphones differ in how accurately they reproduce sounds at different frequencies, as has been mentioned above. Most microphones are marketed with graphs of their typical frequency response. The x axis represents the frequency of the sound wave. The y axis represents the amplitude. Some of the most accurate are small-diaphragm condenser microphones whose response range is virtually flat across the range of human hearing (roughly 20Hz through 20kHz). Large-diaphragm mics tend to distort the sound more than the small-diaphragms. In particular they color the high end of the frequency spectrum, having a boost in that register followed by a roll off. This can be desirable in certain circumstances.

Microphones have what are known as polar patterns, the direction from which they pick up the sound. Omnidirectional microphones pick up sound equally from all directions. The capsules in these microphones are sealed. The diaphram responds to the pressure of the surrounding air. This pressure is present in all directions around the diaphragm, and thus the microphone has an omnidirectional polar pattern. Figure eight microphones pick up sound from the front and from the rear, but not from the sides. The capsules or ribbons of these microphones are open on both sides. They do not respond to the pressure of the air, but rather the difference in air pressure between the front of the diaphragm and the back of the diaphragm, known as the pressure gradient. Some ribbons are so light that they respond somewhat to the velocity of the air itself. As they respond to the difference in front to back pressure, they have less of a response to pressure from other directions. Hence the figure eight pattern. Ribbon mics almost universally have figure eight polar patterns. Cardioid microphones have a heart shaped polar pattern that picks up sound from one general direction. These microphones are a combination of the signals of a figure eight and omni designs.

Cardioid and figure eight microphones have what is known as the proximity effect. If they are placed close to a sound source, the amplitude of the bass frequencies are increased. In this way record engineers can manipulate the placement of the microphone to change the color of the sound. The sound color can also be manipulated by using a carioid mic off-axis, getting sound from the edge of its polar pattern.

An important part of recording classical music is recording the ambient sound in the room, and the reverberation and reflections of the sound. An aspect that is related to this is capturing a stereo signal. In early recordings of music, omnidirectional mics were used. They picked up the ambient sound, as well as the music. Two omnidirectional mics that were placed a distance from one another could produce a stereo image. This is known as the spaced omni technique. Other stereo techniques were developed such as ORTF, X/Y, mid-side recording, and Blumlein. I will not go into those here. More emphasis today is placed on changing the sound after it has been recorded. To facilitate this it has become the norm to mic each instrument or group of instruments, as opposed to capturing the stereo image in the room. It is desirable for the microphone to capture as few other instruments as possible, so that the balance of the instruments can be adjusted in post production. For this reason, cardioid type microphones have become very popular. This is not to say that omnis are not used. They certainly are, especially when recording pipe organs, or choral groups. However, cardioids are used quite frequently when recording larger ensembles.

Now that we have reviewed the basic aspects of microphones, we can get down to brass tacks, the ones I recommend that you consider. If you are going to purchase a single microphone ... wait a minute that will never do. Do you have a single instrument? No. Well in any case, what I was going to say was that if you were to purchase a single microphone you may want to consider a USB mic. (I am regretting this more and more as I write it.) They eliminate the need to purchase other equipment to connect them to your computer. They have a downside. They include all of the A/D converters. To keep the costs down, these are not always of the highest quality. Further, each time you purchase a USB mic, you pay for the converters again. Whereas if you purchase a microphone with an XML connector, you do not pay this tax. Also, USB connectors are already becoming obsolete. There is USB c, etc. XML has been around for quite some time. It is used by professionals, and I would expect it to remain in use for quite a while. Getting back to USB mics. Another issue, is that most USB mics are not designed to record classical music. Their audio fidelity is simply lacking. However, if you just need something to plug and play, then you may want to consider the Audio-Technica AT2020 USB. One step up would be the Rode NT-USB. All of this being said, I do not think that USB mics are the way to go. A terrible decision in fact.

If you are on a tight budget and are purchasing your first microphone I recommend the Shure SM57. It is a dynamic microphone. Ordinarily I would not recommend a dynamic microphone. However, the SM57 is a wonderful mic. It has a small diaphragm and is good at capturing transients, such as the attack of a note. It smooths things out just a bit, somewhat more than condenser. It has a mid to upper range boost which gives it a fairly bright character, however, it is balanced by a marked drop in the frequency response in the high end of the spectrum keeping the mic from being too bright. The high frequency drop and somewhat smoother sound can take some of the shrillness out of certain instruments, such as the recorder. It is also very durable and thus is a good first mic.

If you are to step up from the SM57 there are two different paths to take. One has microphones that reproduce the sound fairly accurately. This is the path of the small diaphragm condenser microphones. The other path colors the sound. This path has the large diaphragm condensers and the ribbon microphones.

Small-Diaphragm Condensers

The least expensive small-diaphragm condensers that I would recommend are the Oktava MK-012, which cost approximately $250 each. These mics have a darker sound than many others, and I find it highly desirable. If you want something a bit brighter, in approximately the same price range, I recommend the sE Electronics sE8. (Remember that these are both condensers and they are brighter sounding than other types of mics. Thus, although I say dark, they are dark for condensers.)

One step up from those is the Microtech Gefell M 300. It retails for about $900. This is a really beautiful sounding microphone. Its sound is smoother and darker than the Neumann KM184. I also prefer the Gefell over the Beyerdynamic MC 930. It should be noted that the Microtech Gefell M 300, Neumann KM184, and Beyerdynamic MC 930 are all superb microphones. Choosing between them is a matter of taste.

Above this price point are the most desirable microphones in the class. Two of the top ones to consider are the Schoeps CMC 6 MK 4 (for cardioid), and the DPA 4006 (for omni). Too much ink cannot be spilled over these mics. They are simply incredible and must be experienced. If you want a very realistic sound, then you may want to consider the Earthworks QTC50 which is an omni. It has an amazing clarity. One downside it its small diaphragm size which increases its noise level.

Large-Diaphragm Condensers

A good inexpensive large-diaphragm mic to consider is the Audio Technica 4040. It runs about $300. This is a microphone that has very good characteristics. It has a fairly detailed high end, but also has some warmth and body in the lower registers. Its sound is colored by a 5 db boost around 6,000 and again at 11,000. It rolls off after 16,000. Some professionals use them even when they have many other much more expensive microphones at their disposal.

Moving up from there, you may want to consider the Avantone CV-12. It sells for approximately $500, although there are upgraded versions with better transformers that sell for closer to $800. It has a lot more color than the 4040. It is powered by tubes, and is smoother and more compressed.

One more step up is the AKG C414 XLS. This is the modern descendant of the C12. It is approximately $1,000. It is a very versatile mic. It has a dip in the frequency response around 1,500 Hz. It has a boost around 12,000 Hz and the falls off slowly. If you want something darker then you may want to consider the Neumann 102. It has a flat frequency response up to 5,000 Hz. It then has a slight dip and then a boost at about 8,000 Hz. It keeps this up until 11,000 and falls off at 15,000.

One giant step up is one of the most desirable large-diaphragm mics is the Neumann U67. It is tube powered and has 'it'. You should listen to recordings done with this mic. (Note that this is different than the modern U67 with FET electronics.)

Normally one does not speak of clarity of large diaphragm mics. However in the case of the Neumann D-01 it is appropriate. It is a digital mic, that converts the analog signal into digital form in the capsule itself. It has a very good 28 bit A/D converter, and its sound is very crisp. It should be noted that the mic has not been well received in the press. However, there is a place for its clear tone. Sadly it going out of production.

Ribbon Microphones

One of the better entry level long ribbon mics is the Golden Age Projects R1 MkII. (Note that they make many different models, including the R1 that has active power. Each mic has its own sound. My comments apply to the passive version of the mic.) The R1 MkII is very much what you would expect from a ribbon. It has a warm sound with smooth highs. No harsh esses, or sharp sounds or brittleness. Despite all of this coloration, the sound is still very transparent.

Moving up from there are two excellent medium length ribbon mics. The first is the Cascade Fathead II. It is a dark warm mic, with a slight boost to the mids. It sound is colored more by the lower register than the R1 MkII. The second is the SE Electronics Voodoo VR1 is another great medium length ribbon. It has an extended high frequency response and is more even than most ribbon mics.

If you want an inexpensive dual ribbon mic then the Avatone CR 14 is a good option. Having two ribbons increases the mics sensitivity. However, its short ribbons decrease its high frequency response. In spite of this, it still has a bit of a bright character. Nothing grainy like a condenser though.

Stepping up from these mics there are two classic short ribbon mics from Beyerdynamic, the M160 and M130. The M160 is a hypercardioid microphone, one of the few ribbons designed this way. The M130 is its figure eight sibling. It is dark with lots of lows and is scooped in mids.

Above this range are the top line ribbons. Three staples are the Coles 4038, the AEA R84, and the Royer R-121. The Coles is the oldest of the three, dating back to 1954. It was developed as a microphone for voice work by the BBC, but has seen significant use in music. It is great on strings. Violinist Itzahk Perlman is said to own a pair of them. It has the warmest sound of the three, with the least high end detail.

The AEA R84 was inspired by the RCA 44. If you judged this mic by its frequency response it may not make the cut, as it has lots of ups and downs. However, aurally, it is a wonderful mic. It still has much of the warmth of the Coles, but has more high frequency detail.

The Royer R-121 was the first of the new breed of modern ribbons, and did a lot of repopularize the class of mics. The ribbon is offset, which gives the front and back of the mic very different characters. It has a very natural tone. It does not have as much bass as some other ribbons, but neither is it too airy in the high end. A true modern classic.

Microphones deteriorate with age. Most condenser microphones have charged plates that attract microscopic particles. Over time these particles interfere with the operation of the microphone. Other components such as transformers can also deteriorate. In ribbon microphones the corrugation of the ribbon stretches and the ribbon becomes too lax. This renders them all but useless. In dynamic microphones the diaphragm becomes less flexible.

In addition to their aging, I mentioned before that microphones were delicate. Impacts from drops, humidity, etc. can damage them. For these reasons, you need to be exceptionally careful when purchasing a used microphone. I advise purchasing them new if possible.

So now that you have decided on a mic, what do you do with it? Well, you need to connect it to some kind of recording device. If you are using a computer, you will need a digital interface, which commonly come with preamps. USB 2 and Firewire interfaces are both good options. The Thunderbolt interfaces can transmit more data than the aforementioned connectors, but are not needed. I recommend an interface that has at least 24-bit encoding. The difference between 92 and 192mHz recording options is usually not noticeable. It is probably worth purchasing an interface with at least two inputs, so that you can record in stereo if you wish. However, your use case may differ, and a single input may suit you just fine. Interfaces create latency in the signal. Thus, if you wish to record something and transmit in real time, the interface will create a small delay. The latency can also influence workflows that involve other inputs such as midi signals, or playing along with music that is being played by the computer. Thus, some users may wish to pay a bit more money for an interface with low latency. As a basic interface I recommend the Focusrite Scarlet 2i2 3rd gen. It is inexpensive, and works with Linux. If you want to step up you can purchase the Audient iD4. It has superior preamps and digital converters. If you want a higher end interface I recommend the Universal Audio Twin Apollo X Duo. It has led metering, and an optical input which are not always available on basic units. More significantly it has a fair amount of power for onboard digital signal processing for adding effects to your sound. This can be used to emulate the effect of difference impedence levels, or particular amplifiers.

If you are more selective, then you may purchase a separate preamplifier, and digital converter. I mentioned above that ribbon microphones require a preamp with a lot of gain. Two preamps that have been designed to be used with ribbon mics are the TRP, The Ribbon Preamp, by AEA, and the RMP2, Ribbon Microphone Preamp, by Integer Audio. The TRP is designed by the legendary Fred Forssell. It is a great preamp if you want clean sound, regardless of whether or want to use ribbon mics. Naturally it has plenty of gain. The RMP, is made by in Rochester, home of the famous Eastman School of Music. I guess it is so cold, there is nothing to do but to play music and design great preamps. The RMP does not have phantom power, and thus is truly just for ribbon and dynamic mics. It is good as it prevents accidents involving phantom power that can destroy ribbon mics. However, the unit is a bit less versatile. It also does not have any other frills, such as high pass filters, or metering. The absence of these features keeps the cost low. If you have a ribbon mic, the RMP is simply the right tool for the job. It truly excels at what it does. If you do not want to invest in a dedicated preamp for a ribbon, you may want to consider the Cloud Lifter CL-1. It provides clean gain and can be connected to any preamp with phantom power. Cloud also makes the Cloudlifter-Z which in addition to providing gain, allows you to adjust the impedance to better match your microphone.

You may simply be in the market for a preamp. Grace Design M201 is an exceptionally uncolored preamplifier. It has a ribbon mode button and can easily handle the gain needed for ribbon mics. Other clean preamps in this price range are the Millenia HV-37 and the True Systems P-2. Stepping up are the John Hardy Co. M-1 and the GML 8302, which was truly revolutionary in its day.

Another option is to use a stand alone digital recorder. Several years ago I purchased the Tascam DR 680, so that I could easily record on location without dragging a laptop and interfaces around. It is a good field recorder with four mic inputs. It has a fairly clean preamp and suited my needs somewhat well. One feature that it lacks is the ability to record music and play back another track at the same time. This makes overdubbing less convenient. However, I have found that it is useful to have visual cues when overdubbing, and thus I do not miss the feature as much as I initially thought that I would.

More modern field recorders to consider are the Zoom F6 and the Sound Devices MixPre-6 II Six-Channel Multitrack Field Recorder. If you are in the market for a very high end unit then Nagra is the brand to look for. They invented the portable audio recorder.

That should be more than enough to get you started.


Bawu in f made of bamboo with added key
Bawu mouthpiece and reed
Bawu disassembled in its case
Bawu case
Bawu in f made of bamboo with added key

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