Best Type of Microphone for Recording the Classical Guitar
One of the most usual questions I get asked is which microphone is the best for capturing the classical guitar, but as with all deep questions in life, I'm afraid there is no simple answer. Our guitars, nails as well as playing techniques differ vastly. Besides, our rooms have unique properties, and of course, our tastes vary. Another decisive factor is our listening environments, but that's a subject for another day.
I've written on Classical Guitar Tones extensively about the different microphones, brands and models. If you have been here for a while, you've seen me test all sorts of microphones, entry-level to high-end. In this article, I take a step back and present my thoughts on the different types of microphones, their strengths and weaknesses. Plus some words on the different polar patterns.
On being passive
Ribbon microphones have a relatively simple design with no active circuitry and use a thin metal ribbon suspended in a magnetic field. Most ribbon designs hear sound bi-directionally and produce natural and complex recordings. They have the reputation of being fragile and need careful handling and storage.
Dynamic microphones are similar to ribbons as both capture sound by magnetic induction. In contrast, they are very robust, resistant to moisture, and have low sensitivity. In practice, they offer no real asset in classical guitar recordings as their advantages benefit mainly on-stage use and capturing of loud sources.
For the most part, I don't get along well with ribbon or dynamic microphones, mainly because of their sensitivity or lack of. I often play soft passages or employ silence in my music, and with passive microphones, one has to crank the gain on the preamps to get sufficient levels, resulting in unwanted noise. After all, the classical guitar is a soft and delicate instrument, and no matter which preamps you use, it is impossible to get noiseless classical guitar recordings with passive microphones.
Ribbon microphones are also quite forgiving to the various mechanical "non-musical" noises, such as nail and fretting sounds. And this is why some people love them, especially on harsher and louder instruments and a less subtle repertoire. But, I find the response of most but the finest ribbon microphones, principally with the thinnest ribbons (some Royer, AEA, and Samar makes come to mind), quite sluggish.
Phantom power required
Nowadays, there are a plethora of active ribbon microphones, purposed for capturing softer sources and being less dependent on the preamp choice. These tend to work better with classical guitar. Yet, even high-end active ribbon microphones are far from being noiseless. I understand that for some people noise is a nonissue, but for me, it is a distracting element. I like deep blacks and hate when the softer parts or rests are being washed away by preamp hiss.
Also, the figure-eight polar pattern found in most ribbons makes them less than ideal for many recording situations. They do work nicely as a side microphone in an M/S stereo array.
Capacitors move the (recording) world
Condenser microphones require a power source to function and generally produce a high-quality audio signal mainly due to the small mass of the capsule. They can capture on tape utmost detail, sometimes even too much of it, and are the most used transducers in recording sessions and concert halls.
Most of the classic designs have been either tube or transformer equipped condensers, but with the dominance of digital recording, transformerless solid-state condensers have increasingly gained popularity in classical recordings for their additional clarity and lower self-noise.
Size matters
Condenser microphones are categorized by the size of their diaphragm and come in two main types: small-diaphragm, like most Schoeps' and the Neumann KM184, and large-diaphragm, like the Neumann U87 and AKG C414.
So, which one is better for the classical guitar, you may ask? Not so fast. Again, the answer is not straightforward.
Let's talk first about their differences.
Small diaphragm condensers are usually more accurate, with a faster transient response and superior off-axis response. They are also smaller and lighter, so they are easier to carry, besides being visually unobtrusive. The latter is a decisive factor in why SDCs dominate the concert world.
Paying audiences generally don't enjoy seeing a stage the musicians surrounded by several dozens of microphones and bulky heavy-duty stands to support them. Neumann, Schoeps and DPA provide small-diaphragm condenser systems with every possible polar response and mounting option a classical sound engineer might on location.
Polar patterns say more than you think
The downsides of using SDC's on a classical guitar, especially at home, are only a few but nontrivial. Small-diaphragm condensers are tuned for specific roles. Directional microphones are either purposed for close spots on soloists, used in combination with a stereo array at some distance, or for the main pickup and thus are tuned to compensate for the high-end frequency loss that occurs. The result, when used inappropriately, is either a poor low-end response or hyperrealistic recordings with exaggerated high-end. In other words, they can easily sound thin and harsh.
On the other hand, SDCs with an omnidirectional response (the real microphones), especially those that have been tuned for the free field, offer an optimal response at both ends of the spectrum. Additionally, they provide greater flexibility in positioning owing to the absence of proximity side-effects but become a challenge to use in non-treated rooms that universally suffer from early reflections and standing waves.
Microphones with wide- or sub-cardioid polar characteristics come to close the gap, with a better low-end response than their cardioid cousins, some room rejection, and sometimes less pronounced high-end. Unfortunately, small-diaphragm cardioids with such polar patterns are rare, and except for the bargain Line Audio CM3 / CM4, they are always on the expensive side.
So, where does the good old large-diaphragm condenser fit?
Generally speaking, LDC's suffer from a pronounced proximity effect, transient smoothing and suboptimal off-axis colouration. In addition, they require sturdier stands, are more difficult to position due to their size and weight, and can be quite visually intrusive in videos.
All these intricacies cannot be good, right? Moreover, excellent sounding large-diaphragm condensers suitable for the classical guitar are quite rare and expensive, as most LDC's are targeted for vocal pickup.
Any advantages?
As I wrote above, noise on a recording can be distracting. The smaller the size of the capsule, the greater the self-noise of condensers. Tube and transformer-based microphones are also subject to higher noise levels. Therefore, transformerless large-diaphragm condensers have lower noise to signal ratios, with several Gefell, Austrian Audio, and Neumann models reaching nonexistent self-noise figures.
Likewise, many universal studio LDC's grant additional flexibility, as they bring multiple polar patterns, removing the need to own or carry multiple microphones or capsules on a session. With a modern microphone, like the excellent and most versatile Austrian Audio OC818, you can not only choose on the fly between any possible polar pattern, but you can also do it long after the recording has been completed.
Here is my recording of Debussy’s Prelude VIII. Recorded on location with a pair of Austrian Audio OC818s.
Let's proceed to checkout.
One can make a good recording with any decent microphone, some experimentation and post-production skills to boot. There are no excuses for bad recordings in 2022.
On a budget, neither ribbon nor large-diaphragm condenser microphones of decent quality can be found as cheaper offerings are made either for a vintage vibe or vocalists in mind. Line Audio's small-diaphragm condensers are the undenied kings of the entry-level recording setup.
When searching for a high-end classical guitar recording setup to capture a world-class guitarist with a magnificent guitar in an excellent sounding room, a pair of exceptional and well-positioned omnidirectional or somewhat directional condenser microphones is hard to beat. DPA, Gefell, Austrian Audio and several high-end Neumann condensers come to mind. In such a scenario, the size of the diaphragm is incidental. With less ideal conditions, even high-end SDC's on a solo classical guitar, be it directional or not, can expose flaws and produce unattractive recordings.
To conclude, in most situations I favour large-diaphragm condenser microphones for their inherent sound qualities and noiseless behaviour. First-class LDCs can produce a luxurious recording and provide a pleasant listening experience. I also like how they look on videos; unapologetic, proud and predominant, almost commanding. With that said, the realism that some of the best SDCs treat the listener when every element is exemplary can be breathtaking.
Perhaps it is more advantageous to bring together small- and large-diaphragm condensers in an elaborate three- or four-microphone array.
A Three-Microphone Setup for Recording Classical Guitar
An M/S Stereo alternative.
Classical Guitar is a complex and rich sounding instrument; as such, it sounds better when is recorded with at least two microphones. A statement that you must have read several times already if you hang out at this site. Some engineers argue though that guitar is a relatively small instrument which tends to sound too "wide" when recorded with the most conventional stereo techniques; thus sounding unrealistic in playback.
Neumann TLM 193 and TLM 170 in M/S Stereo Configuration
Mid/Side stereo, which I discuss in my Three M/S Stereo Setups for the Classical Guitar article, is usually praised for its truthful representation of the classical guitar. The elimination of phasing problems and the flexibility it offers during mixing are additional important advantages, however, it is not immune to potential issues. Namely, the collapse of the room information in mono reproduction, and the inability to hear the resulted-combined sound without some processing to the channels (or the use of an M/S matrix). Lastly, symmetrical Figure-8 microphones, required for the "Side" channels, with a balanced response are generally expensive.
Alternatively, the combination of a "Mono" microphone placed at close-proximity and a "Stereo Pair" at some distance, shares some similar advantages without the drawbacks of M/S Stereo. Hence the Three-Microphone Setup is an appropriate option for capturing the subtleties of the classical guitar.
Purpose in position
Austrian Audio OC18 - A Large Diaphragm Cardioid Condenser
The "Mono" microphone is positioned close to the instrument (at about 50cm, although some could go as close as 30cm) to capture a full-bodied sound. I recommend a large-diaphragm condenser with a smooth treble response for this position; as not only it will capture the fullest sound, but the slower transient response of the large capsule will also give a less analytic, more relaxed response.
The "Stereo Pair" is placed a little further away to capture the sound of the room. A pair of small-diaphragm condensers is ideal here due to the better off-axis response and can be either Omni or Cardioid patterns depending on the acoustics. The actual distance depends mainly on the room; accordingly, as the distance increases, the height of the microphones should be increased as well. The distant pair brings to the mix crucial depth, space and some high-end articulation.
Decisions; Player vs Audience
Another way to see the three-microphone setup is as a fine compromise between the intimacy of what the player hears and the somewhat distant experience of an audience member.
During mixing, the three channels can be balanced to the desired sound; from close to distant and everything in between. Either the "mono" or the "stereo pair" can be used as the base sound. Think about a mono capture with some extra space or a distant pair with added fulness.
Examples
For the first recording, I used a Neumann TLM 193 relatively close to the guitar, and a wide pair of DPA 4011As as room microphones.
In isolation, neither the Mono signal nor the AB pair sounds particularly great. The first is somewhat plain and too direct, while body and weight are missing from the AB pair. When mixing all three microphones, the combined sound gets defined and three-dimensional; thus more real.
I made another example of the same setup and the exact same distances, this time with an Austrian Audio OC818 in Cardioid for the Mono duties. The AB pair is still the DPA 4011A. If you have read my Austrian Audio OC818 review, you already know that I love their sound, and I wanted to hear how well they can mix with the DPA microphones.
Combining M/S and Room Microphones
A few months ago, I also experimented with combining an M/S pair of Neumann TLM 193 and AEA N8 up close and a stereo pair of Austrian Audio OC818s at some distance, you can hear the result in this recording of Bach's Cello Prelude no.2.
Some things to take care of
If you want to try the Three-microphone setup, it is important to listen to the recording as a whole before committing to any microphone position. The Mono microphone may be judged alone if you plan to use for the main sound, but don't make bold decisions without listening to the combined audio.
Potential phasing nightmares is one of the biggest drawbacks of this setup, so take extra care to eliminate any issue and check with a proper phase meter plugin regularly (read my article on the Three Most Essential Plugins for Classical Guitar).
Lastly, although the recording should be evaluated as a whole, the close and distant setups might need to be EQed separately. Nevertheless, you may apply a catholic EQ with basic filters and sculpturing.
Cheaper Alternatives
Line Audio CM3 - A budget SDC with an surprisingly good sound
Apart from the aforementioned combinations, any microphone could do a decent job. If you just starting and your budget is limited, buy the best large-diaphragm condenser you can afford and a pair of cheaper small-diaphragm condensers, like the Line Audio CM3/CM4 (read my comparison of the Line Audio CM3 and DPA 4011A).
Final thoughts
I've seen mostly AB, XY, ORTF and sometimes M/S setups explored by engineers and home recordists for the classical guitar. All of which can produce excellent recordings given the right circumstances. Yet, I find that with more elaborate techniques I can capture the instrument, at home or on location, with exceptional precision, without any disadvantages. Except maybe for needing more input channels, cables, stands, and more time for the setup.
A Three-Microphone setup can shine in a very wet hall, as it allows us to capture the body and definition of the instrument while including as much ambience as desired. In a home recording of the classical guitar, it offers great flexibility, if not to provide ambience, it combines the intimacy and fullness of a close pick-up with some extra depth provided by the spaced pair.
So, what do you think? Have you tried a three-microphone setup? Which microphones have you used?