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.
6 Common Mistakes When Recording the Classical Guitar at Home, Part II
Part II - Post Processing
Professional sounding classical guitar at home is not a fantasy anymore or at least achieving a recording quality that is not embarrassing to share. Affordable audio interfaces, preamps and microphones have flooded the market these last decades, with increasing performance and processing power. Rooms, recording techniques and mixing are holding us back.
In the first part on the 6 Common Mistakes When Recording the Classical Guitar at Home, I tried to encourage you to try out different microphone positions and to study your room acoustics.
The second part focuses on some of the common mistakes of beginner classical guitar recordists on utilizing a proper signal chain and achieving satisfactory results in post-processing.
Mistake no.1 - Improper gain staging
AEA TRP2 Gain Knobs
The fear of clipping the converters leads some amateur recordists to use too little gain, resulting in recordings that are low in level. Without adequate signal-to-noise rations, these recordings will become noisy when any attempt is made to bring them at a normal level during mixing or playback. Contrarily, recording too “hot” will possibly clip the converters and can introduce nasty sonic artifacts to the audio. In either case, the recording will suffer from a limited dynamic range and high noise; attributes that we don't usually associate high-quality classical guitar recordings.
My advice is to aim between -6dB to -12dB as a maximum peak level (not average), per channel. Therefore, when you are happy with the placing and distance of your microphones, do a couple of test recordings, play as loud as you would normally do and set the gain levels accordingly. If you set the levels correctly, you will have a healthy and strong signal, but even if you (or another guitarist you are recording) eventually get carried away during the performance, you still have enough headroom to avoid digital clipping.
Mistake no.2 - Unrealistic panning
Classical guitar is a small instrument, radiating sound from a definite point in space. One of the worst choices you can make if you record in stereo (which you should) is to use a too wide panning. Regardless of if the listener is an audiophile type, sitting on his couch perfectly balanced in front of a pair of top-tier speakers, or a regular person listening to music with earbuds. A hard-panned left and right guitar will sound unnaturally wide and cloudy.
Proper panning of Stereo AB channels
A realistic classical guitar recording is one that creates a phantom image of the instrument right in the middle of the speakers, but with some space around it. Such recordings can remove the playback medium and transport the listener in the room with the player.
In typical AB Stereo scenarios, I pan one channel at 3 o'clock and the other at 9 o'clock. I fine-tune the panning according to the polar pattern of the microphones, how apart they are set, and the distance from the guitar.
Mistake no.3 - Limiting dynamics
Classical guitar is not the most dynamic instrument, and if anything, we should strive to capture as much dynamic range as possible (it starts from the player, so we should also prioritise dynamics in performance). Compressors, on the other hand, are designed to do just the opposite; minimize the dynamic information of an audio track by limiting the loudest notes and boosting the softest signal.
The classic Universal Audio limiting amplifier
Compressors do make the initial playback sound more exciting and powerful… for a few seconds, but in my opinion, it never pays back. Some of the problems that are introduced with the use of compressors in solo classical guitar recordings are squeezed dynamics, increased noise level and altered instrument tone.
Cross-genre guitarists employ compressors more often, as they learn that they can be invaluable in a dense mix. But I haven't found any use for dynamic limiting in a properly captured classical guitar recording.
Therefore, unless you have to deal with issues of the room or improper microphone positioning, don't use compressors on classical guitar recordings.
Mistake no. 4 - Being afraid of using filters
High-pass filter’s switch on an Austrian Audio OC18
Many microphones feature high-pass filters, the most common are 40Hz, 80Hz and 120Hz; the same is true for some dedicated outboard preamps. But many beginner recordists are afraid to take advantage of them. The truth is that in the context of the classical guitar, not much musical information is presented at the low-end frequencies. Most of what is below around 80Hz is unwanted room rumble and weird resonances; therefore by attenuating them, we end up with a cleaner recording. Capturing what is essential and leaving out the rest.
As low frequencies can have a lot of energy, it is preferable to cut undesirable low-end before the signal hits the converters, if possible. This tactic allows us to set the gain and levels appropriately and leads to better signal-to-noise ratios. But even if your microphones or preamps don't have any filters, you can still apply a high-pass filter in your DAW to remove non-essential information.
I also like to use a low-pass filter to remove high-end information that is inaudible, so that my audio consists of only the frequencies I can hear. A gentle roll-off of the low (below 50Hz) and high frequencies (above 18000Hz) is a good starting point. An EQ plugin with these basic filters is the first plugin I load on every track. You can read more on the article Three Most Essential Plugins for the Classical Guitar.
Mistake no.5 - Not learning how to use an equalizer
Other than the low- and high-end unwanted information that we can simply remove with the appropriate filters, undesirable resonances can occur in the audible range as well. These can be caused by the imperfect rooms that we are recording in, our instruments or our technique. Obnoxious resonances can and will distract the listener.
Learning how to use an equalizer to detect and attenuate or eliminate such issues will make the listening experience much more pleasurable.
The best way to identify an offending frequency is by using your ears. I know that this doesn't sound like great advice, but keep reading. When you detect something that you don't like, add a bell-shaped point on your EQ with an extreme boost and search through the suspected range, like dialling in an analogue radio.
Once you find the irritating frequency, the sound should be quite disturbing at that point, apply a notch or a generous cut with a narrow Q. Toy around with the Q value to find the sweet spot; a setting that makes the problematic sound disappear but lets the rest of the audio unaffected.
FabFilter Pro-Q 3 with HP & LP Filters, a narrow Q Cut and a High Shelf Boost
Another use for an EQ is to change the overall balance of the recording. Sometimes you'd prefer a slightly fuller recording, or there is just a bit too much low-end. Perhaps the treble is a bit piercing, or you'd like to add some more clarity and articulation. Making gentle adjustments like these are generally uncomplicated with the use of Low or High Shelf adjustments. Just a couple of dB's can make a drastic difference to the evenness and impact of our music.
Just be careful not to overdo it, and always compare your mixes to your favourite recordings.
Finally, you can also use an equalizer to completely change the sound of an instrument and shape it to your liking. But if you've been diligent with the microphone positioning, and you like your guitar sound, you won't have to.
Mistake no.6 - Too much reverb
Placing the music into an artificial hall is a necessary lie
As I write on the Three Most Essential Plugins for the Classical Guitar article, nothing will affect the listener more than the physical space that the music takes place.
When we record at home, most rooms are not interesting enough, and so we need to enhance their sound with artificial reverb. But it is easy to overuse reverb, as it makes everything sound "better". Or so we think when we first enter the home recording world.
Most beginner recordists tend to choose a random church preset without any consideration to requirements of the music, tempo and other aesthetic choices. The result is a flood of unnatural and unattractive recordings which instead of sounding realistic or enchanted, they feel cheap.
Learn how the Time, Size and EQ settings found on your reverb plugin of choice to fine-tune the sound the ambience. Then turn down the Mix a little bit more than what you think it should be. Lastly, compare your efforts to commercial recordings (not that those are not guilty of overusing fake church algorithms).
Closing thoughts
Proper mixing can turn a decent recording into a great one
I hope that this article will make you more conscious of your post-processing choices. I need to write dedicated articles for the use of equalizers and reverb as there is a ton of things to discuss.
I know that many guitarists don't want to fuzz around with plugins, but proper audio processing can transform a recording. Mixing is an art in itself; a necessary evil that can turn a decent recording to a great one. Quality classical guitar recordings are important for your audience and benefit the classical guitar community as a whole. Thus, it's definitely worth the time and effort to learn how to mix your audio. Alternatively, you may search for someone else to do that for you.
Tip: You don't have to mix every track from scratch; after all, you probably record the same instrument with the same microphone technique and in the same room all the time. Create a template in your DAW with your basic panning, filter and reverb settings. You'll still have to tweak around a bit, as not every piece favours the same settings, nor every day is the same. Templates are great time savers.
Three M/S Setups for Classical Guitar
Capturing the natural room sound of the guitar.
The Mid/Side microphone technique has almost a century of history. Developed by Alan Blumlein in the early 1930s, it became popular in the broadcast studios because of its compatibility with mono. Even in the recording studio, it appears to have many advantages over the most commonly used stereo techniques.
With small instruments like the guitar, it is easy to capture a too wide of an image, resulting in an unrealistic and often a blurry reproduction, especially with ORTF and AB techniques.
Neumann TLM 193 & TLM 170 in M/S Stereo
The "Mid" microphone of M/S provides a solid capture of the instrument, while the "Side" microphone is responsible for picking up the ambience of the room. The right balance of the two microphones allows for a truthful image of the guitar realistically placed in the sound field.
The M/S technique gives you the most control over the stereo spread, but the best part is that you don't have to commit to any balance until the mixdown, as you can always change the balance long time after the recording is finished.
Things to consider
As the "Mid" microphone is responsible for capturing the actual sound of the guitar, it is essential to take the time and make sure that it's placement is optimal. Otherwise, there is not a lot you can do to fix it. Also, if the room ambience is not pleasant there is not a lot you could do to improve it, so you are better off with a close AB technique and using artificial reverb in your DAW during mixing.
Here is one of several M/S setups that I've tried this week. I placed the "Mid" microphone at a distance of 55cm from the top of the guitar, aiming at the midpoint from the bridge and hole. With the capsule being at 96cm high, slightly angled downwards, placing it on-axis with the angle the I hold my classical guitar.
The "Side" microphone with a Figure-8 pattern was simply placed on top of the other at 90 degrees, aligning the capsules as close together as possible, minimizing phase issues. The whole setup was angled slightly to the sidewalls of my room. The room is medium-sized, with a wooden floor, high ceiling and a few interesting angles on the wall, making it relatively live-sounding.
Austrian Audio OC818 M/S Pair
Austrian Audio OC818 in M/S Setup
In this first example, I used an Austrian Audio OC818 pair with the "Mid" microphone was set to cardioid. The response of the Austrian Audio microphones is fairly natural, especially at the low and mid registers. A slight boost is present at the higher frequencies, but it retains the very smooth character of the classic ceramic capsule, making the classical guitar recording to sound polished and vivacious, without any sign of harshness.
Gefell UMT70s M/S Pair
Gefell UMT70s in M/S Setup
The second example utilises a Gefell UMT70s pair, these mics have a unique appearance, an incredibly small grill and an unquestionably satisfying feeling to the touch, the craftsmanship is second to none. The UMT70s shows a distinct bright character with slightly recessed lows in its cardioid pattern. The Gefell microphones offer coloured pickup but maintain a smooth quality. In a way, this combination produces a somewhat more finished recording, with nostalgic charm, it reminded me of some Julian Bream albums. The result is pleasing but differs from the sound that I hear when I play my guitar, in my room.
Neumann TLM 193 and AEA N8 in M/S
Neumann TLM193 and AEA N8 in M/S Setup
An often overlooked aspect of the M/S microphone technique is that it doesn't require a matched pair of microphones. So for the last test, I decided to combine the Neumann TLM 193 with a ribbon microphone for "Side" duties, in this case, an AEA N8.
The TLM 193 has a natural pickup, with good low-end extension, flat mids and unhyped high-end. The most gratifying aspect of the Neumann is that it captures all the nuances of the classical guitar without emphasising any frequency. Additionally, it is dead silent which enhances dynamic playing styles as it allows the notes to fade to complete silence.
The AEA N8 offers an extended high-end in comparison to more traditional ribbons and a very juicy low end. This combination in an M/S setup produces a bigger soundstage and a sound that is reminiscing of the what I hear when I play.
Conclusions
All three setups can produce high-quality recordings, although the perspectives of their designs are different. I'm used to the Neumann sound, and I gravitate towards that, together with the N8 I think they produce the purest and calmest recording, but with the expense of some definition and the higher noise floor of the ribbon. The Austrian Audio microphones are the most versatile and they take EQ well. They are detailed, without sounding overly analytical, and offer an elegant and smooth sounding result. The Gefell combo sounds like an excellent record from perhaps a different era, but if you love that sound, it is impossible to get it with the other microphones.
Coda
The M/S Stereo technique has the potential to create outstanding recordings, captures a full-bodied and defined sound while eliminating phasing issues. Larger halls and resonant spaces are where it excels as it allows us to concentrate on the recording and fine-tune the balance of ambience and close sound during mixing.