Tuesday, September 12, 2023

What is a good low noise microphone for field recording?

This is another blog post in my everyone-asks-this-question-a-million-times-so-now-I-can-just-link-them-here series (patent pending). The problem with most such questions asked on social media is that not enough information is provided. Answers depend on the use case, available equipment, and budget.

All prices provided are for two mics, since I assume that stereo recording is desirable. 

Note that I have used very few of these mics in practice but have been aware of their performance for, in some cases, decades. Here I am compiling the expert opinions of others, based on my training as an audio engineer.

We can start by assuming a condenser is the best microphone variety to choose. These require some sort of powering, either 48 V phantom power or 5 V plug-in power (PIP). The former is a professional standard on robust XLR cables. The latter is a convenient consumer standard on minijack TRS. Which you choose depends on the recorder you have to use. To increase your options, it's possible to buy a phantom to PiP converter, which both reduces the maximum voltage and converts the plug type.

The next decision pertains to bulk. The three distinct categories are: small diameter, large diameter, and electrets (lavaliers).

Small diameter condensers were often designed for the studio, but certain models are optimised for field work. A common choice of professionals is the Sennheiser MKH 8020 (10 dB-A) at €2500. Combine with a Rycote ORTF blimp (€760) and suitable stand. The cost increases if you want to mount each mic separately for a spaced omni configuration. (Because then you need two smaller blimps.)

This mic has many exceptional qualities. It has minimum colouration in the direct and diffuse fields, so will sound equally good close to a source or further away. This also pertains to the accurate rendering of moving sources. The frequency range extends an octave below and two octaves above nominal hearing, so you can re-pitch material for sound design applications, and still have rich content. The mic capsule is resistant to humidity and hence works in adverse conditions. Finally, it's part of an entire family with different polar patterns, so you can buy a mid-side pair or something else.

Schoeps mics are great in a concert hall, but hate humidity and have more self-noise.

Another option is the Audio-Technica AT 4022 (13 dB-A) at €760. That company used to sell lower noise mics but they are all discontinued. This is possibly because their frequency response wasn't that consistent (I own a pair of 3032) but nonetheless it would be nice to have the choice.

Large diameter condensers are, well, large, being designed for studio use. They are often more susceptible to handling noise and can be difficult to accommodate in a blimp (which is essential for wind protection).

The Lewitt LCT 540 S is likely the quietest microphone in existence, advertised as being below the threshold of hearing (4 dB-A) at €1400. The Rode NT1-A (5 dB-A) is popular due to its bargain basement €360, which is amazing for the quality.

Electret mics are commonly based on the Primo EM 272 capsule (14 dB-A) due to is affordability and low power requirements. Several small companies make these, often as cottage industries. Depending on your location and availability, choose from Immersive Soundscapes (France), Audiotalaia (Spain), LOM (Slovakia), Micbooster (UK), and Sonorous Objects (New York). Disclosure: I have endorsed a couple of these brands, but only because I'm a happy customer. 

These will run you €80-125 depending on fittings. Some are made to put in your ear for binaural recording, others come ready to clip onto objects. All are tiny and conveniently run on plug-in power (PiP), allowing the use of small recorders and hidden mic placement. You can carry them everywhere, every day, unlike larger rigs. But don't expect them to have smooth frequency plots, good impulse responses, or the lowest noise... though they aren't bad!

Final word

Though I've used dB (A-weighted) as a measure of noise, this is only for convenience, since manufacturers readily provide this number. But in truth it's not that useful a measure. For one, it's based on experimental results published in 1933 that have long been superseded.

More important, two microphones will sound completely different even with the same dB-A number, because this says nothing about the frequency distribution of the noise.

Audio recording is a lot more complicated than simply "what is the best". For every answer there are provisos and limitations.

The reason that the MKH 20 is the gold standard is not because it's got the lowest self-noise. But because it has sufficiently low noise while being easy to rig, robust, and great sounding. In the field you will never need the lowest self-noise because real life has more acoustic activity than a dampened recording studio.

This doesn't stop people chasing numbers and ideals of perfect, but maybe it should. 


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