Selecting A Microphone For Recording The Native American Flute - Part 1

There is often a lot of conversation regarding microphones for live play and recording with the Native American Flute. With so many brands and models on the market the initial task of choosing one can be somewhat daunting. Before I go any further it is important that I make some delineations between microphones used for live sound reinforcement and recording. Although NOT highly recommended (for flute) one can record with either type. The condenser type microphones used frequently for recording have greater sensitivity and frequency range over the live dynamic microphones and generally produce a “flatter” hence truer recording. The condenser microphone can also be used for live sound but by their sensitive nature are fragile and susceptible to breakage, improper positioning, and they cost so much more to risk the rigors of the road. Some mics are positioned as “cross-over” microphones, which attempt to service both arenas and are often referred to as home recording or project microphone in the sales literature. The expectation of a “good” recording microphone is to record the “truest” sound. This means the tone is near as listening with the human ear without coloring the sound, or adding artifact or signal noise over the entire range of the instrument or voice. This would be referred to as “flat” sound.

 Recently I had the opportunity to test a number of different microphones and record the sound for both audio and visual comparisons. My purpose here is NOT t make a recommendation of a particular mic but to give you the analysis of our work and through that work give you the working knowledge to choose a mic that might be good for you. The testing was more specific to recording that live play but results can be universally applied. The 6 microphones were of the “studio class” or condenser mics and 1 live or dynamic mic (specifications only) thrown in for a reference point. All adjustable pattern/response microphones were set to flat response and cardioid pickup pattern.

The diagram on the left displays the Cardioid’s pickup pattern by the green highlighted area. Notice the absence of sound pickup at the rear of the microphone. Using this type of pattern the diaphragm of the microphone should be directly facing the sound source to be recorded. Notice also as the direction of source moves laterally, starting with 30 degrees, the pickup ability begins to fall off and at 90 degrees falls off very sharply. This is important information when positioning the microphone and player (sound source). By example if you were to do a duet with this type of mic, you would not want either player 90 degrees to the diaphragm as sensitivity would be decreased while 30 degrees to the face the results would markedly improve the reception of sound. Many new or advanced microphones now include options to change the pickup patterns and there by increase the usefulness of the product.

We tested the microphones specific to recording use with Native American Flute, so keep in mind the results may differ with their use with other types of instruments. Wireless or Lavalier microphones were not tested but I will share my personal opinion on as a sidebar of these results at the end as well as my recommended method to mic a NAF flute.   We recorded each microphone with three different range flutes a C4 Medium B, a C4 Medium F#, and a C3 Low A. for each flute the same musical phrase was played and included verity of long, short, incidentals, and expressive note effects.

The recordings were made on an all-digital system with the only exception of the Analog to Digital conversion at the Microphone to A/D processor. The recording were made using a Mark of the Unicorn (Motu 896) digital interface/converter, Digital Performer 3.1 DSP software, and a 500 mHz Mac iBook  computer under OS 9.22. The signal was recorded in 16-bit format and 44.1mHz using identical gain settings for all microphones and test recordings. The reason we used the same gain level was to identify how “hot” (sensitivity) the microphones would be on a comparative basis. The hotter a microphone is the greater the saturation of the signal on the recording. The signal was even allowed to “clip” if the signal was greater than 10db over the unity gain setting (balanced zero).

The microphones were attached to a tripod boom microphone stand using the manufacturer’s supplied attachment support. The diaphragms of the microphones were directed to the mid bore position of the flute (between holes 3 and 4) and was parallel to the angle of the flute. The proximity of the microphone to the bore was set at 1 foot from the diaphragm. As we were interested in overall performance we made no efforts to compensate for the length differences of the flute bores to the focus of the mic and the distances to the foot of the bore. The fundamental on longer flutes can often require a second microphone to pick-up the sound, as it is directed and further away from the pickup patterns of most microphones.  The following table lists the microphones tested in price rank order:

This test had two distinct parts, Objective – technical specifications and visual wave form review of the recorded frequencies, and Subjective – how it sounded to me. One’s choice in a mic should be a combination of both aspects. You have to get a good recording but you also have to like the sound.

Before we get to the factory specifications I would like to give you some reference points of sound. Sound frequency is measured in Hz. Below is a table that describes the pitch, frequency, Native flute frequency, and some reference notes. The pitches are described as a reference to the octave it compares to the full size piano. The NAF’s generally classed as Medium would be in the C4 fourth octave on a piano which means as in the case of a NAF C of the fourth octave most refer to this as a Low C but the reality it is of the fourth octave or Middle C.  

 As you can see in the chart above the range of the current scope of available NAF’s is quite narrow even over the scope of commercially available models. Below you will find some “lay” description of the specification terms, sort of a “mics for dummies” thing where the full descriptions might confuse the general point of this report. The specific data was taken directly from the manufacturers specifications sheets as posted on the manufacturers websites. I have found retailer information to be less accurate at times. If you have any question about sales materials always check out he manufacturers site before final decisions are made.  

Frequency Response shows us the mics ability to “pick-up” the sound within a specific range of pitches as measured in hertz. The first number is the lowest frequency or bottom end and the second number is the high frequency or top end. The human ears generally can pick-up sound in the range of 20 Hz to 20,000 Hz, which is only 1/1millionth of a percent of the total sound spectrum. Many people have undetected upper or lower frequency hearing loss, which can affect the total range they are able to hear. The NAF pitches fall in the lower half of this range so its potential for doing well with most microphone response is quite good. If your intent is to play or record other instruments you can see that the range must expand top and bottom to include instruments of low pitches like Bass guitar and Drums and to Highs like some percussive instruments like egg shakers, chimes etc. so keep in mind what you might want to include in a recording other than flute and make sure the mic can respond properly in the overall desired range.

The diagram above is a plotted response curve for the Shure SM-81 condenser microphone. We will be dealing with the solid line on the response curve only at this time. As you can see the total response range of the mic is about 40Hz to 20,000 Hz, however printed materials state the range is from 20 Hz to 20,000 Hz. If we look at the graph the response (light orange) is quite flat (good thing!) and begins to falls off at about 15,000 Hz. So we might say that the effective range is only 40Hz to 15,000Hz (med orange). The other two dashed lines on lower frequencies show two other user selectable options for adjusting the low-end sensitivity of the microphone. These are used to decrease bass levels that can become “boomie” if not controlled. This mic has settings to start the “roll-off” at two separate frequencies.

Roll Off is the area on the graph where the sensitivity begins to decrease from flat response. This point in a response curve it maybe either intentional or just a limitation of the microphone. It can be important to have some roll off with use of a mic on drums to when recording sound directly from a speaker to keep things from getting “muddy” sounding but say for strings/voice/flute it may loose some of the intensity of the sound after the roll off frequency. In the SM-81 graphic above we can also see some high end roll off as well starting with 15,000 Hz. Some microphones will show a positive response enhancement above the “flat” signal. This can be either design intent to enhance the higher frequency reception or a negative as it can make the sound more “tin-ny”. Knowing this you can better pick the mic you need for the job or avoid the wrong microphone. 

Sensitivity:
I won’t bore you with the specifics of the “technical description” of the ratings of sensitivity only to say the higher the number the better its response to pickup and transmission of the sound to be recorded. Just be sure when reviewing specifications that all manufacturers use the same units of measure in order to do an apple-to-apple comparison.   

Signal to Noise:
All electronic devices have produce “noise”. Controlling this in the recording environment is essential will give you a “clean” sound. The sound can be a hiss, hum, or buzz heard in the background most noticeable on silent portions of recording. First in line to produce and control this noise is the microphone. In this case also the higher the number better the control.

Maximum Sound Pressure Level (SPL):
This is a measure measurement in decibels (dB) of the maximum pressure level a sound can make on the microphone before it distortion of the sound. This is less applicable to the flute but very important with drum. Drum produce a percussion wave form that can distort the sound the mic picks up. So if you plan to recording drumming you need to have a mic with a high SPL rating so it will record cleanly. The good news is that one of the more modest priced mics, the SM57 is also very popular for recording drum sets. This dynamic mic also makes a good live performance microphone so it can have use in and out of the studio.

Technical Specifications per manufacturers product information:
** Note: The yellow shading indicates highest performance in a given category but not specific to NAF use.

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