Microphone Primer For NAF

Eastern Woodlands Design

Microphones are a lot like flutes everyone has a favorite...

Positioning of the microphones will dictate the color or tone of the sound being played or recorded. Each has a place and none of them are wrong just different.  It is a known fact that acoustically that the player does not hear the same sound that the listener does. That is because the player is behind the actual source of the sound. Many folks are often amazed that when they record their flute (dry - no effects) or when someone else plays it and they are standing in front of it that it sounds different to them. This is a result of repositioning their ears to the sound source. When we hear an ambient flute from an audience position we are not hearing it from the players point of reference. The actual sound of the flute exits three areas; the sound hole, the finger holes, and the bore end (all holes closed).  With all holes closed the primary sound source is the bore end. As we raise our fingers and go up the scale the primary source shifts to the top most open holes and to some degree the open holes below. The influence of the open bore end becomes increasingly less for each hole we open up the flute bore till it has minor influence on what a listener would hear. The sound at the sound hole changes also during play but is less influential to the overall content of what the listener hears. We need to remind ourselves that it is the listener reference that is the most important to the sound we are projecting when recording or performing. We also need to remember the microphone is the facsimile of the audience's ears when we use sound reinforcement or make a recording. What we hear behind the flute is only a guide to your playing much like stage monitors are helping you hear not what the audience hears but what is needed to help you play.  

Positioning a microphone is a lot like re-positioning your ears, the proximity and direction of the sound source will have a different color to the sound. You can hear the  difference of positioning even if you are alone. To do this stand a couple of feet from a hard blank wall, with the flute opening direct to the wall and holes diagonal to the wall. When you play what you will hear and experience is a combination of the sound generated from all three zones (A,B,C). This is because the wall will reflect the sound back to you (reverb in it most natural form) the sound that will include a sum of the sound hole, the playing holes, and the fundamental of the flute. This is a slightly skewed but more representative of what a listener would hear being positioned in front of your flute. In the diagram below we see three different methods I will endeavor to make so observations of each one based on both experience and the physics of the flute. 

Common Microphone Placement Positions (Fig 1.)

Microphone Positions

Method A
In this scenario we are getting a sound that is primarily from the sound generating mechanism of the flute, the splitting edge. Methods for this position most often are either as shown in A. from either the side or above the sound hole. A microphone on a stand with a boom arm can easily accommodate the directional needs. Another method includes the use of a micro microphone, clip-on, lavelier. These are generally attached to the flute in someway and positioned in proximity to the sound hole. Some clip the mic to the fetish ties or the bodies of the flute in some fashion and some even have a tiny adjustable goose neck to assist in positioning. In all cases it is important to make sure that the face of the microphone is directed to your intended source of sound. A mic such as this provides a biased and colored but consistent sound quality flute to flute and can be easily moved from one flute to the next, and mirrors more the sound a player hears from the player position. Always remember to turn down the volume when changing the microphone position or from flute to flute. Microphone rumble is not very professional even for an amature.  Some micro mics have an option for wireless connection between the mic system and your amplification device. This requires a transmitter, commonly attached to you belt, and a receiver that is connected at the amplifier end. If moving around the stage a lot or going out into the audience is important to your performance then this the best method to accommodate that. I mentioned biased and colored tone in my description above. Microphones in this position have the most distal placement to the primary sound sources and what the audience would hear. Being the furthest from the fundamental it will not pick up this tone as well as other positions, The same is applied to the tone holes but as we climb the scale the source of the sound gets closer to the mic diaphragm. The result is that the fundamental note with be softer and cooler and that the top note will be louder and brighter making the overall timbre of the flute less uniform. Another down side to this technique is the amplification of artifacts of sound. Being close to the sound hole it will amplify the both the sound of the air exiting the flue, created by the fetish design, and by the air hitting the splitting edge. Also you have to find a way to insulate the microphone from its attachment to the flute to prevent the sound of your fingers tapping the flute bore as you play from being transmitted through the body of the flute into the microphone and being amplified. Attaching the the mic to the ties improves this or by placing some insulating material between the flute and the microphone attachment device such as a layer of open cell foam.   
   
Method B
With this method we are getting the most uniform sound, but still position influenced, that represents what the listener hears. All microphones have a pickup pattern dictated by their design that limits what frequency range, sphere of influence, and color of the sound (EQ) that they respond best to. In the diagram above (Fig 1.) I am showing the a performance type microphone (dynamic - cardioid) much like the Shure SM57 or SM58 microphones or facimilies. The gradation of the spheres color indicates an approximation of sensitivity of this type of microphone in that pattern. The central part of the sphere is very dense indicating that the great response by the microphone to the sound source will occur at these points while the outer edges are less dense and the response will be more diminished. Most manufacturers include a polar pattern diagram and technical specs in their user guides or can be download as a PDF file from their websites. For our purposes these simple illustrations will suffice. A microphone used in this way is best done with a microphone, on a boom arm attached to a mic stand. The face of the mic would be positioned so the face of the mic is at the mid point level of flute bore, between holes three and four and always perpendicular to the flute bore. This can require the player who plays their flute horizontally to have to position the boom differently than the person who plays diagonally to their body. Positioned here the microphone is closest to the greatest number primary sound exits on the flute body. So it will be more representative of what the listener hears being in front of the flute rather than behind it like the player. As the active holes move further away from the microphone diaphragm the less sensitive the microphone will be to those sounds. This is described as being "off axis" to the diaphragm of the microphone.  So looking at the diagram we can see that the sound generated at the sound hole and at the open end of the flute will pickup less of those sounds due to decrease sensitivity to the now off axis sources and being outside the primary polar pattern. This can be exaggerated by larger flutes due to the greater distances between the holes, the sound hole, and the open end of the flute. For the mid range flute however this one microphone setup gives the best result. mic'ed at about one foot you can get a fairly uniform tone to the sound and in most representative to the listeners perception of the sound. If you need to use a larger low flute you can back up from the mic and turn up the amplification an achieve imporoved results in tone. If you have a three band EQ on your amplifier setup you can raise the levels of the high and low tones to balance this somewhat.  I will however show you a better two mic configuration later in this primer. Keep in mind when mic'ing smaller higher flutes to move back away from the microphone as the amplitude or intensity of the sound produced by a small flute is much greater than that of lower pitched flutes. In this B method you will also introduce less finger and sound hole artifact into the sound field.

Method C
Much like Method A, Method C is also influenced by its positioning away from the greater sound sources. Here the fundamental tone exiting the open end of the flute will be accentuated and muting tone begins as the source gets further away from the microphone face. So once again we will get a change in the timbre over the range of the flute, being more robust in the lower octave and thinner in the upper with graduations between.  Some compensation could be made with a three band EQ by decreasing the low frequencies and increasing slightly the mids and more so the highs to balance it out.

So what can I do to get a more representative and balanced listener sound? 

Method B/C
The down side of this method is not sound quality or timbre but technical and costs a bit more because it requires two microphones and the amplification device that can accommodate two inputs as well. By placing the microphones in the B and C positions you are getting near optimal sound that most closely represents what the listener would hear if listening to the flute in ambient conditions (not amplified). The B microphone will pickup the tone hole sounds while the C microphone will pickup the fundamental. The upper microphone would be attached to the mic stand normally and pointed to mid flute and about 8-10 inches from the source of the sound at mid bore. The second microphone will require an accessory bracket to attach it to the same stand but lower so it can point up toward the bore opening at about the same distance of 8-10 inches. There are many sources for these devices and they only run about $10-$15 dollars either from retail or mail order. These images, Fig 2 and 3 are from the Musicians Friend site. I use them for much of my music gear. They are known best for "selling boxes" at a good price (when you don't need a lot of sales support).  You have a lot choices in Internet wholesale distributors. Figure 2 is a fixed angle bar design which would only give you vertical adjustments and angular control would have to be supplied by an adjustable angle mic clip. Figure 3 not only gives you the vertical adjustment but also 360 degree angle adjustment with a locking mechanism so it has a lot of adjustment. I have about five of these some in the studio and some for the live gear. They work excellent for an acoustic guitar micing for the player that sings and plays.  

Microphone Accessory Arms


Fig 2.
Microphone Extension

Fig 3. 
Side Boom

The next image is of the stand in actual use so you can see for yourself  how it would look. The two different microphones shown have no special meaning  I just grabbed two for the picture. Mixing microphones can give you a wonderful blended sound or it can really be bad. Intention is everything. Feel free to mix them up to either test or creative a specific sound. I did not include mic cables or the flute in the picture but I am sure you get the idea well enough.

Dual Microphone Setup (Fig 4.)

Dual Mic Setup

Intended Use Considerations

Many will already have chosen their microphone and for newbies, price or peer feedback in often a factor in selection. These are valuable criteria but should not be the primary basis for selection it really boils down to technical specifications (range, sensitivity, durability, and polar pattern) and most important how does it sound. Also understand that peer feedback although important you must always consider the "expertise" of the person giving you the recommendation. I have friends who have been in the music industry for 40 years but still don't realize that microphones have a polar patterns and that not understanding them can decrease the effectiveness.  I personally like the way the flute sounds on its own, that was the primary selection criteria for having it, so I want a mic that will support that sound the amplification of the flute with the least amount of change to the color and tone. How it performs and sounds are the best criteria and then get the best you can afford. There are two other microphone primers on this site which address understanding microphone technical specifications so check that out but I would like to expand on a couple of areas.

Microphone Classification

Dynamic microphones employ a diaphragm coupled electronic coil technology to capture the sound. As the sound strikes the diaphragm it moves back and forth with the coil attached there by creating an energy which is transmittable.  The magnitude and direction of that current is directly related to the motion of the coil, and the current generated is an electrical representation of the sound wave. The dynamic microphone is the most popular in live sound reinforcement. Although they have a reduced sensitivity over the condenser microphones they are much less fragile than the condensers and can be exposed to much louder sound sources (SPL - sound pressure levels) without fear of damage.

Condenser microphones employ a diaphragm that is very thin, most often made today of mylar, which has been coated with gold or nickel on the face, is  housed very close to a fixed back plate. An electrical current is applied to the diaphragm giving it a baseline polarity. This is why condenser microphones need some source of electrical current to power them. This can be supplied a number of different of ways most common being either a battery in or outside of the microphone or from a device such as a mixer through your XLR cable, known as "phantom power". The diaphragm and back plate are separated by a fixed air space, this sets up a fixed electrical resistance between them when the diaphragm is not moving. As sound is applied to the diaphragm it move back and forth and changes the electrical resistance. This change or fluctuating voltage is the electrical representation of the diaphragm's motion. Generally condenser microphones offer many advantages over dynamic microphones such as greater sensitivity, frequency range, and more uniform frequency response. Because of their increased sensitivity these mic are the choice for recording. On the down side they do require that electrical source and are much more fragile so taking them "on the road" requires greater handling precautions. They are also generally more expensive and sometimes, with exceptions, are more bulky in size.

Pickup Patterns

The microphone pickup pattern (where it is most sensitive) is important to understand as it will dictate which type to use for your intended purpose. Left to right I have simplified diaphragms of the four most common microphone pickup patterns. The gray "M" circle indicates the microphone position relative to it pattern of pickup.  The large gradient bubble is the area in which the microphone will best pickup the sound with the most effectiveness being the denser blue and the least the light blue The orange "F" indicates the direction the primary direction the microphones diaphragm faces, this is also the best direction to address the microphone (where you stand). All microphones tend to roll off in effectiveness at the peripheral edges of the pickup patterns this is know as off axis addressing, an important to understand when doing duets of any type. 

The Cardioid pattern is the most common of all the pickup patterns of microphones made today. Generally the pickup pattern is a bubble like area "in front of" the microphone diaphragm and very little effectiveness from the rear if any. Actually the cardioid pattern was designed to help in rejecting sounds coming from the rear. So we can see it is most effective when we stand directly in front of the diaphragm but afford a reasonable amount of movement off axis till we get to about 35-40 degrees off axis and reduced sensitivity begins till we are 90 degrees off axis to the face and there is greatly reduced effectiveness. This is not the microphone of choice for duet micing however if this is the only mic you have setup then make sure each player is no more than 30-40 degrees off axis to the mic face. Because this microphone rejects sounds from the rear you can place a monitor down and behind it facing you so you can hear yourself playing and it will have very few feedback problems.

The Hyper Cardioid microphone was designed more specifically for vocal singers. It is basically a cardioid pattern that has been truncated on its off axis. So addressing this microphone from the side will be very ineffective. With singers this however is a distinct advantage as it rejects all the other sounds happening around them on the stage such as the other instruments and the loudspeakers themselves. For the flute player this is a disadvantage as it greatly restricts the player to being directly in front of the face at all times and would not support duet playing very well at all. This is the least recommended microphone for flutes unless you require the side address sound rejection. 

The Figure Eight is a dual diaphragm designed with two mylar skins and a plate in the middle. So it is kind of like having two Cardioid microphones being placed back to back in a single housing. The figure eight microphones are most often only when used for recording and are larger in size but are especially effective in recording two players and rejecting the sound coming from the opposite players flute or instrument. This way you will have two distinct sounds being recorded or amplified. They also work great when you want to record the primary source sound plus some of the sound of the room ambiance as well. 

The Omni design is, "pun intended", an all round microphone. With this design the polar pattern extends in a bubble of 360 degrees around the microphone. This microphone offers the greatest flexibility for the player to move and still be assured to good sound pickup. This design is frequently used to record wide area sound sources like groups of musicians or choral groups where the microphone is central to the group itself. As I have mentioned above sound rejection can be an import consideration to selection so the down side of this type of microphone is that it will not reject sounds and requires special considerations in its placement to other sound sources such as your loudspeakers. As it will pick them up it will create a feedback loop of disastrous proportions. If a omni microphone is used you will need to place it well back from your loudspeakers to minimize this problem. If you depend on your loudspeakers to monitor your playing as well this can create problems for you. Smaller omni microphones have smaller pickup bubbles so this will less of a problem the smaller the microphone diaphragm is. Bottom line for live work this is a less desirable design but does have specific use application with groups and close micing with smaller diaphragm omni mics.

Microphone Pickup Patterns (Fig 5.)

Microphone Polar Pattterns

Try before you Buy!

As I mentioned above the way it sounds is the most important consideration for your purchase so the only way you can determine what is right for you is to try them out. Unfortunately most wholesale/Internet sales companies have a policy that microphones can not be returned for any reason except in the case of damage. This is done for to reasons the more fragile aspect of the design and for hygiene reasons, as you can't really clean a microphone without risk of damage (unless you are the maker). The alternative is to try out different microphones at places like flute circles or talk to experienced performers. One of the down sides to periodic testing is that audio memory is very very short so making comparisons between mic models from one gathering to the next is nearly impossible for those without "gold ears". Here is a recommended alternative for those that are not intimidated by playing in public.

First do some research to chose a number of microphone models based on intended use and manufacturer specifics. This will help you both rule out those that do not meet your needs and provide you with a list of dealers in your area that sell them.

Second take your list and your flute to the nearest dealer and actually try them out. Most resellers have demo products for you to test. Try to do side by side comparisons of the different models. It is very important to focus your listening on the sound the microphone is capturing. If you have to really think a lot while you play it will be difficult to focus on the sound if you are thinking about your playing. If that is a problem for you bring along a flute friend to play your flute and you just do the listening. 

Lastly shop around don't buy from the first place you look, especially small local music stores as they tend to be close to the list prices rather than the actual "street" prices you can find by going on-line and doing some homework. If you like to work with local sources don't be afraid to ask if they do price matching. Some smaller resellers will do price matching but often are required to include shipping costs by the competition into the comparison to their prices.

Setting up the Food Chain!

Now that you have done all the work to select your microphone it is important to make sure your amp setup will be up to transmitting the full range of the sound being captured. Most casual players utilize a guitar amp setup with a microphone because they are both more cost effective and offer a range of sizes and hence weight configurations. Many of the newer designs also incorporate built in effects making the need for additional outlay for an additional outboard device such as a guitar "stomp box" delay or reverb a cost savings. The quality and flexibility of the built in effects maybe less than outboard devices but you can judge this for your self. A lot of work has gone into the design of an amp that has been designed for guitars to bring out the best of the guitars characteristics, but a guitar is NOT a flute and therefore you should consider what that means to your overall sound good or bad. The frequency range of mid range flute is much much higher than a guitar so the emphasis of the guitar amp is less favorable to a flutes playing range than a guitar. This results in the sound being colored by more emphasis of the lower frequencies and less on the higher frequencies.  A smaller speaker in the cabinet will be better at representing the flute than larger ones. So there is a cut off point where they will work well. The usual case is that as the watts of power increases so does the speaker size. You really want to keep the speak below 8" for flute use otherwise you will start getting muddy sounding bottom end tones from your flute and background music. An alternative is to NOT select a guitar amp but consider a keyboard amp which has a very wide range of response because it is designed to cover the full 8 octave range of the piano which is much more than all the different flute keys currently being made placed end to end. So the use of a keyboard amp will improve the tone of the flute but still has an inherent problem to be addressed. Guitar and keyboards connect to the amplifiers via a 1/4' unbalanced connector. Most quality microphones use a balanced three wire connector called XLR. This means in many cases (some amp offer XLR) you can not connect the microphone directly to the amp with out some intermediary device or adapter. However you should not use just any adapter because the impedance of a microphone is not the same as a guitar or a keyboard. There are simple interconnect cables or adapters available for purchase than have an XLR on one end and a 1/4" on the other but these cable were not and are not designed for use with microphones. Such a cable does not change the impedance of the cable so you risk potential equipment harm and will decrease the effectiveness of your microphone by as much as 50 percent. The solution is to use an adapter or device that will transform the impedance to match the devices. The least costly is the short is a "pigtail" adapter (Fig 6) called an impedance matching transformer. Because there are simple XLR to 1/4" line adapters available it is important to make sure that it specifically says it is a transformer as well.  These range in price form $15 to $30 each and you would need one on each microphone cable. This makes connection to a instrument amp a breeze and give you the full effectiveness of the microphone.        

Fig 6.
pigtail transformer
Fig 7.
mixer

The more versatile method is to use a small mixer (Fig 7.) to give you both impedance matching and many other valuable connection options. By example often I use backing tracks when I perform. With the mixer I can attach a CD player or my mini disc to the mixer and easily control the mix of the music independent of the flute. Some new guitar amps ofter a similar CD input on them but may not have the degree of mix control the independant mixer gives you. The number of inputs on a mixer and extra features varies quite widely. The small unit shown in Fig 7 offers 2 XLR inputs and 2 stereo, 2 channel EQ, Aux inputs for blending outboard effects processors, tape in (cd) and tape out (recorder) as well as main outs to your amplifier and control outs if you use a self powered monitoring system. A reminder also here that stomp boxes are also made for use with guitars and by the limits of their design may also be very noisy because they are not a balanced device. Rack mount effects processors have little noise and support balance connection operation. They can cost a little more (some less) but in general they offer more flexible and have improved quality results. The example above gives you a total input potential of 6 different sources to be mixed as well the tape inputs and axillary inputs. On most mixers the XLR inputs have pre-amplifiers which will give your signal a boost in power before going out to the amp again this will help you balance the mix. Just be careful not to have the preamp gain to high as it is possible to have distortion occur before the signal get to the amp. So all in all this $50 purchase can give you a lot of great options and control over your sound.  The output of the mixer goes to your amp stereo ready so you will have to use an adapter cable to get the L and R signals into a single 1/4" mono output if the amp only supports a single mono input.  The other nice thing about small mixers (this one is 8" X 10") is that you can locate them close, even on your mic stand, to your playing position so you can easily adjust the setting without having to walk over to your amp.

I pray this has been helpful, always enjoy your music and those you are playing for.

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