Microphones pick up sound waves (pressure changes in the air in the longitudinal direction) and convert them into weak electrical signals, which in turn are further amplified electrically. This applies equally to all microphones, for example instrument and vocal microphones. When miking instruments, however, there is often the problem that they are moved intensively on stage. A pickup with microphone and stand is therefore difficult to realize.
What are instrument microphones?
Instrument microphones have the task of capturing the sound of an instrument as realistically as possible. The sound spectrum of different sound sources naturally differs considerably from one another. If you compare the sound of a snare drum with that of an oboe just once – not to mention the sound of a human voice. Therefore, different microphones are used for the different sound generators, which are tailored to the respective requirements. Dynamic instrument microphones are particularly well suited for loud instruments, where condenser microphones are used when a wealth of sound detail is required.
Why miking instruments is anything but easy
The technician who microphones instruments must solve three major problems. First: How do I ensure that the constant movement of the instrument maintains a constant distance between the instrument and the microphone? This question can usually be easily solved by attaching the microphone to the instrument or by installing it. Built-in microphones are not always popular with musicians, as the body of the instrument often has to be manipulated for installation.
Clip-on microphones, on the other hand, do not offer absolute stability, especially in the case of strong movements. The microphone – mounted or connected to the instrument – is usually connected to the system or an amplifier via its own cable. Of course, the cable is also moved when playing. To prevent this cable from restricting the freedom of movement of the musician too much, wireless systems are often used live for signal transmission.
Problem two of the miking is to find the right microphone for the respective instrument, because the microphones differ not only in their frequency response, but also in their sound conversion.
Problem three of the miking is to consider the given environment. While there is no risk of possible feedback in a recording studio, in live operation it is very important to select suitable microphones or an appropriate microphone position so that the risk of feedback is minimized.
Also, when recording with more than one microphone simultaneously, such as when miking a drum set, a clean channel separation should be taken into account. If possible, the respective microphone should only record the instrument for which it is used. For example, the bass drum microphone should record as little as possible of a snare drum or hi-hat.
This problem occurs even more strongly in live operation. For example, if you like to record a choir or similar ensembles with a few microphones in order to record the room and the integration of the individual voices and instruments among each other, this channel separation should be as exact as possible for an individual pickup of the instruments. With pickups and special microphones, almost 100% channel separation is achieved in some cases. For example, various clarinets and saxophones can be picked up completely separately from other instruments with our K1X and WP-1 pickups. Since these pickups are built into the respective instrument, no external sound, e.g. from the stage monitor or other loud instruments, can reach the pickup.
Even with attached and built-in microphone systems such as the TA3000X, TA3000eco and TA20, extremely good channel separation is achieved. The individual microphone capsules are so close to the sound source that virtually no external sound can scatter onto the capsule.
What are the special features of the individual instruments and what does the microphone have to be able to do?
There are several points to consider with the bass drum. The microphone must be designed for very high sound pressure levels and have a very high frequency response. The position is also very important. For example, while boundary microphones are placed in the bass drum and pick up the sound inside, there are also various microphones that pick up the bass drum from the outside. Here the sound can be very strongly determined by the choice of the microphone as well as the distance between microphone and resonance skin. The distance and the directional characteristic also strongly determine the possible channel separation. An optimal result is achieved with our CBM-1 boundary microphone, which can be placed in the bass drum or mounted on the side inside.
A condenser microphone has proven to be the standard microphone for a HiHat. A small diaphragm condenser microphone best underlines the lively character of a HiHat. The position of the microphone, the distance to the hi-hat and its directional characteristic determine the timbre and the channel separation.
The snare drum is one of the loudest and most percussive instruments, which can cause some problems with its recording. A dynamic microphone has established itself here as a “quasi-standard”. The timbre can be determined by the position of the microphone and its orientation, i.e. more towards the centre of the coat or the edge of the coat. Space problems can prove to be problematic. With a normal microphone stand it is often very difficult to get a reasonable grip on the snare drum, which is why clip-on microphones or selected snare drum microphones with special holders are often used for pickup.
The pickup of the cymbals is of special importance. Channel separation is often not desired here. The cymbals are usually miked with a stereo configuration, although an additional individual pickup of the cymbals is of course not excluded. This stereo configuration makes a significant contribution to mapping the drums as a whole and also classifying the individual instruments spatially. A pair of small diaphragm condenser microphones, which are best matched, has proven to be the best choice. The small diaphragm microphones reflect the brilliance of the cymbals. The greater the desire for a complete miking of the entire set and the less important it is the basin acceptance itself, large diaphragm condenser microphones are also often used for a more frequency-true imaging.
The principle of the miking of the toms is similar to the pickup of a snare drum. Since usually two to four toms are used with a drum set, a pickup with a classical microphone on microphone stand per tom is difficult. This is why clip-on microphones or tom microphones with special holders are often used here as well.
While the pickup of electric guitars seems unproblematic, a good pickup of acoustic guitars is often very difficult to realize. Due to the geometry of the instrument and the low volume level, feedback-free pickup is difficult to achieve. This can be remedied by a pickup integrated in the instrument, which picks up the structure-borne sound of the instrument and converts it into electrical signals. Otherwise, condenser microphones or ribbon microphones are often used to reproduce the brilliance of the instrument as well as possible.
The pickup is very difficult with many wind instruments. On instruments such as trumpet, flugelhorn, tenor horn, baritone, trombone, etc., the sound exits the funnel in a very directed manner. The relatively high level gives the sound engineer a very good and clean signal with which he can work well. However, the disadvantage of microphones with normal microphones is that even the smallest movements of the musician cause a change in the sound spectrum. Clipped microphones, which are placed on the sound cone, provide a remedy. The distance and direction to the sound generator are always the same. The often bulky design and possibly insufficient hold of the microphones cause problems here. In contrast, the pickups of Rumberger Soundproducts are built directly into the barrel or the mouthpiece of the clarinet or the saxophone, so that an even tone pickup over the entire frequency spectrum is achieved and there can be no level fluctuations. The inconspicuous design and the possibility of operation via wireless systems enables optimum conditions for stage use.
Accordions and harmonicas:
This type of instrument always presents sound engineers with great challenges. A present and even sound pickup can usually only be achieved with several microphones. The difficulty is that bass and treble are to be miked separately – but the bass part constantly takes up a different position due to the playing movement. Microphoning with fixed microphones becomes very difficult. Attaching clip-on microphones is a solution – but from our point of view not optimal. For the mounting the instrument body has to be drilled and on the other hand the decrease is not even over the whole frequency spectrum. The TA Series microphones from Rumberger Soundproducts are dedicated to this problem. With the TA20 indoor microphone, a microphone strip with several capsules is mounted under the hood. The microphone systems TA3000X and TA3000eco are mounted on the canopy. Also with these systems several microphone capsules are used, whereby an absolutely even pickup of the descant side is achieved. Exactly one bass microphone with spherical characteristic is used for miking the bass side. This special microphone also offers an absolutely balanced pickup and a very harmonious, balanced sound overall.
The miking of the Cajon is comparable to that of a bass drum. A closed wooden housing with a sound outlet. A microphone can either be placed at the sound hole or inside the Cajon. Dynamic microphones, condenser microphones or boundary layer microphones are used for this purpose. Also in this area there are special microphones, e.g. with bass boost, to achieve a powerful sound. With a Cajon, however, there is a special feature: it should replace a whole drum set as well as possible. Therefore not only low frequencies should be increased, but also medium and higher frequencies should be reduced transparently. The solution here is the CBM-1 developed by Rumberger sound products, a boundary microphone specially designed for Cajon and bass drum. The result: connect and experience a great sound without EQ settings.
String instruments can be picked up in very different ways, either with clip-on microphones with special holders or with condenser microphones directed at the F-hole. It can become difficult if you not only play with the bow, but also pluck very percussively. In such cases, professionals usually use compressors to achieve a rich sound.