Microphones and placement techniques.

Microphone selection:

Condenser Microphones: Condenser microphones are what I will be using to record most of my instruments to capture the best tone possible. Condensers are great as they have a large frequency range that is perfect for recording instruments with a wide frequency range like vocals, guitars and pianos. Condenser microphones come in different types: Small and Large Diaphragm. The diaphragm is the small membrane part of the microphones that moves in reaction to external sound pressure variation. The Microphone diaphragm is the key transducer component in converting acoustic energy into electrical energy. The 3 main diaphragm types are condenser, moving coil and ribbon. Small diaphragm condenser microphones are used mainly for recording instruments like acoustics guitars and strings. Large diaphragm microphones are most commonly used to record vocals. As these microphones are highly sensitive, they are not ideal for live situations as they can pick a lot of background noise and can cause bad feedback issues. Although these microphones are not ideal for live use they are very perfect for recording purposes as they produce clean, crisp recordings without any distortion or clipping. Condenser microphones require +48 volt phantom power. This means they need power to work.

Dynamic Microphones: Dynamic microphones are most commonly used in a live environment and are great as they don’t pick up much background noise and do not require any phantom power. Dynamic mics have a moving-coil diaphragm. These microphones are very rarely used for recording as the clarity of recording is inferior to that of a condenser. Dynamic microphones are great for live vocals along with miking up guitar cabinets and amplifiers. The most commonly used dynamic microphones are the Shure SM58 and the Shure SM57.

Ribbon Microphones:

Ribbon Microphones are great for recording instruments like guitars, brass, woodwinds, drums, and strings. The clarity of ribbon microphones is superior to most other microphones. The diaphragm in a ribbon microphones is a light metal ribbon suspended between the poles of a magnet, this is slightly different to the diaphragm of a condenser or dynamic microphone.

Microphone Placement and mic selection:

Mic placement fully depends on what the target subject you are miking up is. For a guitar cabinet, we would tend to use a dynamic microphone and place it slightly off of the centre of the cap. This takes away the harshness of the volume of the amp. Often the microphone is placed off-axis and pointing towards the cone. Distance from the amp often depends on the tone you are looking for. Although, it does require the microphone to be pretty close considering it would not pick up the sound if it was too far away. This obviously depends hugely on the microphone you are planning to use. With a dynamic microphone like an SM57, it requires being close to the source to get the best and clearest sound possible. Alternatively, a large-diaphragm condenser microphone like a Rode NT1A or an Audio Technica AT202, you would be required to place it further away as it is considerably more sensitive to sound and noise. By placing it further away it also incorporates the reverb and sound of the room the amp is in.

1. A/B Stereo Recording

Microphones used:

Two Omnidirectional microphones, usually small diaphragm condenser microphones.

Microphone placement:

Both microphones are placed pointing towards the guitar, 1ft away from the subject you are recording and spaced 2ft away from each other. When experimenting with this technique try moving the microphones further away from each other and/or further away from the subject.

How to mix the stereo signals?

The mono signals from the stereo recording are panned to the left and right to give a warmer and more spaced mix. This is to create a sense of depth in the recording.

How should it sound?

The stereo image was created because the time of arrival at each microphone is slightly staggered. The frequency balance is different as well, which will provide an added level of stereo width.

The drawback to A/B stereo recording is that because of the timing offset between each microphone, you will be likely to have issues with phase cancellation when combining the stereo image to mono.

2. X/Y Stereo Recording

Mics used: two omnidirectional microphones, usually small diaphragm condenser microphones.

Positioning:

At an angle between 90-135 degrees so that their capsules coincide at a single point. The wider the angle the wider the stereo image.

How to mix the signals:

Same as A/B Stereo recordings

How it should sound:

Compared to A/B stereo recording, this technique will have less of a stereo effect. The reason is that both microphones are positioned at the same point in space, there will be no difference in timing.

The entire stereo effect will be created from the difference in frequency balance the upside to this is that there are no issues with monophase cancellation either.

3. ORTF Stereo Recordings

History: The ORTF technique was developed in France in the early 1960’s by the Office de Radiodiffusion Télévision Française ( Which later became Radio France) It employs

Mics Used: Two Directional Mics, usually small-diaphragm condensers.

Positioning: Spread outwards at an angle of about 110 degrees, with the capsules spaced 17cm apart.

How to mix the signals: Same as A/B Stereo Recording

How it should sound: The technique is basically a combination of the previous two. The microphone is physically spaced apart, like with A/B Recording, Which will yield a wider stereo image. Then is used directional mics, like with X/Y recording, so it should pick up less of the ambient room sound.

4. Blumlein Pair

Mics Used:

Two figure 8 Bi-Directional Microphones (Example: AKG C414)

Positioning: Same as X/Y Technique

How to mix the signals: Same as X/Y Technique

How it should sound: Compared to the X/Y Technique, the Blumlein pair technique captures a greater portion of the room sound and adds a bit more ambience to the stereo image, thanks to the use of the figure 8 mics.

5. Mid/Side stereo recording

Mics Used: One small-diaphragm condenser mic - either cardioid or omnidirectional.

One large diaphragm condenser mic (Must be Figure 8)

Positioning: Figure 8 mic is placed sideways at a 90-degree angle from the instrument. This mic will record sound on both sides and will function as the ‘side’ in term mid/side.

The other mic is positioned on top or below the figure 8 mic, and is positioned directly towards the instrument. It will function as the “mid” in the term mid/side.

How to mix the signals:

1. Duplicate the “Side” Channel

2. Reverse the polarity of the duplicated channel

3. Combine the two side channels onto one stereo track

4. Mix the mid-channel with stereo side channels to adjust the width. The greater levels of the sides compared to the mid, the greater the stereo width.

How it should sound:

Mid side recording may be complicated, but it offers all the advantages of the other 3 techniques, without the downsides.

• It offers the added stereo width of the A/B technique

• It offers the mono compatibility of the X/Y Technique

• And it allows you ( If you want) to increase the room ambience to something resembling the Blumlein pair technique.

When is mono more appropriate than stereo?

Stereo recordings can be a great technique to improve sound quality and overall improve the depth and warmth of the sound recordings. It also gives the option to space the recording out to make the track less crowded and messy. Although this is a great technique used in some situations it is not always necessary for example Lead vocals, this would normally be recorded in mono as you would be dropping this right down the centre of the mix to make sure that they cut through the mix of instruments. This is the same for the kick drum, snare drum and bass. These you would typically record in mono as you would not want to pan them as it would sound strange having the snare drum of the centre. This is based typically on how a stage is set up, and you would normally have the kick drum right in the centre of the stage.

1. Lead Vocals

2. Snare Drum

3. Bass Drum

4. Bass Guitar

From my research, I have learnt when and where to use different microphones. Along with the best ways to use theses microphones to capture the best quality audio.

JWJ