Some MXL microphones come with switches that serve different purposes. These can be high pass filters (low frequency roll-off), pads (signal pre-attenuation) and pick up pattern selection.
High Pass Filter
A high pass filter cuts out low frequencies up to a set frequency, which you can find on the Spec Sheet of your microphone.
- When switched to the 'bent line' position, the high pass filter is engaged and will attenuate low frequencies.
- When set to the "straight line" position, all frequencies will be picked up by the microphone like normal.
- Example: MXL 770X (pictured) cuts frequencies below 135Hz at 6dB/octave when high pass is engaged
If you're recording a source that doesn't need a lot of low frequencies represented, like certain stringed instruments, percussion, or even voice, you can engage the high pass filter to reduce 'muddiness' and leave room for other instruments in the mix that occupy that frequency range.
Pad
A pad attenuates, or reduces, the signal by a certain level, the amount of which is usually indicated on the switch itself. It does not affect the characteristics of the sound.
- When set to 0dB, no attenuation happens and the signal remains the same.
- When set to -10dB, the signal will be reduced before hitting the preamp
- Example: MXL 770X (pictured) has a -10dB pad, reducing the signal by 10 decibels when engaged
If the incoming signal results in overloading the microphone preamp, you can use the pad to decrease the signal level to avoid distortion and increase the amount of headroom on your preamp.
Pick Up Pattern Selection
Some microphones have the ability to switch pick up patterns (also know as polar patterns). This changes where the microphone 'listens' for incoming sound, giving the user more sonic options for different recording scenarios.
- Cardioid (in this example, all the way to the left) will pick up sound from the front of the microphone, but reject sound from behind it
- Figure 8 (in this example, center position) will pick up sound equally from the front and back of the microphone, but will reject sound coming from the sides
- Omnidirectional (in this example, all the way to the right) will pick up sound 360 degrees around the microphone, from all sides.