A recording microphone is a device that picks up audio waves in the air and converts them to electrical signals that are identical. Maybe you are wondering what each specification means and which type can satisfy your recording needs when searching for one. Today let’s go through all these basics so you can decide whether it is a good mic for you.
Three main types of microphone for recording and their uses
Classifies by the way that it turns sounds into electrical signal, there are three types, including dynamic, ribbon, and condenser.
Condenser recording microphone - Good at capturing subtle audio details and ample tones
It features a thin conductive diaphragm sitting near to a metal backplate. This setup operates like a capacitor, with sound pressure vibrating the diaphragm, which causes the capacitance to change, resulting in the audio output. It is great for precision recording in the studio because it use capacitance instead of actual moving coils, which improves fidelity and sound quality.
To go deeper, it consists of two sub-types, which are large diaphragm condenser and small diaphragm condenser microphone. We can clearly realize what their differences are according to the name.
- Wide frequency range of 20Hz to 20,000Hz
- Sensitive to detailed sound
- lower input sensitivity
As is often the case, condenser microphone is really sensitive to sound, so it can capture subtle audio details and ample tones. This professional microphone for recording can record vocals and voice-over and can also help record acoustic instruments especially in studio.
Dynamic microphone - Good choice for live recording scenarios
Dynamic recording microphone converts sound waves to an electric signal through a process known as electromagnetic induction. A conductive coil is linked to a diaphragm within the capsule. When the sound hits the diaphragm, it vibrates, moving the coil in a magnetic field and providing an AC voltage.
- Rougher frequency response, but still usable
- Rugged and reliable
- More durable than condenser because it can handle heat, cold, and high humidity
- Won’t distort when recording loud sources
Since it is less sensitive, it is ideal to work as an outdoor recording microphone for live situations such as press conference, music concert, or a field interview.
Ribbon microphone - Capture detailed audio but rejects room noise and off-axis sound
Ribbon microphone for recording technically belongs to dynamic microphone, but is usually recognized as a separate design because of how they work and sound. It owns an extended rectangular diaphragm composed of thin aluminum with magnets on both ends. It vibrates when sound waves hit it, creating an electrical charge. The vast majority of ribbon microphones are bi-directional.
- Deliver warm and smooth tone quality
- Complements digital recording very well
We can decide when to use the recording microphone based on its features. It is able to capture detailed audio but rejects room noise and off-axis sound, which makes it ideal for recording guitar cabinets or choirs in large space. In additional, the bidirectional pickup pattern enables it to perform well in radio and television talk-show. It is also a good idea to use it as podcast recording microphone.
Nine recording microphone specifications explained
Polar pattern, frequency response, etc. are all commonly seen specs you will find in the recording microphone manual. Next let’s have a look at them.
Polar pattern - It tells how audio recording microphone responds to sounds from different directions
It refers to the way that microphone for recording responds to the sounds from various directions. It can be roughly divided into three types.
- Omnidirectional: this means the mic captures sounds from all directions.
- Unidirectional: A mic with this pickup pattern is sensitive to sounds in front of it but blocks audios from sides and rear.
- Bidirectional: As its name suggests, it indicates that the mic is sensitive to sounds from two directions, namely the front and back, but rejects sounds from the sides.
To go further, we can divide directional recording microphone into three types, including cardioid, supercardioid, and hypercardioid.
If you utilize a recording microphone with cardioid pickup pattern and records sounds from all sides, you will find that the front sounds are the loudest while audio from rear is the softest.
As for supercardioid and hypercardioid, they are more directional than cardioid, rejecting more sounds from the sides but capturing more audio from the rear.
You can have a visualized understanding with the following graph, which is made in the principle of sensitivity VS coming angles of sounds.
Frequency response - Range of frequencies that external recording microphone reproduces
To define it, frequency response is the range of frequencies that a studio or home recording microphone reproduces within a small tolerance and at the same level.
The following graph displays the output level of the mic in decibels at various frequencies. The 0 dB line on the graph represents the output level at 1 kHz, and the levels at other frequencies are represented as a number of decibels above or below that reference.
Proximity effect - Voice get bassy when making really close sound recording
Low-frequency output boosts when you use the microphone for video recording and place it really close to the sound source. This is what we call proximity effect. Therefore, you may have heard that a vocalist’s voice gets bassy when he or she sings incredibly close to the microphone. It will also be plotted on the frequency response curve to show the effect of extremely close up recording.
Impedance - Effective output resistance at 1kHz
Impedance measures the effective output resistance of the recording microphone at 1kHz. There are three levels.
- Low: 150-600 ohms
- Medium: 1000-4000 ohms
- High: 25 kilohms
It is good to use a low-impedance microphone for computer recording. It enables you to use longer cable without capturing hiss or losing high frequencies. In addition, you should make sure that the impedance of a mic input is higher than that of microphone. Otherwise, it will distort and sound thin.
Maximum SPL (Sound Pressure Level) - It tells when home or studio recording microphone begins to distort
SPL, short for Sound Pressure Level, refers to the audio intensity or how loud the sound is. So what does the maximum SPL mean in specification? For example, if a voice recording microphone features a maximum SPL of 125dB, it begins to distort when the target sound throws out 125dB SPL at it. Generally speaking, it is good to use a mic with the maximum SPL of 120dB while 135dB is better. The best recording microphone features the maximum SPL of 150dB.
However, audio distortion differs among different types. Dynamic mic won’t distort even the sounds are really loud, so will some condensers. In addition, a pad is used in some cases to stop distortion. But this will reduce signal-to-noise ratio, so just use it when it is needed.
Sensitivity - The higher it is, the stronger signals recording microphone puts out
It refers to how much the output voltage is when recording microphone is pushed by a specific SPL. When exposed to the same intensity of sound, the higher sensitivity a mic features, the strong signals it puts out. There are three levels.
- Low: 1.1mV/Pa (usually seen in Ribbon or small dynamic)
- Medium: 1.8mV/Pa (common for dynamic)
- High: 5.6mV/Pa (for condenser)
Self noise - The lower the better
This is also called equivalent noise. It stands for the signal that a microphone itself produces even there is no sound source.
The self-noise spec is usually A-weighted. That indicates the noise was filtered before being measured, resulting in a measurement that is more closely related to the annoyance value. To replicate the frequency response of the ear, the filter rolls off low and high frequencies.
So how can we decide on a good recording microphone according to self-noise?
- Below 10dB-A: It is extremely low noise since even a incredibly quiet recording room has noise higher than 10dB-A. This is only found in modern large diaphragm condenser microphone.
- 11-15dB-A: It is still excellent. Self-noise within this range is impossible to hear in mix.
- 16-19dB-A: This is pretty good for a majority of recordings. Noise can only be heard when a quiet instrument is recorded.
- 20-23dB-A: For a studio recording microphone, this figure is high. It is acceptable for recording loud sources.
- 24dB-A and above: If you are looking for a studio microphone, this figure cannot be considered.
Signal-to-noise ratio - The higher the number is, the quieter the recording will be
SNR is a term that evaluates the signal difference between the sound you wish the recording microphone to record and undesired noise. As a result, the higher the number is, the quieter the recording will be. In most circumstances, an optimum SNR should be greater than 70dB, with a high end of up to 110dB.
This does not, however, imply that you must acquire a microphone with a high SNR because such one is typically expensive. You can invest in a mic based on the volume of the target sound. For your convenience, we have concluded the tips.
- 73-75dB SNR: This is good when the target sounds are 50dB or louder.
- 78+dB SNR: It is ideal to record sound at 40dB or below.
Polarity - Right polarity of microphone cords is the key to high quality recording
Here we talks about the polarity of the electrical output signal to the audio input signal whose standard is “pin 2 hot”. That is, when the sound pressure pushes the diaphragm in, the microphone recording set produces a positive voltage at pin 2 that corresponds to pin 3.
You must be very careful not to reverse the polarity of microphone cords. Pin 1 should be shielded, pin 2 red, and pin 3 white or black on both ends of each cable. OR, on both ends, the wiring should be pin 1 shield, pin 2 white, and pin 3 black.
If you mix the mics to mono and some of cables are right polarity and some are inverted, the bass may cancel.