There are a few factors to consider when comparing these two sized diaphragms.
A large diaphragm condenser has a diaphragm diameter of 1″ or larger, while a small diaphragm is under 1″. The smaller diaphragm is more rigid, which prevents other types of distortion.
The small diaphragm microphone has higher self noise than a large diaphragm.
Air molecules attack the diaphragm, creating air pressure. Because the smaller diaphragm behaves as a hard surface, the air molecules hitting it exchange a greater amount of energy, producing a higher SPL (sound pressure level) relative to the area and sensitivity of the diaphragm. What is SPL?
The larger diaphragm mic is more sensitive than a small diaphragm mic.
The large diaphragm provides a larger output, and is thus easier to move. It’s also more sensitive because of variances in capacitance. Basically, the changes in capacitance due to the vibration of the diaphragm are bigger for an LDC. This means that the output signal voltage is higher.
Also, because the LDC has a larger diaphragm, the sound waves force it to move more than a small one.
The signal to noise ratio of an LDC also tends to be higher because of it’s stronger signal above the noise floor. An LDC is a good choice when recording a quiet instrument without adding noise from the mic or mic preamp. Preamp vs. Interface.
An SDC has a lower sensitivity because the diaphragm is smaller, stiffer, and more difficult to move.
Sound Pressure Level
The smaller diaphragm mic can handle a higher SPL than the large diaphragm.
Inside the microphone capsule, the distance between the diaphragm and the back plate, coupled with the rigidity of the diaphragm, means it can only move so much before distortion becomes too high. Due to this, a large diaphragm cannot handle a high SPL as well. The smaller and stiffer diaphragm can handle higher SPL’s.
Both large and diaphragms are equally capable of picking up the low frequencies, but a large diaphragm mic has a more limited frequency range than a small diaphragm.
Because of the upper limiting frequency (ULF), which is set by several factors relating to the dimensions of the diaphragm.
The large diaphragm breaks up and no longer acts as a true piston.
The weight of the diaphragm will reduce the displacement of the diaphragm for higher frequencies.
The diffraction around the edges of the microphone capsule will limit the microphones capability of handling very high frequencies.
All this means is that the LDC’s diaphragm is bigger and has more mass to move, thus not being able to react as fast to changes in sound.
The LDC is capable of a deeper low frequency response than and SDC.
The resonance frequency of the diaphragm is lower in the LDC due to it’s higher mass.
The grill of an LDC causes internal reflections and filtering, resulting in a rougher response. An SDC lacks a grill, thus doesn’t have this problem.
Because of this:
An LDC does better in capturing the deep tones of a tom or some low vocals.
An SDC responds better to really high frequencies such as cymbals and various other hats and crashes.
A small diaphragm microphone has a higher dynamic range than a large diaphragm mic. Because of this, it’s SPL (sound pressure level) can reach greater heights without harmonic distortion.
Directional mics have a louder low frequency response when used close. This is it’s proximity effect.
An SDC is designed to roll off these lower frequencies, or minimize/eradicate them after a certain frequency is met.
An LDC’s proximity effect tends to sound better, making it more useful for vocalists in studio. The SDC may sound a bit bloated up close.
An SDC is better because of it’s smaller mass, which enables it to more closely follow any air disturbances that it’s met with. It’s ability to capture acoustics, metal percussion, cymbals, or any other fast transients cleanly is the result.
Off Axis coloration
When sound waves hit the diaphragm off axis, they are traveling across.
High frequency sounds with short wavelengths tend to phase out or cancel due to interference.
The smaller the diaphragm, the less phase shift there is.
Less phase shift means less cancellation of high frequencies.
This all means that an SDC has a flatter high frequency response off-axis, while an LDC rolls off in the highs.
The placement of the capsule also has a lot to do with it.
The capsule in an LDC is inside the grill. This creates reflections and filtering in the grille which affect the response and polar pattern.
An SDC’s capsule is housed near the end of the mic. The capsule has no grille around it to alter it’s response and polar pattern.
What does this mean?
It’s another reason for an SDC’s lack of off axis coloration.
When off axis coloration is a problem
When the sound hits from the side, or at a wide angle. Luckily SDC’s pick up off axis high frequencies well, and work great in recording orchestras, grand pianos, and symphonic bands.
Wow. That was a lot of mumbo jumbo, huh? To keep it simple:
Choose an LDC when:
You need low noise and high sensitivity
You need a deep low frequency response.
You need a good sounding proximity effect on singers.
You want a cool look.
Applications: Studio vocals, ambience, deep sounding drums, miking a drum kit as a whole, quiet or distance instruments or vocals, guitar or bass amps, big brass.
Choose an SDC when:
You need an extended high-frequency response, and need to capture transients and other high frequency information.
You need a flatter frequency response.
Lower handling noise.
Excellent transient response.
You need less coloration, or “Low off-axis coloration” (A wider pattern at high frequencies).
Applications: Acoustic instruments, percussion, cymbals, hats, orchestral, spot miking, woodwinds, other delicate orchestral instruments, and anything with detail that needs to be captured.
In a nutshell?
LDC: More flattering.
SDC: More accurate.
Well that’s about it for today my friend! I hope you’ve enjoyed this article on large diaphragm vs. small diaphragm microphones, and your head doesn’t hurt too much (mine does) :).
Questions? Comments? Requests? Did I miss the mark on something? Please Contact me!!
Which mike are you more likely to go with? I would love to hear from you. Until next time..