Ribbon versus Condenser.


Microphones are elements of pure physics, where the domains of electromagnetic, mechanical, and fluid intertwine. It's just an object. In this case a sheet, with its stiffness, mass and shape, immersed in the viscosity of air and subjected to the damping caused by Eddy currents, of a strong magnetic field. This film follows the movement of the waves, which push and pull it periodically or impulses. Any mechanical structure, either a steel plate, a drum, a formula 1 or a swing, all have one or more resonance frequencies themselves. The lowest frequency resonance, called fundamental is critical. At this frequency, the object offers no resistance to vibrate. Requires very little energy to vibrate. If not for the friction losses in the viscosity of the surrounding air and the rigidity of the membrane, the movement would be infinite, would be an undamped system .
The resonant frequency is an important factor in the issue of this article. In ribbon microphones , this frequency is handled differently form the capacitor. In this image



see an example of system in which the resonance frequency is located at 100Hz. In purple see phase changes . We see that this movement is delayed in phase below the resonance frequency and phase advance above it, from 100 Hz in this example. Also see in red displacement amplitude of the membrane. At the resonance frequency shows a peak, resulting in a hump in the response , very characteristic of condenser microphones. This is your main problem. Ribbon microphones , by their mechanical characteristics, the low stiffness and low mass attached to the freedoms of movement, have a very low resonant frequency, 30 or 40 Hz Therefore, the entire audible range is free from the peak caused by phase shifts, delays and advances near the resonance frequency. If we observe a frequency response graph without filtering, the hump we talked about earlier would become a chaos of prominent peaks and bumps near the resonance frequency. Logically, manufacturers no displays its graphics without filter, at least 1 /3 octave, much less a plot of phase.
In condenser microphones small diaphragm resonance frequency is close to the 10KHz, this area is affected considerably. Condenser microphones Large diaphragm, its dimensions are somewhat lower resonance, depending on the manufacturer. There are between 800 Hz and 5000 Hz, resulting in a large color at those frequencies. Just in critical frequencies have zones of uncertainty and chaos that some may seem interesting for certain shots. But the widespread use in many instruments recorded with condenser, make a recording of a monster phase distortions, which according to some, are not perceptible by the human ear, but only in pure frequencies. When many different recording offsets unite, they become not only remarkable, but in a real ear fatigue .

Why is it almost impossible to avoid this problem in condenser microphones ?

1 - . A capacitor needs its fixed plate ( plate damping ) and the diaphragm are very close to electrically charged , about 25 microns . How can we avoid touching not reach in case of an intense wave front ? , Then tightening the diaphragm , which greatly increases the resonance frequency . The head of a drum tuning frequency increases with stress.

2. - Could increase the mass to lower the resonant frequency ? . No, because it would lower the sensitivity too .

3. - What happens to the air trapped between the two electrodes ? . The camera may not be airtight , since it would increase the mechanical impedance , therefore we must redirect outwardly through holes , but their actions , their depth , modify both its polar pattern as its frequency response .

4. - Polar patterns of condenser microphones are aberrations . In some cases two opposing diafrgamas are combined in phase and sometimes against other phase . The single diaphragm, perhaps the most natural , but they have their limitations.

5.- Diffraction problems . When the wavelength is large relative to the diameter of the diaphragm , the uptake is acceptable, but when the wavelengths are small ( high frequency ) , compared to the diameter of the diaphragm , some frequencies are enhanced and other canceled .