Gear / Technical Help > Microphones & Setup
Side Vents on Mics
DSatz:
What MIQ said. If you block the vents, you'll get a boomy, dull-sounding microphone with generally (but not uniformly) reduced directivity, depending on what you block them with.
borjam:
--- Quote from: Sevoflurane on May 19, 2019, 06:21:33 PM ---If they are pointed straight at the source, I don't see this inhibiting much of the sound?
Would love someone to chime in on this as well.
--- End quote ---
It's critical.
Covering them turns a directional microphone (pressure gradient) microphone into an omnidirectional. It's the typical singer mistake I hate with a passion. "Embracing" the microphone while singing and, whoa! Here comes the feedback!
Anyone interested on microphones should read this book:
https://www.amazon.com/Eargles-Microphone-Book-Third-Application/dp/0240820754
mfrench:
The croaky isn't going to provide enough blocking to have any effect. You'd need to wrap it, the capsule, in some form of non-flexible shroud that would eliminate 100% of the side venting in order to have it create a drastic change. You could even go so far as to wrap them in a bit of electrical tape, which would still allow for some pressure change to the rear of the capsule, due to the flex of the tape. Those vents allows for similar pressure in front and behind the capsule, in varying amounts, depending on the mics intended response. The croaky is not sufficient enough to change that bit of physics. And, at worse, it might make it a sub-cardioid response (which I dig).
Gutbucket:
The general impact of blocking vents is well known. They shouldn't be covered or closed, unless the microphone was specifically designed to provide mechanically switched patterns. Proper practice is to arrange things so you do not to block the vents or the front of the capsule at all.
The actual effect will not be easily predictable, partly because the croakie weave material covering the vents will not block them completely but present an acoustic resistance that varies with frequency. In the frequency ranges in which it changes the acoustic impedance through the vent system, it will affect frequency and polar responses. It is not at all likely to affect things for the better, but comparative listening is the only practical way to determine how much effect it has.
The real world-
You've been recording this way.. how do you like those tapes?
Try recording a few things using the same microphone arrangement but with vents uncovered. Notice any significant difference?
Weigh that difference against the microphone rearrangement practicalities.
If you notice a significant difference after running the above test a few times, yet need to keep the mics hidden in the croakies:
Try pushing the microphones completely inside the croakie.
-or-
Try placing a layer of the identical croakie fabric across the front of the capsule. If you do this, keep the fabric in front stretched by about the same amount as the fabric over the vents.
^
Both these methods seek to apply the identical acoustic impedance modification to either side of the diaphragm, such that the effect is simply attenuation of the frequency range affected rather than a difference of impedance on the backside. This is similar to what happens when you use a windscreen or faux-fur cover over a directional microphone. Compare after a making any necessary high frequency response EQ correction.
Or perhaps modify the croakie so you can continue to run them as you have been doing, but without covering the vents. To do that, I'd heat a small section of metal tubing of the appropriate diameter with a torch to heat and use it like a hot-knife, "cookie-cutter style" to make small windows for each vent hole through in the croakie material. The material is presumably polyester and the hot tubing should both cut the holes and heat-seal them. Insert a dowel of the same diameter as the microphone to stretch the fabric by the same amount and to present something to push the red-hot tubing against.
flask:
Won't the croaks just act similar to a windscreen?
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