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Is it a fallacy that dynamic microphones are better at rejecting room sound?

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sfs1:
I'm not having much luck with this question in music production circles, it very quickly goes into personal experience and received wisdom.

It's commonly said that a dynamic microphone is better at rejecting background noise / room sound / reflections compared to a condenser microphone. I don't understand why this should be the case. When I look at the polar response graphs for different mics, I don't see any pattern that would let me determine that I'm looking at a condenser mic or a dynamic. They're just all over the place (you can get a shotgun condenser and an omni dynamic for example). So if the polar response isn't characteristic, what else could make a difference? Maybe it's just that there are lots of dynamic mics that have a tight polar response and lots of condenser mics that have a wider response, so when you look at a typical mic cabinet in a studio, that rule of thumb holds. But people (and manufacturers) talk about it as if it was an intrinsic thing. I'm interested to find out if I missed anything or got anything wrong.

dmills:
There is nothing intrinsic about either technology that impacts this, and contrary to popular belief in music circles the ONLY thing the mass of the diaphragm impacts is sensitivity.

What I think may be going on is that a condenser is often really a large diaphragm condenser and those (because the diameter is greater then the wavelength at high frequency) tend to have significant side lobes in the response at high frequency, thus making them more prone to pick up reflections from a badly behaved room.

Narrower patterns do of course pick up less room, and those are often (but not always) condenser designs.

JohnnyMalaria:
I suspect it's because, for many cases, a particular dynamic microphone is chosen because it is cardioid (e.g., Shure SM57). Hence, many people would simply associate the two and claim a dynamic mic is better for rejecting room sound.

TimFox:
The basic sensitivity patterns are omnidirectional and figure-8.  The latter is the default pattern for a ribbon microphone, where both sides of the ribbon diaphragm are exposed to sound, and the voltage from one side is inverted in polarity from the voltage from the other side.
Summing these responses with appropriate weighting produces the "cardioid" directional pattern (heart-shaped) and its variations.  Some microphones (including condensers) incorporate electrical switching to set the response to omni, figure-8, or cardioid.
Cardioid is the usual choice when response to sound from one direction needs to be attenuated, for example when acoustic feedback in sound-reinforcement systems is a problem.

SiliconWizard:

--- Quote from: JohnnyMalaria on March 08, 2021, 03:59:50 pm ---I suspect it's because, for many cases, a particular dynamic microphone is chosen because it is cardioid (e.g., Shure SM57). Hence, many people would simply associate the two and claim a dynamic mic is better for rejecting room sound.

--- End quote ---

Well. Yeah. This point is certainly a major factor.

Another, more objective one, is that condenser microphones tend to be more sensitive than dynamic ones. One side-effect of this, is that you tend to get a dynamic microphone closer to the sound source - which in turn will tend to get you a better signal-to-noise ratio. But this approach doesn't necessarily work well for recording everything. So, as always, the right tool for the job.

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