Do dynamic mics with changeable polar patterns exist?

[Sax2]

(Preface: I'm new to recording. )

I've noticed that there are plenty of condensers that are capable of multiple polar patterns, but I haven't heard of any dynamics with the same functionality. Is there something about the way dynamic mics work that makes it impossible (or impractical) for them to have multiple polar patterns?

 

[Steenamaroo]

Hey.

Most condensers achieve a combination of patterns through different uses of the output of two diaphragms; Whether it be adding their voltages, subtracting them, or just ignoring one.

As far as I know, dynamic mics are cardioid by design, and can achieve omni by isolating the rear of the diaphragm from the outside world, meaning that no sound can reach the mic from behind and cancel out with the on axis sound.


Here's a great article explaining what goes on.

Hope that helps.

 

[moresound]

Rappers while *cupping* the head of say a ... SM58 microphone will turn it sorta into an Omni pattern.

Some dynamic microphones have multiple low end roll off selections or mid range scoops though. The Sennheiser MD421 and the EV RE38R/D come to mind very quickly.

 

[snow lizard]

Technically a ribbon mic is a dynamic mic. I think RCA's 77 model (post C versions) had a switch that you could turn with a screw diriver to select polar patterns. This was done electrically with the use of 2 ribbon elements. The D models used a single ribbon with a series of shutters inside to modify the innards of the mic mechanically to operate as pressure or velocity or wherever you had the thing set to. I'm going off of memory here, but I think there was also an Altec or something which was basically a figure 8 ribbon with a moving coil omni that you could switch electrically for different patterns.

The "covering up the holes at the back" idea (mechanical) the other guys are talking about is essentially how a couple of Shure pencil condensers switch from uni to omni. Would probably work good with a Beyer 201 if you made a little mylar sleeve for it or something to cover up the holes at the back of the capsule.