Sony Betacam SP broadcast camera - microphone type

[shianne]

Hello,

I have a microphone which seems to be from an Sony Betacam SP broadcast camera.
I am interested in how the contruction of this microphone works and what is the benefit in comparison to an classical shotgun microphone.

From a first view it seems to be a clasic shotgun mic (mic.jpg).
Even the directional sensitivity "feels" like a shotgun mic (I did not measure it, only trying it with a recorder).
If I look inside, it is not the classical construction.

Inside the outer slottet tube is another tube mounted with a shock mount rubber part (front_view.jpg).

The inner tube has a slot along one side. One end shows into the direction of the sound source,
the other end is directly coupled to the electret capsule. The slot itself is covered with thin felt to prevent wind noise (inner_tube.jpg)

The electret capsule is back vented and so it must be a pressure gradient receiver based on the construction.


The idea behind seems to be to make the capsule longer and so have a longer travel time for the sound pressure wave from the front side to the back side of the membrane.
The slot on the inner tube helps to prevent a sound like an "microphone inside a watering can", which I guess coming from the resonances indise a tube.

But why did the designers prefer this instead of a classic shotgun?
Is there a special name for this contruction?


Best regards,

shianne

[AndyBeez]

It's a cardioid microphone design. Which isa type of sensitive uni directional microphone. For broadcast use it records general ambient sound ahead of the camera. However most live sound is recorded on seperate mics plugged into the XLR socket on the back of the cam; including the highly directional shotgun mics maintained by the sound operator.

http://www.learningaboutelectronics.com/Articles/What-are-cardioid-microphones

[shianne]

Thank you for your reply.

I find it odd that the design principle doesn't seem to be described anywhere.
The classic interference tube design, on the other hand, is described everywhere.

If I compare it this design to the classic shotgun mic, the cardioid seems to be the better one if it comes to audio quality from off-position-sounds.

Well, I didn't think of the use for ambient sound.
I tried the microphone and wondered why they put a mic like that on the camera.
My only thought was: You can't film that close, can you?