Microphones What is it, and what is its use?

[AtlanticSmith]

I'm at a new school and trying to figure out what the thought process of my predecessors was. I found these two microphones in a cabinet protected by a terrycloth towel. The Janitor (who has been charged with setting and striking all sound equip.) said that they were expensive and used as ceiling mics. What are they?

 

[chausman]

Are there any markings on it anywhere?


Sent from my iPhone using Tapatalk

 

[AtlanticSmith]

Sadly, no. The back looks like a cardboard box wrapped with gaff tape (arguably) wrapped around it The microphone membrane is some form of plastic.

 

[Ric]

at first glance they look like some one has made ups some 'mics' from old radio speakers.
If that's what they are then all they're probably good for is Kick drum.

 

[n1ist]

It looks like a speaker, not a mic (though of course a speaker can be used as a mic)
/mike

 

[Footer]

at first glance they look like some one has made ups some 'mics' from old radio speakers.
If that's what they are then all they're probably good for is Kick drum.

Yup, looks kind of like a sub kick.

Sent from my Galaxy Nexus using Tapatalk

 

[cmckeeman]

what connectors does it have?

 

[BillESC]

I'd submit they were not expensive and are currently worthless.

 

[Chris15]

Is that piece of perspex attached?

It's been done before to place PZM onto a piece of perspex of adequate size and fly that off the bottom of a line array for ambient input into IEMs.
Doubtful in this instance, but a possibility none the less...

 

[jstroming]

Contact mic?

Do you do many dance shows?

 

[jstroming]

We have occasionally put a thin, hard, fiberboard in between the contact element and deck to dampen noise, if it is some sort of contact mic...

 

[museav]

Is that piece of perspex attached?

It's been done before to place PZM onto a piece of perspex of adequate size and fly that off the bottom of a line array for ambient input into IEMs.
Doubtful in this instance, but a possibility none the less...

A PZM requires a large enough surface to provide a 'boundary' at all of the relevant frequencies so for PZMs that would otherwise not be on a large surface it has been fairly common for many years, and before line arrays were common, to mount them to plexiglas panels. However, a pressure zone microphone would have the element slightly above and facing the boundary, not in the surface and facing out. It was also common in security systems to use the back EMF of a speaker to allow the speaker to function as a microphone.

That looks like an attempt to use a speaker as the diaphragm of a pressure field microphone (one of the three basic microphone types along with free field and random incidence or diffuse field) for ambient pickup, although I can't say I've ever seen something like that in use.

 

[Nelson]

It was also common in security systems to use the back EMF of a speaker to allow the speaker to function as a microphone.

That's where our paging system came from! We had an old burglar alarm with "acoustic sensors". We just unhooked the sensors from the security system and connected them to our 70v paging amp. Works well, I don't see any difference between the acoustic sensors and loudspeakers for this application.

 

[AtlanticSmith]

It has an XLR cabinet receptacle on the back. The sound is VERY treble heavy and tinny.

 

[bishopthomas]

That looks like an attempt to use a speaker as the diaphragm of a pressure field microphone (one of the three basic microphone types along with free field and random incidence or diffuse field) for ambient pickup, although I can't say I've ever seen something like that in use.

Yeah, that's exactly what I thought as soon as I saw it. Now I'll have to go with a similar response as the "What is it?" thread in the lighting forum:

What are they?

An idiot's project that surely failed immediately? Garbage?