Speaker as a microphone

posted Oct 27th 2007 9:25pm by Will O'Brien
filed under: misc hacks

[Nathan] sent in his speaker microphone project. Speakers and microphones are physically similar – usually mics are much smaller to allow decent high frequency response. In this case, [Nathan] wanted something to pick up kick drums or bass guitars, without the cost of a commercial version like the subkick. It’s build around a dual coil 6.5 inch subwoofer. The passive circuit design allows the coils in the speaker to be configured for differing impedance, phase and isolation.

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Comments [20]

Reader Comments

i once saw a guy from Shure re-wire an sm58 as a tiny speaker as a demonstration of this very concept.

I especially like that he’s wired it up to be more than just a mic.

Doing cool shit with junk is awesome.

Posted at 10:53 pm on Oct 27th, 2007 by lonas

of interest to any people with ipod earbuds:

stick them in your mic input on your computer, and you can use the left earbud as a microphone. very handy in a pinch, and it also sounds fine through line in

Posted at 11:01 pm on Oct 27th, 2007 by peter hajas

@1
Or anyone with any other earbuds – they all are pretty much the same.

Posted at 11:12 pm on Oct 27th, 2007 by gm

ahhhhhh the oldest trick in the book

Posted at 1:40 am on Oct 28th, 2007 by alex mccown

Hmmm, not so sure about using headphones as a PC mic, The PC provides a DC voltage to the right bud, I guess that others here might know if that DC voltage was enough to overheat the bud over time.

Posted at 5:24 am on Oct 28th, 2007 by Will

Hmm, might have to try this with the Sub from my Logitech Z2300’s when i get my Z5500’s

Posted at 6:48 am on Oct 28th, 2007 by EthanV2

While this is very cool, I am beginning to find the instructables website rather annoying.

Posted at 7:36 am on Oct 28th, 2007 by Bhima

open headphones work reasonably well as a microphone

Posted at 8:45 am on Oct 28th, 2007 by Wesley

I was using speakers as microphones back in 1980. I accidentally discovered it playing with my brand new state of the art cassette recorder. I actually got better sound of the speaker than I ever did any mic that I could hook up to it AND it was significantly more sensitive. I used it to record my parents talking with my uncle 2 rooms away and I couldn’t physically hear them at all with my ears but I could hear them loud and clear through the recorder. Since then I’ve used speakers as microphones several times, even recently.

Posted at 11:36 am on Oct 28th, 2007 by eric

will: you can solve the dc voltage problem by putting a capacitor in series with the headphones.

Posted at 11:39 am on Oct 28th, 2007 by eric

I saw this in… “Honey, We Shrunk Ourselves”
http://www.imdb.com/title/tt0119310/
I believe, in his midget status, he scrapes some of the solder off, which does some funky film magic and makes it a microphone…

Posted at 11:50 am on Oct 28th, 2007 by Will

this has been a common dj trick since the late 70s… if you dont have a mic at your mixer, just plug your headphones into the mic jack, make your announcement, and plug em back into the cue jack.

Posted at 5:32 pm on Oct 28th, 2007 by samurai

All hail transducers!

yay

Posted at 7:03 pm on Oct 28th, 2007 by strider_mt2k

This is a classic ‘hack’.

Since I have virtually no cash, I use a car speaker (found in trash, of course) as my main mic. It sounds terrible, but alright for rough demos. From a 4 track tape recorder.

Posted at 5:19 am on Oct 29th, 2007 by neoxide

Just think, if someone had discovered this 45 years ago, Jack in the Box might have pioneered the drive-up window…

Posted at 2:22 pm on Oct 29th, 2007 by Stephen-C

Wow, I mean just wow. In other news, water can be used for drinking AND bathing!
Seriously, folks. Take apart an old microphone from the 50’s; it’s a speaker!
Remember in grade school how the PA system speaker was also a microphone?
This goes waaaay back to when they actually were the same thing; I even have an ancient bakelite telephone where instead of the mouthpiece having a carbon mike, it’…just another speaker!

So as to not just gripe and groan;

Other uses for speakers and/or microphones:
-Poor man’s laser show:
lay raw speaker on back.
lay a mirror on it so that one end is supported by the speaker.
Aim laser pointer at mirror onto ceiling. play music.

-Poor man’s actuator:
-strip most of the cone off or make holes so that air movement is reduced.
use to move parts of halloween display, such as eyelids or lips.
recorded speech makes a good signal source.

-passive (resonance) amplifier / frequency selective microphone:
-take Aluminum tubes about 1/4 inch in dia, cut to various lengths. Bundle together.
attach speaker to end of bundle (air tight, please).
Each tube if cut carefully will amplify a single frequency only, picked up by the speaker.

Posted at 2:31 pm on Oct 29th, 2007 by Scrappylaptop

“Hmmm, not so sure about using headphones as a PC mic, The PC provides a DC voltage to the right bud, I guess that others here might know if that DC voltage was enough to overheat the bud over time.”

Shouldn’t be a problem. Typically it’s only a 5V bias designed to drive the electret microphone pre-amp at ca. 1 mA. I would be surprised to find a commercial device that does not have some kind of current limiting in case of a short circuit.

Posted at 4:48 pm on Oct 29th, 2007 by Marco

after looking at the circuit, i wonder about impedance of this device since the transformer is a 1:1 and the coils are 4 ohm each. does it react favorably with preamps, and how would it compare with commercially manufactured mics?

Posted at 11:24 am on Oct 31st, 2007 by cliff

I particularly liked the results I got whan I used an 18″ woofer for a microphone. I’ve heard of large-diaphragm microphones, but 18 in (457 mm) is huge.

Posted at 10:12 pm on Aug 16th, 2009 by Thomas Bailey

To reader
im so glad to see various devices on the net i want take your help for donin something on my life.

Posted at 2:46 am on Nov 14th, 2009 by sandeep chaudhary