Make a LoFi Mic From an Old Telephone Speaker





Introduction: Make a LoFi Mic From an Old Telephone Speaker

The speaker in an old telephone makes a great lo-fi mic. Just wire a 1/4 inch jack straight up to the speaker and enlarge the telephone jack hole to mount it. A small piece of towel helps to muffle some of the air noise.

You can hear an audio sample on our blog entry. Made by recompas and friends.

Tools and supplies needed:

-old phone headset
- 1/4" audio jack
-about 20" of hook-up wire
-solder / soldering iron
-screw driver
-small piece of towel

Step 1: Unscrew the Speaker and Microphone Caps and Remove Innards

The covers simply unscrew. The only part you'll be keeping from the insides is the speaker. Get rid of everything else, including the telephone jack.

Step 2: Drill Out Telephone Jack Hole to Make Room for 1/4" Audio Jack.

Enlarge the existing telephone jack hole with a 5/16" drill.

Step 3: Solder Wires to and Install 1/4" Audio Jack

First solder wires to the audio jack, then install in the newly enlarged hole. Cut the wires to be long enough so you can easily attach them to the speaker (next step) after the audio jack is installed. The audio jack won't fit through the body of the phone, so you need to install the jack before screwing the wires to the speaker.

Step 4: Screw Wires to Speaker

Some phones will have a resistor across the speaker. Just leave that there.

Step 5: Screw the Caps Back on With a Little Piece of Towel on the Speaker

To help reduce some air noise, put a little piece of towel underneath the cap that goes over the speaker (the new lo-fi mic). Screw both caps back on and you're done.

Again, an audio sample on our blog entry.



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well I took this same idea and planted the plug in to the bottom of a soup can.

I mounted the speaker over the plug inside the can(yes I made a plastic holder).

Now I have a sexy tinny sound while I play one of my harmonicas.

Fun project I liked.

Awesome, i wanna try this sometime!!

how long did it take you?

HEY ;) !! If the sound from the microphone is too weak, theres a way to "amplify" it : just solder a 9v battery to the wires , and add a on/off switch ;)

I used telephone speeker and telephone mic.
Mic worked but it was to noisy, quiet and I soldered badly.
Telephone speaker worked good untill I realized that opened soledring between to cables is bad. I taked off short pre wired cables. I but longer ones and it stop working.

Hello People,

I just picked up an old telephone and intent to make one of these mics. However there are two on instructables as you might know. The other one, by Randolfo is found here:
Now I hear some of you are talking about a preamp. Is this what Randolfo has done? And is that the difference with this one? Or is it essential to get it to work to add a little voltage on the mic, like with a condenser microphone. I don't understand this very well and I'm new at the whole electronics and diy-business. So if someone could explain me the difference between the two, I would be very thankfull.

Thanks for the great posts all of you. I really love this site.



I'm working on my second right now (the first shifted into another project before I finished it as a mic).

I have had no problems running mine directly into a PA or a guitar amp. I get full volume, in fact I generally get a lot of feed back.

You're fine without it, but you're probably done by now either way.

Yes, I'm done by now and it works perfectly. But what did was slightl different from your original design; I used the speaker as mic and that did the trick for me. Thanks for the reply though.

how does the speaker pick up sound? im sorry i dont know.

There is not much difference in the design of a speaker and a dynamic microphone.  The main difference is that one is optimized for making sound and one is optimized for hearing sound.  Beyond that, the guts of the two are very similar.  This is probably why the microphone in this project is "lo-fi."