DIY lo-fi speaker element

[Mursu]

Originally posted by Stocker
Well, that last statement is a bit of a leap indeed!

anyhow. One member here has put a bit of aluminium foil over a strong magnet and fed it output from his amp, and it moved to the music. That would probably be simplest

Intresting... I have one O-shaped magnet... But you are talking about electrical magnet?

Originally posted by redunzelizer


One of the simplest ways to get a real "kitchenoid" speaker is the ever so (in)famous "Tin Can Driver". Grab a bigger (already opened and empty) tin can, approx 2-3 inches in diameter. Get a large inductor of a couple of mH, and a power-resistor of ~4 ohms. Wire the coil & res. in series and connect to your amp. (nominal impedance then 4 ohms, very HiFi conforming...)

Place the coil right near the bottom of the can, leaving only a small space of ~1mm so these just don't touch. Turn on the music...

A variation of the above would implement drilling a small hole into the middle of the can bottom, mounting a lengthy steel screw through that hole and placing the coil centered "around" that screw...

Cool... I have to try that one. Thank you. That might be just what I am looking for.

Originally posted by dnsey
The simplest I can think of is a magnetostrictor.
Just a fairly loosely-wound coil, which will 'tighten' slightly as current passes through it.
Slightly more sophisticated versions are used for underwater sound propagation, etc.

Sounds intresting... In practice? What do I have to do?

Originally posted by infinia
I assume you are mostly after different sound effects for speech right?
Old telephone microphones driven in reverse by small BW limited amps sound pretty cool.

Actually that speach thing was just an example... I would like to overdrive my analogue synths and other stuff... But yes... I have allready experimented with diffirent kinds of microphones... And destroyed couple of those too... very interesting efects and organic distortion.

Originally posted by angsuman
This brings me back. When i was 11 or 12 I was learning about loudspeakers, and I learned about this ribbon. I wondered how this thing worked? So what i did was take a wrigley's gum wrapper rip off the paper after soaking in hot water. then take the most powerful two magnets you can get ahold of or even just one. Then place the ribbon near these magnets but make sure your amp is at low volume. The sound is surprisingly clear. Definately enough for voice intelliigabilty and will probably be your most sucessful expermient. You can then experiement with magnet positions, folding the diaphram in a V shape etc.

Hmm.... Variation of Stocker's vision. What kind of magnet do I need?

To increase the resistence of the ribbon take a long coil of wire 30gauge or smaller and put it in series with the ribbon. You'll probably need to do this to prevent your amp from self reseting itself.

Yes... That thing is very familiar... If my amp had used disposable fuses I could not affort this hobby of mine.

Thank you all...

I found this one from Wikipedia:

Reis' speaker worked by magnetostriction. In his first receiver he wound a coil of wire around an iron knitting needle and rested the needle against the "F" hole of a violin. As current passed through the needle, the iron shrank and a click was formed. The image shown below is a more advanced version where the iron bar is clamped to a cigar box shaped resonator. This receiver is very insensitive; it produces weak sound but has good fidelity. It requires very high current and is a current sensitive device rather than a voltage sensitive device. Reis was marginally successful. This instrument could transmit continuous musical tones but produced indistinct speech.

(http://en.wikipedia.org/wiki/Reis'_telephone)

With modern aps that should work fine?

[Mursu]

Hmm... I missed this one on last reply...

Originally posted by infinia
Got an old Hard Disk Drive you can take apart?

Actually.. Yes...

How about hooking up an amp to a HDD seek arm coil? should work and may be very interesting for speech sounds.

I shopuld try that.. How can I locate arm coil there? Where to connect my amp.

Many HD drives use a "voice coil" approach -- the same technique used to move the cone of a speaker on your stereo is used to move the arm.

But not all? So this works with some hardrives only?

[infinia]

Originally posted by Mursu

I shopuld try that.. How can I locate arm coil there? Where to connect my amp.

see attached pic

Measure the coil resistance with an ohm meter should be 10 to 20 ohms or so. May have to limit low freq for best results try using a series non polar cap 2 - 10 uF. Sound will come from platter as the head touches there> the platter is not spinning for this experiment.

[karma]

heh that has a lot of diy applications

[mightydub]

use the cardboard tube from a roll of toilet paper as a former, wind a bunch of magnet wire around it to make a voice coil, hot glue to the bottom of a disposable styrofoam plate. Put the voicecoil over a stack of ring magnets.

saw this at science fair at my kids' school, worked pretty well.

[Ron E]

Originally posted by Mursu
I am intrested in building speaker element for my lo-fi experiments.

I am intrested in diffirent type of elements... Is there an easy way of buildin simple lo-fi ribbon? simple lo-fi Moving-coil?

Does anybody know anythong about Nikola Tesla's or Alexander Graham Bell's fist ideas as speaker elements? I Know they are fron 19th centyry so they can't be that complicated?

Speakers back in the day were armature type (moving magnet), and would probably be harder to make.

The easiest ribbon is a bit of very thin aluminum foil, pleated and stuck between two magnets. You will need a transformer because the impedance is very low. The impedance ratio is teh turns ratio squared, so if you wanted to multiply the impedance by 100, you would need a transformer that had a 10:1 turns ratio. For low fi duty, I suppose you could try (for starters) a mains power transformer that reduced the mains voltage by 10. Don't blame me if you blow up your amp, though.

The easiest moving coil speaker is a tube connected to a diaphragm of some sort. wrap a number of turns of wire (calculate length by DC resistance) around the tube at the bottom, then place the tube around a high strength magnet, suspended by some folded paper "springs". (stretched strings also make fair suspensions, but require a better frame) The surround (if you want one) is a bit harder to manage, I suppose you could glue stretch kitchen plastic or window film to the edges of the diaphragm, and use a large bowl, with cutouts in it, for the frame.

Have fun!