Hard Drive Speaker

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About: I study (civil) electronics engineering at the VUB in Belgium. I have a passion for making things, both useful and cool.

Intro: Hard Drive Speaker

Many people have an old hard drive laying around. In this project we will reuse it by turning it into a speaker! While it's not super useful, it surely looks cool and people are taken aback when they see it.

You might ask yourself: how can a hard drive produce sound? There is no speaker in it.
If we take a look at the Wikipedia page, a loudspeaker can be described as follows:
When an alternating current electrical audio signal is applied to a voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth (...), which causes a diaphragm attached to the coil to move back and forth, pushing on the air to create sound waves.

In our hard drive we have exactly this, as can be seen in the picture: 2 permanent magnets with a coil in between; thus it can act as a loudspeaker! When we apply a current to the coil in the read/write head, it will move between the magnets and produce sound.

Now let's put this theory into practice and let's get building!

Step 1: Parts & Tools

Parts

  • Old harddrive (although a new one would also work :p)
  • USB cable
  • 3.5 mm audio cable
  • LM386 audio amplifier
  • 2x 1 kOhm resistor
  • 2x 100 uF capacitor
  • 1x 100 nF capacitor

Total cost: less than $10!

Tools

  • Torx screwdrivers
  • Soldering iron
  • Multimeter

Step 2: Disassembly

The first step of the build is disassembling the hard drive. Simply remove all the screws; there will probably be one under the sticker as well.

Next, we'll need to take out the guts. Undo all the screws you see and remove the components. You might have to use some force to remove the magnets.

We only need to keep the read/write head and the magnets, the other parts can be thrown away. Therefore, the ribbon cable attached to the read/write head can be removed.

Step 3: Electronics

Prepare the voice coil

The first thing that we will do is connect 2 wires to the coil of the read/write head. It is easiest to solder the wires while the head is removed from the case. It can then be reinstalled together with the magnets.

Make an amplifier

We now have a speaker, but we still need an audio source to drive it. The output from a headphone jack is not powerful enough to drive it, so we'll make an amplifier to fix that.

The circuit of the amplifier comes from Afrotechmods, an awesome youtuber; his video can be found here. Check it out for an in depth explanation, I'll stick to a short version.

The heart of the circuit is the LM386, an audio amplifier chip which will do all the hard work for us. It takes the audio signal from our audio device as an input and drives the speaker.
While the input signal should be Mono, the 3.5 mm headphone jack outputs a Stereo sound. A conversion is necessary, and accomplished with the two 1 kOhm resistors.

Solder everything together according to the schematic and attach the speaker. You might need to use some sandpaper to remove the coating on the headphone wires. The power will be provided by the USB.

Mounting

Now that our amplifier is fully functional, all that's left to do is mount it in the case.

You can use some double sided tape, velcro, or drill a hole in the PCB and mount it with a screw like I did.
Route the cables through the hole in the casing and secure them with a zip tie to finish it all off.

Step 4: Test & Enjoy

We're done! The only thing left to do is to test our new hard drive speaker.

Connect it to a USB port and an audio device, crank up the volume and witness the magic!
I hope you liked the project and have found a good use for that unused old hard drive!

Feel free to check out my other instructables:https://www.instructables.com/member/ThomasVDD/

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30 Discussions

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diy_bloke

10 months ago

Fantastic. Totally useless but nevertheless fantastic ;-)

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tvengineer

11 months ago

Years ago a coworker took the voice coil from a monster hard drive (something like 5 10 inch platters) and hooked it up to an amplifier and a function generator to drive it and connected the arm to a sheet of plywood. man that thing could make a racket :-)

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The Lightning Stalker

11 months ago

The LM386 is prone to hiss when run like that. What you need to do is set the gain on pins one and eight and run the low pass filter on the output like it says in the datasheet. Keep all connections short and it looks like you have done that.

Also solder flux goes a long way toward producing nice shiny and consistent joints. It's literally so much easier to solder when you use it. Like night and day difference. You can get the good stuff in small quantities on eBay. Liquid or tacky, I have some Kester stuff it's great.

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+1

Rosin core solder works well for novices. Well worth spending on.

So many people don't have a clue how to solder. A good quality, high wattage temp controlled iron is a good investment.

Fun project :)

If the joints are dull and cold like that it won't last more than a couple years before it starts corroding. It will stop running and it's very difficult to fix even with flux. It's better to do it right the first time.

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ThomasVDDThe Lightning Stalker

Reply 11 months ago

I have not experimented with setting the gain.

The soldering quality is fine, I have quite a lot of experience with that. I guess the picture doesn't do it justice.

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AdamB333

11 months ago

Cool project. Reminds me of the old 80's project for making a line printer play music. This isn't a useful speaker. Possibly harvesting the coil and magnets, and putting a cone will yield better results. The fact this works is amazing, but it reminds me of teaching a pig to dance: it wastes your time, and annoys the pig. :)

1 reply
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ThomasVDDAdamB333

Reply 11 months ago

I know it isn't useful, but it's not meant to be at all :p Just the fact that people don't understand it when they see it makes it great :d

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LesB

11 months ago

Next thing is to take an old speaker and turn it into a hard drive.

3 replies
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kasssaLesB

Reply 11 months ago

I look forward to your Instructable on doing that, LesB! :-)

Best thing I've read so far today!

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AnthonyJ79

11 months ago

A cool design! Just one question, where is the diaphragm?

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rocketrideGordonP13

Reply 11 months ago

No, the heads move along the platters, not up and down, so they don't make the platter move in a way that would efficiently move air, either.

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ThomasVDDAnthonyJ79

Reply 11 months ago

The diaphragm is simply the read/write head, the part where the voice coil is mounted to.

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AnthonyJ79ThomasVDD

Reply 11 months ago

Thank you for your reply. Are you suggesting that the read/write head is vibrating resulting in a sound wave? But doesn't that only generate the buzzy sound of vibration? I thought the diaphragm must have some shape so it would shape the air into pressure waves of certain patterns to generate so-called music we hear. Sorry, I feel I'm lacking the basic knowledge of a loudspeaker, for which I should have done a research by myself but I'm asking here.

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miguelg89

11 months ago

Se podria hacer us sismografo..

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ExORL

11 months ago

the sound is genersted by the moving srm snd coil pushing air bsck and forth. In fact, the surface that moves air is very small. No sound is radiated from the larger side of the moving structure. If you were to fasten a stiff wire to the arm, and connect it to a sheet of paper, aligned so the arm pushes on the paper, you would probably get quite a better volume and sound quality. You could experiment with the size or stiffness of paper, or use a plastic surface from a margarine tub, e g.. This is a non tech example of impedance matching.

Nice instructable!

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winnetui

11 months ago

continuing (problems with the editor here), ... and the reactive force on the case. If you remove the disks and mount a perpendicular, lightwight but stif rectanguar piece, you may get a better, louder sound, and as a gift, on low frequencies a wingtype low noise soft blower.