Springverb Experiments

another use for old hard-drives

>>>>>>>((((((audio and video files)))))))))<<<<<<<<< <<<<description>>>> <<<<conclusions>>>>

Inspired by the wealth of hard-drive recycling ideas on hacked-gadgets and the >springverb research posted at Electronic Peasant.
When looking at both these pages... this hack becomes pretty obvious. It helps that i had all the materials laying around already.

2 junked hard-disc-drives which are pretty similar.

top removed and platters removed thanks to the handy torx-8 screwdriver.

had to remove the voice-coil to get the bottom platter out. The motor shaft has a little cap to hold the platters in so this is used to mount the spring by threading some wire through the holes and bolting back onto the shaft.

One drive was bolted to a metal plate and the plate bolted to a heavy vice. The vice was bolted to a piece of wood. The other drive is just held in place with a smaller vice. as can be seen in the first picture at top, the circuit board was removed from the drive and 2 connectors on the back are connected via alligator-clips to the speaker output of a normal stereo amplifier.

It took a bit of searching to find which pins were actually connected to the voice-coil. I used an amp which has electronic circuit-breaker protection on the speaker outputs just in case... this would be recommended so as not to accidentally blow a fuse, or worse, wreck the amp.

At first i was going to use the voice-coils as the spring's actuators, but then i realized that the platter motors could do the same job. This did work, however, there were numerous problems. The driver was very sensitive to overloading and tripped the amp's circuit breaker all the time, even at fairly modest power levels. further, using one of these motors as a receiver lacked a good amount of gain. Getting this set-up to work well would probably be possible with some op-amps and stuff... who knows.

The drive's voice coils work much better as drivers and as pickups and it's a much more dramatic effect than the limited back and forth rotation of the platter motors. The whole drive starts to act as an audio speaker which is kind of cool, and cranking up the volume turns the thing into a sort of a percussion instrument.

I'm still trying to think of a good way to attach the voice-coils to the spring, but for the time being, I opted for a piece of slightly stiff wire. This adds a lot of resistance to the movement of the arm but (and) it does the job of transmitting sound rather well. A better solution needs to be found though, at the very least because the wire attached to the driver coil tends to break after some wear.

The angle of the wire to the spring, the physical resistance of the wire to the VC, the placement (rotation) of the spring all have a pretty dramatic affect on the sound, so the eventual solution should take all of this into account. As noted in the EP site, the spring should be allowed to freely rotate. The shafts to which the springs are attached achieve this, however, the motor around the shaft has magnets which can affect the rotation depending on where the resting point of the spring is. This could also come in handy in the future as it also has an affect on the sound.

audio and video files

springverb.manorastro.mp3 A man or astro_man song is here run through the spring. Starts with just spring sound then, at 2min, some controls are messed with, and at 3min, some of the source is dialled back in to the mix. 4:26min
here is the sound of a cassette tape running through the spring.
the left channel is coming from the spring, the right channel from the cassette tape.
also shows a bit of what touching the spring does to the sound.
Shows a bit of what messing around with position and tension of the voice coils does to the sound.
Again: spring left, source right.
Instead of the spring, a metal wire is attached between the driver and pickup voice-coils.
A video signal is run through an audio mixer, then sent down the wire as vibrations, to be rejoined with the original video signal - via the audio mixer.
The wire becomes a bit of an interface with which to affect the resulting video picture.
Another video/spring experiment. This time the platter-motors are used as driver and pick-up, and the spring is used instead of a wire. Takes quite a bit of tuning with the audio eqs, but it's a cool effect.
As in the previous example, video/audio interfacing is done with the vs001 box, but just a hacked VGA cable will do the trick here.
springverb.pole.mp3 To conclude this batch, here is a song from pole as run through the spring and thus rendered pretty much unrecognizable. 5:59min


The sound quality was "not too bad" and some extra op-amps in the right places would probably help a lot.
Using a big heavy spring is not as handy in general audio terms as it tends to only add more bass than useful... of course there will be some killer subs added to the picture in future... + the way that spring is mounted, it's just begging to go for a spin, so we'll set what that does.

But so far, the tuned wire (rather than springs) had the most interesting possibilities, particularly for video use. I'm not exactly sure about what's going on there, but the blanking pluses of a video signal (which tend to be within audible range) were causing the wire to vibrate. These vibrations could be mixed back into the video picture in such a way that touching the wire at different points will affect the image in different ways. Seems that, even though this driver/wire/pickup combo is way below video bandwidth in terms of getting any picture detail, with a bit of eq tuning and signal mixing, the wire's signals can harmonically influence what the picture doing way up in the (inaudible) frequency ranges which carry a bit more picture detail... I like that.
If that's even what's happening... lots to do on this yet.