Diy Piezo Spring Reverb

[mac]

Recently I had to repair the secondary coil of an Accutronics tank because it's a real PITA to import even small packages where I live.
I decided to kill two birds with one shot, a plan B in case the tank fails again, and a reverb unit for my Epi Valve Jr.

I started with ferrite magnets inside coils, and springs and rubber bands.
As audio source, guitar to npn preamp to LM386 to first coil. Second coil to npn to amp.

Some drawbacks, the magnets move perpendicular to the coil axis, not a big deal.
And the coils were big, so the first one induced dry audio into the second coil.
Besides, the magnets I have are not strong, and to hold them in place make weak vibrations.

I decided to use a cheap speaker, a piezo and a copper spring, one side taped to the cone, the other side taped to the piezo.

The spring in the sound demo is about one meter of solid core, alarm systems wire.
I used a pencil to form the spring.
In the pictures you can see bigger one too.





Schematic is almost included in the first picture. Please do not make me draw one

The demo starts with clean sound, then a bit of reverb, a bit more, and finally Marty McFly settings,

https://www.aronnelson.com/gallery/main.php/v/mac/sound+demos+of+my+circuits/reverb1.mp3.html

Mobile recording.
The speaker distorts, and the coil should be glued, not taped.
It's getting feedback from the Epi speaker too.

But it's good sounding, nice balance of lows, mids and highs. And when I tried the bigger spring lows were deeper, at the expense of highs, of course.
Two springs would be killer, one inside the other.

I'm having trouble trying to play the sound demo from the Gallery, maybe a Flash thing.

Enjoy,

mac

[Rob Strand]

Pretty cool idea mac.   

Actually works better than I expected from the pics.  There's a bit of "single delay"  reverb sound like you get from a Flanger.   Normally the spring is in tension and they tune the wire-size, winding pitch, spring length and tension to fine tune the sound.  Many even have damping at the mounts.

[Rob Strand]

Check out this one with tension tuning  (note more turns of thin wire on the spring.)
http://www.instructables.com/id/DIY-Spring-Reverb/

The spring is too loose on the video.  Maybe need even thinner wires and more turns.

[mac]

There are lots of thing to tweak, wire gauge, lenght, materials, compression or expansion, number of piezos, feedback, etc, etc.

I have to re-think the driving and mixing circuit.
Opamps might be a better choice.

mac

[Rob Strand]

This one uses a transverse drive and undamped pivot points for the spring.  IMHO this set up is more like the reverb tanks.  It should have a lot less damping at the ends but there's still some as the spring is connected to the speaker.  Probably would sound better.
https://c1.staticflickr.com/3/2613/3948219750_e1abb6ab48.jpg

World's biggest spring reverb

Yeah there's some insane reverb constructions.

[mac]

The flickr pict is similar to what I was trying to do with coils, but in axial mode.
I was getting transverse vibrations.
If I place the coils facing upward, the magnets or ferrites vibrations would be along the spring.
I can compare transverse and axial waves.
Thanks.

Yeah there's some insane reverb constructions.

Speaker -> non-newtonian fluid -> speaker, just another idea

mac

[Rob Strand]

Speaker -> non-newtonian fluid -> speaker, just another idea

Good idea.  Maybe a piezo driver and piezo receiver.  They would be easy to adapt to a liquid.
I'm pretty sure blood is non-newtonian.   Mac's Blood-Bath reverb sounds cool.  Ideal for scary movies.  You can even plop things in the liquid for sound effects.

[PS: If I get a chance I might try to extract the spring parameters off some reverbs I have.   I don't want to stuff them.]

[mac]

I'm pretty sure blood is non-newtonian.   Mac's Blood-Bath reverb sounds cool.  Ideal for scary movies.  You can even plop things in the liquid for sound effects.

Unfortunately it's illegal to sacrifice animals, or humans, in the name of science.
I'll have to resign myself to use Ketchup 

Or corn and red water, which behaves inversely.

mac

[Rob Strand]

I'll have to resign myself to use Ketchup

That's the movies for ya.

Unfortunately it's illegal to sacrifice animals, or humans, in the name of science.

There's actually blood mimicking fluid you can buy for that.   For example when you test heart pumps and valves. When we did ultrasound testing for blood flow we put cornstarch in the water to mimic the reflections off the red blood cells.  For the magnetic flow meter we used salt.  We didn't need to mimic the fluid dynamics.

[duck_arse]

I'm pretty sure blood is non-newtonian.   Mac's Blood-Bath reverb sounds cool.  Ideal for scary movies.  You can even plop things in the liquid for sound effects.

Unfortunately it's illegal to sacrifice animals, or humans, in the name of science.

both are allowed, however, in the name of art.

[mac]

Another demo, but with a longer and thicker copper wire.
4" speaker.
Spring about 40cm long, diameter 1cm.

I'm getting a bit of short delay, and lots of mids and lows.

https://www.aronnelson.com/gallery/main.php/v/mac/sound+demos+of+my+circuits/reverb2.mp3.html

mac

[Marcos - Munky]

Don't know why, but I can't listen to the demos

[Rob Strand]

Don't know why, but I can't listen to the demos

I had that problem the other day.  On the left bar there's a duplicate name.  Just click the other
link with the same name and it has the sound file (.m4a).   The ones that come-up blank for me are the .mp3 links, there's actually no link.

[Rob Strand]

Another demo, but with a longer and thicker copper wire.
4" speaker.
Spring about 40cm long, diameter 1cm.

I'm getting a bit of short delay, and lots of mids and lows.

That one sounds pretty good.

[Marcos - Munky]

Thanks for the tip, Rob. Now I got it working. This one really sounds pretty good! Just to clarify, you've ended up with just the coil glued to the speaker and the piezo, no magnets?

[mac]

It´s taped in the demo.
The speaker side must be glued.
The piezo side could be soldered, or glued as long as the coil is in contact with the piezo.

Don't know why, but I can't listen to the demos

I had that problem the other day.  On the left bar there's a duplicate name.  Just click the other
link with the same name and it has the sound file (.m4a).   The ones that come-up blank for me are the .mp3 links, there's actually no link.

I can't play the mp3 either, that's why I left the .m4a 

New host issue?

.m4a links,

https://www.aronnelson.com/gallery/main.php/v/mac/sound+demos+of+my+circuits/reverb1_m4a.html

https://www.aronnelson.com/gallery/main.php/v/mac/sound+demos+of+my+circuits/reverb2_m4a.html

mac

[thermionix]

I can't play them in the browser.  I could download the .m4a, had to change the end of the file name from "_m4a" to ".m4a" to play it.  Don't see a download option for the .mp3.

[Marcos - Munky]

What happened with the mp3 files is what Rob mentioned. No download link, then click on the duplicate name on the left side. Then the file is downloaded as "_m4a", but it plays correctly after renaming it to ".m4a".

Question on the schematic. Could you draw one? just kidding.
"As audio source, guitar to npn preamp to LM386 to first coil. Second coil to npn to amp."
The npn preamp is something like the LPB? Then you split the signal into an 386 (pins 1 and 8 opened?), which feeds the speaker. The piezo is connected to an npn preamp (LPB?), then the wet signal is mixed with the dry signal that cames from the first LPB. Is that correct?

[mac]

In the first demo I used a mpsa42, 10k to vcc, 1M C to B, 2k2@emitter to reduce gain,  then a 50kA pot to lm386 to speaker.
The mixer amp is a BMP 1st stage, 1k@emitter.
Guitar to input cap to 47k to Npn.
Piezo from B to Gnd, not a good idea because it cuts highs, piezo capacitance?

Second demo,
Signal to Npn buffer to 50kA pot to lm386 to speaker.
Mixer unchanged.
One side of the piezo to base, the other to 47k to gnd.
Guitar to cap to 250kA to mixer base.

mac

[mac]

What happened with the mp3 files is what Rob mentioned. No download link

The audio player is missing, new host issue?

Question on the schematic. Could you draw one? just kidding.

mac