How do I build an electro magnet strong enough to vibrate piano strings?

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Discussion Overview

The discussion revolves around the construction of an electro magnet or similar device capable of vibrating piano strings without physical contact, aiming to create sustained sounds. Participants explore various methods, including the use of loudspeakers and tactile transducers, as well as referencing existing technologies like Hammond organs and guitar sustainers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes building an electro magnet that can vibrate piano strings without striking them, aiming for a sustained sound by lifting hammers silently.
  • Another participant suggests that a normal loudspeaker, when hard mounted to the piano frame, could achieve the desired effect.
  • A participant questions whether a loudspeaker could create vibrations without producing noise, seeking clarification on its mechanism when attached to the piano soundboard.
  • It is noted that sound is vibration, and connecting a speaker to the soundboard would force the strings to vibrate as well.
  • One participant references the construction of Hammond organs, suggesting that existing technology could fulfill the OP's needs without reinventing the wheel.
  • A participant shares their past experience with a similar concept, mentioning that tactile transducers could excite piano strings, but expresses uncertainty about the best signal source for the transducer.
  • Another participant mentions that while there are patents for devices that excite piano strings, none can provide feedback like a "sustainer" circuit.

Areas of Agreement / Disagreement

Participants express various ideas and methods for achieving the desired effect, but there is no consensus on the best approach or the feasibility of the proposed solutions. Multiple competing views remain regarding the effectiveness of loudspeakers, tactile transducers, and existing technologies.

Contextual Notes

Some participants express uncertainty about the noise production of loudspeakers and the effectiveness of different devices in achieving the desired vibration of piano strings. There are references to existing technologies and patents, but no detailed exploration of their limitations or specific mechanisms is provided.

no.juan
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I would like to build an electro magnet capable of causing piano strings to vibrate without the strings being struck first. As long as the hammers are up, the strings would vibrate on their own accord.
An E-bow, used by guitarist for the same purpose, will (sort of) work on a limited range on the piano - but on only one note at a time. I would like to build something that can be hung inside the piano, close to the strings, that covers a wide range of notes. Hopefully I would be able to silently depress the keys, lifting hammers on those keys only, and thus creating an infinitely sustained piano sound, but without the attack the hammer gives. Thanks!
 
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A normal loudspeaker will do this, especially if 'hard mounted' to the piano frame.
 
Hi - thanks for writing. Please excuse my ignorance, as I know nothing of physics. Would a speaker create this effect w/o producing any noise itself? Is there something inherent about a loud speaker that, if attached to the bottom of the piano sound board, would cause the strings to vibrate enough to produce sound themselves?
 
Sound is vibration. The speaker will vibrate, pushing a column of air that will also vibrate. Connecting it to the sound board will just force the strings to vibrate too.
 
@OP: have you studied the construction of Hammond organs? There is no sense in re-inventing the wheel when there is very old and well-tested technology that can already do what you want.
 
I made this in 1981, showed it to Fernandes and tom sholz, and was told it had zero marketability.

A few years later, fernandes comes out with "the sustainer'.

30 years later, many big name guitarists have at least one "sustaining axe" in their collection.

I came up with this one day when I pushed down the tremolo bar (way down) on a kramer beretta guitar in a room lit by only one flourescent light and saw the string and speaker cone vibrating in synch. while wondering how I can get feel of standing in front of a cranked 4x12 cabinet while using a headphone amp.

Maniac music makes a sustainiac like the sustainer but they have an older model that is a tactile transducer that mounted to the headstock of the guitar.

I believe a tactile transducer attached to the soundboard of a piano could get you what you want to excite the strings but I'm not sure a mic. would be best for being the source of the signal you send to the transducer.
 
There are many patents of devices that excite piano strings to vibrate but none that will cause feedback the way a "sustainer" circuit can.
 

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