Is it possible to change a woofer speaker to a tweeter speaker for ultrasonic purpose ?

 

Is it possible to change a woofer speaker to a tweeter speaker for ultrasonic purpose ?

Depends. If it has a crossover network inside, the woofer is only being fed low frequency signals.

 

Due to the nature of the frequencies reproduced by each 'driver', certain physical attributes are unavoidably apparent with a moments consideration.
Lower frequencies are more easily produced by larger size diaphragms and high frequency drivers benefit from physically tiny cone areas. A fact that can be arrived at solely from considering wavelengths become smaller(shorter) as they increase in frequency.

Any other arrangement can be used.

It will be less efficient and less 'pure' in output. (harmonics and distortions would increase)

a woofer used at super-sonic freqs would almost certainly be 'audible' to humans in some very unpleasant form as well I would guess, and useable power at the desired freq of operation would, would, ...well, it would 'suck'.

 

Remove the paper cone and associated metal structures and use only the magnet assy+voice coil(spyder) portion of the speaker. Place something structurally similar to one half of a ping pong ball, but suitably larger, over the coil assy. Something very light, and very stiff. Then it would begin to behave and sound more like a high freq horn driver.

 

But the coil assy would probably have way too much mass to make a usable tweeter.

 

Woofers are designed to produce low audio frequencies, not high audio frequencies and not ultrasonic frequencies.

Tweeters are designed to produce high audio frequencies, not ultrasonic frequencies but a few can produce low ultrasonic frequencies. Tweeters are lightweight and fragile and quickly burn out if they play a continuous high power tone because high frequency sounds in music are for very short durations.

What frequencies, how much power and what duration?

 

Remove the paper cone and associated metal structures and use only the magnet assy+voice coil(spyder) portion of the speaker. Place something structurally similar to one half of a ping pong ball, but suitably larger, over the coil assy. Something very light, and very stiff. Then it would begin to behave and sound more like a high freq horn driver.

Bravo, This is what I had found it out before ( replacing the paper cone with a slim foil metal cone and deleting the rippled cloth which speaker coil is installed on it ) but I doubted and intended to question.

Also I have another simple idea but don't know whether it works or no. Is it possible we put a flat spring ( in the shape of cone) on the paper cone to limit its shaking (frequency) ?

 

Also I have another simple idea but don't know whether it works or no. Is it possible we put a flat spring ( in the shape of cone) on the paper cone to limit its shaking (frequency) ?

I don't see what purpose would that serve, you will not get louder high frequencies by damping the speaker even more.

 

Simply wind an electrical extension cable around a large nail and hold one end of the nail near the bottom of a large empty tin can.
Apply audio power to the extension cord then you have a speaker. It will not WOOF and it will not TWEET but it will shriek pretty well. Like a cheap AM radio.

I suspect that a "shaking frequency" of a speaker is its resonant frequency.
The extremely low output impedance of a solid state amplifier (0.04 ohms or less) damps the resonance very well. But when a speaker is used as a microphone then the resonance is not damped properly and the sound is very boomy.

An old TV has a speaker that is not damped properly and sounds very boomy.