In full range speaker high freq force source is not moving, the same as low frequency force source is not moving. What is moving, is a counter-force source (cone and air).
Now, here is the question: when voices sing, acoustic instruments play, do they produce Doppler effect? I don't mean marching brass band, I mean sitting musicians, standing singers...
Now, here is the question: when voices sing, acoustic instruments play, do they produce Doppler effect? I don't mean marching brass band, I mean sitting musicians, standing singers...
Did some quick calcs (might need someone to check them).
Take a driver with 1 cm excursion at 100hz. The max velocity is about .6m/s. If we take the speed of sound as 340m/s we get a max doppler freq shift of f*.998 (a 1khz tone will shift 2 hz max) Not much. Do you hear a doppler shift when a car horn goes by at 2 miles an hour? Youd here even less as a 2hz modulation of 100hz. (the 1khz goes from 998 to 1002hz 100 times a second.) I would guess in extreme cases it would sound like TT flutter.
Take a driver with 1 cm excursion at 100hz. The max velocity is about .6m/s. If we take the speed of sound as 340m/s we get a max doppler freq shift of f*.998 (a 1khz tone will shift 2 hz max) Not much. Do you hear a doppler shift when a car horn goes by at 2 miles an hour? Youd here even less as a 2hz modulation of 100hz. (the 1khz goes from 998 to 1002hz 100 times a second.) I would guess in extreme cases it would sound like TT flutter.
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This guy used considerably fewer than 5k, still looks quite a bit of soldering involved though
It looks like pioneers are going to solder for him all that multiple speakers, amps, and digital control lines.
The cone moves, the air moves. But the magnet does not. If we excite an air directly by magnet/coil without use of any cone, do we get Doppler?
What is so different in Piano? It's deck is "moving".
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This is the nub of the whole thing. And why everyone is so convinced that there must be Doppler.
You are correctly seeing that the cone excites the air and produces the sound and is therefore, the 'source'. You are correctly seeing that the cone is moving. And so you reason that as this is a case of a moving source there will be Doppler shift.
It's a darn confusing thing to think about - but...
If you were to be a small alien and sit on a cone being drivel with LF and HF you'd notice yourself moving back and forth at, say, 0.5Hz (in a nice sinusoid with respect to the magnet). You'd also feel a tingling sensation from the HF vibrations of the cone surface. But if you measured them you would find that they are not a sinusoidal motion relative to yourself, to the surface of the cone. In fact, you would see that the time between 'peaks' varied with the slow movement of the cone. If instead you were to measure the HF vibrations with respect to the magnet you would then see them as sinusoidal, but only with respect to the main magnet and not to the surface of the cone. In a bassackwards way of thinking you could say that the HF vibrations as measured relative to the cone surface are not only non-sinusoidal but pre-doppler corrected, and the movement of the cone then Doppler shifts them them back to a steady frequency for the listener. As Einstein said, it's all relative to the observer.
The 'effective' source for the HF vibrations as a sinusoidal sound wave is non-moving, it is in fact stationary with respect to the magnet.
p.s. Wavebourn, I like your cigar lighter
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If the Doppler effect occurs in loudspeakers, it must be very (irrelevantly?) small, (although I believe that Linkwitz says that with other distortions being lessened with improvements in technology it MAY be of interest).
With reference to cbdb’s thought experiment:
I am under the impression that for the Doppler effect to occur, the source of a (fixed) tone only needs to move relative to the listener, observer, IN ONE DIRECTION (a galaxy say, with respect to the viewer).
If the train is coming towards you and the horn is switched off the instant it is level with you, as the listener you will experience the Doppler effect.
Equally, if the horn is started as it is level with you, as the moving train recedes you will experience the Doppler effect (would that be called opposite “polarity”?).
In cbdb’s extreme frequency difference case, it seems to me that taking the physical (not electrical) source of the high frequency tone (the voice coil) as it passes through the center of it’s frequency modulated sinusoidal motion IN ONE DIRECTION, if the physical source could maintain the exact same velocity, I would be inclined to think that the conditions for the Doppler effect would be satisfied.
The velocity is not constant of course, and at maximum displacement (i.e. instantaneously zero velocity), I can’t see that the Doppler effect would occur.
It seems to me that as we go from maximum Doppler effect at the maximum velocity of the carrier of the tone (zero displacement) to zero effect at maximum displacement, the Doppler effect is “modulated” (the frequency is modulated of course, and if we moved backwards and forwards at the frequency of the carrier tone, rather than being stationary, it seems to me that there would not be a Doppler effect).
Wondering,
David
.
With reference to cbdb’s thought experiment:
I am under the impression that for the Doppler effect to occur, the source of a (fixed) tone only needs to move relative to the listener, observer, IN ONE DIRECTION (a galaxy say, with respect to the viewer).
If the train is coming towards you and the horn is switched off the instant it is level with you, as the listener you will experience the Doppler effect.
Equally, if the horn is started as it is level with you, as the moving train recedes you will experience the Doppler effect (would that be called opposite “polarity”?).
In cbdb’s extreme frequency difference case, it seems to me that taking the physical (not electrical) source of the high frequency tone (the voice coil) as it passes through the center of it’s frequency modulated sinusoidal motion IN ONE DIRECTION, if the physical source could maintain the exact same velocity, I would be inclined to think that the conditions for the Doppler effect would be satisfied.
The velocity is not constant of course, and at maximum displacement (i.e. instantaneously zero velocity), I can’t see that the Doppler effect would occur.
It seems to me that as we go from maximum Doppler effect at the maximum velocity of the carrier of the tone (zero displacement) to zero effect at maximum displacement, the Doppler effect is “modulated” (the frequency is modulated of course, and if we moved backwards and forwards at the frequency of the carrier tone, rather than being stationary, it seems to me that there would not be a Doppler effect).
Wondering,
David
.
Math is very stubborn lady. When I was a student I was obsessed by idea to create chorus-effect. I decided that I can take SSB modulator, demodulator with shifted carrier, and get as the result the signal with shifted pitch. I did, actually. But when I mixed original and pitch-shifted signals what did I get?
Yes indeed Wavebourn, we are looking at a system.
This is why I believe the Doppler effect in loudspeakers would seem to be irrelevant (a theoretical curiosity).
BTW I tend to think that, theoretically, a differentiation can bemade as to whether the origin of the sound occurrs at the magnet, as I think has been proposed, or the voicecoil.
I don't believe that I have ever heard an oscillating electro-magnetic field, but I have heard a buzzing piece of paper.
Regards,
David
This is why I believe the Doppler effect in loudspeakers would seem to be irrelevant (a theoretical curiosity).
BTW I tend to think that, theoretically, a differentiation can bemade as to whether the origin of the sound occurrs at the magnet, as I think has been proposed, or the voicecoil.
I don't believe that I have ever heard an oscillating electro-magnetic field, but I have heard a buzzing piece of paper.
Regards,
David
Then David you should get one of that cigar lighters like on that picture that I posted before.
Here's a muisical cigar lighter using those fancy new Silicon Carbide FETs like I've heard Nelson Pass talk about...
Cree's Silicon Carbide Mosfets -- Another Geek Moment - YouTube
Cree's Silicon Carbide Mosfets -- Another Geek Moment - YouTube
Actually, I started talking about them earlier, but Nelson found the way to buy them and use for his amps.
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