sound quality vs sound quantity.

[Wavebourn]

Sorry, but your explanations sound like mix of data from under-digested articles. I never said nothing about acoustic centers, nor I said that they are at coils. What I said, that Doppler effect is not a property of a speaker driver. If your cone is infinitely rugged and infinitely light you have no Doppler effect at all. Or, at least if it does not resonate on the frequency that "rides" on cone movement.

[DBMandrake]

Originally Posted by Wavebourn

I never said nothing about acoustic centers, nor I said that they are at coils.

If you haven't considered the acoustic centre of the driver you haven't understood the problem. Modulation of the acoustic centre position is the crux of the whole issue. The acoustic centre is the zero reference point for the phase of the high frequency signal around which the phase is modulated.

What I said, that Doppler effect is not a property of a speaker driver.

You can say it all you like, but that doesn't make it true.

If your cone is infinitely rugged and infinitely light you have no Doppler effect at all. Or, at least if it does not resonate on the frequency that "rides" on cone movement.

Doppler distortion / phase modulation still occurs on a perfectly terminated cone (where no standing wave resonances occur because the bending wave is fully terminated at the edge) and it also still occurs on a driver working as a perfect piston. It's nothing to do with standing wave resonances on the cone.

Honestly, do some reading on the subject (there are some references in Rod's article as a starting point) and take some measurements of your own if you're still not convinced. Seriously.

[Wavebourn]

Honestly, please do some reading on elementary physics to understand the difference between phase-related distortions caused by modulation of properties, and Doppler effect that is totally linear phenomenon. I often take measurements, in order to improve things. When people take measurements and assume wrong causes of effects they observed, they often make things worse trying to improve things.

[CopperTop]

Originally Posted by Wavebourn

Sorry, but your explanations sound like mix of data from under-digested articles. I never said nothing about acoustic centers, nor I said that they are at coils. What I said, that Doppler effect is not a property of a speaker driver. If your cone is infinitely rugged and infinitely light you have no Doppler effect at all. Or, at least if it does not resonate on the frequency that "rides" on cone movement.

I don't get it. If I vibrate a cone sinusoidally at 10 kHz my microphone will pick up a pure tone at 10kHz, hopefully. If I start to move the cone (still vibrating at 10kHz) away from the microphone at a constant 1m/s my microphone will pick up a tone of 330/331 x 10kHz = 9969 Hz. And proportionately the same the other way. Isn't this what happens to my cone if I start vibrating it with loud bass notes while reproducing a 10kHz tone? What has this got to do with the cone's mass, ruggedness, and resonances?

[cyclecamper]

Originally Posted by DBMandrake

- the bass excursion is a significant fraction of a physical wavelength of the high frequency.

A microphone measuring a low frequency note and high frequency note at once has negligible excursion, hence there is no intermodulation effect. Microphones and speakers are not reciprocal in this regard.

I'll be thinking about this all night now! We all know "doppler" effects happen in air, when the source and target are in relative motion. But if I introduce a really loud really low bassoon note in the orchestra, does that modulate the pitch of the triangle? Can I tell? Why? I guess the 'displacement' of the air due to the bassoon, compared to the wavelength of the treble from the triangle, is again the critical issue? In the air, in the mic dipahragm, in the speaker, the problem arises due to the amplitude? So, what about in my chair back at my ear, where the bass amplitude is again very small. The amplitude diperses but the frequency doesn't...the treble source is moving with respect to the target. OK I guess I buy it but now I have to quantify it.

And is the effect the same in the air as in the driver? If we separate the signal into woofer and tweeter mounted close to each other, won't the bass again modulate the frequency of the treble when the amplitude gets sufficient?

Why is it that we don't notice this? I assume it takes a LOT of bass excursion to be significant, and I'm not sure my pitch discrimination is very good at the extreme treble.

So is this one reason huge planars sound "good" (not my assessment)? Sure makes an arguement for square inches versus excursion.

[FrankWW]

Originally Posted by Wavebourn

Honestly, please do some reading on elementary physics to understand the difference between phase-related distortions caused by modulation of properties, and Doppler effect that is totally linear phenomenon. I often take measurements, in order to improve things. When people take measurements and assume wrong causes of effects they observed, they often make things worse trying to improve things.

Making sure I understand you: Areas of the speaker cone are excited by the motor's input and radiate sound according to area, shape of speaker, surround terminus qualities, mass and stiffness of cone, frequency and energy of inputted energy, etc. This radiated sound from the surface of the cone is then "doppler modified" by the pistonic movement of the whole cone. Is that it?

[Wavebourn]

Originally Posted by CopperTop

I don't get it. If I vibrate a cone sinusoidally at 10 kHz my microphone will pick up a pure tone at 10kHz, hopefully. If I start to move the cone (still vibrating at 10kHz) away from the microphone at a constant 1m/s my microphone will pick up a tone of 330/331 x 10kHz = 9969 Hz. And proportionately the same the other way. Isn't this what happens to my cone if I start vibrating it with loud bass notes while reproducing a 10kHz tone? What has this got to do with the cone's mass, ruggedness, and resonances?

No. Electric signal does not create movement. It creates forces that move the membrane and the air. The membrane is moved by vector of already summed forces, with a curve that is already the result of sum of 10 kHz tone and bass tone. No Doppler effect. But when you move with bass frequency already excited membrane that oscillates by itself on 10 KHz frequency, you have Doppler effect.

[CopperTop]

Originally Posted by Wavebourn

The membrane is moved by vector of already summed forces, with a curve that is already the result of sum of 10 kHz tone and bass tone. No Doppler effect.

My head hurts! If the bass tone was DC and the cone could keep moving in one direction, would we not hear Doppler on the 10kHz then?

[Wavebourn]

Originally Posted by FrankWW

Making sure I understand you: Areas of the speaker cone are excited by the motor's input and radiate sound according to area, shape of speaker, surround terminus qualities, mass and stiffness of cone, frequency and energy of inputted energy, etc. This radiated sound from the surface of the cone is then "doppler modified" by the pistonic movement of the whole cone. Is that it?

When the whole thing does pistonic movement it renders already "modified" curve. No separate bass and highs that ride on bass. Just a curve that is the sum of two signals.

However, it is like a theoretical "Round Horse in Vacuum", so when you go to real thing from this ideal model you should add other effects that are non-linear. Areas are excited differently by different shapes of the signal, that creates distortions. And that creates also Doppler effect that is caused by resonating areas of cones. Once excited, they literally ride on cone.

[Wavebourn]

Originally Posted by CopperTop

My head hurts! If the bass tone was DC and the cone could keep moving in one direction, would we not hear Doppler on the 10kHz then?

No. We would be forced to move by the same DC, if the membrane is infinitely large. Or, we would hear nothing if it is infinitely small.