Right, and I even invented new IC: output stage inside of cathode of preamp tube.
That is known as EBS or Electron Bombarded Silicon. There used to be amplifiers made that way. They had very wide bandwidth at moderate (10W) power levels. A cathode fired electrons at a silicon semiconductor. The idea was the speed of light is faster in a vacuum than in a chunk of refined dirt!
There has also got to be a property of reciprocity with speakers.
If I surrounded a super-light large-displacement full range speaker with a near-hemisphere or sphere (whichever was appropriate corresponding to the shape of wave front emanating from the speaker), of tiny super-light diaphragms, and started playing music through the speaker, according to the Doppler-ites I would hear Doppler-distorted music if I put my ear to one of the diaphragms, because each small diaphragm would be vibrating in sympathy with the speaker - like a microphone recording the output of a Doppler-prone speaker. If I removed the small diaphragm, it would make no difference as I would be listening directly to a Doppler-prone large-displacement speaker.
However, if I reversed the system, and simultaneously drove all the tiny diaphragms with music and disconnected the speaker in the middle, the Doppler-ites claim that there would be much less Doppler distortion because each diaphragm would be displaced only a tiny amount. Yet the diaphragm in the middle would now be vibrating strongly in sympathy with the tiny diaphragms.
If someone listened to the back of the disconnected speaker diaphragm, what would he hear? According to the Doppler-ites he would hear Doppler from the strongly-vibrating large-displacement full-range diaphragm playing a direct scaled-up copy of the displacement of the smaller diaphragms. But, if we removed the speaker's diaphragm he would merely be listening directly to an array of near-perfect small-displacement diaphragms, so no Doppler to speak of.
How to explain the conundrum? The only explanation is that there is no Doppler in either case.
If I surrounded a super-light large-displacement full range speaker with a near-hemisphere or sphere (whichever was appropriate corresponding to the shape of wave front emanating from the speaker), of tiny super-light diaphragms, and started playing music through the speaker, according to the Doppler-ites I would hear Doppler-distorted music if I put my ear to one of the diaphragms, because each small diaphragm would be vibrating in sympathy with the speaker - like a microphone recording the output of a Doppler-prone speaker. If I removed the small diaphragm, it would make no difference as I would be listening directly to a Doppler-prone large-displacement speaker.
However, if I reversed the system, and simultaneously drove all the tiny diaphragms with music and disconnected the speaker in the middle, the Doppler-ites claim that there would be much less Doppler distortion because each diaphragm would be displaced only a tiny amount. Yet the diaphragm in the middle would now be vibrating strongly in sympathy with the tiny diaphragms.
If someone listened to the back of the disconnected speaker diaphragm, what would he hear? According to the Doppler-ites he would hear Doppler from the strongly-vibrating large-displacement full-range diaphragm playing a direct scaled-up copy of the displacement of the smaller diaphragms. But, if we removed the speaker's diaphragm he would merely be listening directly to an array of near-perfect small-displacement diaphragms, so no Doppler to speak of.
How to explain the conundrum? The only explanation is that there is no Doppler in either case.
Okay, folks, this is just a "short" 20-post thread from the time on rec.audio.pro, where the OP clearly was wondering about the large number of "doppler" posts he just saw. My name "Ben Bradley" is mentioned in the thread, though my post(s) aren't here but in the other thread(s) around this time on this topic. This was from a quick search on Google's Usenet interface and archive Google Groups and I'm too lazy to find the other threads (right now).
Enjoy, if you dare...
Doppler Distortion - What Started the Discussion? - rec.audio.pro | Google Groups
Enjoy, if you dare...
Doppler Distortion - What Started the Discussion? - rec.audio.pro | Google Groups
There is no conundrum.
Speakers and microphones are not reciprocal in operation because producing sound and measuring sound are two different things.
To create a sound you have to move air. Period. Because SPL is proportional not to cone displacement but to cone velocity the lower the frequency the more volume of air you need to move to generate a given SPL. (A given peak velocity at a lower frequency results in a greater peak amplitude than a higher frequency with the same peak velocity)
It very rapidly reaches a point where bass frequencies require considerable volume displacement even for modest SPL which means for a given cone area you need a significant cone excursion.
There is no getting around the fact that producing bass requires air volume displacement.
A microphone on the other hand only has to measure the resultant variations in air pressure caused by the SPL. Whilst dynamic microphones do have some small amount of excursion the excursion is tiny at the same SPL compared to the speaker producing it despite its small diaphragm, thus minimal doppler effect.
Furthermore there is no fundamental requirement that a microphone must have any excursion at all. If a microphone is entirely pressure sensitive it can respond to large pressure variations at any frequency without the diaphragm actually moving. If the diaphragm doesn't move the microphone will add zero doppler distortion of its own. Electric condenser microphones are essentially pressure sensitive and their diaphragms don't move any meaningful amount.
Think also of your own ear drums. When your sub woofers are moving 20mm at 30Hz, are your eardrums moving 20mm ? No. They move if anything a microscopic amount even at quite high SPL's.
That's the fundamental non-reciprocity of the situation. Producing bass requires excursion, measuring it does not.
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It all depends on the music
One of these days I should lay out the maths of this to show that there is no Doppler shift in an idealized speaker.
I am sceptical that maths would satisfy everyone...
After all, f' = f0(v - v0)/v is 'maths'. It is where and when it is applicable that is the controversial bit.
And the definition of an idealised speaker is open to debate. Would it be infinitely big, or a point source etc.? Would it have anything to say about a paper cone in a box in room?
For me the interesting thing is whether a small (and therefore small displacement) conventional cone is any better, Doppler-wise, than a larger, but similar design of cone which is capable of going louder and lower. My intuition is that they are the same. Can the maths prove this, or otherwise?
After all, f' = f0(v - v0)/v is 'maths'. It is where and when it is applicable that is the controversial bit.
And the definition of an idealised speaker is open to debate. Would it be infinitely big, or a point source etc.? Would it have anything to say about a paper cone in a box in room?
For me the interesting thing is whether a small (and therefore small displacement) conventional cone is any better, Doppler-wise, than a larger, but similar design of cone which is capable of going louder and lower. My intuition is that they are the same. Can the maths prove this, or otherwise?
Is it in free air, or inside a 1" tube and we're listening with a mic in there? I believe it makes a huge difference.
I see. But I see as well a force that controls it's movements. The force is a sum of forces with frequencies 100 Hz and 1 KHz. And sum of them is applied to the same center point of that piston. Also I see a spring that holds the piston and does not allow it to accelerate endlessly
Yes, it's only when the excursion is going through 0 that +- velocity is greatest. At both excursion peaks the 1k sine is momentarily unmodulated.
I don't know the math, but seems like just a little bit of could give peak velocity thereby peak 1k FM.
I'm not clear about what you're pondering earlier. Something actions and reactions, okay to neglect for the sake of the Doppler investigation.
I don't know the math, but seems like just a little bit of could give peak velocity thereby peak 1k FM.
I'm not clear about what you're pondering earlier. Something actions and reactions, okay to neglect for the sake of the Doppler investigation.
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Similarly we can go further, neglect membrane, and assume that electricity pushes air directly.
Well, except that I can't assume that. It doesn't except in plasma tweeters. I've thought about using ion wind to make a woofer, but I think the idea is kinda goofy for a handful of reasons.
You're thinking about the difference in Doppler effects of this arrangement? I think it would still exist in some form. The only way to fully minimize it is multi-way.
You're thinking about the difference in Doppler effects of this arrangement? I think it would still exist in some form. The only way to fully minimize it is multi-way.
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I’m inclined to think that the Doppler discussion may be at cross purposes.
Are we actually in agreement as to what the Doppler effect is?
First of all, I’m assuming that most of us have heard the Doppler effect somewhere or other.
For example, the sound of a horn on a train passing by.
Or being on a train passing through a level crossing with the bells ringing.
At this point, are we in agreement that these are instances of the Doppler effect?
Hopefully we are in agreement.
Hopefully we would still be in agreement if the train was diesel or electric.
Whether it ran on rails or by magnetic levitation.
Whether the horn produced sound by steam or electricity.
It’s the “effect” that constitutes the Doppler effect.
Now the contentious bit.
Is the description in post #112 actually describing what we call the Doppler effect?
If not, why not?
That is, for the purposes of this particular enquiry, in this particular post, not bringing in some other scenarios or thought experiments, if you don’t mind me insisting, just answering this particular question.
Are we actually in agreement as to what the Doppler effect is?
First of all, I’m assuming that most of us have heard the Doppler effect somewhere or other.
For example, the sound of a horn on a train passing by.
Or being on a train passing through a level crossing with the bells ringing.
At this point, are we in agreement that these are instances of the Doppler effect?
Hopefully we are in agreement.
Hopefully we would still be in agreement if the train was diesel or electric.
Whether it ran on rails or by magnetic levitation.
Whether the horn produced sound by steam or electricity.
It’s the “effect” that constitutes the Doppler effect.
Now the contentious bit.
Is the description in post #112 actually describing what we call the Doppler effect?
If not, why not?
That is, for the purposes of this particular enquiry, in this particular post, not bringing in some other scenarios or thought experiments, if you don’t mind me insisting, just answering this particular question.
I don't see what is common between moving source of sound and generation of sound by varying acceleration of an air applying variable force. However, there are 2 common words: "moving" and "sound", nothing more.
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