Tl;Dr
It is mathematically granted to be so, yepp. Remember your calculus class - the Taylor approximation. It is used in science a lot in order to 'linearize' otherwise complex problems. Second and higher order contributions, beyond good plain 'linear', vanish more or less quickly with decreasing amplitude, depends. The more 'linear' the less distortion of any sort.
But if it's moving less distance at the same frequency, doesn't that also imply it's moving slower?
That does not jive with my memory of FMD studies and speakers designed to reduce it way back in the primordial past. It was more an issue with frequency distribution and cone flexure across the driver. Solutions were multiple smaller drivers, bandlimited drivers, flatter stiffer drivers, and perhaps reduced excursion but the latter was handled by multiple drivers and band limiting IIRC. Smaller drivers meant less area for lower frequency modes and displacement (movement) to modulate higher frequencies. There were a number of articles in the 1970's/1980's in various trade (AES, IEE, etc.) and consumer (e.g. Audio) magazines. I remember the solution mainly being a multitude of smaller drivers, but not all the details. Audio even ran an article on constructing a speaker designed to reduce FMD by using a bunch of small drivers IIRC.
This all makes sense, I was only talking about doppler distortion, which (as I understand it) for any given bandwidth you can minimize but not eliminate, since the cone does need to move, after all.
As far as I remember the problem was stated as follows; bigger drivers have a directivity pattern with many lobes or 'fingers'. These lobes move together with the cone, hence output is modulated at any point in the sound field, especially at the rim of those fingers. A fallacy in not mentioning ferquency modulation, the inherent Doppler effect, resolved long ago with multiway speakers.
Subjectively, that's a subjectivist claim and you cannot prove it. Your non-technical argument is over-simplified!I can confidently state that if you lower SPL enough, you will hear nothing at all!
This is about the same thing, like an engine with a shorter stroke has a slower average piston speed at the same RPM. Moving a smaller distance at the same frequency means slower average speed.
That makes sense because with a multitude of smaller drivers each one has smaller displacement of movement for any given SPL. You get the best of both worlds: benefits of high total surface area yet with smaller drivers where the motion can be better controlled.
The reason distortion increases with amplitude isn't necessarily limited to doppler effects. Generally speaking, electro-mechanical systems that are designed to be linear are never perfectly so. They tend to be most linear at/near their neutral/rest position and progressively less so when displaced further away from that position. Small displacements are linear, big displacements, less so.
I think we are re-ventilating old, severely flawed concepts. First of all, regarding the original question, look and see my post #21 for a definite answer.
FMD or Doppler distortion was "the new boogieman" for a while but has been inaudible for practical purposes for a long time (though no doubt there are some flawed designs out there). The voice coil/magnet system (including spider and surround) is nonlinear, becoming more so as excursion increases, and is the dominant distortion mechanism IME/IMO until the cone begins to break up and/or the voice coil physically clips (bottoms out). Not FMD, Doppler, crossover capacitors, wires... In recent history the biggest source of FMD is actually coupling from LF to HF drivers inside the box, one reason isolated internal boxes for mid and high drivers became popular, but IMO other sources still outweigh those effects. Except for those who can hear the virus on the flea on the hair of the dog...
In early days Klipsch advertized their horns as virtually IM free. That cannot be said about tiny two ways of today, used with today's bass heavy music.
I cannot agree, it remains linear if you look at a sufficiently small part of its characteristics. It doesn't need to be around rest position, see my post #21 for reference.
Depends on what you consider relevant for the hearing.
What is the distortion generating mechanism? Did you mean 'surround'?
Again, what is the suggested mechanism to generate FM distortion?
I agree, but do not think Doppler distortion is the primary distortion mechanism.
My world is (was) analog circuit design, so "linear" always refers to a small region and nothing is completely, perfectly, 100% linear though certainly may be inaudible.
Again, do you think Doppler distortion is the most relevant distortion mechanism?
No, standing waves on the cones causing nonlinear acoustic wave production. My old acoustics text book has a series of pictures and we managed to recreate the process in lab experiments for grad school. We used a strobe and motion picture (movie) camera as we did not have all the right pieces to create a laser interferometry system (they did that after I graduated).
Modulation of one cone (driver) via air pressure (sound waves, compression and rarefaction) coupling within the box, e.g. pressure from the woofer moving the tweeter cone.
Because I'm an old fart, researched this topic decades ago to my satisfaction, and it is not a subject in which I have a deep current interest. I leave that to guys like you and others on this thread with more experience, knowledge, and interest. I do remember when B&W was showing laser interferometry plots of cone breakup and such back in the 1980's, when I was looking into this, and it was very neat to see and talk with their designers about it.
If you have data for a specific speaker, how it performs at, for example, 86dB and 96dB, sure. Now I interpreted TS's question generally, or I was too quick and read in a instead of the speaker, that is, in this case the JBL 305P.Tl;Dr
Another problem is rub 'n buzz, but in case the speaker must be considered defective.
I'm proficient in using maths as a tool, like many scientists (ref post #21). In explaining it, I'm not that good.
As I said, and linke into here, speaker distortion is in all its glorious detail accessible via a LASER Klippel analyser - not just harminic distortion ... it is "all in" as you may say. The advent of THE Klippel was a disruptive change, that you may have missed. It is the (only) reason why we have those fantastic speaker chassis today. I said that all before ...
I did not miss it, but my day job was high-speed (RF/mW) analog IC design, not audio, and certainly not speaker design. I never claimed to be an expert in everything and have stated speaker design is not my area of expertise. As far as I know I did not state falsehoods but responded to other posts. In any event I am out as this has gone far enough for me and devolving into personal attacks.
