Can someone verify some speaker projection and mic'ing theory at the molecular level?

De Batz

Member
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3,164
Doppler effect distortion has been a big thing in the HiFi world for a long time, so I am sure you can search out some relevant information there. Doppler is one of the reasons for multi-way speaker systems or horn loading (which reduces excursion).

Which version of the hifi world, though? The $4000 speaker cable one, or the one where you can actually hear the effects without already being told what they are?

I'm quite happy to accept that the effect is real, just asking the questions that try to get a handle on whether or not it's going to be significant for what we hear. And crucially as guitarists most of what we're doing relies on there being some distortion to sound good, so picking up one part and saying 'this is bad distortion' or even claiming to be able to distinguish the effect of one source of distortion from another is always going to fire up the sceptic in me.

As a last observation, a cursory google of Doppler Distortion seems to suggest that it's there in the maths, measurable with the right kit, but not clearly audible to the ear; it's also the case that a guitar speaker with a lowest frequency in the range of 80Hz and a 12" cone is probably not the most likely place to find or hear it, with smaller speakers (and consequent larger throw) being more affected.
 
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2,893
Doppler effect distortion has been a big thing in the HiFi world for a long time, so I am sure you can search out some relevant information there. Doppler is one of the reasons for multi-way speaker systems or horn loading (which reduces excursion).
Which I shall. My application is actually spring reverb, but as measured from a fixed side observation, not an endpoint, where it may turn out that the highs fluctuate propagation rates while traversing the lows, even if the average speed remains a constant.

At this point I'm thinking it will be easier to just do some fast motion photography of a slinky to get my answer.
 
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2,893
Which version of the hifi world, though? The $4000 speaker cable one, or the one where you can actually hear the effects without already being told what they are?

I'm quite happy to accept that the effect is real, just asking the questions that try to get a handle on whether or not it's going to be significant for what we hear. And crucially as guitarists most of what we're doing relies on there being some distortion to sound good, so picking up one part and saying 'this is bad distortion' or even claiming to be able to distinguish the effect of one source of distortion from another is always going to fire up the sceptic in me.

As a last observation, a cursory google of Doppler Distortion seems to suggest that it's there in the maths, measurable with the right kit, but not clearly audible to the ear; it's also the case that a guitar speaker with a lowest frequency in the range of 80Hz and a 12" cone is probably not the most likely place to find or hear it, with smaller speakers (and consequent larger throw) being more affected.
Well yes. As I noted earlier, pure diaphragm displacement distortion (not considering air propagation at all) would be nullified by an ear membrane doing the exact same thing.

...Which makes me wonder why it would be a topic. Yeah, clearly it fully exists, it couldn't not (unless you dedicated speakers to each frequency), but it's also moot.
 
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Jim Hagerman

Vendor
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413
but not clearly audible to the ear

Is it fair to state such conclusions without even having experimented?

Here's what you will see with a microphone: Do the two-tone test, one low one high. It has to be loud to make sure there is significant cone excursion.If 100Hz and 1kHz are used, look for the distortion products at 900Hz and 1100Hz. They will show up.

Is this bad? Like you said, that's an entirely different matter, and perhaps exactly why we prefer some speakers over others.
 

maxbrothman

Member
Messages
914
There are two basic ways to describe subatomic interactions.

  • Waves
  • Particles

You can do it with waves. Or you can do it with particles. Both are correct. It is one of the fundamental observations of quantum mechanics. It is called wave-particle duality.

 
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2,893
Now here is an interesting source for deduction:

Because our ears match speakers in that the current diaphragm location is where a quieter frequency would propagate or be received from, that would suggest that that is exactly how such a signal should be generated.
And yet we would also presume that a live unamplified band should sound ideal with each instrument propagating simultaneously from it's fixed point of origin.

If those two conditions sound identical (multiple adjacent fixed point and multiple stacked diaphragm-relative point), this would in turn suggest that the undulating doppler thing relative to fixed side-observer coordinates, happening through the air medium as I speculated (due to traversing compressed and non compressed air) is in fact going on as well - that air conditions create speaker conditions when sounds pile upon each other.
 
Messages
2,893
Is it fair to state such conclusions without even having experimented?

Here's what you will see with a microphone: Do the two-tone test, one low one high. It has to be loud to make sure there is significant cone excursion.If 100Hz and 1kHz are used, look for the distortion products at 900Hz and 1100Hz. They will show up.

Is this bad? Like you said, that's an entirely different matter, and perhaps exactly why we prefer some speakers over others.
It sounds to me like this is dragging in another concept, side-band/ring-modulation, nothing to do with the Doppler aspect at all, and just simply the compounding of frequencies regardless of mechanics.

Another complication I'm noting here is the conflation of frequency and volume, where it's more incidental that bass tends to employ more excursion, and excursion alone, volume, not frequency, is the ultimate source of that form of spatial-displacement Doppler effect.
It took me awhile to sort out that error in conceptualization myself.
Frequency and wavelength are not the product of extent of excursion, only duration of excursion.
 
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