Question for Geddes and John K

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#161
Or more carefully phrased: will the ear/brain perceive the arrival of a delayed copy differently in the interval of 0-400us than in the interval 400-2000us?

Then there is the point that John referred to, which is the cylindrical wave for a real line source. What do we know about this? Is it a real problem?

The reason I'm asking is that I am interested in electrostatic transducers. I love the fact that they are theoretically perfectly linear and their behaviour can be relatively easy predicted. The real problems with ESLs as far as I can tell are: maximum SPL, bass reproduction (both related) and directivity. I'm currently working on the directivity problem and have run a couple of simulations that look promising, at least for the horizontal dispersion. I was hoping to deal with vertical dispersion by making it a line source. Hence my interest in line sources.
 
#162
thadman said:
Dr. Geddes,

Let us assume we have 5 square copper blocks of variable depth and 5 square aluminum blocks of variable depth and equal area to the copper blocks. The blocks are then stacked randomly. A heat source is connected to the bottom of the structure and a measurement device is connected to the top of the structure.

Due to the multiple thermal interfaces, could we not describe the heat flow through the structure as changing with time. I believe an analog can be taken to velocity. If a system possesses a non-constant velocity, could we not describe it as possessing an *acceleration*?
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No. In your example, which need only be a single block of the same material, if the heat source at the bottom is time invarient, then the temperatures everywhere are time invarient once steady state is reached. If the heat source varies in time then the time variance of the temps in the block follow the source exactly. Hence, it is the source that creates all changes in velocity and NOT any forces within the field itself. There is no inertia term to take the temp field beyond that of the source or to cause anything like a resonance. The field is everywhere in complete sync with the source, albeit there is a phase lag due to distance.

An interesting fact is that the temps below the surface of the earth at about 10 feet depth, lag the surface by about three months. This means that your basement floor is warmest in Oct. and coldest in April. Check it out and you will see thats true.
 
#164
Really I don't think there is enough to go on. It'll depend on the amplitude of the delay, the spectral content and the direction of the delay. If the delay is small enough in amplitude I don't think you would perceive under 2ms at all, if it's a medium amplitude I really don't think summing localization is the word for what I have personally perceived in this situation. In my experience short delays don't exactly mess with the localization as much as they give a strange 3-D effect or in some cases with the right tonal characteristics will change the height localization but not the horizontal. It seems like the Haas effect is very strong from my experience but it does get a bit altered with the right kind of short delay. The same goes for long ones if the amplitude is within a threshold the Haas effect will dominate but if there is alteration of the spectral content and it is within the right amplitude you will hear it as a distinct echo.

I think I also came across something that Earl also observed with some of his controlled tests in that opposite directional echoes seem to be easier to deal with than other directions.
 
#169
Key said:
One can live in ignorance, but when they overtly attempt to convince others, in their ignorance, then the fur must fly.
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this statement is desperately lacking in depth. that's like saying "i went on the forum thinking i was smart and Borat destroyed me"

in reality one has to harmonize his ignorance with that of others.

culture equals common ignorance. individual ignorance is like ripples on top of the ocean of culture.

all people must live in ignorance because truth is intolerable.
 
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#176
gedlee said:
No. In your example, which need only be a single block of the same material, if the heat source at the bottom is time invarient, then the temperatures everywhere are time invarient once steady state is reached. If the heat source varies in time then the time variance of the temps in the block follow the source exactly. Hence, it is the source that creates all changes in velocity and NOT any forces within the field itself. There is no inertia term to take the temp field beyond that of the source or to cause anything like a resonance. The field is everywhere in complete sync with the source, albeit there is a phase lag due to distance.

An interesting fact is that the temps below the surface of the earth at about 10 feet depth, lag the surface by about three months. This means that your basement floor is warmest in Oct. and coldest in April. Check it out and you will see thats true.
Click to expand...

Excellent description😀

Could we then conclude that all thermal circuits are of minimum phase?
 
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#177
Borat said:
i obviously don't know much about wave equations so let's just assume that what you said is true. would it be possible to ( for a given listening position ) restore the impulse response using FIR processing ? and if so how big of a "sweet spot" could one expect to have ?
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Borat,

FIR processing is able to correct for a *single* spatial point. However, the effect represents a global irregularity in response and thus may result in a gross error in the total field if processing is significant.
 
#180
i have good news for everybody here ( except Geddes )

i just invented a technology that solves ALL of the problems discussed in this thread.

i will probably write about it in the next couple weeks unless i decide to keep it secret, which i doubt.

why is this not good news for Geddes ? because apparently his speakers cannot be improved upon 😉
 
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