Hi!
It seems the usual method to calculate diaphragm area for a cone driver is to measure it's diameter (plus some part of the surround) and derive it from that. This way, we get the surface area of a flat circular sheet. But hey, cones are not flat circular sheets.
Why is this important?
For example, to get Vas value of a driver, we need to know its diaphragm area, because Vas derived from that and there can be significant differences if we use different diaphragm area for the calculation.
Usually the larger the driver diameter the deeper its cone, so larger the differences if calculate the diaphragm area with flat circle area vs cone area method.
So why the flat circle method instead of real cone area method?
It seems the usual method to calculate diaphragm area for a cone driver is to measure it's diameter (plus some part of the surround) and derive it from that. This way, we get the surface area of a flat circular sheet. But hey, cones are not flat circular sheets.
Why is this important?
For example, to get Vas value of a driver, we need to know its diaphragm area, because Vas derived from that and there can be significant differences if we use different diaphragm area for the calculation.
Usually the larger the driver diameter the deeper its cone, so larger the differences if calculate the diaphragm area with flat circle area vs cone area method.
So why the flat circle method instead of real cone area method?
It will relate to the air-mass contained within 'the cone'. Plus, a flat circle has LESS area than a cone of same diameter.
Great question though > I will watch with interest. 🙂
( I have an issue regarding 2x woofers = 6dB gain. When 3dB = double power, & 1.4dB = SYNERGY = 4.4dB total )
Great question though > I will watch with interest. 🙂
( I have an issue regarding 2x woofers = 6dB gain. When 3dB = double power, & 1.4dB = SYNERGY = 4.4dB total )
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Yes, if we calculate driver Sd from its circle diameter, we get less area than the real cone area, so we get lesser Vas value than really is.
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If the weight is to be considered a force, then the column of air upon the membrane will have the vector othogonal to it.
Applying a force with differential distribution in both axes means that the one part of the membrane attached to the external surround
will transfer force ...no, ehi, I wanted to make the paradox of the cone being a cylinder so no orthogonal force distributed along the membrane as the result of barometric pressure but radially.
If you know what I mean ( also frictions, heat, yes!)
Applying a force with differential distribution in both axes means that the one part of the membrane attached to the external surround
will transfer force ...no, ehi, I wanted to make the paradox of the cone being a cylinder so no orthogonal force distributed along the membrane as the result of barometric pressure but radially.
If you know what I mean ( also frictions, heat, yes!)
This is not the first time that this subject pops up.
While the shape and depth of the cone have an influence on stiffness, and therefore especially its behaviour at its uppermost frequency range - Sd will always be determined by the square of the cone diameter (including some part of the surround) irrespective of the shape. Just try to imagine that the amount of air that is pushed back and forth is not influenced by the shape of the cone but only by the moving area as seen from the front times the displacement.
Regards
Charles
While the shape and depth of the cone have an influence on stiffness, and therefore especially its behaviour at its uppermost frequency range - Sd will always be determined by the square of the cone diameter (including some part of the surround) irrespective of the shape. Just try to imagine that the amount of air that is pushed back and forth is not influenced by the shape of the cone but only by the moving area as seen from the front times the displacement.
Regards
Charles
Klippel paper
https://www.klippel.de/fileadmin/_migrated/content_uploads/KLIPPEL_Sound_Radiation_Poster_01.pdf
Basically cone/dome profile has an effect only when wavelength is shorter than the diameter.
https://www.klippel.de/fileadmin/_migrated/content_uploads/KLIPPEL_Sound_Radiation_Poster_01.pdf
Basically cone/dome profile has an effect only when wavelength is shorter than the diameter.
Yes, Usually it's the cone surface and 1/2 of the width of the surround.
Sd is call cone surface but that's misleading, only the area of its front is actually effectively doing something. The air within the cone is pushing the air in front of it. Of course that air 'does' something too, because it is moving back and forth with a the membrane. That air mass is added to the the Mms (or with - measured), therefore the shape of the cone is already accouted for.
Aside from the effective area, it would complicate speaker construction a lot. There are a lot of different drivers shapes like oval, square (with or without rounded corners) and dustcaps, often dustcaps of car woofers got erratic complex shapes. Or drivers whizzer cones. It would be a nightmare to calculate all that and compare them. It's a lot easier to just measure the parameters and check for inconsistencies. But keep in mind the measurements got their deviances too, temperature, air pressure got influences too.
Yes and no. What you wrote is ofc right. But the cone breakup, flexibility and therefore the behavior can be different than it's expected to be and act partly like a driver of another size (see Klippel as well). In this case it's irrelevant though because that's far beyond where the TSP are useful.
Take a look in the LIMP Manual, chapter 5.3.2: "The problem of measurement piston area S".
https://artalabs.hr/download/LIMP-user-manual.pdf
Regards
Heinrich
https://artalabs.hr/download/LIMP-user-manual.pdf
Regards
Heinrich
But nitpicking, doesn't the air in the cone's cavity act as spring, causing modulation distortion?
Seriously, IMO deformations of the membrane and surround are much more serious problems. Cone profile, stiffness and possible phase plug make most of the differrences in resonance and directivity behaviour. Low end performane comes mostly from "motor"
Seriously, IMO deformations of the membrane and surround are much more serious problems. Cone profile, stiffness and possible phase plug make most of the differrences in resonance and directivity behaviour. Low end performane comes mostly from "motor"
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It's not acting differently like the air in front of it. Unless there's a compression chamber, the air will act as a linear spring and not add modulated distortion.
Yes, I agree, esp because that are often non-linear distortions.