posted
I'm in the process of reading some DUMAX papers right now. Being the geek I am, I like to use proofs to validate my equations before I use them blindly. (And possibly understand the logic behind the equation.)
Than being said, I need to find a proof(s) as to why the air mass load, Mml = (2.67)po(Sd/pi)^1.5 where "po" = to the density of air "pi" = to the constant pie "Sd" = to the diaphram's surface area.
Even if there are no proofs on that equation, can someone walk me through the logic behind the formula? Where does the 2.67 come frome? Why reduce an area, Sd, to a linear form by dividing by pi?
Then the formula w(s)=1/[(Mmd+Mml)(Cms)]^1/2 where w(s) = angular free-air resonance frequency (??) Mmd = moving mass of diaphram Mml = air mass load cms = suspension mechanical compliance
Again, got any proofs or a thought train behind this?
Im guessing that with the above proofs or logic will make the follow equations clear as well.
posted
IIRC, air load mass is approximation and is subject to change when driver is mounted in different environment. For example, the air load mass is different in free air than in infinite baffle. Exact calculation requires heavy calculus (integration, which leads to some special functions), and as usual, there are no simple closed form expressions for arbitary conditions.
yes, fs is free air resonance in Hz, and ws is corresponding angular frequency in radians/sec. We engineers use angular frequency quite frequently, because it simplifies many equations, which would otherwise be flooded with 2*pi factors.
Ns means Newton-seconds.
Those equations are derived from electrical analogy circuits, which are exactly same than with actual electrical circuits. Usually, inductance represents mass, capacitance represents compliance (or spring), and resistance represents linear friction.
Cms is reciprocal value of driver suspension spring constant, whereas Rms describes how lossy driver suspension is. In practice, electrical damping is much more powerful factor, so Rms plays very little role.
I recommend reading Claus Futtrup's excellent documentation of DPC (Driver Parameter Calculator). It explains many factors of driver parameters, and their relationships.
With Best Regards, Janne
-------------------- For box/port calculations, try these:
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