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Posted: October 21, 2006 at 12:41 AM / IP Logged
Posted: October 21, 2006 at 12:42 AM / IP Logged
Posted: October 21, 2006 at 12:48 AM / IP Logged
Here's a quote by Dan Wiggins explaining parameters and a little bit on how they interact with one another. Think of it as speaker engineering 101. 
"There are only 6 fundamental physical parameters of a driver:
Re - the DC resistance of the voice coil (often called DCR). This includes the voice coil and tinsel leads. Measured in Ohms.
Le - the inductance of the voice coil. Usually measured in millihenries, sometimes microhenries.
Sd - surface area of the cone, usually measured in square centimeters.
Cms - compliance/stiffness of the suspension, usually measured in mm/N. That is, the suspension will sag X millimeters per Newton of force (there are ~4.5 Newtons per pound).
Mms - moving mass of the driver. Typically measured in grams.
BL - motor force factor of the driver. Measured in Tm (Tesla-meters) or N/A (Newtons per Ampere). I prefer the latter, because it is much more explicit about the force factor - X Newtons of force for every Amp of current you put through the driver (note that 1 Tm = 1 N/A).
Xmax isn't really a physical parameter of the driver - it's a "side effect" of a given driver design. Note that you can have the same 6 physical parameters, but Xmax values all over the place. And Xmax does not affect any of the derived T/S parameters.
T/S parameters are typically:
Fs: resonant frequency, set by the moving mass and compliance.
Qms: loss of the compliance, set by the Rms (mechanical impedance) of the suspension.
Qes: loss of the motor. Set by Mms, BL, Re, and Cms.
Qts: Q of the driver - combinatiom of Qms and Qes.
Vas: the stiffness of the driver, scaled by the cone size (Cms and Sd).
Vb is proportional to Vas (double Vas, double Vb). Vb is proportional to Qes squared (halve Qes, quarter Vb). This is for the same Qtc/alignment... And since Qes is inversely proportional to BL squared, if you double BL you cut Qes by a factor of 4, meaning the box volume for a given alignment is cut by a factor of 8.
Now, that is all well and good, but consider what Fb does in relation to Qts/Qes... Fb is inversely proportional to Qts, thus as you raise the BL, and lower the Qts, you raise the Fb accordingly. Double BL, cut Qts by a factor of 4, meaning Fb just jumped up 2 octaves!"
There are only 6 fundamental physical parameters of a driver:
"There are only 6 fundamental physical parameters of a driver:
Re - the DC resistance of the voice coil (often called DCR). This includes the voice coil and tinsel leads. Measured in Ohms.
Le - the inductance of the voice coil. Usually measured in millihenries, sometimes microhenries.
Sd - surface area of the cone, usually measured in square centimeters.
Cms - compliance/stiffness of the suspension, usually measured in mm/N. That is, the suspension will sag X millimeters per Newton of force (there are ~4.5 Newtons per pound).
Mms - moving mass of the driver. Typically measured in grams.
BL - motor force factor of the driver. Measured in Tm (Tesla-meters) or N/A (Newtons per Ampere). I prefer the latter, because it is much more explicit about the force factor - X Newtons of force for every Amp of current you put through the driver (note that 1 Tm = 1 N/A).
Xmax isn't really a physical parameter of the driver - it's a "side effect" of a given driver design. Note that you can have the same 6 physical parameters, but Xmax values all over the place. And Xmax does not affect any of the derived T/S parameters.
T/S parameters are typically:
Fs: resonant frequency, set by the moving mass and compliance.
Qms: loss of the compliance, set by the Rms (mechanical impedance) of the suspension.
Qes: loss of the motor. Set by Mms, BL, Re, and Cms.
Qts: Q of the driver - combinatiom of Qms and Qes.
Vas: the stiffness of the driver, scaled by the cone size (Cms and Sd).
Vb is proportional to Vas (double Vas, double Vb). Vb is proportional to Qes squared (halve Qes, quarter Vb). This is for the same Qtc/alignment... And since Qes is inversely proportional to BL squared, if you double BL you cut Qes by a factor of 4, meaning the box volume for a given alignment is cut by a factor of 8.
Now, that is all well and good, but consider what Fb does in relation to Qts/Qes... Fb is inversely proportional to Qts, thus as you raise the BL, and lower the Qts, you raise the Fb accordingly. Double BL, cut Qts by a factor of 4, meaning Fb just jumped up 2 octaves!"
There are only 6 fundamental physical parameters of a driver:Posted: October 21, 2006 at 1:29 AM / IP Logged
Posted: October 22, 2006 at 5:28 PM / IP Logged
Once again the forum has provided some excelent information. You have definitely helped to clear up some misconceptions about DVC's that I've had since the beginning (I always looked at DVC's as basically being 2 subs in one. stupid me right 
). I figured with dual voice coils it meant that there were 2 instead of 1, like putting 2 SVC subs into 1.
When I said I "heard" a difference, you have to keep in mind that the SVC's and DVC's I was talking about were different models. So there was a definite audible difference, but now I see that it had absolutely no bearing or reference to the topic. I guess I let that make me go down an incorrect way of thinking since the sound and power handling was so different. So thanks again guys for helping to clear it up.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com
). I figured with dual voice coils it meant that there were 2 instead of 1, like putting 2 SVC subs into 1.
When I said I "heard" a difference, you have to keep in mind that the SVC's and DVC's I was talking about were different models. So there was a definite audible difference, but now I see that it had absolutely no bearing or reference to the topic. I guess I let that make me go down an incorrect way of thinking since the sound and power handling was so different. So thanks again guys for helping to clear it up.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.comSorry, you can NOT post a reply.
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