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dvc vs. svc

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Silver - Posts: 1,123
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Posted: October 21, 2006 at 12:41 AM / IP Logged  

I was having trouble with post reply on this topic so will try again.

Nicely put DYhon and Steven. I am (gladly) on the side of the "big boys" with this topic.

As far as any "opposers"  I would like to have verified if ANY manufacturer offers a SVC and DVC of similar models that can possess different acoustical properties or t/s parameters other then the physical measurments mentioned by Steven.

It is documented that there can be a power handling difference but I believe this is negligible for this discussion.

Now it would seem highly illogical for any "real" differences other then ohms configuration to be the case but less logical things have been known to exist, for whatever reasons unknown.

Unlike squirell I have yet to "hear" any difference is the "sound" between an svc and dvc sub of similar models..all else being equal.

However, we have witnessed where basing anything solely on personal experience has put me in a previous debate. (lol, inside, paradoxily).

The only reply to this that I would request is some reliable documentation with specificatons that prove an SVC and DVC of the same model "type" have any other significant difference other then final ohm load configuration.

I personally feel there is no difference but am more then open to be proven wrong.


Silver - Posts: 1,123
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Posted: October 21, 2006 at 12:42 AM / IP Logged  
oops, I meant DYohn, I was backing typwards again.
Steven Kephart 
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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. dvc vs. svc - Page 3 -- posted image.
"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:
Silver - Posts: 1,123
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Posted: October 21, 2006 at 1:29 AM / IP Logged  

That brought back some memories Steven. And I will need to brush up on most of that when I renew my certification.

Good info..thanks

With that said does anyone have documentation that any of the parameters above which can effect the acoustical properties of a sub (SVC vs. DVC) of simlar models be posted to prove the opposing views? 

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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 dvc vs. svc - Page 3 -- posted image.). 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.
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