Ls & Lp question

[Amphiprion]

How do I model a driver using these parameters? I'm trying to predict the response of a TC-2000 15". Thanks,


Mark

[DennisP]

I wasn't clear on that either, good question!! :P

I know that SteveC modeled the enclosure for the 2xTC-2000 sub design I ended up with...on my own cross-check of the recommendations in Unibox, I used the Le from another 15" driver (I already forgot which one) as a baseline. It sure would be nice to know what to do with the Ls and Lp numbers though, like how to generate the Le number based on those 2 numbers somehow...or somethin'!

-Dennis

[Dennis H]

TC Sounds (Kyle?) answered the question in this thread. For subs:

Ls is very close to Le because you can neglect Rp at lower frequency

[Mark Seaton]

This is just a 3 component model of the driver inductance instead of a single component (Le).

If you overlayed a curve of an ideal R+L with a driver's impedance curve, using Re & Le, you would see that the curves would have significant differences in most cases. If Le is taken at 1kHz for a woofer, you generally will see the real impedance being notably higher than the ideal of the inductance plus resistance. A better approximation breaks down the inductive nature of the coil into two sections or three components. You can get a decent curve-fit to the real impedance by modeling the inductance as one inductor in series with another inductor that is in parallel with a resistor.
i.e.: Ls + (Lp || Rp)

So the full driver impedance model then becomes:

Z = Res + Ls + (Lp || Rp) + (driver resonance L||C||R)

Varoius programs allow this input directly. LspCAD includes this and I believe that LEAP/LMS does as well (since that is what system generates the parameters in the testing process). Accounting for this gives much better approximation of measured results.

[Amphiprion]

Thank you guys. I haven't had access to LspCAD Pro since I've moved, but I can whip up something I think from the equations Mark posted.

[DennisP]

Very cool, that helps a great deal, thanks! :T

-Dennis