Ohm measurement for crossover design

I'm using the software linked below to design a passive crossover.

Crossover Design Calculators

For the software inputs, should I use the rated ohms for the drivers I plan to employ or should I measure the ohms using a voltmeter instead?

Thanks...

You need the ohms at the crossover point. The speaker needs to have an impedance sweep done and then measure the ohms at the desired HZ you want to crossover at. That's where a DATS system comes in handy. If you want a really good crossover you could download the free Jeff Bagby PCD program/ excel spreadsheet. It's did me right. But you'll need .ZMA files that DATS will spit out if you ask it to.

I second Jeff Bagby's PCD, I love it! And yes, as cradeldorf points out, you need accurate impedance sweeps to build a proper crossover.

+1 for DATS. It's well worth the $$.
I'm doing some crazy crossover stuff right now; and it makes it easy to do impedance sweeps, tone generator, component and circuit testing, etc. It has a 'scope on it too, but it is pretty limited.

You are a little confused about Ohms. resistance and impedance are BOTH measured in Ohms. A simple meter measures DC resistance. Totally useless for crossover design, as DC is zero Hz. Impedance varies with frequency. As said, you need the IMPEDANCE at crossover point.

Impedance ratings are an approximation, given by the manufacturer. DC resistance is usually lower, not uncommon for 8 Ohm speakers to be 5-6 ohms DC resistance.

If you can measure, then you may be able to find a published impedance plot that will get you close. Not as good as measuring, but a whole lot better than going by the nominal impedance or the DCR, as O.G. points out above.
What are the drivers?