Electrovoice 18" Woofer: smallish Magnet; only 2.3 ohms?

That would be resistance not impedance. Efficiency was a major factor back then because amplifiers were not that powerful. If you are stuck on flea watt amps these old drivers are great it they are in decent shape which is unlikely. Most of them will require remanufacture at some level. 
I can understand collecting old cars they are art but not old audio equipment. Modern material science has improved drivers particularly suspensions. There are many modern High efficiency woofers available up to 32"! https://ds18.com/products/tm-sn32-32-troublemake-subwoofer?currency=USD&variant=13961390850109&a...

rodman99999

thanks for the clarifications. 

Now I see the spec sheets have a separate DC resistance line, thus the 15W link I posted must be a 15WK.

The 18" drivers I found, the foam ones in the Model EV-Six are NOT 18W or 18WK

18W and 18WK are bigger versions of my 15W (or 15WK), with monster magnets as you would expect

https://www.manualslib.com/manual/43604/Electro-Voice-18w.html

the Model EV-Six has 1/2" thick foam cones, the smaller magnets.

I don't know what their impedance was, or, if the DC resistance of 2.4 ohms is 'good/normal' or problematic.

??? Anyone know the specs of the 18" 1/2" thick cone driver???

here is a 18Wk (see the small k stamped into the label) from a Patrician

https://www.ebay.com/p/28028667707?iid=254883146782

     If your drivers did come out of an EV Six system: they should be a nominal 8 Ohm, far as what your amp's output will see, regardless of how they measure with DC.

     Everything changes, depending on the way the woofer is loaded and it's design parameters.

      ie: https://audiojudgement.com/speaker-impedance-curve-explained/#:~:text=Speaker%20impedance%20is%20not.... 

the prior 12/15/18 W's and WK's used huge alnico magnets

the 18" 1/2" thick foam driver uses a ceramic magnet, here are decent photos of a Model EV-Six with that foam woofer

http://www.fisherdoctor.com/ev.html