Quote Originally Posted by Cal Weldon View Post
Here's what Ron measured his 421A's at:

Re - 4 ohms
Fs - 38 hz
Qms - 4
Qts -.3
Qes - .33
Zmax - 52 ohms
Le - .49 mH
Vas - 8.5 cu ft
Eff - 3.86 %
Sens - 97.8 db/watt/1 m

If yours is an 8 ohm it may be an older version?
From the numbers on the basket (etc) I believe it's a 70ish model
Thanks for those numbers