Quote Originally Posted by VolvoHeretic View Post
This 418 has no cooling venting front or back......Just how accurate does the added mass have to be, calculated weight of glue and actual globbed on are two different things?
It takes a considerable amount of added weight referenced to the driver's moving mass [Mms] to make any major change, so the more accurate the added mass, the closer to hitting a target set of specs. For example:

12" driver/40 Hz Fs/0.4 Qts/60 L Vas has a Mms = ~78.4028 g. Adding this amount reduces Fs/SQRT[2] = 28.28 Hz and Qts increases by SQRT[2] = 0.566, SPLeff. drops by a factor of 4 [~6 dB].

Since the motor will run hotter due to lower efficiency, adding a cooling vent seems a good plan, though if used in a MI app it may not sound 'right' anymore.

GM