Originally Posted by Vinculum
+1 for active cooling!
Did you do any air temperature measurements of the vent's exit?
Yes, I did, years back when I built the first protos. I have the numbers in my measurements computer somewhere, but, of course, they would vary depending on the drivers/amplifiers used.
I built a sub using very nice split gap 15s from Zomax (Taiwan) years back. I remember playing the SW II fly over/landing/explosion scene at reference level.
I shut the system down after the quick eval and went to do something else. When I came back and fired the system up to play a SACD, I heard a terrible rattling noise.
After removing the driver and becoming stumped as to the cause of the rattling, I removed the surround/cone/VC assembly and inspected the motor, whereupon I found loose chunks of hardened glue laying at the bottom of the gap.
The SW II scene had melted the glue that attached the VC former to the cone. You could see the streaks of melted glue running down the former. It dripped into the gap and after shutdown it cooled and hardened and was rattling around inside the gap after it was fired up again.
The problem was solved by better adhesives, but the point was made how high the temperature can get in a relatively short time (although that landing scene is fairly sustained compared to most LFE) when high power is applied.
Even more so when certain types of music is played loudly for sustained periods.
I like small, high powered sealed subs, as everyone knows, and it can get quite warm inside the box in many in-use scenarios. Driver self venting designs are useless when the ambient (interior) temperature climbs.
Still waiting for the ACP thread...