Alot of subs are designed to wick heat into the dust cap from the voice coil. If a dustcap gets hot it is usually not a major concern. Now if the glue that attaches the voice coil smokes or gets soft, then you have an issue.
LOL look.... a voice coil is going to get hot, it is simple physics. The key to a drivers performance and durability at high levels is how well the design can wick heat away from the coils, whether that is with forced air cooling using the cone to pump air around the voice coil and out slots in the motor assembly or by other means. Excessive heat causes impedance rises commonly known as power compression when the rising impedance means less power from the amplifier. On some speakers, like I said, the heat is transferred into the dustcap among other methods. To say that a voice coil only gets hot if your amp is clipping is ludicrous.
yup.. if the cone gets super hto your clipping that sub to death or overpowering it.... if you have a aluminum cone it will get alil hot since aluminum has better heat transfer than typical cone of pulp pressed paper..
"Well then it aint the electrical system. That leaves the gain.........."
WRONG. It's very possible that his "200" amp alternator does not produce 200 amps. It's also possible that his wiring is inadequate. He could also have a terrible ground. The other explanation would be clipping or over-powering of the sub.
Oh and a short story for you. My friend owned an MTX 8500 15" which heated up really bad when he played it. I told him not to have the gain up so high and his sub would eventually blow. He didn't listen. Needless to say, a few days later his coil locked up on the pole piece and that sub was history.
id put it this way any dustcap heating up would make me correct the issue... no sense in taking chances ending in possible damage or shortening the life span as well as causing greater impedance rise which robs power anyway...(just my opinion)