Thermodynamics is rocket science. Heat doesn't melt voice coils, temperature does. If I hold a torch for 30 seconds to a needle or for 2 hours to a bathtub full of water, which one gets hotter? Which one absorbed more heat? The lower thermal mass will increase in temperature faster. The fins increase the surface area which is a good thing but for a given input of power (like a 2 second bass note) the smaller thermal mass will get hotter until that heat can get dissapated. However none of that matters if that heat can't leave the cabinet at the same rate that it is applied.Bill Fitzmaurice wrote: You don't want a big mass that holds heat around the voice coil, you want something that sloughs heat away from the voice coil. That's what the finned aluminum heat sink on the 3015LF does.
This isn't rocket science, if you're blowing drivers you don't have enough of them for what you're doing. Either add more cabs or upgrade to a better driver, like the 18Sound NLW 9300.
On a side note with the Lab subs. PK Sound used to use labsubs and they are a provider for the Shambhala EDM music festival where daytime temps can get 34*C - 38*C. They blew every lab12 driver in the rig (over 50 I believe) more than once. To be fair Function 1 blew all theirs too that year. The following year they brought 2 independent rigs so that they could cycle them on and off every 2 hours. They eventually gave up on that idea due to logistics (more trucks, more labour, etc) and sold them for firesale prices (and got in a bunch of IP rights trouble with Tom for that) and went to their own ported direct radiator version.