Transferring heat through the metal parts is relatively easy but there is a large barrier transferring it further on to the air.
The single most important factory getting the heat away into the air is the surface area.
Another important role plays the colour of the parts that transfer the heat on to the air. Black is the best colour in this respect, which is the reason why most heat sinks are black. It’s the same reason why Wavecor uses black colour for most of all magnet parts, voice coil formers, and, of course, heat sinks. All Wavecor standard drivers with neodymium motor use heat sinks because we were simply not satisfied with the power handling capabilities without the heat sinks.
There are, however, still speaker units in the market with neodymium magnet without heat sinks. Lower long term power handling is the consequence.
As an example, the heat sink we use on our 30mm neodymium tweeters increases the effective directly radiating surface area from 20 sq.cm to over 99 sq.cm, or a stunning increase of 400%. Although this does not mean that the power handling goes up 5 times, it does make a huge difference in keeping the voice coil temperature down.
Another example is the neodymium motor we use for some of our 4”, 5” and 6” woofer, where the heat sink allows an increase in heat transferring metal area to 225 sq.cm, which is almost the same area as a large 90mm ferrite motor has.
Having taken this approach to eliminate heat problems using neodymium magnets, the most import technical problem using neodymium has been solved.
We have even taken it a step further by the way our heat sinks are designed and manufactured. It would be a simple process for us to increase the length of the heat sinks, in which case the surface area might be increased even much further resulting in even higher power handling if required.
The result is that by using our custom made heat sinks for all neodymium models Wavecor is able to offer neodymium powered drivers with all the benefits of using neodymium magnets but without loosing out on power handling.