Perhaps too much scope to never land on preferred settings - plays into the audiophile illness. Need for yet another power supply to generate the flux. Okay all very interesting maybe, but what about the negatives? Well as far as I see it, the main issues are very large motor structures with considerable mass. Ferrite performs much worse in this aspect.

Samarium Cobalt and Alnico are much better at retaining their flux under heat.

> Fixed magnets lose their field as the voicecoil heats up with extended use. Clearly this doesn’t apply to an electromagnetic as long as it isn’t broken. Obviously I take that risk and buy vintage drivers. Buying vintage alnico drivers is a little bit of a lottery in this regard since the t/s parameters of the driver could be very different depending on how old they are. > Fixed magnets lose their field over time. For instance, you can adjust the QTS of the driver to get more / less bass or you can adjust the sensitivity to match say your chosen bass solution. As a consequence, you have a very flexible speaker since you can quite dramatically adjust the sound. > The t/s parameters of the driver change quite substantially according the voltage and/or current you apply to the coil. In terms of the purported merits of field coil as deployed for drivers, the following list of advantages seemed to make some sense: I think it is fair to say that there is a certain sense of the exotic associated with the deployment of such technology but does it have any merit in terms of sound? I tried to read the web and learn from a couple of engineers but didn’t really learn a huge amount and struggled to extract the wheat from the chaff. > Turntable bearings such as those reported in the new Wilson Benesch flagship > Cartridges as used in AN / Kondo IO and DaVa

> Tonearms such as the bearing in the Primary control totl arm > Field coil compression drivers such as Cogent being used by OMA in their upper models or GIP WE rebuilds > Field coil modern cone drivers such as Supravox or Atellier Rullit, Gamut Magnetics Lab, Focal Grande Woofer and Utopia sub Where to begin? Well we see electromagnetic tech being deployed in multifarious hifi devices (I am not sure if I missed anything but feel free to add):

Per my other speaker build thread, please find new thread to discuss all things field coil.

Cogent Field Coil Compression Drivers