@curiousjim wrote:
[...] I really wonder why AJ would choose to use 1920’s tech in a 2020’s speaker and don’t field coil speakers have to be plugged into the wall?
Because electromagnets make speakers sound better, and yes they require a DC power supply.
Old tech can be great tech that surpasses modern tech. The former was about what it required, no holds barred, while the latter is usually about working around imposed obstacles such as economy, weight, size, convenience and aesthetics/appeal - all part of an overall business model.
Old tech also had limitations to work around, but while modern tech has evolved it’s still, typically, implemented in the context of physical and monetary limitations. Moreover there’s something to be said of the design prowess and innovation of yore, which conversely I find is suspiciously conservative in current times.
Basically most speakers made today are from designs that saw the light of day decades ago, even millenia, while those that are impractical are omitted - per the above; we shouldn't mistake older design paths that are no longer around as being left behind because they didn't sound great, but rather because they don't fit the modern "narrative."