[Arran]

 The quality started taking a dump at A.K a few years before they shut down, and as a matter of fact they did make some AC/DC sets at the lower end, I can't remember the models now. They also did some things like using obsolete tubes just to keep the costs down, like using 2.5 volt AC tubes in a 1935 model radio, I think that the rubber wire may have been another example. From what I read it had more to do with Mr. Kent losing interest in radio, as well as union problems, and since it was a private company, not publicly traded, he could pretty much do as he liked. 
  Yes they did make their own speakers, A.K used to manufacture auto electric parts so they had the stamping and metal working equipment in house, but the design of those speakers date back at least to the model 82 and 82, which was when they cared more. Speakers can make a large impact on the audio quality of a radio, Canadian Westinghouse had an affinity with using Magnavox speakers in their sets so naturally those sound decent as well, Rogers and Marconi used a lot of Utah and Magnavox as well. It's sort of subjective regarding the performance, and even if not there are many variables involved, alignment, aging of parts, circuit design. I believe that A.K was an RCA licensee so they could use whatever circuits RCA used, which meant technology developed by Westinghouse, G.E, and RCA, Philco did not like to pay royalties to RCA so they sought ways to circumvent RCA's patents, sometimes they worked as well or better, sometimes not.
Regards
Arran