[Arran]

The problems I have heard about the model 50 had nothing to do with the audio, grainy sound, or whether the speaker had a stiff spider in it or not, it has to do with the sensitivity. The model 84B and 37-84B were both sets that employed regeneration, using more modern tubes with a higher amplification factor, so it's like comparing apples and oranges. Often there is a lot more to a sets performance then the tubes that are used, the Mantola may use the same tubes but whoever made it may have used a better front end design, same with the Rogers set I heard.
Regards
Arran