Great, looking forward to that. Hopefully Dan and Ivan will help keep this focused and on topic so we can share positive notes and real, factual info.
I'll add a topic regarding matching of speakers. Just google "reflected impedance in transformers" which will bring up some info on why speaker impedance matching is important. Its not a cut and dried formula and some exceptions exist. The main point is using low impedance speakers on amplifiers tapped for 8-16ohm speakers can result in bad sound (boomy bass and/or rolled off highs) burned output tubes, or in a worst case scenario, blown output transformers. I have a melted/burned transformer on my workbench as proof.
Shindo always designed amplifiers in the context of a system approach as the quote above explains. Every part of the chain is important.
The basic ingredients for a properly matched speaker is:
1) high efficiency- real, not marketing manipulated specs.
2) high impedance. Ideally 16ohms, 8ohms is just fine and in a few rare cases 4ohms such as 1940's Western Electric drivers in the 7 series. 755A being the most well known.
3) Low moving mass. Generally light paper cones. Stiff suspensions on the woofers without floppy rubber surrounds.
The 4ohm exceptions, I believe, come from the fact that the efficiency is high and mass low which offsets the impedance mismatch. Thats a bit of a hypothesis.
More later.
Jonathan
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