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manisandher wrote:

Thanks for taking the time to share your thoughts - I really appreciate this. I'm trying to understand your idea of Severe Mass Deficiency Syndrome. How tightly correlated is this to a speaker's impedance curve? The Druids don't seem to dip below 8R anywhere...

When I said that Volume included a port it was what I meant – the speaker's impedance is included into the Volume Reactance.

manisandher wrote:

1. According to its manual, the Siegfried is a zero-feedback design and has a typical output impedance of 1.5R (measured at 1 amp, 60 Hz). Is this then close enough to your estimated 1.25-1.3R for this attenuator to be unnecessary?

You think about absolute number but I think about relevant number. The point is that your amp might have 1.5R but what if you need 1.42R? What option you have: to change transformer ratio? to change plate current? It all will change the impedance right along with TTH characteristic. How about if you need 6.1R or .04 R You will not be able to get those numbers with change of loading without a severs change of sound.

manisandher wrote:

If you still feel that it might be a worthwhile endeavour, what do you think is the best way of fine-tuning the output impedance precisely? Apologies in advance if there is an obvious answer to this. (BTW, I share your aversion to soldering irons - is there any way that this could be avoided?)

I do not know, I am not an amplifier designer. Running global voltage negative feedback would drive impedance down to a degree and it is possible to design an amp that would be operating more or less stable and identical with different depth of feedback. If you ask me: If is worth it then I would say “no”. In the best case you still will have the best Druids bass. Does the Druids best bass worth build/modify an amp to drive it? I do not think so. It is much more cost per action beneficial would be to get a separate LF section and do not push the last drops from those poor Druids.

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