Sorry for my very slow response to this. Your question is quite substantial. I delayed due to time, then got wrapped up in other stuff and... forgot about it.
First, I should have used the term "reactive" instead of "reflection" in my statement. While I was considering what the amplifier endures due to the varied loudspeaker impedance load as "reflection", this is not accurate given the common use of electrical reflection. Component video folks use the the term reflection to describe the phenomena during impedance mismatch, and I should not have used this term.
1) Impedance is a combination of resistive (real component) and reactive (imaginary component) contributions
2) The reactance of a component varies with frequency
3) Resistive loads are easier for an amplifier to drive
4) Signal reflections occur when two components have mis-matched impedances (with an acoustical result generally described as "smearing" of the sound)
5) Variations in a speaker's impedance curve mean that mis-matches with the amp will almost certainly occur at particular frequencies - even if the amp is well matched to the nominal impedance of the speaker
These statements are correct.
I feel it's important to add that with 99% of amplifiers, the impedance variation is not a problem. This is simply because they are over-engineered and over-built. This is necessary to accomodate the common impedance swings extant in 99% of loudspeakers. I suppose the term "over-built" could also be termed "appropriately-built", but what I wish to convey is the industry has grown to accept increasingly difficult loudspeaker loads, and passed the burden to the amplifier folks. I believe this is true with respect to loudspeaker nominal impedance, loudspeaker impedance variations, and loudspeaker sensitivity. The industry has changed dramatically from the simple tubes and high sensitivity speakers of the 1950s.
Digressing....
Certainly a SET 300b amplifier is the incorect application in 99% of systems today, but given the right loudspeaker, there IS something very special about the SET 300b tube amp.
Digrressing further...
Those old Pilot 232 and Pilot 240 tube amps are very solid units. With some fresh capacitors they can sound very nice. There is a reason these pieces of rusty hardware continue to sell for $200+ on ebay.
Back on track...
Assuming that I have all of that correct, what I was trying to isolate from your statement above was whether a flat impedence curve necessarily means the speaker is primarily a resistive load and therefore easier to drive and a "bumpy" impedance curve means that a speaker is more reactive in nature and therefore harder to drive?
Yes, this is my understanding.
I realize that impedance peaks at particular frequencies indicate regions of increased reactance, but I wasn't sure what you could assume about the overall ratio of resistive to reactive. In otherwords, could the impedence curve be perfectly flat, but still dominated by the reactive contribution?
I don't think so. I believe that if the impedance curve is flat, it's flat. It will be a more benign load.
Is it as simple as reduced current demand = less thermal compression = better dynamics? If so, I still need the connection to impedance...
There are 2 answers.
1. Yes, Reduced current demand = less thermal compression = better dynamics.
2. A flatter impedance load will be easier for the amplifier to drive, and the amplifier design can be simplified (i.e. less feedback and less parts).
Eventually I'll know if these 2 factors are truly significant
The theory certainly looks good, but not all things that look good on paper have an impact in the listening room.
