Autoformer vs Speaker impedance Curve

Thanks Al. Very informative!  Will take a look at the Wikipedia reference 

an Autoformer would work, because it’s one of the only speakers that presents a very benign 3-4 ohm impedance load.

This statement ignores the fact that loop feedback compensates for this sort of thing.

Atmasphere, regarding your link:

1. In general do reactive speakers match better with voltage paradigm amps?

That has to do with the intentions of the speaker designer. In a general fashion, another way to answer this is that most speakers with highly reactive loads are Voltage Paradigm devices and so the answer would be 'yes'.

2. What happens to linearity with a voltage paradigm amp?  Does the sp increase where the ohms dip (ie watts increase)—with an increase in distortion—and decrease where the ohms increase?

Linearity usually refers to distortion... to the latter question, the sound pressure should stay constant, while the power input fluctuates.

3.  Same question as above, but with power paradigm amp. What happens to sp where ohms dip or increase...is it the opposite of voltage paradigm amps?

If the amp is on a speaker that is designed using Power rules, the output will vary only a little since the designer isn't expecting the amp to throttle its output power back on higher impedances. A good example of this phenomena is an electrostatic loudspeaker, whose impedance is based on a capacitor rather than the impedance of a driver in a box. The idea here is that distortion is kept down, with a preference for lower distortion rather than perfectly flat frequency response, since **the latter doesn't exist** despite what speaker or amp is used.

Does this mean Macs are voltage paradigm amps? Doesn’t this conflict with the way autoformers function?  Seems they would be power paradigm, especially given their multiple output taps. A little over my head here, but learning, so please forgive my ignorance!

Mac amplifiers have always been voltage source amplifiers since the 1950s. It does not conflict with the use of an autoformer; such use is not the defining aspect. Most transformer coupled amps are voltage sources too. The taps are used to optimize the interface between the output devices and the speaker to minimize distortion. To make a power paradigm amp you have two pathways- either no feedback at all, or current feedback and voltage feedback of equal amounts. Since all forms of loop feedback are known to add higher ordered harmonic distortions as well as intermodulations, zero feedback is preferred, if adequate means are employed to otherwise suppress distortion in the amplifier. In this way the result can be considerably less colored, despite likely not having perfectly linear frequency response, due to the way the ear perceives distortion. 

Put another way, the ear hears tiny amounts of higher ordered harmonics with striking ease. So if an amp has 0.001THD, but all the distortion it has is the 5th harmonic and above, it will sound bright and harsh. **That** is a coloration, and not a particularly pleasant one. This is why tubes vs transistors has been such an on-going debate and why tubes are still around.

an Autoformer would work, because it’s one of the only speakers that presents a very benign 3-4 ohm impedance load.

This statement ignores the fact that loop feedback compensates for this sort of thing.

Loop feedback compensates for the autoformer

How the designer set up the amplifier with the transformer plays a big role. The reason you do this BTW is to reduce distortion- all amps have higher distortion playing lower impedances, so if you can raise the overall impedance seen by the output devices distortion will be reduced. This is why Mac uses autoformers. 

Autoformers reduce distortion

Since all forms of loop feedback are known to add higher ordered harmonic distortions as well as intermodulations.

Loop feedback causes distortion 

Okay.  Got it:

Autoformers reduce distortion but need to be compensated for with loop feedback which adds higher order harmonic distortion...the worse kind!  🤯

Sorry, couldn’t resist having a bit of fun with this!  🤪

I’m sure the interplay between these forces is well beyond the scope of this discussion  and certainly well beyond my very limited knowledge.

Thanks all for your input!  Much to think about.

Rob 

This statement ignores the fact that loop feedback compensates for this sort of thing.

This statement ignores just how much loop feedback is needed to fully compensate for this sort of thing. We all know what too much feedback has the reputation to sound like.
And also ignores if there is no global feedback just local feedback which many good amps use, as well as some amps that don't use feedback.

Like I said before  73max OP  your better off using an amp that is right for the job, and not spending money on autoformers, better spending it on the right amp instead which your B&W 802D3 deserve.
 
Cheers George  

 your better off using an amp that is right for the job

 ...such as?