Autoformer vs Speaker impedance Curve

Thanks guys for this discussion. Informative and educational.

My confusion stems from the fact that some posts imply that autoformers help

Very simple Max.

Yes they do "help" with amps that can't drive those loads.
Best is to get the right amp that will drive them.
Not to put a band-aid on ones that can't.

Cheers George 

When considering an amp for my Magnepan 3.7 I contacted the factory and a large dealer and both said the autoformer would not make a good match with the Maggie's and that I would need at least 500 watts to even consider a Mc. 

johnto

For an amp that doesn’t drive the Maggie’s to well because it can’t handle a 3-4ohm load, an Autoformer would work, because it’s one of the only speakers that presents a very benign 3-4 ohm impedance load. That 8ohm peak in the graph is bought back down to around 4ohms because of the "dotted" -phase angle dipping down at the similar frequency.
But your right you need big wattage as well for them, as they are also inefficient, these one 83db

https://www.stereophile.com/images/archivesart/magfig1.jpg

Cheers George

Atmasphere, regarding your link:

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

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? 

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? (

(I’m sure the above varies with speaker and amp design, negative feed back and such, but just in the most general of terms)

Mac led the way in the late 1950s towards developing the idea that speakers be ’voltage driven’. 

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!

Even though I addressed this to atmasphere, I welcome and want all input!

Rob