Autoformer vs Speaker impedance Curve

Thanks George.  I’ve actually read that.

My confusion stems from the fact that some posts imply that autoformers help with a difficult load.   This would seem to imply they would be a good match for the 802D3s.   If, in fact, autoformers function similar to an  output transformer, the opossite would seem to be true.

I suppose it depends  how one defines a  difficult load.  Are these posts just considering the nominal impedance and the sensitivity,  ignoring the importance of impedance curve and phase issues??? Much yet to consider.

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