Resistors vs.peltz Autoformer- Differences

@almarg Thanks Al.  Appreciate the education...

Resistors vs. Paul Speltz Autoformers- Differences?

Both band-aid fixes, get the right amp to do the job in the first place and you'll be sonically much better off.
If you can't bear to change that amp that can't do the job, then change the speakers so it can.

Cheers George 

Resistor.... Q of the woofer and of the system will change.... QES and QTS will raise.  The woofer will want a larger box or want to head towards a sealed box rather than ported.  I've never really like what resistors did to the sound of the bass.... Of course,  it does raise the overall system impedance, but there is no free lunch.  
Be aware that depending on other criteria,  it is possible that you could get a sucked out mid range or a rolled off top end.... But,  its an inexpensive and easy experiment.  
I hope this helps,
Tim

Aside from the load impedance, wouldn’t adding a resistor in series with speaker driver affect the high frequency response of the driver, particularly in case of a single driver or a tweeter?

@kalali

Yes, adding a resistor in series will dramatically change the output impedance that is presented to the speaker. That can and in most cases will have major tonal consequences in various parts of the spectrum, depending in part on how the speaker’s impedance varies as a function of frequency.

Best regards,
-- Al

Thanks Almarg, et al.
@millercarbon,
Yes, I agree, getting the right equipment is the best approach. I was curious as to how either method worked, especially with regard to sound reproduction.
Given that Zu has signed off on the resistors, I would imagine they find any tonal differences to not be significant.

B