Resistors vs.peltz Autoformer- Differences

@gdnrbob

Hi Bob,

Thanks for providing the link. Zero autoformers are normally used to increase the impedance seen by the amplifier, so I had assumed that your reference to using resistors as an alternative referred to inserting a resistor in series with the speaker, which would raise the impedance presented to the amp. But I see in the Zu writeups that what they are referring to is placing a resistor in parallel with the speaker, to **reduce** the high impedance some of their speakers would present to the amp.

A Zero autoformer can be connected "backwards" to accomplish the same reduction in the impedance seen by the amp, but the need to do that would only arise in uncommon situations. And in those situations I would expect that the large cost difference between the two approaches would make resistors the preferable alternative.

Best regards,
-- Al

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?

@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