Resistors vs.peltz Autoformer- Differences

Given that Zu has signed off on the resistors, I would imagine they find any tonal differences to not be significant.

The only way I could see that working, is if the speaker was purposely over damped in it’s design, and all you do with the resistors is to ruin the damping factor (output impedance) of the amp so then bass is then becomes correctly damped (to suit the room maybe)? Whatever it is, it’s a wank, so are Autoformers, just get the right speaker or amp to do the job properly. 

Cheers George

I’m not sure if everyone is keeping in mind the distinction between series connection of a resistor and the parallel connection that is being suggested by Zu for some of their high impedance speakers. The effects of the two kinds of connections are of course completely different.

For one thing, the parallel connection being suggested by Zu will actually improve the damping factor, at least a little bit, rather than degrading it. The reason for that is that with a resistor connected across the speaker terrminals the impedance "looking back" from the speaker will be the parallel combination of that resistance and the output impedance of the amp. And the impedance of that parallel combination will be lower than the output impedance of the amp.

Also, Bob, I think you meant to address George in your previous post, not Millercarbon who has not participated in this thread thus far.  An understandable mistake, though, given the latter's posting frequency :-)

Best regards,
-- Al

Parallel connection?  Everything that I said is incorrect. Sorry,  I must have mis read.  From Al's 1st post,  I thought that this was a series connection.  A parallel connection will decrease the load seen by the amp and hurt the amps current capability.  
Good Luck,
Tim 

@almarg ,
Correct as always. I was on another thread with millercarbon and got everyone mixed up.
Bob

In the context of this thread, George's comments don't add up. I have to assume that he didn't read everything here including the link.

The use of paralleled resistors by ZU has nothing to do with the speaker being overdamped. Its has to do with the fact that the drivers are typically 10-12 ohms which is an impedance that isn't matched well by some output transformers. In some cases this makes a difference with the amp, in other cases not so much, but the resistors are there to push the impedance down to a point where the 8 ohm tap (in some cases) will be appropriate. Our amps work fine with the ZU speakers and no resistors (or ZEROs) needed.

Depending on the number of drivers used in the speakers the resistors and taps on the amp will vary so as per usual, simply check with the manufacturers involved.