> >For serial try R1+R2
> >For paralell try  R1*R2/R1+R2
I can't belief no one here knows the difference between "series" resistance 
connections and "serial" data streams.  "Parallel" is used for both.  
> Ah, but he did say _impedance_.....which is why I passed on answering 
> The above works ok for non-reactive loads (i.e. pure resistance). > When 
you start shoving in Xc and Xl as well as delta f, lookout. ;-D
If only serious design and analysis were as simple as taking the vector sums 
of real and imaginary components....  
Speakers are nominally only described in terms of an averaged impedance, 
which is usually used as if it's a DCR for basic system design purposes.  
Under static conditions some drivers do have an actual Z not much over R, 
while passive crossover full range boxes can vary as wildly as 3 to 40 ohms Z 
within a single nominal 8 ohm box.  In addition, mechanical nonlinearities 
and resonances can cause dynamic impedance variations, and an effective 
negative resistance characteristic can result from motor-generator effect.  
 JB> Yeah but it's a good rule of thumb for connecting speaker loads.....
Amps with huge damping factors, which can accept lower than nominal Z load 
extremes and shunt generator output do help make such simplifications 
practical.  
With most users not understanding what's on present day minimal spec sheets 
from even the better pro vendors, formula or topographic presentation of all 
the real dynamic electrical and mechanical driver traits, not to mention box 
interactions, simply wouldn't be within the comprehension of any but a few 
users if published.  Of course, if part of this is about determining system 
power, we could move to discussing how to meter the voltage and current 
related to the real (resistive) load element, and how to distinguish that 
from the imaginary (reactive) load's current that doesn't result in power 
transfer (but may contribute to voice coil heating and consumption of amp 
headroom).  
Terry
--- Maximus 2.01wb
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