Biwiring and impedance

I know that wiring two speakers in parallel to one set of speaker outputs halves the impedance the amp sees. Correct?
So does biwiring a speaker have the same effect on the amp?
In other words, if I biwire my 8 ohm (nominal) speakers, will the amp "see" 4 ohms?
No, it does not.

Your first statement is correct assuming the impedance of the two speakers is the same: 1/R = 1/Rs + 1/Rs.

But, in biwiring the impedance through part of the crossover to the tweeter will likely not be the same as the impedance through part of the crossover to the woofer: 1/R = 1/Rt + 1/Rw.

And remember that impedance varies with frequency.
More specifically, how would this work out?

My amp has two sets of switchable speaker terminals, "Spkr A" and "Spkr B".

If I single bi-wire, I'd have a single pair of bananas connected to the amp's Spkr A terminals, but which would diverge into separate speaker leads to go to the woofer and tweeter inputs of the speakers.

If I double bi-wire, I could connect one set of spkr cables from the Spkr A terminals to the woofers, and run a second set from the Spkr B terminals to the tweeters.

The Spkr A and Spkr B terminals are wired in parallel. If I were to connect 8-ohm loads to both pairs of spkr terminals, the amp would see 4 ohms.

So in this case, wouldn't my amp see a different load with double bi-wiring than with single bi-wiring?
Hold on, folks. It doesn't matter at all what the impedances of the hf and lf parts are and it doesn't matter whether you use single-biwires or double biwires or how many terminals there are on your amp.

If you connect everything to one amp, regardless of the wiring, the impedance load is the same as with single wiring.


Thanks Kal. That's what I was looking for.
Not neccessarily guys. Buffered amps and throughput (Krell) amps can see a super low impedance from the high freq posts. Depends on the crossover. Do a little homework on the speakers you want to try this with if you are not under warranty.
Really? What crossover configuration would have the HF present as a low impedance that is not seen when both HF/LF sections are connected?

I am not trying to be wise-guy but would like to know if such is possible.

Kal, It is quite common in first order crossovers, both the woof and tweet work far outside their sweet spot with such a gentle slope. Tweeters particularly drop impedance in this situation. Amplifier say POOF! If the amp can handle very low impedance, tweeter say POOF! Been there- done that.
OK, that is not too uncommon but the effect would be the same (if not worse) with the the woofer connected. Any woofer load would be in parallel with and, therefore, would lower the impedance even more.

Besides, the same amp is connected to both HF and LF, in parallel, even when biwired.

So, the issue has nothing to do with biwiring. It is just the usual question of whether an amp is stable with that load under any circumstances.

Besides, the same amp is connected to both HF and LF, in parallel, even when biwired.

Yes, yes, yes. It's always a parallel circuit; biwired or not. Sorry for not thinking before typing. Thanks, Kal.
Sorry, Bob, I was not aiming at you. I am trying to see if Zieman has some reasons for his statement that "Buffered amps and throughput (Krell) amps can see a super low impedance from the high freq posts."

Any fisrt order crossover has drivers operating over greater frequencies. Drive a tweeter at 300 cycles and report back with your findings. Blown tweeter or amplifier?
A buffered or throughput amp has no connection with any part of a crossover as is "normal", so depending on how stable the amp is determines which blows/burns first. I have blown a Krell amp this way and can think of no other brand as stable at frequencies approaching DC.
You keep saying the same thing but you still have not answered the question I keep asking. How is this any different from having the same amp drive the same speaker without biwiring? Without addressing this, your statements are not relevant to this thread.

After reading again the OP it seems I may have misinterpreted the question. Somewhere down the responses, anwsers got a bit off topic and I followed along. I have blown up a few things (luckily under warranty) and would not wish this on another member.
OK. I understand. You raised a point that could be critical in some situations but it is not germane to the issue here.

Kal, Thanks for letting me slide. Low impedance is a real issue that newbies can get into trouble with. Several speaker mfgrs refuse to replace tweeters that have been burnt by unstable amps. They claim owner abuse when it is simply a matter of "I didn't know".