Why do you think Bi-Wiring improves the sound ?

The whole reason speakers started to have 2 sets of terminals was not for bi-wiring, but for bi-amping. Current starvation in the output devices, increased IM in the output stage from non-linear effects at higher currents, and IM from modulation of the power supply from bass frequencies is eliminated from the amplifier that only supplies the typically much lower current mids/highs. Voltage induced distortion effects at other stages in the amplifier will still occur of course, but traditionally this has been less of an issue.


There is no technical justification for "systems with properly designed passive crossovers make poor candidates for bi-amping", since the benefits are not for the speaker, they are for improvements in amplification. For amplifiers with lower THD at high power (typically because of high distortion near the 0-crossing), the high frequency amplifier will increase in IM, but will reduce in THD by riding on the high voltage bass signal. That same amp with an input passive filter for the highs can have sonically unacceptable distortion characteristics on real music.

Systems designed to be bi-amped typically do not have internal crossovers. Systems with properly designed passive crossovers make poor candidates for bi-amping.

The parallel loading of the additional drivers on the amplifier is almost always negative (see above) if your goal is accuracy and un-colored sound. Bi-Wiring only adds a very small amount of isolation, basically the impedance of one set of wires, which with competent wires is very little. Bi-Amping completely electrically (and back EMF) decouples the two driver sets.

driver response varies in combination with the driving amplifier and the parallel loads of the additional drivers.

Which loudspeaker manufacturer first put biwire binding posts on the back of their speakers?  Anybody know?

I don't know the exact model, but for the progression, it is one of the rare times I would agree with Paul McGowan, as it is the same story I have heard from truly old-time audiophiles (my dad included) and matched the stories I read. First DIY, with SS base and tube for the mid/highs, and then speaker companies started to build the capability in. It never really took off, but it was a differentiator between cheap and "good".

With one set of binding posts on the speaker end, in theory, unless you are modifying the connections to/thru the crossover, the only benefit would be thicker wire.  If the speaker has 2 sets of binding posts, and they give you a choice of paths through the crossover, then some changed response is possible.  However, dedicating copper to frequency bands leads to less than optimal use of the copper.  At some points in time the base may need a lot of energy from the amp and it cannot make use of the lower resistance that a common thicker wire would provide.

I think there are potential downsides of biwiring. The speaker designer (assuming they are competent) went to great pains to develop a crossover that effectively splits the signal between drivers, assuming the SAME SIGNAL on the inputs to the two parts of the crossover. Anything that might result in a different signal on the two input connections is going to defeat this design effort. 

Now, I suppose, if you prefer the sound from two separate connections to the speaker, then that's really all that counts. But if you are asking a theoretical question, I'd stick with a single connection to the speaker unless it was specific engineered to use an active crossover with biamping.