Impedance of biwire-able speakers

It will vary with the individual speaker design. Given that most speakers vary impedance with frequency, it is quite possible to have two completely different loads presented to each amp. The one thing that will be consistent though is that the amp will typically see a much higher impedance at and around the resonance point(s) of the woofer and / or the vents ( if used ). It is not uncommon for a large dynamic woofer in a vented alignment to produce an impedance peak of 30 - 100 ohms. Needless to say, power transfer and control over the driver is greatly reduced in that region due to this. It is for this reason that larger woofers / designs using multiple woofers tend to benefit the most from bi-amping as the amp can now cope more efficiently with the higher levels of reactance and reduced power transfer without dragging the other frequency regions into the mess. Designs using smaller woofers with less excursion and / or designs with controlled impedance may not benefit nearly as much from bi-amping. As a general rule, most sealed and stuffed designs have a MUCH lower impedance peak at resonance, increasing both power transfer and control. Then again, sealed designs do have make slightly longer excursions than a vented design, negating some of those benefits due to slightly higher levels of reflected EMF. Sean
>

Greg: To take that a step further, the nominal impedance of the speaker cable is also inserted in series with the speaker as part of the load. This is why some cables are more neutral in some systems than others. Running your .08 ohm output stage from your solid state amp into a 60 - 100 ohm loudspeaker cable to feed your 4 - 8 ohm speaker seems a bit ridiculous to me, but hey, what do i know??? : ) Sean
>

You're losing me here. Bi-amping a pair of stereo speakers would mean using four channels of amplification i.e. one channel for the left woofer, one for the left tweeter, one for the right woofer, one for the right tweeter, etc... Is this what you are talking about or can you better describe what it is you're interested in doing? Sean
>

Duece1: What model receiver are you using? Is it a stereo receiver with multiple speaker jacks or is it a multi-channel surround sound receiver? Sean
>

This would be bi-wiring not bi-amping and it might not be advantageous at all.

To see if the wiring configuration of the receiver is in series or parallel, try hooking up the woofers to channel A and nothing to Channel B. Then select A+B and see if you hear anything coming out of the woofers. If you do, the speaker jacks are wired in parallel you can use both sets of speaker terminals as you intended. How much of a gain you get from this, if any, may not be worth the added cost or trouble. The only way to find out would be to try it out. Either way, it wouldn't hurt anything. The setting would still remain at 8 ohms.

If you do the A+B test and you get no sound out of the woofers, you shouldn't use both sets of terminals for the speakers. That's because the outputs are wired in series, which means that the signal would have to go from the receiver out to the woofers, back to the receiver and then out to the tweeters. This would create a time delay with increased signal smearing.

Hope this helps.... Sean
>