biamping and curent

I am looking for help understanding different biamp options and how they affect current and power, If my speakers are 6 ohm, I understand that with biamping, they are 3 ohm. Is this a problem for the amps? Also what about cable configuration? What is optimum? Do I need two sets of cables? Can I do it with a single biwire?
Good question! This is my understanding of "bi-amping" Bi-amping is using two (2) amps running in stereo to amplify one (1) pair of speakers. Your speakers must be set-up to be bi-wired. Generally on bi-wired speakers, each speaker has two pair of binding posts. One pair for hooking up speaker cables for the bass woofer and another pair for the midrange/tweeters. The idea is to run two amplifiers, both in stereo. One amp will power the bass woofers of each speaker and the other amp will power the mids/tweeters. You will need two pair of speaker cables in this configuration. Impedance is a little tricky. In general terms, nominal impedance is the combined average of drivers in a speaker. If the bass woofer is 4 ohms and the mid/tweeter is 8 ohms your nominal impedance is 6 ohms. In this scenario, the bass amp would be driving a 4ohm load and the amp driving the mid/tweeters would be driving an 8 ohm load. Bi-Wired speaker cables are used when you have one amp driving a pair of speakers that have b-wire connections. The amp end of the speaker cable will have one negative and one positive spade while the speaker end of the cable will have two pair of spades, two positive and two negative. I hope this helps.
Taken at face value, your message implies a misunderstanding of biamplification. Biamping a system means that you are providing separate power amplifiers to drive your woofers and your mid/high drivers in your speaker system. Essentially you have a power amplifier connected directly to the speaker instead of going through a crossover. My first biamped system used a crossover that was connected to my pre-amp outputs, and the crossover had separate outputs for bass and treble which connected to the inputs of the two amplifiers which drove each stereo channel. My current system uses B&W Nautilus 801 speakers which have internal crossovers and per the manufacturers instructions, I am not using an external crossover. My preamp has two outputs and I run two sets of cables from my preamp to my power amps. So to shorten things and answer your specific questions, you are splitting up your speakers somehow into high and low frequency units, and this will affect the impedance of the speakers, but you really would need to put a meter across the terminals of each input (low and high frequency) to really know what they are because the differing drivers probably have different impedances. As to causing a problem with your amps, that depends on the specific amp and how it can handle the required impedance for that low or high frequency driver. You need two sets of speaker cables per channel and while biwire could possibly work, it probably would be a problem because it would need to split out to 2 separate amplifiers at one end, and two speaker inputs at the other. Separate cabling is more convenient. One last thing--just because your speaker cabinet has two sets of inputs (as for biwiring), that doesn't necessarily mean that those inputs are completely separate internally. There could be a shared ground in the crossover, for example. You should ensure that the two sets of speaker inputs are completely separate before attempting to connect separate amplifiers to them, as this could result in a bad thing._Bill
Interesting post Bill. I'm not quite sure what the "implied" misunderstanding in my post was as you said the same thing except for the electronic cross over and I was trying to keep things simple to be helpful. Your recommendation for testing the driver impedance load with a volt meter is not such a great idea. The impedance load of all drivers will fluctuate given the Q and free air resonance of the driver. The impedance loads stated by driver manufacturers are averages. A given driver may have a nominal impedance of 4 ohms but at 500 Hz it might have an impedance of 6 ohms. Someone testing a driver as you describe could easily come to a very wrong conclusion. Internal cross over and wiring topology can further impact the circuit impedance load. The nominal impedance for bi-wired speaker circuits are usually listed in the manufacturers spec sheet. I would strongly recommend using those parameters. Your idea of being careful hooking up two amps for bi-wire speakers is interesting. I would think that having these two circuits sharing a common ground could be possible, but I can think of no reason why they would. I have never seen this applied to any speaker, internal crossover or wiring topology I have ever heard about or seen! That doesn't mean it doesn't exist, but if a speaker manufacturer did such a thing, it certainly goes against industry standard practices. Sounds more like the boogie-man than reality to me.
Bi-amping does not change the Ohms of the speakers.