TEACH ME ABOUT BI-WIRE

Jostler, you are right and I stand corrected. Here is the real scientific explanation on why biamping effects sound. This came off the net if anybody is interested. When a current is pushed forward by the amplifier through the voice-coil in the magnetic field of a loudspeaker driver, the voice coil and attached cone move forward - the electric motor effect. However, the voice coil moving in the
magnetic field generates a back voltage - the electric generator effect. In a perfect driver, the back voltage matches the forward voltage, giving rise to the driver's dynamic impedance. In the real world, the back emf is distorted by nonlinearities in the magnetic field etc giving rise to harmonic distortions and so does not exactly cancel the forward voltage. These harmonic products from one driver's terminals end up across other drivers in the loudspeaker if they have common terminals and can cause further muddling of the sound. By connecting each driver through separate leads back to the amplifier, the distorted harmonics generated by each driver can be short-circuited by the low impedance output of the amplifier. The ability of the amplifier to sink this back emf from the low frequency driver is the damping factor. Where I went off course is not knowing that when the jumpers are removed the crossover is in effect halfed, so that the amp always sees the same impedance and does not effect damping factor. There now I feel better.

Liguy - You realize that when bi-wiring both the high and low side of the crossovers are still hooked together. It's just at the amp instead of the speaker. You can accomplish the same thing with larger speaker wire.

Damping factor is the ability of the amplifier to maintain a constant output voltage as speaker impedance changes. It can be very high in SS amps and good enough with tubes.

Take a woofer with a powerful motor and connect its terminals together. When you move the cone it feels like there is a shock absorber connected. Its a very strong effect. As you move the cone a current is generated that opposes the motion of the cone. In a system this effect improves the accuracy of the cone movement. So, it would be nice if there were nothing to impede this correction current generated by the speaker itself. Decent sized speaker wire and reasonable amplifier damping factor help. Typically, far more resistance is created by the crossover networks themselves. The slightest driver efficiency mismatch will have required the speaker designers to provide resistance to the louder driver. Resistance is unavoidably high throughout crossover regions.

Fully utilizing an amplifiers damping factor may be achieved with bi-amping or tri-amping, since there are no passive crossover components between the drivers and amplifiers. How much real world gain there is to bi-amping, I don't really know. I am undertaking a DIY speaker project shortly and it will be tri-amped with very high damping factor amps. When I am done with the project I still won't know ;-)

Just in case anybody missed it, Liguy's most recent post refers to bi-AMPING, not bi-WIRING. There's an important difference, as Steve points out.

i was under the impression that biwiring, in some cases, can be effective because the back-voltage going thru the wiring of the woofer is now separated from the wiring to the the tweeter, even tho it eventually meets up back at the amplifier. i believe that having the connection point several feet of wire away, at the amp, instead of at the speaker, can make a difference. i know my monitors sound better w/a stereo amp when bi-wired, as opposed to having a single run w/the speaker mfr's factory yumpers in place. but, perhaps its sonic degradation of the yumpers? or yust the fact that, when bi-wiring, i am doubling the quantity of copper cabling? i admit that i havent tried doubling the speaker-wire to only *one* set of terminals w/the yumpers in place...

doug s.

Liguy is right, it makes a big difference with Martin Logan speakers. The first set of Aerius i I tried out where set up for single wire only, I ordered Bi-wire option just in case it would benefit ( only 100.00 or so ) The new set came, I broke them in then bi-wired. Big change.