Zaikesman, as far as the audibility of back emf many of us will disagree, however the existance of back emf is measureable and even intuitively understandable. A speaker is a transducer; it converts one form of energy into another. When an electrical stimulus is applied the motor converts it into the mechanical energy of cone movement. The motor can work either way. If you push in the cone an electrical impulse will be generated at the input terminals of the speaker. When a speaker is excited and moves outward in response to an impulse it does not stay there. No, it is returned to center mechanically by the spider. This centering of the cone causes an electical impulse at the speaker terminals. I think that even your Thiels operate this way. It seems to be unproven but some believe that the back emf of one driver creates a signal at the input of the other driver through the crossover which is a much shorter path, with less resistance than through speaker wire, down and back as it were. It would seem possible that this signal could also have an effect on the output stage of the amp. Marty
Why bi-wiring is bad
From a link at the Chris Van-Haus website:
THE DISADVANTAGE WITH BI-WIRE
One thing that happens when you biwire your loudspeakers is that the input of the high- and the low-pass filters are fed with different input signals. The difference is a result of the high frequencies and the low frequencies being forced to travel different paths, perhaps through different types of cables, but under all circumstances through cables who have seen different loads (a tweeter with a high pass filter has a completely different impedance response compared to a woofer with a low pass filter!).
What happens is that the drivers will work less good together than when their filter halves were fed with equal signals. The result is a generation of more static and stochastic phase error sounds at different directions from the loudspeaker. The stochastic phase error sounds appear because there may be different types of unlinearities in the low- and high-frequency paths.
What does this sound like? Well, usually, just as you may expect from physics, it appears as a change in the reproduction of space and sound stage. Often, the first impression is that the "biwired" sound presents extended "dimensions", more "air", and is more "living". The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play. No wonder, since it is not a real, recorded quality but a "speaker characteristic" added to all reproduced material. "Sameness" is another word for it.
I just went back to bi-wiring over the weekend. The first thing I noticed was cymbal-like instruments shimmer much more. Secondly the bass now seemed to be less perhaps due to the greater high frequency information.
On orchestra music the orchestra is now well behind the speakers instead of right at the speaker. Like the article said, this may be a phase or time shift error and the depth may become wearing over time.
Finally there is slighlty better separation between instruments. It's easier to pick out each instrument.
THE DISADVANTAGE WITH BI-WIRE
One thing that happens when you biwire your loudspeakers is that the input of the high- and the low-pass filters are fed with different input signals. The difference is a result of the high frequencies and the low frequencies being forced to travel different paths, perhaps through different types of cables, but under all circumstances through cables who have seen different loads (a tweeter with a high pass filter has a completely different impedance response compared to a woofer with a low pass filter!).
What happens is that the drivers will work less good together than when their filter halves were fed with equal signals. The result is a generation of more static and stochastic phase error sounds at different directions from the loudspeaker. The stochastic phase error sounds appear because there may be different types of unlinearities in the low- and high-frequency paths.
What does this sound like? Well, usually, just as you may expect from physics, it appears as a change in the reproduction of space and sound stage. Often, the first impression is that the "biwired" sound presents extended "dimensions", more "air", and is more "living". The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play. No wonder, since it is not a real, recorded quality but a "speaker characteristic" added to all reproduced material. "Sameness" is another word for it.
I just went back to bi-wiring over the weekend. The first thing I noticed was cymbal-like instruments shimmer much more. Secondly the bass now seemed to be less perhaps due to the greater high frequency information.
On orchestra music the orchestra is now well behind the speakers instead of right at the speaker. Like the article said, this may be a phase or time shift error and the depth may become wearing over time.
Finally there is slighlty better separation between instruments. It's easier to pick out each instrument.
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- 28 posts total
- 28 posts total