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In the Forum: Horn-Loaded Speakers
In the Thread: Vitavox S2 with Electromagnets
Post Subject: The active flux recuperationPosted by Romy the Cat on: 7/5/2011
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 decoud wrote:
If a magnetic field is static, who cares how it is created? Isn't the main potential advantage of electromagnets one that no one has explored at all - the possibility of modulating the field strength in direct response to the audio signal? So, one extracts some parameter of the signal in parallel - say instantaneous frequency power - and adjusts the field strength on-line. 

Yes, I had this idea a few years back: to drive electromagnet with current that is synchronized with signal strength. Then I realized that on compression drivers there is no such a thing as flax modulation as the flux is too strong and the current in VC are too low.  If you have voice coil that care let say 1000W and very loose magnetic field at 1.2T then the magnetic file of such voice coil do stress the gap’s flux. In compression drivers we deal with very low currents. My own MF driver run at 250mV, which makes 0.25W/15R=16mA if I am not mistaken with my math. If I turn a coil and will drive across it 16mA then with my gauss meter n micro-Tesla mode I will not be able to read something but this something will be at the level of background noise. From another side the magnetic force in gap of compression drivers is huge. My driver has 1.7T and some of the drivers have 2.4Tesla. The 2.4T is huge magnetic force. The medical magnetic imaging resonance systems create 3T magnetic field. Do you know the force of that magnetic strength? This magnetic force reportedly wipes out memory from human mind and a technician who work with those machines and who go into the gap to serve MRI machines told me that he writes a note to himself what to do in the gap as when he in then he will not remember why he went there. So, if somebody tell me that a magnetic force of 2T can be in any way upset /demodulated by a current from few dozen milliampere then I would be very suspicions.

Again, somebody who feels that flax demodulation is a factor in compression driver – publish the data of flux transient drop during loud play of the compression driver. It would very indicative and very honest: here is the driver that at given instance out this signal, this is the graph of VC current and this is the graph of gap’s magnetic force. On graph indicating that with perm magnet the flux sagging and another graph indicating that with electromagnet of the same force and the same magnetizing surface the sagging does not take place. That will be no BS explanation but you know why no one did it so far? I presume that it is because it never happened in reality.

The Cat

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