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In the Forum: Horn-Loaded Speakers
In the Thread: The African compression electromagnet drivers?
Post Subject: FCs again.......Posted by haralanov on: 8/12/2010
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 Romy the Cat wrote:
I think to conduct any more or less methodologically cleaner experiment the best would be to have the field coil with multiple taps. Make the coil standard 600V rated and to design the coil to have let say 4 taps that identically fill the bobbin. Let say it would be 12-48-96 and 192V. Then driving the coil from a powerful PS that has a lot of buffer it would be possible to switch taps on the field coil and adjusting the PS to maintain the same faux.

Unfortunately this method is not going to have success, simply because you can't mantain the same flux in gap using the low voltage taps (compared to the 192V tap) because you need substantially more current (192/12=16 times more) flowing through the wire and you are going to melt it.


 be wrote:
I agree that the total flux will be the same but therefor in the same iron structure, the field in the gap will be the same, at least in the statical case.

Yes, that's right. But only in statical case.


 be wrote:
If the system is modulated by the speach coil, a simpel measure of how well the system resists this modulation, is the ratio of resistance to inductance of the field coil, lets call it Fc.
If the  insulation thickness of the field coil wire is negligable, this ratio is unchanged and therefor the dynamic behavior will be the same as well.

Real insulations have a thickness and this inperfection will tend to upset the ballance, so that higher voltage coils by unchaged statical flux will tend to be softer (higher Fc) or more easy to modulate and therefore the unit will have higher distortion due to the magnetic nonlinearities of the pole pieces.

the high voltage coil will at the same flux have higher dissipation, this could mean that it will run at a higher temperature and thereby softening the mooving parts more.
If this is the case and is benneficial, the resistor mentionned in the post above could be mounted at the back plate of the electromagnet or the magnet could be insulated to run at a higher temperature!

Be, is that your own thoughts or you had read it somewhere?  

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