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Re: "midrange dip"

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Here is the text of the reply that Roger West sent me a few days ago.

There would be no advantage using thick-film non-inductive resistors. On
the other hand, it would not hurt anything to use them if they can handle
the power. The minimum power that the group of resistors needs to handle is
100 watts minimum (4 x 25 watt resistors). The frequencies that the
resistors work at (the cross-over range - 500Hz) is much too low for the
residual inductance and capacitance of the standard resistors to have any
effect. The values that I mentioned to you in my last note will give the
same crossover point as the original values. If you wish, you can reduce
the crossover point a bit, but I wouldn't go too low. I would increase the
value of the four resistors to 24 ohms each, which would provide a crossover
point on the order of 250Hz. I wouldn't go any lower than this. Also, the
low-frequency transformer needs to have the same crossover point or the high
and low portions of the spectrum will overlap and cause a bulge in the
response between 250 and 500 Hz.

I did not experience the bulge from the low frequency transformer.
The change to 24ohms did improve the dip though. The trouble is, for me only half of the dip.

I did not realise that the Zero’s had such a profound effect on this dip. I will certainly give them a try.




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  • Re: "midrange dip" - Roy 15:49:36 07/15/02 (1)


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