Crossover resistor adjustment help?

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I'm looking for help in selecting the proper ohm resistors to modify a 2-way XO.

Currently the series resistor is 12ohms and the parrallel resistor is 4ohms. If I switch the 12 with a 8.5 I get the desired top end I'm looking for (slightly brighter than the original design). But based on what I've read, when you change the series resistor you also have to change the parallel resistor to keep the XO point constant.

I tried a calculator that was posted in another thread but it was only for attenuation. I'm looking to remove some attenuation and I couldn't figure out how to get the calculator to simulate that.

The finished speaker is 8 ohms and the woofer is 8 ohms. I'm not sure what the CD is. I'd have to measure it. No markings are on it.

I'm also cursious how much the XO point shifts when changing a resistor by 2-4 ohms?
The XO may not shift very much, or by a lot. :) If you are talking about the calculator I posted, you need to be a little more creative in using it. :)

First, change the attenuation until the R values closely align with your current R values. You may need to alter the impedance as well as the attenuation. Then decrease the attenuation.

Ideally, find the tweeter impedance charts and see what the impedance is around the crossover frequency, around 2 kHz usually and use that.

Another trick is to replace your 8.5 ohm resistor with a set of 3 that add up to 8.5. This lets you jumper around until you find the values you like. For instance, try 2Ohms, and then 2 x 3 Ohms. This let's you try 2, 5, 6, and 8 Ohms. :) You can do this with both speakers at once, and avoid soldering until you've picked the right values.


Thanks. I'll try that calculator again with the method you mentioned.

What I have been doing is using alligator clips connected to the XO board. Then grouped a bunch of resistors together at one end. Then I just move the other alligator clip from resistor to resistor until I find what I like. Doing that with both the series and parallel resistor gets a little cumbersome.
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