passive line level Crossovers pllxo

[Preacher]

I would like to make 12db per oct xovers (passive line level) according to this website. I'm having trouble picking starting values. Could someone help me make sense of this?

http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

This is for a car system and I need a xover for about 3.1 khz.

My Head Unit boasts a pre-out of 4v/100k ohm (Pioneer deh-p7500mp)
My amp (aura 2300) claims an input impedance of 14k.

do I just arbitrarily pick a starting value or are these numbers relevant?

Thanks

 

[Rudolf]

My Head Unit boasts a pre-out of 4v/100k ohm (Pioneer deh-p7500mp)

Obviously your pre-out impedance should read 100 ohm instead of your stated 100k ohm. If that is true, you might start with 0,5-1kOhm for R1.

 

[sreten]

Hi,

R1 needs to be 1.5 K (~ R2/10), R2 = 14K (in your power amplifier).

/sreten.

 

[Preacher]

Thank you for the help; That makes sense to me. I didn't expect to see that impedance from my amp.

If I want a xover freq of 3.1 khz for the lowpass I came up with

c1= 3.42 uf
c2= .342 uf

I'm guessing that anything between 2 and 5 volts would be acceptable voltage for the caps. Would I use standard audio crossover capacitors (non-polar)?

If I'm missing something in my values please let me know. How close will this get me to the target frequency? Are these pretty accurate crossovers?

Geoff

 

[sreten]

Hi,

with R1 = 1.5khz and 3.1khz c/o, C1 = 34.2nF nearest = 33nF.

So your values are 33nF and 3.3nF, use any film capacitors.


/sreten.