Help needed on Pll XO

[mertol]

Hi ;

I am trying to fine tune my PLL XO and I seem to need help.
I am mainly trying to use info from

TLS.org | Passive Line-Level Crossover

I have 2 questions :

1. For the first order high pass filter, I don't see an R1 in the figure. And in XLS file linked, there is capacitor value shown in a cell labelled as (No R1), it's exactly the same value as HighPass Cap – Low Pass Cap values. I am not exactly sure about where I should use this value. So I am a little bit confused on using an R1 in the input of the HP filter, and what to do if I don't use one (should I add the cap value shown in the XLS file to Hgih Pass cap or what?)

2. I want to put a VR (potans) to control volume of each driver. I have a few ALPS 5k log pot's that I can use. I prefer to use them at the output of the filters but I am afraid that this can change the impedence that the filters see and will shift the XO point greatly. Is there a way to use VR at the output, or should I use it at the input only?

very best regards
Mertol

 

[patriz]

Just curios , how did you end up with the pot , first or after the filter?

 

[mertol]

before the filter , I didn't want the pot's resistance to effect the amps impedance

 

[PeteMcK]

re:'For the first order high pass filter, I don't see an R1 in the figure' - use the R1 from the formula beside the LP filter
re: "Is there a way to use VR at the output' - if the Input impedance of the amp, i.e. the input pot is much higher (say 10x) than R1, then it won't have much effect on the xo point