Online Crossover Calculators - Which One?

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sarsicism

Member
Joined 2009
#1
Hi,

I have been trying to use some online calculators to figure out a high pass filter and a narrow band filter. My issue is that I am getting different results with the different calculators and do not know which is correct.

What I am trying to solve:
Second order, Linkwitz-Riley, high pass filter at 5000Hz @ 7.2 Ohm.
Second order, Linkwitz-Riley, narrow band pass filter from 1250 to 5000Hz @ 3.6 Ohm.

Just trying to figure out the high pass portion:

Using this calculator...
Speaker Crossover Calculators by V-Cap
(Second Order Two Way)
It says C1 = 2.21 uF, and L1 = 0.46 mH

This one...
https://www.the12volt.com/caraudio/passive-crossover-calculator.asp#ccc
(2nd Order (12 dB per Octave))
It says C2 = 3.13 uF, and L2 = 0.32 mH

This one...
High-pass filter 12dB per octave
It says C1 = 2.76 uF, and L1 = 0.23 mH

Any help would be appreciated.
 
#2
I recommend you look at boxsim by Visaton or Xsim. A quick google search will lead you to where to download these. There are support threads on this site. Each of these will compute component values for Linkwitz filters. These are free crossover design programs that you can load your driver and box information into and then design the crossover taking into account the complicated impedance vs frequency characteristics of each driver. The simple crossover calculators will only work once the driver impedance has been compensated to be constant over the frequency range you are using the crossover. So simply using one of those and building it will likely not produce the desired frequency response. The boxsim program has an automated optimization that you can use to fine tune values of the crossover for you. I would also look at using a modern approach like the miniDSP 2x4hd digital crossover. For little or no additional cost you can create an excellent system and will be able to change the crossover and equalization at will any time you please.
 
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#3
Thank you. I actually have a couple MiniDSP products, but the cost there is the additional channels of amplification... I agree about the benefits though. I'm looking to handle the broad strokes with passive crossovers.

I'll look into the software, but was hoping to avoid having to learn a new program (vs plugging a few numbers into an online calculator).
 
#5
Passive bandpass filters are the most difficult, as the output impedance of the first stage isn't low, so you have to deal with that somehow. Most of the equations used to calculate these filters assume a zero amplifier output impedance and a fixed speaker impedance. To really design passive crossovers you will want an impedance measuring device. You can use your PC with a sound card and free software like Limp, from the Arta software suite, and just two resistors. If you already have a closet full of coils and caps just build up one of those calculated designs and measure what you get. Hey, there's no where to go right now anyway.
 
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