In Line Filter for NX-Treme

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subsonic1050

In Line Filter for NX-Treme
« on: 21 Jun 2022, 02:30 am »
I'm looking to add an in-line filter to my NX-Treme's. How do I know what value capacitors to use? Also, most of the high pass filters I see online also have a resistor in the circuit - the ones I've seen here simply have a capacitor. What's the difference?

Danny Richie

Re: In Line Filter for NX-Treme
« Reply #1 on: 21 Jun 2022, 02:50 am »
The cap value that you need depends on the input impedance of your amp. No resistor needed.

Hobbsmeerkat

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Re: In Line Filter for NX-Treme
« Reply #2 on: 21 Jun 2022, 02:53 am »
the "resistor" you're seeing is a representation of the "input impedance" of your amplifier.
so in order to get the cap value you need, you will need to know the roll-off point you want, and the input impedance of your amplifier, then you can use that to determine the cap value of your filter.

THis links is helpful to determine the cap or Frequency you can get so long as you know those 2 things.
http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php

subsonic1050

Re: In Line Filter for NX-Treme
« Reply #3 on: 21 Jun 2022, 02:57 am »
Thanks for the reply Danny. Once I determine the input impedance of my amp (it's 100k ohms) - how do I calculate what size capacitor to use? I'm using the NX-Treme's with the triple OB subs. I'm guessing i want the roll-off to occur around 45 Hz? I'm getting some decent distortion at moderately loud levels on certain tracks from lower frequencies and I'm assuming this will fix the issue.

Danny Richie

Re: In Line Filter for NX-Treme
« Reply #4 on: 21 Jun 2022, 03:33 am »
In that case a .047uF cap will get you a -3db of 34Hz.

A .033uF cap will give you a -3db of 48Hz (good choice).

A .022uF cap will give you a -3db of 72Hz (also a good choice).

Keep in mind that you want to cross to your subs where they are each 6db down.

subsonic1050

Re: In Line Filter for NX-Treme
« Reply #5 on: 21 Jun 2022, 03:51 am »
Thanks Danny and Hobbs! I just want to make sure you meant .047uF, .033uF, and .022uF instead of .47uF, .33uF, and .22uF before I order some up. I do see some sonicaps for those values, but they seem to be much more rarely used than the .47, .33 and .22 uF caps. Also, for posterity as well as if I need to modify my filter for a different amp with a different input impedance - how did you calculate that?

Danny Richie

Re: In Line Filter for NX-Treme
« Reply #6 on: 21 Jun 2022, 12:46 pm »
Thanks Danny and Hobbs! I just want to make sure you meant .047uF, .033uF, and .022uF instead of .47uF, .33uF, and .22uF before I order some up. I do see some sonicaps for those values, but they seem to be much more rarely used than the .47, .33 and .22 uF caps. Also, for posterity as well as if I need to modify my filter for a different amp with a different input impedance - how did you calculate that?

Yes, those values are correct. Have a look at some of the Copper foil caps like the Miflex.

Hobbsmeerkat

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Re: In Line Filter for NX-Treme
« Reply #7 on: 21 Jun 2022, 12:59 pm »
Thanks Danny and Hobbs! I just want to make sure you meant .047uF, .033uF, and .022uF instead of .47uF, .33uF, and .22uF before I order some up. I do see some sonicaps for those values, but they seem to be much more rarely used than the .47, .33 and .22 uF caps. Also, for posterity as well as if I need to modify my filter for a different amp with a different input impedance - how did you calculate that?
Use the calculator in the link i provided.

If you enter the input impedance of your amp and the cap value it will spit out the new roll off point for that amp.
Then you can use input impedance and roll off point to find the nearest value cap to reach the desired roll off point.

subsonic1050

Re: In Line Filter for NX-Treme
« Reply #8 on: 21 Jun 2022, 03:54 pm »
Wow - I don't know how I missed that link before! Thanks guys, huge help!

Rikard Ekval

Re: In Line Filter for NX-Treme
« Reply #9 on: 21 Jun 2022, 07:36 pm »
the "resistor" you're seeing is a representation of the "input impedance" of your amplifier.
so in order to get the cap value you need, you will need to know the roll-off point you want, and the input impedance of your amplifier, then you can use that to determine the cap value of your filter.

THis links is helpful to determine the cap or Frequency you can get so long as you know those 2 things.
http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php

Thanks Hobbs.
This is useful for an amateur.