Hi team, I have an bi amped horn system that I’d like to tweak a little. The mid horn has a passive hi pass filter that I’d like to do away with, looking to install the hi pass on the input of the mid-range amp.
The passive filter is a 2nd order and this combined with the horn roll off makes for a very step slope. Not 100% sure of the exact filter frequency so I’ll need to do some trials but its around 450hz.
Is there anyone out there that is willing to help with the numbers for a passive hi pass filter driving 100k ohms? I can build anything but fall down on the design skills, yes I know this is one of the easiest circuits but what I’ve tried so far hasn’t worked as planned…..
I've looked into this a few times but never got it sorted so time to try again.
Cheers Dave
The passive filter is a 2nd order and this combined with the horn roll off makes for a very step slope. Not 100% sure of the exact filter frequency so I’ll need to do some trials but its around 450hz.
Is there anyone out there that is willing to help with the numbers for a passive hi pass filter driving 100k ohms? I can build anything but fall down on the design skills, yes I know this is one of the easiest circuits but what I’ve tried so far hasn’t worked as planned…..
I've looked into this a few times but never got it sorted so time to try again.
Cheers Dave
f = 1 / ( 2Pi x √(R1C1R2C2) )
https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/filter-fil84.gif
f = 450Hz
R2 = 100k
R2 = 10 x R1 ... for light loading of first stage
R1 = 10k
C1 = 10 x C2 ... for light loading of first stage
Solve for C2:
C2 = 1 / (2Pi x 450 x 10 x 10k )
C2 = 3.54nF
C1 = 35.4nF
To change the frequency, sub the new frequency for 450 in the last equation.
https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/filter-fil84.gif
f = 450Hz
R2 = 100k
R2 = 10 x R1 ... for light loading of first stage
R1 = 10k
C1 = 10 x C2 ... for light loading of first stage
Solve for C2:
C2 = 1 / (2Pi x 450 x 10 x 10k )
C2 = 3.54nF
C1 = 35.4nF
To change the frequency, sub the new frequency for 450 in the last equation.
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Is this a compression driver you're filtering for? And a tube amp that you're feeding?
450 Hz is pretty low for most CD's. And 100k is pretty high for an amp input impedance.
I ask 'cause I've got a whole shoe box full of shredded diaphragms from my long struggles to arrive at a proper crossover design/cutoff frequency. (as recently as 1975!)
Then just yesterday, sorting out a passive filter for another member, I was reminded of the 'penalty' for high impedance outputs -- MUCH larger coils. If you skip the coil and use just resistors and capacitors, you can only make a 'highly damped', or Bessel, filter function. Usually that will not have a steep-enough 'skirt' -- enough attenuation in the first octave below the cutoff frequency -- for a compression driver to be driven to full power. (Probably a dozen of those shredded diaphragms would agree!) Nevertheless, some listeners prefer the highly-damped sound.
Are you really stuck on making it passive? Many active circuits are only slightly more complicated, and have a much easier design approach.
Cheers
450 Hz is pretty low for most CD's. And 100k is pretty high for an amp input impedance.
I ask 'cause I've got a whole shoe box full of shredded diaphragms from my long struggles to arrive at a proper crossover design/cutoff frequency. (as recently as 1975!)
Then just yesterday, sorting out a passive filter for another member, I was reminded of the 'penalty' for high impedance outputs -- MUCH larger coils. If you skip the coil and use just resistors and capacitors, you can only make a 'highly damped', or Bessel, filter function. Usually that will not have a steep-enough 'skirt' -- enough attenuation in the first octave below the cutoff frequency -- for a compression driver to be driven to full power. (Probably a dozen of those shredded diaphragms would agree!) Nevertheless, some listeners prefer the highly-damped sound.
Are you really stuck on making it passive? Many active circuits are only slightly more complicated, and have a much easier design approach.
Cheers
Well... Yes 100k input impedance, it's a Sun Audio 2A3. The CD is a Yamaha 6681b so will go that low.
Want to go passive as it's easy to throw together and the Sun has more than enough gain so don't need any gain in the filter section. Also passive should be quieter (not really an issue I know) Could also look at the Pass active crossover.
The current filter on the speakers now sounds absolutely beautiful but I just want to try passive on the input as apposed to the output.
Appreciate your thoughts.
Dave
Want to go passive as it's easy to throw together and the Sun has more than enough gain so don't need any gain in the filter section. Also passive should be quieter (not really an issue I know) Could also look at the Pass active crossover.
The current filter on the speakers now sounds absolutely beautiful but I just want to try passive on the input as apposed to the output.
Appreciate your thoughts.
Dave
