Need advice for 80hz high pass

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Need advice for 80hz high pass
« on: 17 Jan 2022, 11:43 pm »
I want a 1st order 80hz high pass on smallish bookshelf speakers.  Does it matter to choose between low end or high end capacitors?  Will a cheap Bennec capacitor smear the signal?

corndog71

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Re: Need advice for 80hz high pass
« Reply #1 on: 18 Jan 2022, 01:07 am »
What speakers?  Are you referring to an inline cap between preamp and amp?

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Re: Need advice for 80hz high pass
« Reply #2 on: 18 Jan 2022, 01:22 am »
Any speaker.  Yes, before amp. Or is it better in the speaker itself?

Hobbsmeerkat

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Re: Need advice for 80hz high pass
« Reply #3 on: 18 Jan 2022, 01:22 am »
I want a 1st order 80hz high pass on smallish bookshelf speakers.  Does it matter to choose between low end or high end capacitors?  Will a cheap Bennec capacitor smear the signal?

In order to create a highpass filter, we will need to know the input impedance of your power amp(s) if you have an integrated unit, it may not be possible. Unless it has both pre-out and amplifier in.

You dont need to go crazy expensive, but in most cases you will only need a tiny cap between your preamp and amp so it's not overly expensive even for goot quality caps.

If you want to create a high pass filter after the power amp, its going to need to be a massive value. (Roughly 250uF for 8ohm or 500uF for 4ohm) and even budget brand polycaps get BIG and expensive, or you need to bundle multiple caps in parallel (2x125uF or 5x 50uF or) neither of which are ideal as they will smear the sound vs a tiny cap between the amp and preamp.

If you know the input impedance of your power amp we can figure out the rest.

richidoo

Re: Need advice for 80hz high pass
« Reply #4 on: 18 Jan 2022, 01:40 am »
For low pass it doesnt matter as much since other distortions in the low bass will swamp out anything subtly wrong with a cheap film cap.
For hi pass is a different story, because everything above 80Hz, including the treble signal will pass through the cheap cap and be colored in the bands that we are more sensitive to distortion and where there is less of other distortions to mask the caps flaws. So a hipass is usually worth spending alittle more if your gear and ears know the difference.

Bennic is not bad. I’ve heard worse coughcoughsolencough
Splurge and try a few different caps.
YOLO!  :thumb:

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Re: Need advice for 80hz high pass
« Reply #5 on: 18 Jan 2022, 01:44 am »
Input impedance 27 kOhms. It's an Emotiva a5.  It's all I have til I get what I really want. I really want a Jeff Rowland 125.

Cheytak.408

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Re: Need advice for 80hz high pass
« Reply #6 on: 18 Jan 2022, 02:15 am »

Bennic is not bad. I’ve heard worse coughcoughsolencough
Splurge and try a few different caps.
YOLO!  :thumb:
Agreed.  If gritty highs are your thing, Solen is the thing 😏

richidoo

Re: Need advice for 80hz high pass
« Reply #7 on: 18 Jan 2022, 02:21 am »
For active xo caps the Vishay polyester MKT1813 caps are excellent.

Hobbsmeerkat

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Re: Need advice for 80hz high pass
« Reply #8 on: 18 Jan 2022, 02:32 am »
For a 27 Kohm amp, you will need a roughly 0.072uF capacitor which isn't a common value. 2x 0.033uF in parallel (0.066uF) will get you -3dB at 89Hz two 0.047uF caps (0.094uF) will get you -3dB at 63Hz.
The closest you can get will be to parallel 5x 0.015uF caps to make a 0.075uF but that ads up quick as you'll need a total of 10. 5 per channel

It's also not a good idea to mix dissimilar cap values as it leads to phase shift issues. (Ex: 0.022uF + 0.047uF)

In the future, if/when you change your amp, the cap values will also need to change based on the new input impedance.
For the Rowland 125 the input impedance is 41Kohms, which would need a 0.047uF capacitor to be -3dB at 82Hz.

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Re: Need advice for 80hz high pass
« Reply #9 on: 18 Jan 2022, 02:39 am »
For a 27 Kohm amp, you will need a roughly 0.072uF capacitor which isn't a common value. 2x 0.033uF in parallel (0.066uF) will get you -3dB at 89Hz two 0.047uF caps (0.094uF) will get you -3dB at 63Hz.
The closest you can get will be to parallel 5x 0.015uF caps to make a 0.075uF but that ads up quick as you'll need a total of 10. 5 per channel

It's also not a good idea to mix dissimilar cap values as it leads to phase shift issues. (Ex: 0.022uF + 0.047uF)

In the future, if/when you change your amp, the cap values will also need to change based on the new input impedance.
For the Rowland 125 the input impedance is 41Kohms, which would need a 0.047uF capacitor to be -3dB at 82Hz.

Thanks a bunch.

Cheytak.408

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Re: Need advice for 80hz high pass
« Reply #10 on: 18 Jan 2022, 02:54 am »
Input impedance 27 kOhms. It's an Emotiva a5.  It's all I have til I get what I really want. I really want a Jeff Rowland 125.
C = 0.074 µF for 80Hz  Odd size.  You can parallel two .039 ,to end up with a .078 which will get you close: 75Hz.  Mouser has these values in stock in CDE polypropylene axial caps.

What Hobbs said about paralleling the same values  :thumb: