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Making a passive high shelf filter?

infratuna

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High there. There has been a thread about making loh shelf filter but my need is the opposite.

I would like to make it passive for the sake of size and not having to charge anything.

I'am using my CustomArt Music One IEM headphones with my Macbook pro and iPhone. Problem is, that the headphones are lacking bass so much I don't like to listen many music genres with them. I was trying with Reaper to check out what kind of eq would be needed. Even -8dB drop isn't a problem.

Ideal eq would be band 50hZ +12dB with 1.55 bandwidth (oct). How ever I believe high shelf filter would be easier to build passively. For high shelf filter something like 70hZ -16dB would be nice.

Any way to do this? I am amateur but I can use soldering iron :)
 

DonH56

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You cannot make a passive filter with gain. I am not sure exactly what you are looking for, however. Could you sketch (draw) the filter response and annotate key points like the corner frequency, passband loss, stopband loss? It sounds like you want to reduce the highs so you effectively get a bass "boost"? Something like this (below)? A simple single-pole filter starting at 20 Hz will provide about -12 dB at 80 Hz, is that close enough?

1568897459327.png
 
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infratuna

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Sorry for being unclear. English is not my mother language.

Yes I am trying to get bass boost. No need for gain. I guess in your single-pole filter could work. I would need to try what dB and hZ's would sound the best. I would prefer not to boost frequencies below 30 Hz (or something) but that might be hard to do with passive circuit.
 

DonH56

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Remember a passive filter is also affected by the input (driving, source) and output (load) impedances so you'll have to design with that in mind.

Would it not be much easier to just turn up the bass, or turn down the treble, or use a software equalizer application in your phone and Mac? That is what I would do.

Here is a very simple circuit that does more-or-less what you want; you would have to adjust the resistor and capacitor values for your system. Probably much lower R values since this is for headphones, resulting in much bigger capacitors (maybe 10 ohms and thus 270 uF and 2700 uF).

1568898492888.png

1568898508577.png


The basic equations are (sorry for changing up the numbers):
  • Vout = Vin * Z2 / (Z1 + Z2)
  • Z2 = R2 / (1 + s * R2 * C1)
  • Z1 = R1 / (1 + s * R1 * C2)
  • s = j * 2 * pi * f
  • j = sqrt(-1)
You'll want to take the magnitude of this. Z2 sets the low-frequency pole and Z1 the high-frequency zero that creates the upper shelf.

Note a passive circuit is going to have high loss so might make it hard to get the volume (loudness) you want from the headphones.

HTH - Don
 

solderdude

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You want a passive filter between the source and headphone amp or a passive filter in the headphones cable ?

When you want to go passive low-shelf in the headphone cable consider that it will be very hard to do this steeper than 6dB/oct (20dB per decade)
Maybe 12dB/oct is technically possible but not feasible.
'Bass boost' (mid and treble attenuation actually as Don already mentioned) for an 8 Ohm IEM would require huge inductors.
If that were easy/possible to do I would be selling those filters like hotcakes.

Attenuating lows is much easier to do.
 
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DonH56

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^^^ Yah, I assumed line-level betwixt source and amp, then realized I was not sure where since he talked of MAC and phone to headphones. Still think just using tone controls is a better idea.
 

carlosmante

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You cannot make a passive filter with gain. I am not sure exactly what you are looking for, however. Could you sketch (draw) the filter response and annotate key points like the corner frequency, passband loss, stopband loss? It sounds like you want to reduce the highs so you effectively get a bass "boost"? Something like this (below)? A simple single-pole filter starting at 20 Hz will provide about -12 dB at 80 Hz, is that close enough?

View attachment 33841
That is the response of a Low pass Filter Not a high pass filter.
 
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infratuna

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Big thanks for the help. I wanted the filter between my phone and headphones so probably in the cable. I don't know how to apply filter in my iPhone or iPad. In Macbook it is easier.

So it sounds like the thing I would like to do it is not easy or possible?
 

DonH56

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That is the response of a Low pass Filter Not a high pass filter.

It's what the OP called a shelf filter for high frequencies; I went with what I thought he asked for rather than getting buried in the terminology. It's not what I would call a standard LPF as the rolloff does not continue past the zero frequency corner.

Big thanks for the help. I wanted the filter between my phone and headphones so probably in the cable. I don't know how to apply filter in my iPhone or iPad. In Macbook it is easier.

So it sounds like the thing I would like to do it is not easy or possible?

Well, "easy" and "possible" are relative to your skill and ability to figure out the numbers and component values you'd need. I think it would be much easier/better to find an EQ app that allows you to create a similar curve in your laptop or phone. The Macbook may already have it someplace in the audio setup; I am not a Mac or iPhone user so can't help with that. Bet there are folk on ASR who are, however. That would give you a lot more control of the sound.
 
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infratuna

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I agree that this would be best to do with iPhone eq app. I think you cannot apply eq in the main output of iPhone.
 

levimax

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The Linkwitz lab web site has some passive filters https://www.linkwitzlab.com/filters.htm like you are looking for but I don't think they have the slope you are after, see attached. Seems like you should be able to do what you want in software on your phone and iPad but since I am not part of the Apple world I can't offer any suggestions.
 

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DonH56

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The Linkwitz lab web site has some passive filters https://www.linkwitzlab.com/filters.htm like you are looking for but I don't think they have the slope you are after, see attached. Seems like you should be able to do what you want in software on your phone and iPad but since I am not part of the Apple world I can't offer any suggestions.

Duh, thanks, easier solution, does not use the through (series) zero I added so saves a capacitor and makes it much easier to set the gain where you want. If the impedances work out! Still think there's an app for that...

Too used to RF LC filters so tend to think in orders of two...
 

pkane

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Big thanks for the help. I wanted the filter between my phone and headphones so probably in the cable. I don't know how to apply filter in my iPhone or iPad. In Macbook it is easier.

So it sounds like the thing I would like to do it is not easy or possible?

Take a look at Neutron audio player app on apple AppStore (free eval). Has lots of DSP effects and is an excellent player. Maybe much easier than doing this in hardware.

0DE1E058-A893-4831-A899-C720715C5524.jpeg
 
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DonH56

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carlosmante

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Link broke for me? I'll try later. Perhaps definitions have changed since my last course in filter theory.

I always thought of the shelf being below (low) or above (high) the corner frequency. It can be a boost or a cut.

View attachment 33870

In contrast to low-pass and high-pass filters:

View attachment 33871

FWIWFM - Don
I'm posting the link again. That is what I said when I used the word "ambiguous": capable of being understood in two or more possible senses or ways
https://www.audiorecording.me/what-...-shelf-filter-in-parametric-equalization.html
 

DonH56

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Krunok

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Head_Unit

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I agree that this would be best to do with iPhone eq app. I think you cannot apply eq in the main output of iPhone.
I wanted to do the opposite, CUT too much bass. My research seems to indicate you can only EQ the headphone out for Apple Music, and then only with their presets. :mad:
And as a loudspeaker engineer, forget about the passive filter, real headphone impedances mean that bass-ically (ha ha ha) it will not work.
So, you need different headphones, sorry! I'm getting a different set myself, sigh.
 
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