Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Components for building a high pass filter
Components for building a high pass filter
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 5th December 2016, 04:14 PM   #1
san1c99 is offline san1c99
diyAudio Member
Join Date: Jul 2016
Default Components for building a high pass filter

Hey guys, I have recently started designing a ported box for desktop speakers I will soon be building. However, using Winisd I have noticed the speaker will exceed its xmax at full power. To limit over-excursion at low frequency I have added a first order high pass RC filter at 130hz.

Using an online high pass calculator I have found two different ways to make this filter. The first uses these components: Capacitor and Resistor, these are both high end audio components so building a high pass filter (HPF) with these would cost $10 each.

The second option is with these parts: Capacitor and Resistor. The difference is that these parts only cost $2 for making a HPF.

Since the resistor in an RC HPF is in parallel and the signal going to the speaker doesn't pass through the resistor I assume that a far cheaper non-'audio-grade' component can be used instead. I just want to know if using the low quality resistor in parallel will still have an effect on the quality of the audio signal or not.

One more question i want to ask is will the first order high pass filter shift the phase by 90 degrees? Thanks, Joseph
Attached Images
File Type: png High-pass-filter-diagram2.png (9.5 KB, 48 views)

Last edited by san1c99; 5th December 2016 at 04:25 PM.
  Reply With Quote
Old 5th December 2016, 09:28 PM   #2
AllenB is offline AllenB  Australia
diyAudio Member
Join Date: Oct 2008
The fact that a component is in parallel does not mean it can't make a difference. If it were to modify the current draw through the series component then the signal available to the load is also modified. This is the method of a second order filter.

Resistor types are not very critical with speakers, eg the non-inductive quality is not much of a concern. The power rating could be.
  Reply With Quote
Old 6th December 2016, 01:16 AM   #3
san1c99 is offline san1c99
diyAudio Member
Join Date: Jul 2016
Ok so despite being in parallel, the resistor will still have an affect on audio quality but this will be negligible.
This is the method of a second order filter.
I don't quite understand what you are saying, do you mean my filter is a second order type or that a second order uses the principles you just mentioned?

Another question I had was if capacitors with higher values (farads) add more distortion to the signal? I think I read this somewhere and just want to confirm is this is true. Thanks, Joseph
  Reply With Quote
Old 6th December 2016, 05:21 AM   #4
PRR is offline PRR  United States
diyAudio Member
PRR's Avatar
Join Date: Jun 2003
Location: Maine USA
Why do you have a resistor?

A loudspeaker "IS" a resistor.

If you compute your C-R for 100 Ohms, then throw an 8 Ohm speaker across the 100 Ohms, it becomes 7.4 Ohms for all practical purpose.

First compute a C for your nominal loudspeaker impedance. Say 8 Ohms, try 150uFd.

THEN remember a loudspeaker is not a *constant* resistance. It can be very "lumpy". Especially around bass resonance. Which is also about the point you are likely to run into Xmax trouble.

You can then use a somewhat small C. The rising impedance of speaker will semi-match the cap above resonance, and below resonance the cap will severely reduce speaker voltage. It is not uncommon to end up with even 1/3rd of the cap you compute from nominal speaker impedance.

BUT this added cap shifts all the speaker electromagnetic parameters. The result is not what your speaker calculator predicted.

A second-order choke and cap is a somewhat better way to cut bass excursion. Steeper, but mainly because loudspeaker impedance has less effect.

All in all, it is usually better to bass-cut BEFORE the power amp, rather than after. The impedances are higher (smaller caps) and more predictable. You are not making bass power that you will not use.
  Reply With Quote
Old 6th December 2016, 07:59 AM   #5
san1c99 is offline san1c99
diyAudio Member
Join Date: Jul 2016
Thanks PRR for the information but I do not quite understand what you said about the capacitor. Firstly a filter before the amp is not an option for me and I prefer using a first order high pass filter because it produces a more desirable frequency response curve.

Now I am quite sure the program I use (WinISD v0.7) shows the effect of bass attenuation with the varying impedance curve taken into account. So I expect the real change to match the simulation.

But lets say that this is not the case and like you said, a smaller capacitor than calculated can be used. How would I determine the size of this cap? do I just get one of one third the capacitance and hope it works properly?
  Reply With Quote


Components for building a high pass filterHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
simple low pass RC filter noob question mr.duck Parts 18 18th October 2015 11:37 AM
calculating high-pass filter for these components roger2 Solid State 10 17th May 2015 05:21 AM
Building a high pass filter / crossover for my small full range speakers Howard Full Range 3 24th October 2013 02:15 PM
building high pass filter nanok66 Multi-Way 7 7th May 2012 11:07 PM
Building a simple high pass filter mjg100 Subwoofers 2 19th March 2009 04:38 PM

New To Site? Need Help?

All times are GMT. The time now is 03:12 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio