High Pass Filter (HPF) and Low Pass Filter (LPF) Mega Thread

[GrapeBass]

Why would you think this? Can you give us some rationale for your recommendation?

For me, having the spacial effects (which I rarely use) after the HPF/LPF allows them 'space,' unaltered. I also wouldn't compress a spacial effect either. Any envelope filters or distortion (for me) would be before the HPF/LPF.

If you had an envelop filter, a distortion pedal, a compressor (w/side-chain Filter), a reverb and a HPF/LPF what would you suggest is a good order?

 

[Al Kraft]

Maybe I'm on the wrong frequency (no pun intended) with my thinking, but I like to remove the unwanted stuff while maximizing the stuff I'm interesting in hearing out of my speakers as early in the signal chain as possible. I do accept there are some logical guiding principles (not necessarily hard and fast rules) when it comes to effects placement, but if there's a frequency or noise that I am not interested in having anywhere in my signal chain, I like to get it gone as early as possible. For me a HPF is something I apply first/as early as possible when I use it - and I use it often.

I suppose it's possible in an amplifier design situation there might be some reason to have the HPF located further downstream, but I would imagine in those cases it has to do with preserving original signal integrity as long as possible before feeding the "finished product" to the power amp. Even then, I think my preference would be to drop out the frequencies I don't plan to amplify as soon as possible so I could optimize/fine tune the circuits for the signal range I'm most interested in reproducing. To me this would follow the same logic as how one approaches optimizing S/N ratio.

Thoughts offered...prepared to listen and learn!

 

[agedhorse]

For me, having the spacial effects (which I rarely use) after the HPF/LPF allows them 'space,' unaltered. I also wouldn't compress a spacial effect either. Any envelope filters or distortion (for me) would be before the HPF/LPF.

If you had an envelop filter, a distortion pedal, a compressor (w/side-chain Filter), a reverb and a HPF/LPF what would you suggest is a good order?

I would put the external HPF first, so the effects do not act (or try to act) on LF artifacts. Fortunately many of the high quality effects manufacturers have figured this out already and high pass as needed. Those who haven't would benefit.

 

[Al Kraft]

I would put the external HPF first, so the effects do not act (or try to act) on LF artifacts. Fortunately many of the high quality effects manufacturers have figured this out already and high pass as needed. Those who haven't would benefit.

It just seems to make sense to eliminate things you don't want downstream/in the end product as early in the process as practicable. However, if you need something at some point to act as say a trigger for something else, but don't want that triggering signal in the end product, I could see making a different decision...but I have no idea when that thought might apply to my bass guitar signal chain.

 

[JimmyM]

I would put the external HPF first, so the effects do not act (or try to act) on LF artifacts. Fortunately many of the high quality effects manufacturers have figured this out already and high pass as needed. Those who haven't would benefit.

Hmmm...never thought of that. My thinking was that it's better to let the effects act on them as it comes from the bass and then filter out what you don't need at the end. I'll have to try this when I get time and see if it makes any difference in my setup.

 

[agedhorse]

Jimmy, this is the reason pro level comps like the DBX-160 has a sidechain path on the key signal. It's common to place a HPF on this signal to reduce the effects of pumping. Especially true for popping Ps on vocals where even though the main signal may already be highpassed, the key signal may be highpassed an octave higher which minimizes the effects of pumping the full range signal without having to resort to a longer attack or hold off time.

 

[Downunderwonder]

Exception for octavers which trigger off of the low end.

 

[agedhorse]

Exception for octavers which trigger off of the low end.

No, I would suggest ESPECIALLY for octavers, don't want them generating signals that are derived from artifacts. Most better quality units already high pass and process the control signals that generate the audio for this reason. This improves tracking.

 

[Stumbo]

Exception for octavers which trigger off of the low end.

Trigger off the fundamental or overtones/harmonics? Where is the sweet spot?

Do octaver manufactures provide such detailed info?

If you high pass at 35hz or 4Ohz, will it seriously hamper an octaver that works on the second E harmonic around 82hz?

Anyone test this?

 

[JimmyM]

Jimmy, this is the reason pro level comps like the DBX-160 has a sidechain path on the key signal. It's common to place a HPF on this signal to reduce the effects of pumping. Especially true for popping Ps on vocals where even though the main signal may already be highpassed, the key signal may be highpassed an octave higher which minimizes the effects of pumping the full range signal without having to resort to a longer attack or hold off time.

Exception for octavers which trigger off of the low end.

No, I would suggest ESPECIALLY for octavers, don't want them generating signals that are derived from artifacts. Most better quality units already high pass and process the control signals that generate the audio for this reason. This improves tracking.

Wow, now I'm so confused! I don't use a comp but I do use an OC-2. I guess the best thing for me to do is bust out everything and try it both ways.

What about LPF? Same thing for it?

 

[Downunderwonder]

I guess everyone else with an octaver has dual HPFs.

 

[JimmyM]

Wow, now I'm so confused! I don't use a comp but I do use an OC-2. I guess the best thing for me to do is bust out everything and try it both ways.

What about LPF? Same thing for it?

Well so much for that idea. Once I busted out my board, I remembered that I have to have the HPF last in the chain because I double on upright, and I bounce the separate upright and electric signals down to one line with a Saturnworks active summing box. You'd think I could remember that after 2 or 3 years of doing it. So the only way the HPF can go in my board to get both is last. On the bright side, I've never once had a sonic problem with my board. Everything seems to work as well as it always does.

I also remembered that I tried LPF in front of my dirt boxes once before and thought it took off a little too much edginess so I left it at the end before the summing box.

 

[beans-on-toast]

I don’t think that there’s an easy answer as to where a filter is best applied. Below is an example of a mic that has a built in HPF (also called low cut). In this case the knee of the filter can be off, or at 40Hz, 80Hz, or 160Hz. There are reasons for filter at the mic such as removing stage rumble or footfall noise that is competing with the source. That same noise can be removed at the mixing desk preamp if desired. What is best to do depends on the situation. Filters are also incorporated in EQ in the desk or outboard rack gear which can be more precise.

 

[BadExample]

IMO, it's probably best to kill it upstream, unless there are reasons not to.

 

[agedhorse]

I guess everyone else with an octaver has dual HPFs.

The better quality octavers (especially the DAP/modelers) have solved this challenge by including the HPF within the device itself.

The reason is that subharmonics and low frequency noise can cause "mis-tracking", and the noises generated being particularly intrusive and more audible than the original noise that may not have been even audible.

Place your HPF where you think it works best.

 

[Wisebass]

this is worth a try?

Hi basst scho

60 bucks gone

That' s cheaper than 6 Mass beer at the Oktoberfest!

Tell us if it works!


greetings


Wise(b)ass

 

[basst scho]

thats right, wisebass.
and from that 6 beer, i have only headache for 1 day.
if i can get more headroom with the pedal, i can have headache everyday for the same money

i´ll report back when i tried it

 

[Downunderwonder]

thats right, wisebass.
and from that 6 beer, i have only headache for 1 day.
if i can get more headroom with the pedal, i can have headache everyday for the same money

i´ll report back when i tried it

I wouldn't expect a huge difference in volume but pre invest in some earplugs, the better to hear the tonal changes.

 

[basst scho]

i have earplugs, its already too loud in our small room
don´t have to be much louder, but i hope to cut through better with a clearer signal...

and as i understand my amp should have a little more power left for the audible
frequencies by not having to deal with that low mud, right?

 

[dabis]

Generally wireless system rolloff is 6dB/oct but there are exceptions such as some AT models.

Thanks @agedhorse . Do you think using the wireless and a HPF will affect the corner as you described when using multiple HPF's in cascade? I'm asking because we rehearsel with cables but perform live with wireless, and is good to know what to adjust or not.