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

[Al Kraft]

Lots of references to HPF/LPFs:
No, you don't really know how you sound in the house.

Just the title there is advice no musician should ever forget! It's also the reason to always treat the sound techs as the most important (honorary) members of the band at a gig!!

 

[ahc]

My fdeck HPF 3 just walked in the door... too late to crank up an amp (because neighbors). For you fdeck users, where do you run the volume? I think I've read that the volume is at unity when full up. Is this correct?

 

[Stumbo]

My fdeck HPF 3 just walked in the door... too late to crank up an amp (because neighbors). For you fdeck users, where do you run the volume? I think I've read that the volume is at unity when full up. Is this correct?

Maybe @fdeck will chime in.

Oh, congrats! You'll love what it does. And report back after you try it out.

 

[fdeck]

My fdeck HPF 3 just walked in the door... too late to crank up an amp (because neighbors). For you fdeck users, where do you run the volume? I think I've read that the volume is at unity when full up. Is this correct?

Yes, volume is at unity when full up, i.e., 0 dB gain. The volume control is kind of an obscure feature, since you've already got controls on your bass and amp. It can come in handy for DB situations where you've got your amp further away from you as a way to manage feedback. Then you can tweak your volume without putting your bass down.

 

[ahc]

Yes, volume is at unity when full up, i.e., 0 dB gain. The volume control is kind of an obscure feature, since you've already got controls on your bass and amp. It can come in handy for DB situations where you've got your amp further away from you as a way to manage feedback. Then you can tweak your volume without putting your bass down.

Thank you sir!

 

[Al Kraft]

My fdeck HPF 3 just walked in the door... too late to crank up an amp (because neighbors). For you fdeck users, where do you run the volume? I think I've read that the volume is at unity when full up. Is this correct?

I run mine full up and it is a high quality box that proves its worth time after time for me. I always have one in my gig bag and while I have never been a big pedal/effects user, the HPF-Pre Series 3 has earned a place in my heart (and in my my signal chain). It really works!

 

[superpanget2]

curious which one to put first in the signal chain EQ or HPF/LPF?

 

[Al Kraft]

curious which one to put first in the signal chain EQ or HPF/LPF?

There are two schools of thought I've heard expressed. One is to remove the unwanted lows as soon as possible
in the signal chain (i.e. first) so that none of your effects or pre-amps are reacting to those low frequencies. Maybe with something like a compressor (as an example) that would make sense. My approach is to use the HPF last (right before the head) to remove any low frequency artifacts introduced by anything in the signal chain (even a LPF) as well from my bass.

The usual suspects in the effects column would likely have strong opinions on this question. Since I'm not a big effects user, this is mostly an academic argument for me. However, my vote would be LPF and then HPF. In my mind I'm not protecting anything or creating headroom with a LPF, just shaping tone. Whereas the HPF is a tone shaper and providing valuable protection for my speakers plus helping me with headroom. That could be flawed logic and I would be interested in hearing feedback from some of our EE experts.

 

[Jebberz]

There are two schools of thought I've heard expressed. One is to remove the unwanted lows as soon as possible
in the signal chain (i.e. first) so that none of your effects or pre-amps are reacting to those low frequencies. Maybe with something like a compressor (as an example) that would make sense. My approach is to use the HPF last (right before the head) to remove any low frequency artifacts introduced by anything in the signal chain (even a LPF) as well from my bass.

The usual suspects in the effects column would likely have strong opinions on this question. Since I'm not a big effects user, this is mostly an academic argument for me. However, my vote would be LPF and then HPF. In my mind I'm not protecting anything or creating headroom with a LPF, just shaping tone. Whereas the HPF is a tone shaper and providing valuable protection for my speakers plus helping me with headroom. That could be flawed logic and I would be interested in hearing feedback from some of our EE experts.

I do both - (I process my sound through a computer, which facilitates this)

One HPF directly after my bass to clean the signal to prevent unwanted subfrequencies to mess with the compressor and other other effects sensible to volume (like auto-wah).

One HPF-LPF at the end of the chain to taylor the sounds depending on the room (and to tame extra lows or highs that my effect chain could induce). I use our mixer HPF and LPF to do that, and always in relation with the mix so I make sure I don't overwhelm anything in the mix.

 

[Btbp]

Dumb question maybe but is there a way to know what changed in the HPF Wiki when someone edits it? I see @Stumbo just updated it.

 

[Stumbo]

Dumb question maybe but is there a way to know what changed in the HPF Wiki when someone edits it? I see @Stumbo just updated it.

I can tell you that I didn't add new info, just a bit of clarifying reason 24.

 

[Btbp]

There is a lot of great info in that Wiki, it takes a few reads to absorb it all.

 

[Stumbo]

Which power supply for my Broughton always on HPF?

 

[Stumbo]

v

Certainly somebody (FOH) who understands how it is important to clean up everything under 200 hz and leave that space for Bass and kick to not finish burning in inferno. (HiPass on everything except...)

Where have I seen that before?

 

[Btbp]

So anyone besides @dabis use a Vong for their HPF/LPF?

 

[fermata]

Would you be able to post a schematic?

That was in the 80’s, when I still had a working memory. It was just a small cap...maybe .0047uF, bypassed with a 500k or 1meg pot. The signal went through the cap from input jack to output, and the pot progressively shorted across the cap. I don’t remember the values, but that would get you into the ballpark.

If you want to make a passive HPF, here's a thread with some diagrams:
Dropping the bass - love at 50Hz
And this is a fun tool for choosing component values: High Pass Filter Calculator

This type of simple passive HPF circuit does work--it'll help reduce mud and is capable of reducing bass, too, if desired, but it's not really a substitute for an active design. It's only a 3 dB/octave roll-off vs. 12 or 24 dB/octave for an active unit. And if the pot value is too low/cap value is too high, it'll start to suck some highs, too. (500K or 1 Meg works best for the pot.)

 

[Balog]

Barefaced 610 booming issue

So, I wanted to conclude this thread.


Test Case 4: Hi-Pass filter
A lot of you suggested the use of a HPF, which seems counterintuitive.

However, it did wonders.

I bought a Broughton HPF which sweeps from 25HZ to 190HZ (12dB). This gave me a control to the low-end. At the lowest point the room would be filled with boom and at the highest it would sound much more crispy (210AV like). I would sweep the filter high to low until the boom just starts to come in, but doesn't get out of control.

 

[Leo was right]

Just to be sure everybody understand well about what I was talking about, it is the Hi pass filter on the the channels strips oh the FOH board I was talking about, when the big E string of the guitar produce more bass than the bass, it is not normal, call it big mud specialy into the subwoofer.

 

[Feral Feline]

... when the big E string of the guitar produce more bass than the bass, it is not normal, call it big mud specialy into the subwoofer.

This is exactly what happened to me this past Friday night. Had my Fdeck on my DB, but I wasn't anywhere near the bass amp. Singer kept turning me down/up trying to dial in the bass... so I stopped playing to show her it was her guitar that the sound-temp had boosted her bass WAY up. Add another instrument with a broad frequency spectrum run through a delay that was too loud...

The entire night, a GenuWhine washed out $%^& mess-O-mush®™.


It got worse as the night wore on, as the sound-temp abandoned the board to serve customers drinks. Will be glad to have the regular sound-tech back next time we play that venue. Ear fatigue, mental fatigue, even physical fatigue by the end of the gig.



I think I'm going to move to Jebberz idea: I'll run the Fdeck HPF right after my bass as I am now, but add a Vong Filterung LPF/HPF to the end of the FX chain.

 

[Leo was right]

When I listen to a song or whatever part of music on my sound system I expect to be able to distinguish every notes every instruments are playing, as most musicians I have a relative ear so I can have a good idea what the bass player is playing note by note before taking my instrument and try to play it, this is probably true to almost all of you also.

How come most of big show I saw (big names!) I have no ******* idea what the bass player (upright or electric the same) is playing. This is happening recently (3 years) to a Rush concert!!! Geddy Lee is not the muddiest bass player AFIK.

I could be wrong but IMO I put the blame on subwoofer systems that are misused by FOH tech (pro or amateur).

The kick is suppose to give a kick not a undamped low frequency note. The big string of the guitar is not intend to produce something under 200 hz that come mud the bass part (Keith Richard had understand this, he remove the E srting), same thing for the keyboard.

There is some physical law that say that the human ear cannot distinguish two notes played under a certain frequency (something around 250 hz), try to play a CHORD in the left end of a piano for example) that why you can have many instruments play in the same registry if they are producing sound above this frequency, NOT UNDER! And this is what is happennig with bass (upright, electric, tuba, left hand of keyboard ect, everything producing something below the critical frequency have to be left alone in this spectrum, every techs or musicians should know that. On a drum, kick, floor tom, can produce a lot of unwanted low frequency

That's why also if we play a chord on a bass, it is high on the neck or with the harmonics (Jaco) with a trebly sound, not a woofy sound.

Please have respect for the bass player which is a complete musician who have something to say musicaly and leave the low frequency spectrum clean.