High pass filter : frequency?

[Passinwind]

I believe some of @fdeck 's units have a fixed 12dB per octave filter and also a variable 12dB per octave filter. I don't know about his current offerings but I believe one had 35hz fixed and 35hz - 140hz variable.

That's become something of a standard for several other builders too.

Hi!

I'm curious about HPF and lots of people seem to use them. I've got a simple question : from which frequency and below are you setting your HPF?

I've got a device with a low cut switch set at 70 Hz. It felt high, but am I wrong? At which frequency should I start?

I start at between 32 and 40, typically. But where I end up depends greatly on how much boost or cut I dial in on the Bass EQ control. Mine use a similar format to what @Wasnex described above, FWIW. With Josh's format I'd probably go a bithigher in many cases, depending on whether I was primarily using it in protection or EQ mode.

 

[crguti]

 

[jdjk7]

Hi!

I'm curious about HPF and lots of people seem to use them. I've got a simple question : from which frequency and below are you setting your HPF?

I've got a device with a low cut switch set at 70 Hz. It felt high, but am I wrong? At which frequency should I start?

It depends on your application. For live use, you can tune to the room. Basically, if you've got a lot of low frequency in an acoustically poor room, just dial up the HPF from minimum until you've got a bit more balance. You may need to bump up the overall volume just slightly to compensate. You will want to make sure to test this at volume such as during sound check, as sometimes you can end up with a tone that sounded good at lower volume that can suddenly sound crap when bumped up.

In the studio, it's entirely about your mix. Different settings between 40Hz-100Hz can work depending on your bass and desired mix.

I usually tend to set mine to 60Hz-100Hz, as I like to have a balanced tone. It can also differ by bass... I have one bass that is super low-end heavy, and unless I cut bass or use an HPF, it doesn't sound balanced at all. I don't have this issue with some of my other basses.

 

[Zooberwerx]

Interesting thread. What is the general consensus on where to put the HPF in the signal chain? Before effects, after effects, somewhere in the middle?

Usually on the front side of a plain-jane compressor to keep from slamming the durn thing...conventional wisdom but not necessarily a general consensus. IME, once you tame the low end, the effects downstream will thank you.

On my PA rig, I use 45-50 hz but with a Butterworth 18 slope because somebody much smarter suggested it and I have the capability.

Riis

 

[bassbrad]

On my pedalboards I use [sfx] micro Thumpinators that use a cutoff frequency of 25Hz that seems to do a good job of cutting transients. I also have a Broughton HPF that I use for various things but mainly when using my small sealed 15" cab that grumbles if it gets too much low end, it is in the effects loop of my GK MB500, I set it by ear.

 

[ctmullins]

I have the "Always On," HPF, however, I have no way of knowing what my numbers are, being it comes with no instructions, and the only way I can kinda' tell anything is to twist it, and listen.

I have one too. I like the fact that it's numberless, because it forces me to set it with my ears, and not try to cognitively obsess over a frequency. Turn the knob until it sounds right.

 

[brianrost]

there's a separate line for "usable low frequency' that goes down to 35Hz. I'm unclear on the difference here, is anything actually happening between that 35 and 50 Hz range?

Sure, anything between 35 and 50 is being attenuated by the HPF but there can still be some signal present there. It won't be a lot of attenuation either, because it's only 3dB down at 40Hz it won't be much more at 35Hz. A 40Hz corner frequency means there is already 3dB gain reduction at 40Hz, so it actually is kicking in around 50-60Hz.

Lowest usable frequency means that if you try to pass frequencies below that at a high enough level, the speaker can be damaged.

 

[LetItGrowTone]

In a different context (rolloff of lows in a speaker cabinet), it was explained by one of the experts (EDIT: @alexclaber , here ) that a more rapid rolloff implies something like greater group delay, and that this can have a negative effect on transient response (an example was, what many hear as better transient response of sealed cabinets is due to less group delay because the rolloff is not as steep). Sorry if I said it wrong.
He explained that this was a basic, inevitable consequence of filter theory (the driver/cab being an electromechanical filter).

Is this ever an audible, negative side-effect of a HPF? Is it worth mentioning in HPF threads?

 

[lomo]

I have the "Always On," HPF, however, I have no way of knowing what my numbers are, being it comes with no instructions, and the only way I can kinda' tell anything is to twist it, and listen.

I have one "always on" and 1 with the freq marked....based on my comparisons/ear, the always on one is around 60 when the arrow on the knob is turned a hair past the blue indicator light....which is where all the nasty, muddy boom disappears from my ears

 

[Egg250]

Hi!

I'm curious about HPF and lots of people seem to use them. I've got a simple question : from which frequency and below are you setting your HPF?

I've got a device with a low cut switch set at 70 Hz. It felt high, but am I wrong? At which frequency should I start?

Depending on your tuning, a 4 string in standard tuning would get a low cut (high pass) at around 40 hz. It is really something the sound tech would do if you are going through the PA. All sorts of reasons to use a HPF but if you are playing through your combo or amp/head, it is not necessary, IMHO.

 

[Wasnex]

I was curious about the frequency response of my cabinet (Ampeg PF115 HE) and according to the spec sheet the frequency response is 50Hz - 17kHz, but then there's a separate line for "usable low frequency' that goes down to 35Hz. I'm unclear on the difference here, is anything actually happening between that 35 and 50 Hz range? If I set my HPF at say 40Hz is it doing anything at all?

Often usable frequency response indicates the point where output is down -10dB. Just a guess, but its probably -3db to 50hz and -10dB to 35hz.

IMHO it would be useful if you knew the port tuning frequency Fb. If you are interest you could do the rice test to find Fb. For woofer protection the HPF, should be at, or just under Fb. That doesn't mean you can't adjust it higher though.

 

[Bar Band Bassman]

I just got an fdeck and it's great! It's not marked but I don't really need that. I plug it in and turn the variable HPF knob until I hear the sweet spot. No fuss, no muss. should've gotten one decades ago!

The Bar Band Bassman

 

[Wasnex]

Do you play 4 string or 5 string? Low E is 41hz and low B is 30hz.

Do you know the 'slope' of your HPF? For the sake of argument let's say it's -12dB/octave. If you play 4 string, setting your HPF to 40hz makes no difference. If you play 5 string it means the 30hz fundamental of your B will be roughly -6dB.

Keep in mind part of the reason to use the HPF is to protect the woofer from over excursion. If the cab is not designed to reproduce 30hz, then it's best to not force it to try. Not a lot of cabs are -6db to 30hz. If you have played the old Acme Low B series, they were -6dB to 30hz.

You may find it surprising, but a properly set HPF can actually give you more headroom and also make the low end sound fuller and tighter. If the woofer is not bouncing around like crazy below it's intended pass band, it works better in the passband.

Beyond that: Bass guitars typically do not put out a strong fundamental. Most of the energy is the 2nd harmonic. To cleanly reproduce the second harmonic, for the low E you need strong response to 80hz and for the low B you need strong response down to 60hz.

 

[monsterthompson]

27556014[/URL], member: 397369"]Interesting thread. What is the general consensus on where to put the HPF in the signal chain? Before effects, after effects, somewhere in the middle?

Generally (broad generalization) HPF does the most work early in the chain. As soon as you cut frequencies out, then they get ignored by downstream processing. It cuts out low frequency information from minor subsonic string movements and rumble from bass-body bumps. It also changes the clipping behavior of distortion circuits by limiting the deep low information going into the circuit. Similarly, compressors can be triggered by low end rumble, so cutting that portion of the signal will change how the compressor behaves.

You'll often see effects like delay and reverb, and even some modulation effects, behaving better in a mix if you run parallel processing of wet/dry signals and the wet signal gets high passed fairly high up. This way the full body of the signal is in the dry path, while only the higher frequencies get the effect/treatment for decoration.

You're certainly free to experiment, but these are some general considerations.

 

[Bar Band Bassman]

BTW - If you listen to the fundamental bass notes as sine waves you might be surprised how little program material is contained there. Even first order harmonics are not that strong. 2nd order is where bass starts to really shine. Please, any tech types feel free to correct me and clarify, just don't launch any attacks!

The Bar Band Bassman

 

[Wasnex]

BTW - If you listen to the fundamental bass notes as sine waves you might be surprised how little program material is contained there. Even first order harmonics are not that strong. 2nd order is where bass starts to really shine. Please, any tech types feel free to correct me and clarify, just don't launch any attacks!

The Bar Band Bassman

Correct, except the fundamental is the first harmonic. The second harmonic is an octave higher.

This is F1 which is 43.65hz

Ref: Bass frequency/waterfall plots: what they mean to rigs

 

[Joe Lonsdale]

The fundamental of the Low E on a bass guitar is just above 40 Hz so it makes sense to set your HPF to 40Hz. However, if you are using the HPF for something specific other than system and headroom protection (for instance to feed other effects and/or condition the signal chain, split the signal) then you set it wherever you want!

A High Pass Filter is useful for protecting your speakers from trying to deliver super-low frequencies that can't be heard and are not musically helpful, so even if your speaker/s can't deliver anything below 60Hz, it is worth using a HPF to remove the need for them to even try. The HPF is also used for increasing the headroom of your amplifier, the theory is that it doesn't have to work so hard to deliver the power-hungry inaudible <20Hz frequencies. I use a HPF with my live rig but am not 100% I can hear any difference, it "feels good" but this could be placebo. However, I like having the safety of a HPF in my chain - theoretically reducing the risk of me blowing things up.

it doesn't matter where it goes in the chain unless you use an Octaver set to deliver frequencies below 40Hz, in which case, the HPF needs to come AFTER the Octaver. There are other effects that can generate new frequencies, such as distortion, but these are unlikely to create problematic <40Hz frequencies. I have it FIRST in my signal chain to clean up the signal for my tuner and compressor etc, but I don't think it'll make a huge difference if that is not convenient in your own rig.

I've been using a Micro-Thumpinator which is tiny and works perfectly. I analysed it in the studio and it does indeed gently roll off the frequencies from 40Hz downwards.

 

[Bar Band Bassman]

Correct, except the fundamental is the first harmonic. The second harmonic is an octave higher.

This is F1 which is 43.65hz

Ref: Bass frequency/waterfall plots: what they mean to rigs

Thanks for the clarification and correction! I am not as smart as I think I am!

The Bar Band Bassman

 

[Passinwind]

Correct, except the fundamental is the first harmonic. The second harmonic is an octave higher.

This is F1 which is 43.65hz

Ref: Bass frequency/waterfall plots: what they mean to rigs

Wish I had the time and energy for a do-over on my parts of that thread, a lot of useful info got eaten in the software upgrade back in 2014 or so. The tools for waterfall graphs have improved a lot too, that was done in an old version of Wavelab. I was also just doing specific graphs that Greenboy and a few other posters requested, for the most part, there were and are many other interesting sidebars.

 

[Cleezmo]

I'm also in the Broughton Always On group, and like most others have said here, I have a baseline setting (just past the blue light) but tweak for the room/stage.