High pass filter : frequency?

[sunbeast]

I have one on my Mesa amp. I do not know what the filter's slope is, I was surprised to see many with only 12dB/octave roll-offs. I always figured it was at least 24dB/octave on the Mesa.

So I set mine to taste somewhere between 35 and 45 Hz. I play a 4 string in standard tuning.

My understanding is that the Mesa Subway amps have both a fixed integrated HPF (as the majority of bass/guitar amps do) as well as the adjustable HPF filter on top of that. If both were 12db/octave that would essentially make a combined 24db/octave at the frequency of the lower filter

 

[Auspuff]

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.

Mine has an always on, white light.

 

[fourfinger]

I use an fdeck series 3, varied from approximately 50 to 80, first in signal chain. I am playing a 4-string in standard tuning, fingerstyle, passive with flats.

 

[superheavyfunk]

I find it interesting that so many ppl actually move the HPF setting. I absolutely never do. It's set where it sounds good and does what i need it to do… i guess i never thought to use it to "tune a room."

I use it more to reduce speaker excursion… I used to use it to reduce the amount that my compressor and drive pedals reacted to the bass content but I've since moved it to the end of my chain.

Anyway, lots of interesting replies to this thread.

 

[bass12]

I've been using an HPF for a few years (I originally bought one to tame DB feedback) but really only had a rudimentary understanding of how they work/how to apply them. I've learned a lot in this thread largely due to Wasnex's posts. Thank you!

 

[agedhorse]

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?

No, it's not even a minor problem unless the designer really screwed this up.

I have one on my Mesa amp. I do not know what the filter's slope is, I was surprised to see many with only 12dB/octave roll-offs. I always figured it was at least 24dB/octave on the Mesa.

So I set mine to taste somewhere between 35 and 45 Hz. I play a 4 string in standard tuning.

It depends. Most are 24dB/octave.

My understanding is that the Mesa Subway amps have both a fixed integrated HPF (as the majority of bass/guitar amps do) as well as the adjustable HPF filter on top of that. If both were 12db/octave that would essentially make a combined 24db/octave at the frequency of the lower filter

Correct, this generally works out to the best compromise between protection and tone control.

 

[Camarillo]

I don't know.
I have the Broughton little version, where the knob don't have any numbers.
I just use ears. I start all the way off and gently rotate until I hear a lack of bottom end. Then I roll it back off until I can hear it again. And it's not at "zero".

 

[Wasnex]

I don't know.
I have the Broughton little version, where the knob don't have any numbers.
I just use ears. I start all the way off and gently rotate until I hear a lack of bottom end. Then I roll it back off until I can hear it again. And it's not at "zero".

That's the way too do it!

 

[NoSlapForYou]

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?

At the beginning. You want to clean up your signal before you feed it into other effects.

 

[NoSlapForYou]

You can go a lot higher than you think you should. The low E on a bass guitar is 40 Hz. But that doesn't mean you should set your high pass filter to 40 Hz. High pass filters cut off low frequencies on a slope. So even if you set your high pass filter to 100 Hz, it doesn't mean you hear no frequencies below 100 Hz. It also doesn't mean the filtering stops at 100 Hz. It can often can go from 0-400 Hz depending on the slope.

I come at this from the perspective not of a bassist but of a mix engineer. I don't think people understand how radical mixing moves often are in the studio. A mix engineer doesn't give a damn about whether your bass sounds like a bass should. They care about whether it works in a mix.

Here is a high pass at 100 Hz with a 6db per octave slope. Notice that it's attenuating all the way up to 400 Hz.

 

[Zbysek]

I set mine anywhere between 30Hz and 100Hz…depending number of factors such as the type of bass, room, cab being used, etc.

I often end up between 40-60Hz for my bass guitar and 60-80Hz for my EUB.

 

[Zbysek]

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?

I don't think there is a general consensus.

I currently have one HPF after octaver, and I have HPF/LPF combo at the end of the signal chain…

 

[Deleted member 271037]

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?

Definitely last in the signal chain for me. If not, my other pedals/settings may add more deep lows AFTER the HPF, which would make the HPF rather pointless. Of course there are situations where it could make sense to use a HPF earlier in the chain too, like if you're playing a 5-string and don't want your compressors overshooting on low notes (although a good bass-specific compressor should have a HPF in the side chain to avoid this).

I usually set my HPF (Broughton) around 40 Hz as I want to retain most of the lows and just want to filter out the deepest sub-bass rumble. This is a matter of taste. For someone who likes the more rolled off low end extension you get with an Ampeg 810 it might be a good idea to go higher, although the Ampeg 810 will have a more gradual roll-off than most HPFs.

Basically, use your ears.

I would also like to add that a HPF is NOT the right tool for fixing issues with boomy, standing waves in rooms. This seems to be a very common misconception.

 

[Rootzilla]

I guess my question really is, does the pedal do anything at all if I have it set below the 50Hz frequency response? 'Usable low frequency' kind of sounds like marketing mumbo-jumbo but I don't really know enough about it to say for certain.

Maybe this has been answered already (didn't get to the end of the thread yet), but Ampeg specifies "frequency response" at +/-3 dB and "usable low frequency" at -10 dB. So you'll get audio under the low end of the "response" bracket, but you'll need to eq for it and it will eat up more power.

 

[Zbysek]

My approach to HPF placement depends on other pedals in the signal chain and is the following:

1. if my chain contains octaver or other sub-lows-creating effects (such as synth), HPF needs to come after those (to tame the sub-lows)
2. if my chain contains dirt pedal(s), my LPF/HPF combo pedal need to come after those (to tame highs created by dirt pedals).

In other words: I would place HPF first in the chain (only) if the chain does not contain any of the following: octaver, synth, dirts.

 

[Boneless]

My opinion is:

- a HPF may make the bass sound subtly different (not worse! Different) even if the cutoff frequency is set lower than the actual bass content. Our ears are kinda sensitive to phase in the bass region. Bear in mind that peaks will generally get higher with a HPF as well if set below the frequency region where most of the energy is, so a HPF actually might demand some additional headroom. My mixing experience tells me that applying an (additional) HPF set even at 20Hz on bass will make the bass sound... sometimes better, sometimes worse. Sometimes it makes it punchier, sometimes it brings it too "forward".
- if you do not slap, use percussive techniques, etc. there is little reason to use a HPF for protection, provided the bass cabinet is an actual bass cabinet. For example, I would always use a HPF if I were to play a Bass VI-like instrument into a guitar amp.
- remember that mathematical overexcursion (Xmax) is not mechanical overexcursion (Xvar). Approaching and exceeding Xmax merely causes distortion (which may be inconsequential, or even pleasing in moderate amounts). When people say that they don't like high powered cabinets at low volumes, part of the reason is that the speaker is no longer distorting appreciably.

A HPF is a tool to be used if necessary. My personal suggestion would be to start low and increase the cutoff frequency until it feels like you're missing something, then lower it a notch. Also, depending on the filter's resonance (Q), a HPF may actually make things worse for overexcursion because it is effectively boosting stuff around the cutoff frequency (high-Q filters essentially work as if there were a peaking filter around the cutoff frequency). Moreover, ported cabinets actually have more excursion problems in the second octave (around 80Hz) than around their tuning frequency, which is bound to be in the mid-40s up to the mid-50s.

 

[_Tay_]

I use one at start and one near the end of my chain. Microthumpinator at beginning which is constantly set at 25hz steep cutoff. Then my EQ2 is doing similar near end to tame any effects before like octave,synth sounds and to also set the bass at gigs since i often play through a cab and there is no sound engineer out front to tame the bass low end.

 

[ezstep]

No simple answer. It would always depend on the room.

 

[butterfingers1]

Mine is at 40Hz but I use two (first and last pedal in chain). The frequency suppression is a curve which trends lower when filtered. Each additional filter has an effect. If I use only one HPF I set it at 60, even 80, to take out enough signal below 40Hz.

 

[J.Wolf]

FWIW, I prefer to use my Empress Para Eq for fixing room boom. That pedal has a notch setting with a super narrow Q. You can find the low note that has the most boom/room excitement by: set a narrow q, add a ton of gain to the low band, and sweep to hear which frequency is exciting the room the most, and then cut that frequency by a few db at a narrow q. To me, that cleans up the low end better than a shelving HPF. In some really bad rooms, I still use an HPF, but in most reasonable rooms, this works better for me.

While Im at it, I usually do the same trick with the mid band to find and remove any ugly mid/upper mid gank, and add a little wide Q upper treble "air" to the sound. I've said it before, and I'll say it again, it's almost like a quasi mastered bass tone, with 30 seconds of EQ work.