High pass filter : frequency?

[Inconnu]

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?

 

[2saddleslab]

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 about the mid 40's Hz. Then adjust more to the room if needed.

 

[T-34]

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?

HPF at 70Hz doesn't mean there is nothing left under the 70 anymore. The frequencies are gradually rolled off but how fast will depend on the kind of the filter used. 70 might be anything between too much or not enough depending on that.

So I guess what I'm saying is you need to listen and not to decide based on a number!

 

[lomo]

I generally like setting mine around 60 Hz, which allows me to goose "bass" controls on my amp and/or pedals without boom. I use the Broughton, which provides a fairly hard stop/ steep dropoff below the selected level.

 

[sloppy_phil]

I find it really depends on a few factors. A big one is the room/stage you are playing on, and how boomy/muddy the low end can get. And then there is the style of music being played, as well. When I'm playing reggae music, I set it for about 40Hz, but when I'm doing rock, or acoustic/folk-type stuff, I set it more like 60-80Hz.

Thinking about it a bit more, I definitely start with the HPF set for where I think the music needs it to be set. But then I listen to the room/amp, and will tweak from there as needed!

 

[Killing Floor]

Dee-pends on the room and your speakers and volume. Start where you are and adjust higher and lower until it sounds better or worse.
In my room at this moment it's 65 Hz (approx) so the best setting is 65 +/- 1 Hz.

 

[CatOnTheBass]

Around 70-80 is where I like to keep mine (for 4 string bass).

Your choice of cabinet matters a lot! This might seem like a "duh, obvious" statement, but if your cabinet only goes down to 50hz, you're not going to hear any difference from a HPF at 40hz. If you want to hear the HPF actually "doing something" it has to be within the frequency range of your cabinet.

 

[Wasnex]

If the HPF is variable it's generally adjusted to taste. That means the frequency can change depending on the room and you tone goals.

However, an HPF does have an important role in protecting your woofers from overexcursion, especially in ported designs.

The excursion plot of a woofer in a ported design has sort of an S shape. The precise shape of this curve is determine by the Thiele Small characteristics of the driver and how the box is tuned. In other words, put the same driver in different boxes and you get a different a different excursion plot and also a different frequency response.

These cone excursion and frequency response plots are for an Eminence 2512 II in a larger ported cabinet:

Ref: 290-593--eminence-deltalite-2512-cabinet-design.pdf (parts-express.com)

In general: Starting around 500hz, as the frequency goes lower, cone excursion increases. The excursion continues increasing until a bit under 100hz, and then it starts to decrease. The reason this reversal occurs is because the port is starting to become active.

The port tuning frequency (Fb) for this design is 44hz. You can clearly see this in the excursion plot; it's where the excursion dips. At 44hz, the port is providing maximum suppression of cone excursion and also producing most of the sound.

Below Fb cone excursion increase dramatically and acoustic output of the system drops (typically) by 24dB per octave. Because of this it does not make much sense to feed the system power very far below Fb. Doing so does not produce any usable output, and it puts the woofers at risk from over excursion.

For context, the 2512 is rated for 250W RMS / 500W Program and has an Xmax of 4.9mm. But in this box the 2512 is mechanically limited to 125W and requires a steep HPF set no lower than 35hz.

Ref: 290-593--eminence-deltalite-2512-spec-sheet.pdf (parts-express.com)

If you look at the cone displacement chart, you will notice the driver exceeds Xmax at about 35hz. This is where the trace turns from black to gray.

If you adjust the HPF to 35 hz, it means it is reducing power by 3dB at 35hz. So if you are feeding the speaker 125W at 35hz and apply a 35hz HPF, the power drops by 3dB to 62.5W.

Keep in mind that an HPF is not a limiter. So if you crank up the gain by 6dB, the power level will rise to 250W.

 

[Wasnex]

The frequencies are gradually rolled off but how fast will depend on the kind of the filter used.

Not sure I would call it gradual on the typical HPF.

AFAIK the filters in HPFs are usually at least 12dB per octave. Often they are 24db per octave and may be even steeper. Lower order filters could potentially sound better, but I would go for 24db for better woofer protection. I think I have the HPFs for my crappy little PA subs set to 48dB per octave.

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.

I believe the Broughton is 12dB per octave and can be set from 25hz to 190hz.

 

[Ggaa]

On different stages I've run mine between 70 and 100, but usually around 80. I have a Broughton on my pedalboard and an Fdeck for when I don't bring pedals.

 

[djmay]

I use a resonant filter (Alembic SF-2 Superfilter). I set the HPF at about 110, with a damping factor of about 3.5, which means about 7db boost at the cutoff frequency.

 

[brianrost]

I use my HPF for feedback control, so it gets tweaked by ear in each room. I'd say usually somewhere in the 80-100Hz range.

 

[Solude]

At least as high as the cabinet you're using and then to the room. Which is fancy for no longer rattling the building

 

[Isaac_James]

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?

 

[Auspuff]

I generally like setting mine around 60 Hz, which allows me to goose "bass" controls on my amp and/or pedals without boom. I use the Broughton, which provides a fairly hard stop/ steep dropoff below the selected level.

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.

 

[CatOnTheBass]

If I set my HPF at say 40Hz is it doing anything at all?

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.

 

[Isaac_James]

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.

I play both 4 and 5 string basses. It's a Broughton Low/High pass filter and their site says the slope for both is 12dB per octave.

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.

 

[Isaac_James]

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.

It'll be a guessing game no matter what without any numbers printed but according to this the range is 25 Hz to 190 Hz.

 

[SpeakerBoxxx]

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?

 

[Auspuff]

It'll be a guessing game no matter what without any numbers printed but according to this the range is 25 Hz to 190 Hz.

Thank you.