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

[Gremson]

So here's a question that might be as upsetting as my earlier compression question:
How is a LPF different from just rolling off the tone knob?
I know I'd benefit from a HPF after playing with the built in filter on my Fishman preamp. And I usually cruise with the tone knob rolled down a bit on my bass. But I don't have any kind of real LPF to play with to learn if it'd be any better or different from just rolling off my tone knob. Any comparisons?

 

[JimmyM]

So here's a question that might be as upsetting as my earlier compression question:
How is a LPF different from just rolling off the tone knob?
I know I'd benefit from a HPF after playing with the built in filter on my Fishman preamp. And I usually cruise with the tone knob rolled down a bit on my bass. But I don't have any kind of real LPF to play with to learn if it'd be any better or different from just rolling off my tone knob. Any comparisons?

They're kind of sort of similar, but an LPF has a different frequency sweep than your typical tone knob, which does other things to your frequency response besides cut treble. Plus I find that an LPF acts in a more linear fashion, whereas the tone knob seems to be more drastic at times. I suppose you could do the job with the tone knob, but I like the LPF a little better for doing the job of cutting treble like my favorite tweeterless cabs.

 

[SoulReflection]

So here's a question that might be as upsetting as my earlier compression question:
How is a LPF different from just rolling off the tone knob?
I know I'd benefit from a HPF after playing with the built in filter on my Fishman preamp. And I usually cruise with the tone knob rolled down a bit on my bass. But I don't have any kind of real LPF to play with to learn if it'd be any better or different from just rolling off my tone knob. Any comparisons?

@Stumbo ...where are you?

 

[Stumbo]

@Stumbo ...where are you?

Passinwind covers the HPF below.

If you have a bass cab with a tweeter or tweeter/mid-range, an LPF effects will probably be more noticeable. No tweeter? Probably less noticeable.

A few posters stated they liked the LPF because, once set, the treble controls, to some degree, are still operational because their Qs are much wider (area affected) and can still have an effect on your tone.

v

@Passinwind:
In a similar vein, here's a set of curves I've posted in a few other threads. A friend who had a simple ten band graphic EQ wanted to know why just cutting the lowest fader (32Hz) wouldn't work as well or better than using a dedicated 4th order HPF. And as usual, that just depends on what you are needing and/or wanting to accomplish:

GEQ, -10dB @32Hz:

View attachment 3018890

Variable 2nd order HPF + fixed 2nd order HPF, -3dB @ 32Hz:

View attachment 3018891

Note that these are just quick and dirty general case representations, the HPF model being one out of several of my DIY builds. Don't remember specifically which GEQ pedal that was, but IIRC it was a pretty common one.

 

[Kro]

So here's a question that might be as upsetting as my earlier compression question:
How is a LPF different from just rolling off the tone knob?

Just one more image to add that I personally like given that a large number of amp bass and treble EQ controls are of the shelving variety. Reverse for LPF.

 

[BadExample]

They're kind of sort of similar, but an LPF has a different frequency sweep than your typical tone knob, which does other things to your frequency response besides cut treble. Plus I find that an LPF acts in a more linear fashion, whereas the tone knob seems to be more drastic at times. I suppose you could do the job with the tone knob, but I like the LPF a little better for doing the job of cutting treble like my favorite tweeterless cabs.

Jimmy, you can also jab out the tweeter with a screwdriver and it will usually stop tweeting.

@Stumbo ...where are you?

I'm afraid he's back in witness protection. Not for ratting out the mafia, but for reasons I can't disclose. Let's just say, three letter acronyms.

Seriously,

So here's a question that might be as upsetting as my earlier compression question:
How is a LPF different from just rolling off the tone knob?
I know I'd benefit from a HPF after playing with the built in filter on my Fishman preamp. And I usually cruise with the tone knob rolled down a bit on my bass. But I don't have any kind of real LPF to play with to learn if it'd be any better or different from just rolling off my tone knob. Any comparisons?

An HPF is a shelf filter, meaning it cuts all the lows before the set point (although with a slope). Most eq. does not work this way. It messes with a center frequency and to some degree above and below depending on the "Q." YET, your bass amp probably has some HPF built in... not all do, up to you to discover. AND some graphic eq's do have shelf filter at the top and bottom frequencies, again, you need to discover this.

Hoy, brother @Stumbo I see they let you out now. I really didn't think it was that big of deal, other than you heroism.

 

[Kro]

An HPF is a shelf filter, meaning it cuts all the lows before the set point (although with a slope).

I'm pretty certain that an HPF isn't a shelf filter. Not 100%, but sure enough to post this post.

Just using the screenshot that I posted two posts above, unless the filter increases or decreases all frequences either above or below in tandem, it doesn't seem very shelving to me.

If an HPF is a shelf, I wouldn't want to put anything on it for fear of it sliding to the ground!

 

[BadExample]

I'm pretty certain that an HPF isn't a shelf filter. Not 100%, but sure enough to post this post.

Perhaps my terminology is off, but an HPF should cut everything under the set frequency. Again, at the desired slope.

 

[Passinwind]

Perhaps my terminology is off, but an HPF should cut everything under the set frequency. Again, at the desired slope.

The shelf would be the part where the slope levels out while the frequency goes progressively lower. Like so: Using Your Sequencer's Equalisers |

Most analog MI bass controls don't actually do that either, even when labeled as shelving controls, at least the many I've measured. Although if you only look at response to say 40, 30, or maybe 20Hz they may still appear to.

 

[Kro]

The shelf would be the part where the slope levels out while the frequency goes progressively lower. Like so: Using Your Sequencer's Equalisers |

Most analog MI bass controls don't actually do that either, even when labeled as shelving controls, at least the many I've measured. Although if you only look at response to say 40, 30, or maybe 20Hz they may still appear to.

It seems to me like a 100% true shelving filter would be somewhat difficult to pull off without adding a ton of complexity to an analog preamp. My knowledge of how EQs work is extremely limited, but what little I do know leads me to believe that might be the case. Curious if I'm extremely off base there @Passinwind .

To be honest the only place I've ever seen a true shelving filter in action is in the studio with digital filtering at play.

 

[BadExample]

Perhaps the best terminology for an HPF is a High Pass Filter

 

[Passinwind]

It seems to me like a 100% true shelving filter would be somewhat difficult to pull off without adding a ton of complexity to an analog preamp. My knowledge of how EQs work is extremely limited, but what little I do know leads me to believe that might be the case. Curious if I'm extremely off base there @Passinwind .

To be honest the only place I've ever seen a true shelving filter in action is in the studio with digital filtering at play.

That mirrors my experience as well, but in all honesty I've never been that motivated to try to duplicate the textbook curves.

 

[Kro]

Perhaps the best terminology for an HPF is a High Pass Filter

Except for the dozens of people that confuse it each and every day with a low-pass-filter ("I want to filter LOWS")!

I propose that from this point forward we refer to them as LRFs (pronounced Luhrfffs), or "Low Roll-Off Filters".

 

[agedhorse]

Shelving filters aren't all that difficult to design.

 

[Passinwind]

Shelving filters aren't all that difficult to design.

No peak, just an angled level off with no curve and a dead flat line beyond that?

 

[agedhorse]

Yes, pretty straight forward if you studied some of Peter Baxandall's work on filters it's possible to get reasonable close to ideal.

 

[Passinwind]

Yes, pretty straight forward if you studied some of Peter Baxandall's work on filters it's possible to get reasonable close to ideal.

Cool, I'll have to give it a serious go sometime. I've built right off the original white paper and it wasn't all that close by my standards, but few people call me reasonable about this stuff!

 

[Stumbo]

For Sale - Broughton HPF High Pass Filter

 

[Dubsly]

I read most of this thread, but really made mind up around page 30, so I jumped in. As a long time Gibson fan, the bane of my existence has been low volume tone vs. high volume tone. I know what sounds good in a band mix (to me anyway), and I can always get that at low volumes at home. But, when I get to our practice space or some 1 foot hollow stage venue at band volume, mud city. I've been playing a Rickenbacker for the last 2 years just so I can cut through, leaving my Gibsons at home. No more.

I went for the Broughton HPF/LPF and I can't believe how loud I can play with no mud. I've had this on my board for a few days now, and I don't imagine that I'd ever turn it off. Unfortunately, we're taking a bit of break right now due to vacations, etc. But, I'm dying to try this thing in a live setting. I've been a/bing it with my Ric and I'm thinking this pedal might be the best thing I've ever purchased.

I'll post my gig/practice results next week. I'm pretty optimistic about how things will sound.

 

[Stumbo]

I read most of this thread, but really made mind up around page 30, so I jumped in. As a long time Gibson fan, the bane of my existence has been low volume tone vs. high volume tone. I know what sounds good in a band mix (to me anyway), and I can always get that at low volumes at home. But, when I get to our practice space or some 1 foot hollow stage venue at band volume, mud city. I've been playing a Rickenbacker for the last 2 years just so I can cut through, leaving my Gibsons at home. No more.

I went for the Broughton HPF/LPF and I can't believe how loud I can play with no mud. I've had this on my board for a few days now, and I don't imagine that I'd ever turn it off. Unfortunately, we're taking a bit of break right now due to vacations, etc. But, I'm dying to try this thing in a live setting. I've been a/bing it with my Ric and I'm thinking this pedal might be the best thing I've ever purchased.

I'll post my gig/practice results next week. I'm pretty optimistic about how things will sound.

Great to hear!

Which rig are you using?

Getting your cab up off the stage a bit on a stand or with some foam will also help. Lots of TBrs use A stand with a tilt.

Looking forward to your future reports!