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

[dabis]

For pro audio, it depends on the cabinets, but between subs and everything else it's typically between 80-100Hz. In part, this is because the location of these are generally not flown (there are exceptions) so it's important to keep the crossover frequency low enough that they remain omnidirectional (except for defined pattern control) and thus the ear can't identify the source location (especially important where the mains are flown and the subs are ground stacked).

In a 3 way top box, the lows to mids might be from the sub xover point to anywhere between 350 and 600Hz, the mids to highs might be anywhere between 800-2khz, all depending on the speaker design.

In a 2 way top box, the low section might cover from 100-1.6kHz and the high frequency section will cover above that.

I did design some line array products for a couple of companies back when I was doing more pro audio design, it all about managing a bunch of delicate tradeoffs. Here's a proof of concept line array system that was used in the field to verify basic performance parameters. This line array is in the center, the in-fill and outfill cabinets were zoned for covering VIP areas and the levels were adjusted depending on the events in those areas at the time. The line array covered the far seating area which was between 200 and 300 feet away, the system is being wired on the ground and the entire structure is flown with at bottom trim of 12' high placing the top at about 30' or so. This is how we reconcile "in theory" to "in practice", the system ran for 120 hours straight:
View attachment 4851066

Thanks Andy. I find very impressive all the pro audio field. As you say often, far more advanced than guitar/bass amplification.
What about to protect the subs with HPF too? Is it necessary?

 

[byacey]

Thanks Andy. I find very impressive all the pro audio field. As you say often, far more advanced than guitar/bass amplification.
What about to protect the subs with HPF too? Is it necessary?

Very Important. Subs argueably work harder than any other driver, it's a fine line between the low end frequency power and excursion limits and safe operating passband.

 

[Count Bassie]

This is a

It depends on the venue and the sight lines as well as the need for active pattern control, sometimes they are flown, sometimes ground stacked, sometimes a combination.

This is a practical science, like carpentry but a notch or two up... You need some heavier math and nuanced physics. But it's also a bit intuitive. I shoulda got into this 30 years ago.

 

[agedhorse]

Thanks Andy. I find very impressive all the pro audio field. As you say often, far more advanced than guitar/bass amplification.
What about to protect the subs with HPF too? Is it necessary?

Agreed, the top boxes are protected by the HPF that's part of the sub to low crossover transition, but the sub output needs a well implemented HPF for sure.

 

[BlueRock]

It depends on the venue and the sight lines as well as the need for active pattern control, sometimes they are flown, sometimes ground stacked, sometimes a combination.

The only big concert rigs I've seen in the last several years with anything stacked on the ground have been outdoor. (Except maybe John Mellencamp who's wringing every last dime out of that Clair Brothers rig.)

 

[agedhorse]

The only big concert rigs I've seen in the last several years with anything stacked on the ground have been outdoor. (Except maybe John Mellencamp who's wringing every last dime out of that Clair Brothers rig.)

I’ve seen it done all 3 ways. When ground stacked, the subs are often in a row below the down stage edge, this way pattern control implementations can be more easily accomplished.

 

[BlueRock]

I’ve seen it done all 3 ways. When ground stacked, the subs are often in a row below the down stage edge, this way pattern control implementations can be more easily accomplished.

34 years of IA gigs and touring (backline and carp mostly) I hear you and 100% agree. Just saying the average 10+ truck arena show these days is using a flown system, no subs down front under the stage. Haven't got much of a clue about the whys and wherefores of PA configuration just reporting what I've seen at the day job.

 

[paskisti]

Subs under the stage makes stage sound a mess very often. At least with double bass drum and high gain guitars it's terrible to monitor your playing.

 

[dabis]

This is a

This is a practical science, like carpentry but a notch or two up... You need some heavier math and nuanced physics. But it's also a bit intuitive. I shoulda got into this 30 years ago.

+1
This solely concept blown my mind this morning:

...active pattern control...

Agreed, the top boxes are protected by the HPF that's part of the sub to low crossover transition, but the sub output needs a well implemented HPF for sure.

Lower than 20 Hz?

 

[beans-on-toast]

To complicate things more, subs can go on the ground, attached to a flown array, or flown in their own group. It’s my understanding that, depending where they are placed, the power requirements differ to achieve the same sonic result.

 

[agedhorse]

Subs under the stage makes stage sound a mess very often. At least with double bass drum and high gain guitars it's terrible to monitor your playing.

Note that I didn’t say under the stage. Generally they are in front of the stage edge or left/right depending on the staging, need for pattern control and the FOH engineer’s preference.

+1
This solely concept blown my mind this morning:

Lower than 20 Hz?

Typically around 25-30Hz but sometimes a little higher.

 

[paskisti]

Note that I didn’t say under the stage. Generally they are in front of the stage edge or left/right depending on the staging, need for pattern control and the FOH engineer’s preference.


Typically around 25-30Hz but sometimes a little higher.

My intension was not to comment your post, it was general statement.

In front of stage subs are much better.

 

[mjcarp79]

The main focus of this thread seems to be relate to bass amps, and live playing in general, so I hope that this isn't too off topic.

I have been wondering: what is typical practice for applying HPF to electric bass when recording/mixing? Thanks!

 

[agedhorse]

The main focus of this thread seems to be relate to bass amps, and live playing in general, so I hope that this isn't too off topic.

I have been wondering: what is typical practice for applying HPF to electric bass when recording/mixing? Thanks!

Depends on the tone the producer or player is trying to achieve, the density of the mix, etc. It’s different with different media too, for example vinyl has different LF limitations than CD, MP3 or raw high bandwidth files.

 

[mjcarp79]

Depends on the tone the producer or player is trying to achieve, the density of the mix, etc. It’s different with different media too, for example vinyl has different LF limitations than CD, MP3 or raw high bandwidth files.

Thanks! Yes, I am sure it varies widely, depending on the factors you mentioned. Would it be safe to say that most recorded bass gets least some HPF? Or is it also fairly common to use none?

 

[superheavyfunk]

Thanks! Yes, I am sure it varies widely, depending on the factors you mentioned. Would it be safe to say that most recorded bass gets least some HPF? Or is it also fairly common to use none?

The vast majority of recording engineers and professional mixing engineers will use HPFs (and LPFs too) across material on various tracks in songs

 

[agedhorse]

Thanks! Yes, I am sure it varies widely, depending on the factors you mentioned. Would it be safe to say that most recorded bass gets least some HPF? Or is it also fairly common to use none?

Most bass tracks are HPF’d IME.

 

[Count Bassie]

HPF is about keeping low freq content you don't want, for various reasons, out of your signal chain (amp and speakers), and out of the mix- live or recorded. That said, you want to accomplish that in a way that makes the most of the sound you're after, esp if you're using outboard stuff like pedals.
I've been hitting a Broughton HPF right out of my bass, and from that into a SansAmp With a DI, then to the interface. I really don't know if that's better than putting the HPF *after* the SansAmp, but there's no fx loop on the SansAmp and it's my recording DI, so there it is.
I generally don't push any lows when recording anyway though, so I'm figuring it's ok. There have been no issues on the tracks or mixes, and no complaints about having to eq what I've put down, so I surmise that it's doing its job.

 

[SoulReflection]

HPF is about keeping low freq content you don't want, for various reasons, out of your signal chain (amp and speakers), and out of the mix- live or recorded. That said, you want to accomplish that in a way that makes the most of the sound you're after, esp if you're using outboard stuff like pedals.
I've been hitting a Broughton HPF right out of my bass, and from that into a SansAmp With a DI, then to the interface. I really don't know if that's better than putting the HPF *after* the SansAmp, but there's no fx loop on the SansAmp and it's my recording DI, so there it is.
I generally don't push any lows when recording anyway though, so I'm figuring it's ok. There have been no issues on the tracks or mixes, and no complaints about having to eq what I've put down, so I surmise that it's doing its job.

I use mine to tame whatever "boom" might be present.

 

[Count Bassie]

I use mine to tame whatever "boom" might be present.

Well, right. You said pretty much what I said in about 1/50th of the bandwidth.