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

[GrapeBass]

No problem. Here it is again with +/- 15dB. It appears to be a 3rd order HPF; there's ~18 dB of drop from 60hz to 30hz.
View attachment 4848052

pretty typical IME.

 

[Passinwind]

No problem. Here it is again with +/- 15dB. It appears to be a 3rd order HPF; there's ~18 dB of drop from 60hz to 30hz.
View attachment 4848052

Thanks, that makes visual correlation to how I measure things a lot easier!

I'm currently working on better understanding how my new pedal's HPF section does or doesn't work with various amps, other pedals, and active basses, it's not always as straighforward as one might expect. Thanks for some more data points!

 

[Drzejzi]

That's what I did too here in the Czech Republic.

The guy who built it for me started offering it-see the link below:

HPFPRExtnd - Soundelirium

May be you can ask him whether he ships to Poland...

There's a guy in Poland that builds and sells this HPF
Invalid Link Removed
It works fine and is really tiny.

 

[paskisti]

Any idea what kind of LPF and HPF are in DSP based Crown XLS series power amps? I'm using mine in bridged mono mode and setting HPF to 50hz, and that seems to settle down speakers in ported cab used for high power application. Why I know? Because I accidentally switched it off and was watching my speakers jumping nervously. When HPF was back on they were much more peaceful and still maintained good amount of low end.

 

[dabis]

Any idea what kind of LPF and HPF are in DSP based Crown XLS series power amps? I'm using mine in bridged mono mode and setting HPF to 50hz, and that seems to settle down speakers in ported cab used for high power application. Why I know? Because I accidentally switched it off and was watching my speakers jumping nervously. When HPF was back on they were much more peaceful and still maintained good amount of low end.

Per the manual:

“PureBandTM Crossover Filter System:
The PureBand Crossover System provides a variable state Linkwitz-Riley 24dB/octave filter allowing you to choose a point between 30Hz and 3kHz on standard 1/12th octave centers. Three filter types are available: Low Pass, High Pass and Band Pass.“

https://www.crownaudio.com/en/product_documents/5055568_xlsdc2_mnl_print_050615-pdf

 

[KJMO]

Any idea what kind of LPF and HPF are in DSP based Crown XLS series power amps? I'm using mine in bridged mono mode and setting HPF to 50hz, and that seems to settle down speakers in ported cab used for high power application. Why I know? Because I accidentally switched it off and was watching my speakers jumping nervously. When HPF was back on they were much more peaceful and still maintained good amount of low end.

I don't use an amp anymore, but I did exactly the same thing with mine, and noticed the same thing. I was tuning my cabinet, so I noticed a lot of stuff when doing that. The lpf seems to work well. I think 50hz is a good spot for most things.

 

[agedhorse]

I don't use an amp anymore, but I did exactly the same thing with mine, and noticed the same thing. I was tuning my cabinet, so I noticed a lot of stuff when doing that. The lpf seems to work well. I think 50hz is a good spot for most things.

Except that it’s a HPF.

 

[paskisti]

But does anybody know the slope of the filters? If I select 50hz, is it -3db, -6db or something else?

 

[Passinwind]

But does anybody know the slope of the filters? If I select 50hz, is it -3db, -6db or something else?

Didn't post #2285 answer that?

 

[paskisti]

Sorry I didn't see that. On the other hand I didn't understand good enough .

So if I have 50hz set point for HPF the 25hz is -24db? Is 50hz 0 or -3db?

 

[ahc]

So if I have 50hz set point for HPF the 25hz is -24db? Is 50hz 0 or -3db?

Yes. 25hz is -24db less than 50. 50hz in this case would depend on the speaker specs, the cabinet specs, and where any other EQ besides hpf is set.

 

[Passinwind]

Sorry I didn't see that. On the other hand I didn't understand good enough .

So if I have 50hz set point for HPF the 25hz is -24db? Is 50hz 0 or -3db?

The usual engineering convention is to spec F3, the 3dB down point. Depending on the shape of the knee we'd then expect to see around -27dB at 25Hz, i.e. a 24dB/octave slope below the knee. Andy could probably fill you in on the reasons that might not be exactly so when using one side of a crossover filter better than I can, different alignments and naming conventions can work differently.

 

[paskisti]

The usual engineering convention is to spec F3, the 3dB down point. Depending on the shape of the knee we'd expect to see around -27dB at 25Hz, i.e. a 24dB/octave slope below the knee.

Thank you. I have understood that named frequency is often -3db point but I didn't realise that the next octave is 3db lower than the slope in specs (24db per octave in this case). Now when you said it, it makes sense. I never also understood the term "knee".

 

[agedhorse]

The usual engineering convention is to spec F3, the 3dB down point. Depending on the shape of the knee we'd then expect to see around -27dB at 25Hz, i.e. a 24dB/octave slope below the knee. Andy could probably fill you in on the reasons that might not be exactly so when using one side of a crossover filter better than I can, different alignments and naming conventions can work differently.

yes, this is generally the case.

 

[dabis]

Except that it’s a HPF.

Andy, there's some typical freq. cut offs for HPF and LPF when biamping a basic PA system or is entirely depending on choosen cabinets/arrays and or aplications/type of music/artist preferences? Must these to overlap any range?

Also, there's some kind of HPF for the subwoofers too, to prevent damage or save energy?
Thanks.

 

[agedhorse]

Andy, there's some typical freq. cut offs for HPF and LPF when biamping a basic PA system or is entirely depending on choosen cabinets/arrays and or aplications/type of music/artist preferences? Must these to overlap any range?

Also, there's some kind of HPF for the subwoofers too, to prevent damage or save energy?
Thanks.

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:

 

[Count Bassie]

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

That would be a nice bass rig.

 

[agedhorse]

That would be a nice bass rig.

It's -3dB at about 30Hz with the processing. Processing includes a 30Hz HPF with a parametric filter that provides an LR correction to the bottom 1/3 octave or so. The subs are a pretty deep box, probably 15CF or so.

 

[CryingBass]

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

Curios: At large events where they utilize modern fly rigs for sound, are subs more often in the air or not? I am guessing not flown often, but that’s why I am asking the pro!

 

[agedhorse]

Curios: At large events where they utilize modern fly rigs for sound, are subs more often in the air or not? I am guessing not flown often, but that’s why I am asking the pro!

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.