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

[Stumbo]

v

@Wasnex posted

...Judgement and restraint are advisable when running a single 112 IMHO.

Also, If you need max SPL, I would suggest using an HPF to limit frequencies that are below the cabs intended pass band.

The way a ported cabinet works is the port is tuned to start resonating as the driver starts to cut off. In a sealed cab the driver's excursion increases as the frequencies goes down. In a ported cab, the resonance of the port works against driver excursion, so the driver's excursion decreases as you approach Fb (the resonance frequency of the port).

Below the port frequency, the driver's excursion increase quickly, while the output of the cab drops quickly. So sending tones below the port frequency is more likely to damage the driver and there is little benefit because the cab cannot efficiently produce sound in this range. This is where the HPF comes in.

I have attached a cab design document for you to review, so you can get an idea of how design and driver characteristics interact. Take a look at the cone displacement graphs for each design and also review the notes for each design that describe the power limits and HPF requirements. Keep in mind the Xmax (max linear excursion) for this driver is 6.2mm.

 

[Wasnex]

@Wasnex posted

...Judgement and restraint are advisable when running a single 112 IMHO.

Also, If you need max SPL, I would suggest using an HPF to limit frequencies that are below the cabs intended pass band.

The way a ported cabinet works is the port is tuned to start resonating as the driver starts to cut off. In a sealed cab the driver's excursion increases as the frequencies goes down. In a ported cab, the resonance of the port works against driver excursion, so the driver's excursion decreases as you approach Fb (the resonance frequency of the port).

Below the port frequency, the driver's excursion increase quickly, while the output of the cab drops quickly. So sending tones below the port frequency is more likely to damage the driver and there is little benefit because the cab cannot efficiently produce sound in this range. This is where the HPF comes in.

I have attached a cab design document for you to review, so you can get an idea of how design and driver characteristics interact. Take a look at the cone displacement graphs for each design and also review the notes for each design that describe the power limits and HPF requirements. Keep in mind the Xmax (max linear excursion) for this driver is 6.2mm.

[/QUOTE]

I attached the cab design document for any who are interested.

 

[MarkA]

@Mike Arnopol posted:
All of the drivers that I know that aren't designed exclusively for subs--all of the woofers used in bass cabs---have a free air resonance of 40 to 50 hz. They don't work well under that.

Most reflex cabs are tuned (typically) in the 42 to 50 hz range. What this means is that any frequency under that tuning frequency--the speaker behaves as in free air. Which means that it's flopping around aimlessly.

What this means is that when you play a note under that tuning frequency--typically under 42hz (or higher in many cases) The speaker is just flopping around trying to reproduce that note.
What happens is that since the cone movement is uncontrolled, the second harmonic (octave) is being reproduced poorly as the cone is uncontrolled.

The second harmonic is what we key off of for pitch. That second harmonic then is boomy and uncontrolled. This is the reason that many guys (correctly) say that having that extension causes too many problems on stage---not the fact of reproducing 30hz.

People should use a HPF set to around 40hz. All of a sudden the B string tightens up and you lose the boom. Running a reflex cab without a HPF will result in a crappy B string sound .

D'oh -- I'm slow on my replies to everything, lately.

Anyway, thanks for posting this. Mike was one of the guys who influenced me to pick up an HPF in the first place and I very much trust his ears and his judgment in these matters. Ironically (maybe that's not the right word here), it is primarily with Mike's cabs (some of them, anyway) that I am interested in trying an HPF that starts just a bit lower. I might not gain anything by it and might decide that I don't like it -- I'd be interested to try it, that's all.

 

[bassically_eli]

D'oh -- I'm slow on my replies to everything, lately.

Anyway, thanks for posting this. Mike was one of the guys who influenced me to pick up an HPF in the first place and I very much trust his ears and his judgment in these matters. Ironically (maybe that's not the right word here), it is primarily with Mike's cabs (some of them, anyway) that I am interested in trying an HPF that starts just a bit lower. I might not gain anything by it and might decide that I don't like it -- I'd be interested to try it, that's all.

I've had that thought as well. I play fivers when I play electric, and I use one of Fdeck's HPF-Pres, which has a minimum of 35hz. I've resisted the urge, though, as I think it's really only my OCD that makes me want it. I use an older MAS-26, which has a -3db in the mid 40s, IIRC, so I really doubt I'd hear any benefits setting an HPF lower. That could be different with Mike's newer cabs, though.

That being said, I guess I accidently picked up an HPF that can be set lower . I recently got a Zoom B1 Four, which has a HPF that can be set really low. The minimum setting is 20Hz, and it goes in 10hz increments, I think--off the top of my head. I'll double check later. It's, of course, a digital HPF. I don't know if that really matters. So far, the modeling seems quite impressive to my ears. Unfortunately, with the current chaos, my electrics haven't left the house a single time since I got the Zoom, so I haven't tried it live. That'll be the real test.

 

[Stumbo]

I've had that thought as well. I play fivers when I play electric, and I use one of Fdeck's HPF-Pres, which has a minimum of 35hz. I've resisted the urge, though, as I think it's really only my OCD that makes me want it. I use an older MAS-26, which has a -3db in the mid 40s, IIRC, so I really doubt I'd hear any benefits setting an HPF lower. That could be different with Mike's newer cabs, though.

That being said, I guess I accidently picked up an HPF that can be set lower . I recently got a Zoom B1 Four, which has a HPF that can be set really low. The minimum setting is 20Hz, and it goes in 10hz increments, I think--off the top of my head. I'll double check later. It's, of course, a digital HPF. I don't know if that really matters. So far, the modeling seems quite impressive to my ears. Unfortunately, with the current chaos, my electrics haven't left the house a single time since I got the Zoom, so I haven't tried it live. That'll be the real test.

The HPF can also tame stage and room boom which may utilize a much higher frequency than the lows your bass and cab can attain to sit your bass well in the mix.

 

[bassically_eli]

The HPF can also tame stage and room boom which may utilize a much higher frequency than the lows your bass and cab can attain to sit your bass well in the mix.

Exactly. I rarely--probably never, actually--have my HPF-Pre at the minimum setting when playing on stage at any appreciable volume. That goes for DB and EBG, four and five string.

 

[lowplaces]

Hi all, Is there any benefit to using a LPF with an archtop guitar with an under saddle p/up ?

And are all under saddle p/ups piezo ?

tia

 

[Stumbo]

Hi all, Is there any benefit to using a LPF with an archtop guitar with an under saddle p/up ?

And are all under saddle p/ups piezo ?

tia

For me, an LPF cuts off overbearing highs and allow you to keep some sheen in your FOH tone. Your amp tone control will adjust the highs in the range you want.

 

[Stumbo]

Messing around with my D800+ and wondering where y'all keep the HPF? I'm pretty glad with what I get resting as close as I can guess to the published low freq. from the cabinet vendor. But what about you folks? Oh, 12" (1 or 2).

What cabinet?

In this case it's a Mesa 1X12 Subway. Either 1 or 2 of them depending on how much I want to subject the family to in tight quarters haha. I don't recall exactly but I think that bottoms somewhere near 50Hz.

v

Ok, this is important because different manufacturers rate their cabinets with different metrics (types of measurements).

In the case of the Subway line, there is specific information related to the mechanical power handling (Xmax, how far the cone can move), and for the 112, the mechanical power rating is 400 watts RMS down to 50Hz, the F6 is 48Hz and the F10 is 41Hz, so somewhere in between this range is about optimum though if you aren't driving the piss out of the cabinet then I would recommend ~40Hz for the HPF.

For cabinets that do not provide this information, I would settle for around the F3 of the speaker if driving anywhere near the rated power (in watts) because generally the information provided is for thermal power limits (in watts, the amount of heat that can melt the voice coil) which can be as much as twice the mechanical limits (power rating in watts) at the F3 point depending on the design of both the driver and the cabinet.

 

[dabis]

Ok, this is important because different manufacturers rate their cabinets with different metrics (types of measurements).

In the case of the Subway line, there is specific information related to the mechanical power handling (Xmax, how far the cone can move), and for the 112, the mechanical power rating is 400 watts RMS down to 50Hz, the F6 is 48Hz and the F10 is 41Hz, so somewhere in between this range is about optimum though if you aren't driving the piss out of the cabinet then I would recommend ~40Hz for the HPF.

For cabinets that do not provide this information, I would settle for around the F3 of the speaker if driving anywhere near the rated power (in watts) because generally the information provided is for thermal power limits (in watts, the amount of heat that can melt the voice coil) which can be as much as twice the mechanical limits (power rating in watts) at the F3 point depending on the design of both the driver and the cabinet.

I've been asking me this too. The speakers in my cabs (SWR GIII and jr.) have a Free resonant freq. at 47Hz, but don't know if the cabinets are tunned different. Usually I set the HPF somwhere between 40 and 60Hz, depending on my feeling about lows and booms.

SWR Goliath III (4x10)
SPL: 105 dB SPL @ 1W1M, (–3dB @ 40 Hz and 15 kHz)
SWR Goliath III jr. (2x10)
SPL: 105 dB SPL @ 1W1M, (–3 db @ 45 Hz and 12 kHz)

P.A.S. 10" SPEAKER SPECIFICATIONS
Free Air Resonance: 47 Hz
Individual Impedance: 8 Ohms (each)
Power Rating: 175 Watts RMS (each)

 

[agedhorse]

Knowing what I know about specs, and also about that particular PAS driver (which has a nice mid voicing), there is no way that the 210 has a 105dB/1W/1M average sensitivity, it's physically impossible. It's also impossible for the 210 and 410 to have the same average sensitivity. If were to speculate, the 105dB number is 2.83V into the 4 ohm cabinet which is 2 watts and that would then translate to be 102dB/1W/1M. I can't speculate a reasonable reason for the 210 being 105dB/1W/1M, which goes to me earlier comments regarding different rating metrics.

I also know that those PAS drivers suffered from chronic mechanical damage when driven very hard. I would think that 125-150 watts would be the maximum safe power below about 60Hz.

That said, I would recommend setting the HPF at about 50Hz firvthe 410 and 60Hz for the 210.

 

[dabis]

Knowing what I know about specs, and also about that particular PAS driver (which has a nice mid voicing), there is no way that the 210 has a 105dB/1W/1M average sensitivity, it's physically impossible. It's also impossible for the 210 and 410 to have the same average sensitivity. If were to speculate, the 105dB number is 2.83V into the 4 ohm cabinet which is 2 watts and that would then translate to be 102dB/1W/1M. I can't speculate a reasonable reason for the 210 being 105dB/1W/1M, which goes to me earlier comments regarding different rating metrics.

I also know that those PAS drivers suffered from chronic mechanical damage when driven very hard. I would think that 125-150 watts would be the maximum safe power below about 60Hz.

That said, I would recommend setting the HPF at about 50Hz firvthe 410 and 60Hz for the 210.

Many thanks! The specs are listed on SWR's brochure ([Invalid or Expired Link Removed]). I noticed too and make me doubt when both cabs had the same sensitivity.

 

[dabis]

Hi everyone! yesterday I did some measurements of my HPF/LPF pedal (VONG-Filterung – Schalltechnik_04) to understand better how are our frequencies modified when using this filters. Some people here asked too from time to time what's the difference between these filters and the EQ, and maybe these plots will help to explain better the difference.

Equipment: a PC, ARTA software (ARTA Software), Alesis Multimix8 USB as the audio interface (Alesis MultiMix 8 USB FX).Amp head (Tone Hammer 350) only on the last plot, to measure how the filters and the preamp eq. are behaving together

This is the frequency response (FR) of my measurement equipment with all the filters off. Note that at 20Hz and at 20KHz there's some kind of rolloff, that I asume that's it's the audio interface and maybe the PC that have these inherent FR:

Now this the HPF set at 30 Hz. (-3dB aprox.):

HPF at 85 Hz aprox:

HPF full on it's 143 Hz:

 

[dabis]

Now the LPF plots.

LPF at 10 KHz:

LPF at 5 KHz (a common tweeter crossover starts here):

 

[dabis]

And finally two interesting measurements:

HPF and LPF at full. This lets only a small window without rolloff from 158 Hz to 200 Hz only. Before anyone ask, yes, the sound from my bass with this settings it's very awful .

And this one plot it's very important to me: I set the HPF at 85 Hz and then the signal goes to my amp head, where I bumped a little the eq., 2dB at 40Hz and 2KHz. Note that the rolloff it's not at 85Hz but at 55Hz due to the impact of the eq. These are my typical live settings.

 

[aproud1]

Hi everyone! yesterday I did some measurements of my HPF/LPF pedal (VONG-Filterung – Schalltechnik_04) to understand better how are our frequencies modified when using this filters. Some people here asked too from time to time what's the difference between these filters and the EQ, and maybe these plots will help to explain better the difference.

Equipment: a PC, ARTA software (ARTA Software), Alesis Multimix8 USB as the audio interface (Alesis MultiMix 8 USB FX).Amp head (Tone Hammer 350) only on the last plot, to measure how the filters and the preamp eq. are behaving together

This is the frequency response (FR) of my measurement equipment with all the filters off. Note that at 20Hz and at 20KHz there's some kind of rolloff, that I asume that's it's the audio interface and maybe the PC that have these inherent FR:
View attachment 3794398

Now this the HPF set at 30 Hz. (-3dB aprox.):
View attachment 3794399

HPF at 85 Hz aprox:
View attachment 3794400
HPF full on it's 143 Hz:
View attachment 3794401

I understood how this worked but seeing it graphed is very helpful. Thanks for posting!

 

[dabis]

Generally wireless system rolloff is 6dB/oct but there are exceptions such as some AT models.

This morning was the turn of my old wireless to be measured: Sennheiser freePORT Instrument Set (archived) - Microphone - freeport Instrument Set. I don't know exactly what is the rolloff but nothing far of what @agedhorse told us 2 years ago.

Also I'm posting the whole frequency response where you can see that isn't as constant as the wired ones I posted yesterday, but don't know if these anomalies are audible or not.Suggestions?

Funny thing it's that I'm not using anymore wireless as failed on the first song of the first concert with my actual band (altough I checked extensively the whole rig the day before and during the soundchecks). I'm used to move around with cables so it's not so important.

Also, who dares to contradict this boy?

 

[Stumbo]

Lots of HPF love here: What are your favourite always-on effects that slightly alter your tone for the better?

 

[Stumbo]

...

I want to ask - if you're currently using a HPF with a 5 string, where do you have it set?

I recently acquired a new 5'er after not having one for years, so I set my HPF to 30Hz as a starting point, but I'm curious to hear from others.

(fEARful/Greenboy F115 cab)

...

Start at the lower end and raise it until you don’t like what you hear. It's usually more room dependent than bass dependent, and often surprising how high the sweet spot is.

 

[superpanget2]

I want to ask - if you're currently using a HPF with a 5 string, where do you have it set?

I recently acquired a new 5'er after not having one for years, so I set my HPF to 30Hz as a starting point, but I'm curious to hear from others.

(fEARful/Greenboy F115 cab)


Start at the lower end and raise it until you don’t like what you hear. its usually more room dependent than bass dependent, and often surprising how high the sweet spot is.