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

[SoulReflection]

Many thanks to Stumbo and others who have contributed to this thread.

I am still trying to come back from the old days, when I had a 60 watt Dynaco MKIII amp and two JBL D140F's in a sealed cabinet. I don't recall "boominess" from from then, nor did I have to replace any speakers. Maybe I was lucky or, just too naive to know the difference . I dunno...

But, I do appreciate the difference between then and now, with a Rumble 200 Combo with more power and a single, ported, 15" speaker. I have to spend much more time in the woodshed before I try the 200 Combo in a gigging situation. I am spending most of my time practicing with earphones through the Ampeg SCR-DI!

By then, I hope to read through more posts on here and have a better understanding of what HPF I may need.

Your contributions are appreciated...

 

[agedhorse]

Many thanks to Stumbo and others who have contributed to this thread.

I am still trying to come back from the old days, when I had a 60 watt Dynaco MKIII amp and two JBL D140F's in a sealed cabinet. I don't recall "boominess" from from then, nor did I have to replace any speakers. Maybe I was lucky or, just too naive to know the difference . I dunno...

Your contributions are appreciated...

At that power level, in a sealed enclosure, I wouldn't expect any issues. Things have come a long way since that time.

 

[ctmullins]

Actually, HPF's are built into MOST high quality bass amp products these days. Each manufacturer makes different choices for different reasons, but most recognize the importance.

I’ve heard that before, but the HPF doesn’t appear to be a feature that the amp manufacturers want to advertise, or even include in their manuals (yes, I’m a manual reader). I for one would love to have access to a reference list of which heads have HPFs, what the knee frequency and slope is for each one, and whether it’s fixed or adjustable.

My “big” head is a three-space rack with a Tech21 RPM and a Crown XLS2 1502. I chose the 1502 partly because its DSP includes a programmable HPF that can go as low as 30 Hz. (My prior amp was an old QSC PLX1202, which had a switchable fixed HPF at 50 Hz.) I’ve done my homework, experimenting with the HPF on versus off, and at different frequencies, and I understand the need and the benefit. I keep the Crown high-passed at 45 Hz.

But I don’t always want to bring the rack. Sometimes (most times, lately) I just want to bring a simple Class D head, like my GK MB500. Before the GK, I used a TC; before the TC, I had an Aguilar TH. I really like today’s micro-heads. But I would like them more if a) they included HPFs, and b) I knew the specs on their HPFs. Not knowing is quite frustrating to me.

 

[Stumbo]

Many thanks to Stumbo and others who have contributed to this thread.

I am still trying to come back from the old days, when I had a 60 watt Dynaco MKIII amp and two JBL D140F's in a sealed cabinet. I don't recall "boominess" from from then, nor did I have to replace any speakers. Maybe I was lucky or, just too naive to know the difference . I dunno...

But, I do appreciate the difference between then and now, with a Rumble 200 Combo with more power and a single, ported, 15" speaker. I have to spend much more time in the woodshed before I try the 200 Combo in a gigging situation. I am spending most of my time practicing with earphones through the Ampeg SCR-DI!

By then, I hope to read through more posts on here and have a better understanding of what HPF I may need.

Your contributions are appreciated...

I played through JBLs too. Early ported cabs. Kustom then Sunn 2000s heads. Fender Jazz or Hofner Beatle bass.

No boominess there. Cabs on casters disconnected from the stage. I always sure my tone was clean and no farting out. Played with a pick back then.

Now, boominess in a venue is another thing. Also, gym echoes and building reverb.

Also, the speakers needed some help down low to gain more clean volume.

So, for me, an HPF would have worked very well to sculpt the tone to fit the venue and protect the speakers.

 

[SoulReflection]

At that power level, in a sealed enclosure, I wouldn't expect any issues. Things have come a long way since that time.

Thanks, Agedhorse...your input is always welcomed. When you say things have come along way since that time, are you referring to more power in smaller (Class D) amps and smaller, ported cabs and that is the reason for the need for HPF's?

What if you had a powerful Class D amp and ran it through a sealed enclosure with 2-15's? This may sound elementary, but that's me .

 

[agedhorse]

I’ve heard that before, but the HPF doesn’t appear to be a feature that the amp manufacturers want to advertise, or even include in their manuals (yes, I’m a manual reader). I for one would love to have access to a reference list of which heads have HPFs, what the knee frequency and slope is for each one, and whether it’s fixed or adjustable.

My “big” head is a three-space rack with a Tech21 RPM and a Crown XLS2 1502. I chose the 1502 partly because its DSP includes a programmable HPF that can go as low as 30 Hz. (My prior amp was an old QSC PLX1202, which had a switchable fixed HPF at 50 Hz.) I’ve done my homework, experimenting with the HPF on versus off, and at different frequencies, and I understand the need and the benefit. I keep the Crown high-passed at 45 Hz.

But I don’t always want to bring the rack. Sometimes (most times, lately) I just want to bring a simple Class D head, like my GK MB500. Before the GK, I used a TC; before the TC, I had an Aguilar TH. I really like today’s micro-heads. But I would like them more if a) they included HPFs, and b) I knew the specs on their HPFs. Not knowing is quite frustrating to me.

All Genz Benz and Mesa Subway bass amps have high pass filters, most are 4th order BW. They are well documented in the manuals.

The other manufacturers are welcome to post their philosophies/features/specs with regard to HPF's.

 

[Al Kraft]

The other manufacturers are welcome to post their philosophies/features/specs with regard to HPF's.

...but few seem to, and this is why many of us really appreciate that extra level of transparency and insight regarding the design of the tools we use to create our sound that we get from engineers like you...thanks!

 

[SoulReflection]

...but few seem to, and this is why many of us really appreciate that extra level of transparency and insight regarding the design of the tools we use to create our sound that we get from engineers like you...thanks!

+1

 

[xk49w]

I don't use a HPF in my current setup, but when I would use it I would set it at a frequency 1/4th below that of the tuning frequency if the cab is ported. E.g. if the port is tuned to 50hz I would set the HPF to approx 38hz. It also depends on the steepness of the HPF (12, 24 or 48 dB/oct).

IMO too much importance is given to the ultimate attenuation slope. By itself it gives no information about the slope in the region of cutoff down to -10 dB, which is in the region that matters and, IMO all the attenuation required for this purpose.

I’ve heard that before, but the HPF doesn’t appear to be a feature that the amp manufacturers want to advertise, or even include in their manuals (yes, I’m a manual reader). I for one would love to have access to a reference list of which heads have HPFs, what the knee frequency and slope is for each one, and whether it’s fixed or adjustable...

OTOH , I can understand that advertising that your new amplifier attenuates low frequencies might be anathema to the marketing department of a bass amplification manufacturer.

 

[Al Kraft]

OTOH , I can understand that advertising that your new amplifier attenuates low frequencies might be anathema to the marketing department of a bass amplification manufacturer.

...and thus the delicate balancing act between catering to consumers whose knowledge is rooted in folklore and hype and those who have truly done their homework and appreciate being informed on product designs so they can make the best choice for their needs. I'll be the first to admit that it's not an easy game for a designer/manufacturer to win at, especially for those who choose to be the most forthcoming, and choose to do it first.

 

[Stumbo]

I have one of these now. Mounted really nicely under the Classic 2. seems to have a goodly amount of juice. A good chunk of my board is filled up with non-effect utility pedals though.

-FDeck HPF-3
-TC Polytune
-IEM pack
-Dunlop Volume/expression pedal
-Switching loop for the volume part of the V/E

I've been fussing a bit with layout and what's staying or not but overall the structure is mostly remaining the same. I did grab that VFE Bumblebee, which I thought would be pretty ideal, but I didn't love it (goes back in it's original box and on the shelf for now). I removed the mini-7-band EQ for now, but may put that back for 'clean' filter. ; and I ditched the little echo. Sticking with the Mooer Slow-Gear clone for swells. Which leaves:
-Iron Ether Divaricator ->
Dr. Scientist Frazz Dazzler v2 ->
Iron Ether Xerograph Deluxe ->
cheap mini analog delay (until my Noisemaker Nebula is fixed)->
Ibanez BC-9 bi-mode chorus-> out

Trying to decide if I drop the OC-2 into the mix...and/or if I find a synth to add. I'm also pondering a Particle.

Haven't taken a picture lately, but:
View attachment 2950155

​

 

[BadExample]

...but few seem to, and this is why many of us really appreciate that extra level of transparency and insight regarding the design of the tools we use to create our sound that we get from engineers like you...thanks!

We (those who follow "TB Amps and Cabs" regularly) might be a unique breed. Not inbred, but unique. Who is the best selling these days, Fender Ruble still? What do they rate their combos and heads at? WRMS, Program? Peak? I don't know and can't find it. What THD @ what rated RMS Watts? Is that a good sounding THD or not (maybe best hide it if not). Unknown to us I think. I've seen Andy scorned by the ignorant several times for his open ratings of probably the best >$1000 class D amps, if not the best period. THD and wattage ratings are just not understood by most people. Not picking on Fender, just an example of specs vs. sales. At least I didn't say the "B" word

 

[Al Kraft]

We (those who follow "TB Amps and Cabs" regularly) might be a unique breed. Not inbred, but unique. Who is the best selling these days, Fender Ruble still? What do they rate their combos and heads at? WRMS, Program? Peak? I don't know and can't find it. What THD @ what rated RMS Watts? Is that a good sounding THD or not (maybe best hide it if not). Unknown to us I think. I've seen Andy scorned by the ignorant several times for his open ratings of probably the best >$1000 class D amps, if not the best period. THD and wattage ratings are just not understood by most people. Not picking on Fender, just an example of specs vs. sales. At least I didn't say the "B" word

It's definitely a "know your audience" situation in the sales game. I recognize that most of us here are unique in that we represent not only technically knowledgeable consumers, but folks who want to understand even more.

I'm actually convinced there are people who would argue that a poor sounding class D amp with a SMPS packaged in a 2u rack space enclosure with brick inside for weight is a great example of why bigger, heavier gear just has that something extra you can't get in the small toy amps...of course that something extra would be a brick, but hey, if it sells product it's cheaper than real engineering...

 

[agedhorse]

My experience with Fender is that they generally rate their amps using RMS metrics.

 

[BadExample]

It's definitely a "know your audience" situation in the sales game. I recognize that most of us here are unique in that we represent not only technically knowledgeable consumers, but folks who want to understand even more.

I'm actually convinced there are people who would argue that a poor sounding class D amp with a SMPS packaged in a 2u rack space enclosure with brick inside for weight is a great example of why bigger, heavier gear just has that something extra you can't get in the small toy amps...of course that something extra would be a brick, but hey, if it sells product it's cheaper than real engineering...

Well, I didn't say some of us are NOT inbred At least they can run fast.


My recently acquired and beloved GB amp manual claims:

"3DPM™ -- 3 DIMENSIONAL POWER MANAGEMENT –
Our proprietary 3DPM™ technology insures greater and
more solid sounding output while retaining the feel and playability of a more traditional tube based power amplifier
.
When driving the power amp hard, the result is increased heft and girth while maintaining the dynamics and
articulation of the individual notes. The result is an amplifier that achieves a more 3 dimensional tone and feel, like
a tube amplifier power section, without the anemic flatness other amplifier designs can exhibit"

And it is sooooooo true

 

[Al Kraft]

Well, I didn't say some of us are NOT inbred At least they can run fast.


My recently acquired and beloved GB amp manual claims:

"3DPM™ -- 3 DIMENSIONAL POWER MANAGEMENT –
Our proprietary 3DPM™ technology insures greater and
more solid sounding output while retaining the feel and playability of a more traditional tube based power amplifier
.
When driving the power amp hard, the result is increased heft and girth while maintaining the dynamics and
articulation of the individual notes. The result is an amplifier that achieves a more 3 dimensional tone and feel, like
a tube amplifier power section, without the anemic flatness other amplifier designs can exhibit"

And it is sooooooo true

Sometimes the cookies really are moist, chewy, and delicious just like it says on the package...

 

[PraiseBassing]

Compressor and HPF in one pedal.




View attachment 2941782​

I did see this earlier, however I think the HPF only affects the compressor triggering. It keeps the lows from triggering the compressor and lets higher frequencies. I believe the site says your tone is not effected by the HPF in this one.

 

[BadExample]

My experience with Fender is that they generally rate their amps using RMS metrics.

I believe that, but it appears not stating so does not hurt sale to the masses. Ampeg also tends to just say Watts on their sale/marketing pages, but IIRC, RTFM reveals WRMS. Of course Fender Rumble is a good bang for the buck, but their professional series stuff is much more expensive.

 

[RoadRanger]

What is the name of the effect in the Zoom B1on that has a HPF in it? Anybody want to share the settings they use on it?

AcBsPre - I generally set the "Depth" an 9 :
" The Depth rolls off the lows :
- at 10 -> no roll off (full bass)
- at 0 -> like an HPF fixed at 200Hz
and inbetween :
- at 5 : 100Hz
- at 6 : 80Hz
- at 7 : 70Hz
- at 8 : 60Hz
- at 9 : 40Hz "

 

[ctmullins]

OTOH , I can understand that advertising that your new amplifier attenuates low frequencies might be anathema to the marketing department of a bass amplification manufacturer.

I don’t exactly buy that. They could market it as a protective feature (which it is). And the PA guys don’t have a problem documenting the HPFs they have built into their mixers and amps.

I just read through the manual for my GK MB500. Not a word about an HPF. Grrrr...