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

#1,321
In this order my gigging rigs chain is:

Gibson SG bass or EB-2 with a Novak Fatbucker
Boss Tu-3
Broughton High Pass / Low Pass Filter
Quilter Bass Block 800
1 or 2 Fender Rumble 15" cabs

I have a MXR Bass Compressor between the HPF and the head, but I haven't used it for a while. I also haven't felt the need for more than one cab since I've been using the HPF, even on outdoor gigs.
 
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#1,322
Nevada Pete said:
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@Nevada Pete:

The sealed design of the Ampeg 810 that's pretty much done at 55Hz. works really well on live stages for many reasons, one of which is that it doesn't muddy up the open drum microphones with low frequencies.

when Swanson Sound was using lets say 2 to 4 JBL 4550 bass cabs on each side of a stage, for example, Tom Coroda always rolled off the bass at 80Hz., 12db / octave. I never noticed any lack of bottom end at the time. Just saying.
 
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#1,323
Mushroo said:
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@Mushroo:

Last night, for the first time, I used the Messenger (pre-amp by
https://www.broughtonaudio.com/ )with a band.

The instrumentation was: unamplified piano, unamplified cello, lightly-amplified acoustic guitar, and myself on fretted P bass.

There is an old Acoustic Image combo at the rehearsal space, which sounds great with some of my basses, but with P bass, I find it's a little "boomy" and lacks the midrange "punch" I associate with a good P bass sound.

I brought a very simple 3-pedal board to rehearsal: tuner (Polytune), dirty boost (One Knob Pony), and the Messenger.

I bypassed the AI combo's preamp and went in through the Effects Return.

I dialed in a hint of saturation with OKP and then on the Messenger, set the HPF to 80hz and the LPF to 2khz. The boominess was tamed, and bam! Instant P bass punch with plenty of rich midrange harmonic content.

In the past, I have usually turned the tone knob all the way down, because I find a P bass sounds too bright with the tone wide open. With the Messenger's powerful EQ, I'm discovering new sounds in my old P bass, and the tone knob is usable over its entire range.

Kudos to Josh for such a versatile and practical design.
 
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#1,324
mcnach said:
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@mcnach:

The speakers will have a lot to say in that, but I would say YES!!!

I use a couple of 210s vertically and enjoy feeling the air move behind me with the D800+. Nice.

The D800 (non 'plus') is no worse in that respect, although I like how on the D800+ you can adjust the low mids frequency centre, and the interplay between the adjustable HPF and bass control is really cool and useful to get those powerful but defined low mids.
 
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#1,325
deepestend said:
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I know it’s been asked before, but what exactly does the hpf do for you?
monkeyland said:
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Gets rid of unwanted low end in a way that is different from the low knob on my amp. I only really use it in rooms that have a lot of rumble. This allows me to still be able to use the bass boost on my metro the way that I normally would. In the diagram, the part to the left of the slope is what is getting cut out. The knob on the filter moves the corner frequency up or down.
View attachment 3211170
 
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#1,326
I’m just going to park this right here...
4DC87206-98F1-481C-84B4-947FEBA11A01.jpeg
 
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#1,327
I would like to buy HPF Pre. Mr. Deck doesn't ship to Europe, unfortunatelly. Would anybody be kind enough to serve as a shipping agent?, i.e. to order from Mr. Deck and then send it to Europe.. I would pay upfront, of course. Or is anybody selling their HPF Pre? Thank you.
 
#1,329
blip said:
Know anything more about this? I assume it's a fixed frequency, always-on HPF with adjustable, switched LPF but the graphic suggests it's a dual HPF.
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I know EVERYTHING about this since it was a custom shop order that I placed and is now en route to me :p

You're correct on the graphic. Max mentioned it to me over email and offered to redo the graphic plate, but I told him not to bother. The pedal is his standard Thumpinator circuit for the HPF side, and it is always-on. The LPF side has an adjustable frequency and a make-up gain circuit. I tried using separate Broughton HPF and LPF pedals, but since my desired LPF functionality was basically a dub/reggae tone filter the LPF didn't work due to the perceived drop in signal level on account of the severely reduced frequency response. To resolve this issue Max added in a level control that goes from silent when fully counterclockwise, to unity gain at noon, a maximum of +24dB when fully clockwise. The frequency response can be seen below.

freq df.png
 
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#1,330
silky smoove said:
I know EVERYTHING about this since it was a custom shop order that I placed and is now en route to me :p

You're correct on the graphic. Max mentioned it to me over email and offered to redo the graphic plate, but I told him not to bother. The pedal is his standard Thumpinator circuit for the HPF side, and it is always-on. The LPF side has an adjustable frequency and a make-up gain circuit. I tried using separate Broughton HPF and LPF pedals, but since my desired LPF functionality was basically a dub/reggae tone filter the LPF didn't work due to the perceived drop in signal level on account of the severely reduced frequency response. To resolve this issue Max added in a level control that goes from silent when fully counterclockwise, to unity gain at noon, a maximum of +24dB when fully clockwise. The frequency response can be seen below.

View attachment 3219876
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That's cool! I assume the Level Control is also bypassed when the LPF is not engaged?
 
#1,331
NKBassman said:
That's cool! I assume the Level Control is also bypassed when the LPF is not engaged?
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Correct

The intent of the pedal was to be an all-in-one filter setup for my needs in my weddings/corporate events/private parties band. I need an HPF that's always-on and immediately downstream of my octave pedal, and I need a dub/reggae tone pedal basically anywhere on the board ahead of the compressor. We've got a few tunes that benefit from a dub/reggae style tone and I wanted the convenience of a footswitch rather than reaching for an EQ knob on my basses or my amp. I really hate fiddling with knobs while playing and much prefer using a footswitch, even if it takes up pedalboard and power supply real estate. This accomplishes both of those things. I'll still probably keep my Broughton Always-On HPF on the board near the end of the chain as I like that it's an adjustable HPF to filter out problem room frequencies without needing to sacrifice an EQ band on my amp for that task.
 
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#1,333
blip said:
Cool implementation! I have a Broughton H/LPF, but keep it at unity gain. Never considered using it as a band pass boost - I'll have to give it a go!
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Could be cool!

I only want the boost function to compensate for the perceived loss of volume when setting the LPF at extremely low frequencies. My goal is to have the engaged and bypassed tones have the same perceived volume. That means a higher volume for the heavily filtered tone since at unity it sounds like the volume is lower due to the reduced frequency response.
 
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#1,335
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#1,339
The Bass Clef said:
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@The Bass Clef:
I know this thread is old, but for the sake of information, I’m pretty sure that the more recently made CMD 121P combos must have gone through a little change since the one that you had years ago Jimmy.

I just picked up an Indonesian-made one (from 2014) off the classifieds here, and the first thing I noticed was that nasty hissing tweeter.

I looked online to see if that was “normal” (which it is for this amp) and if I could just disconnect it. I found out it was safe to do, but I also saw your post above about it having no highs at all afterwards, so then I figured I’d just have to live with it and use the VLE to get rid of the ugly tweeter noise.

The problem was, while the VLE did get rid of the tweeter ugliness, I also found that it had a bit of a negative effect on my overall tone - I was muddier and starting to get lost in the mix now.

So I researched a little more, and found several posts from people who disconnected their tweeter and said it was way better now.

That convinced me to try it out, so I pulled the wires off mine and I found that my 12” main speaker is most definitely operating full range.

I do have to crank the “High” EQ knob on the amp now if I want to get more of the crispy highs, but they are there, and at least now I’m cutting through the mix again (the VLE is turned back down to where it isn’t making me sound muddy anymore).

Another thing to mention... I didn’t even bypass the crossover like I read many others did. I found a couple posts saying that the CMD 121P doesn’t really have a true crossover, it’s really just a high pass filter for the piezo, and the main woofer is wired full range from the factory. And I found this to be the case with mine.

So... now I’m thinking maybe the older combos actually had a true crossover in them (that cut off the highs to the 12”, as well as cut off the lows to the tweeter) that would have needed to be bypassed. That would explain why your combo didn’t get the full range to the 12, and mine did.

Did you ever try bypassing the crossover, or did you just disconnect the tweeter? It seemed like you enjoyed the VLE turned up, so maybe it wasn’t worth the effort for you to dig in there and bypass it.

I know you’ve moved on from this amp long ago Jimmy, but for future readers, I figured I’d let em know that disconnecting my tweeter made it a way better amp.

JimmyM said:
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@JimmyM:

Well that's good to know if they did fix that. I honestly can't remember if I bypassed the crossover network or not. I may not have. I think I decided it was a PITA to do it.

Let's put it this way...I tolerated the VLE doing the highs cut more than disconnecting the tweeter But I actually thought the VLE was the best thing about Markbass amps,

and I wanted something similar in a tiny effect pedal, and that led to the Broughton Low Pass Filter, which along with the subsequent High Pass Filter and the combo HPF/LPF are a couple of Josh's best selling pedals.

I really didn't hear the VLE acting on the amp. I guess it's possible but I don't remember it that way.
 

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