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High Pass Filters

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Thanks Paul - actually looking at the AcBsPre, as you say it does seem to start cutting earlier in the mids and is going to have more impact on tone than the Triple . But the Fishman Pre on which the AcBsPre was designed as a tone shaping EQ rather than an HPF so I guess that's to be expected.

Otherwise, I don't think there is too much in it between the AcBsPre and the Triple PEQ. I'll have to admit I find it easier to get my head around the parameters on the PEQ than the AcBsPre, so for a simple bassist like me that is what I'll stick with for now :) 

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Guest adi77

this some high funda sh!t i use my ears sometimes even a severe high pass doesnt do it because, bad acoustics , pa not tuned etc..

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3 minutes ago, Al Krow said:

Thanks Paul - actually looking at the AcBsPre, as you say it does seem to start cutting earlier in the mids and is going to have more impact on tone than the Triple . But the Fishman Pre on which the AcBsPre was designed as a tone shaping EQ rather than an HPF so I guess that's to be expected.

Otherwise, I don't think there is too much in it between the AcBsPre and the Triple PEQ. I'll have to admit I find it easier to get my head around the parameters on the PEQ than the AcBsPre, so for a simple bassist like me that is what I'll stick with for now :) 

The depth control on the Fishman was designed as an HPF. It works really well as does the LoEq on the B3n.

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Just now, Opticaleye said:

The depth control on the Fishman was designed as an HPF. It works really well as does the LoEq on the B3n.

Well you and I disagree on the LoEq on the B3n, I found that to be pants.

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1 minute ago, Al Krow said:

Well you and I disagree on the LoEq on the B3n, I found that to be pants.

As I said, try it at a higher setting and tell me it doesn't work!

 

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4 minutes ago, Opticaleye said:

As I said, try it at a higher setting and tell me it doesn't work!

Aha! I see what you're driving at, which I missed before i.e. start the Low EQ at 50Hz and between 30Hz and 50Hz it shouldn't be cutting too much (i.e. not impacting on tone) but then it should start cutting significantly in the sub audio 30Hz-and-below range which is where we want it to really bite to take out the 'useless' high energy waves.

Ok penny has dropped - and my apologies for my usual slowness on this stuff! I'll definitely give that a go over the weekend (but I need to go get ready for the more mundane matters of a gig tonight and picking up a new bass en route... :))

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1 hour ago, Al Krow said:

Aha! I see what you're driving at, which I missed before i.e. start the Low EQ at 50Hz and between 30Hz and 50Hz it shouldn't be cutting too much (i.e. not impacting on tone) but then it should start cutting significantly in the sub audio 30Hz-and-below range which is where we want it to really bite to take out the 'useless' high energy waves.

Ok penny has dropped - and my apologies for my usual slowness on this stuff! I'll definitely give that a go over the weekend (but I need to go get ready for the more mundane matters of a gig tonight and picking up a new bass en route... :))

Well... not exactly but getting there. An HPF set at 50hz will be flat down until 50hz and will then drop off sharply to nothing. The PEQ set at 50hz will start to drop off less sharply but at 100hz or so depending on the Q and then raise again in the sub frequencies. It seems that Zoom were listening to us when we were asking for a AcBsPre sim on the B3n (purely for the HPF feature on the Depth control) but provided a fully fledged variable frequency HPF on the Lo EQ. My Quilter BB800 ,on the other hand appears to have a fixed frequency (100hz), variable slope HPF as well as a fixed, steep sloped 25hz HPF too.

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10 minutes ago, Opticaleye said:

Well... not exactly but getting there. An HPF set at 50hz will be flat down until 50hz and will then drop off sharply to nothing. 

Does "dropping off sharply to nothing" tie in with what other folk have been saying about a - 12dB/octave slope,  which seems less steep than you are suggesting? 

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35 minutes ago, Al Krow said:

Does "dropping off sharply to nothing" tie in with what other folk have been saying about a - 12dB/octave slope,  which seems less steep than you are suggesting? 

Zoom haven't quoted any figures (that I've seen) for the LoEq in HPF mode. I would imagine that if they've called it an HPF that's what it does. It certainly sounds like one to me. I would imagine that it would be a sharp slope given the low frequency that you can set it to. A gradual slope from 25hz wouldn't be much use to anyone!

*Edit :  Zoom's quoted -12db is for the "gain" parameter which is redundant when the LowEq sim is set to HPF *

Edited by Opticaleye
Further info

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8 hours ago, bartelby said:

This the sort of thing your after xD, not worked out if this can do signal/noise as it's for room analysis.

 

 

You definitely can derive distortion and probably ballpark S/N at least, but it's a bit tedious. There's a good explanation on the website of the True RTA makers. It's a lot easier to just use RMAA for those tests, but even that often has some "gotchas" involved.

Thanks for taking the time to graph all that stuff. And FWIW, one of the DSP speaker management controllers I have (it's in a plate amp) recommends stacking PEQs as a viable solution for high pass filtering. I may have to revisit that, but programming that particular widget is a real exercise in patience and the way I did the HPF (stacked Butterworth HPF sections) has always worked well for me. And ultimately, if it sounds good it pretty much is good.

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14 hours ago, Al Krow said:

Well you and I disagree on the LoEq on the B3n, I found that to be pants.

But how are you measuring your scale of pants?

Your mentioned previously your marker for whether it was doing its job or not was reducing air movement. Did you stand in front of the cab and measure how much your pants flapped?

My point is that with a HPF designed for speaker protection like the Thumpinator it's really hard to tell is having an effect. When it's on you still hear and feel deep bass, and feel air movement from your cab. But you do notice the cones lurching around less which ultimately gives you more headroom and definition.

Less steep HPFs with a variable frequency like the Broughton are more about reducing sub frequencies on stage and tightening up your low end. Especially handy playing through your rig at home!

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So I said I would try out the (new) LoEQ effect on the B3n, which is not available on the earlier Zoom pedals.

The LoEQ has two settings 'HPF' and 'Shelf'. What I found was as follows:

  • LoEQ on HPF at 50Hz was very comparable to the PEQ patch at 20Hz both in terms of reducing speaker cone excursion with relatively small impact on tone - One to (rather than in) the Opticaleye 
  • The LoEQ 'Shelf' setting was, however, definitely more effective than the HPF setting, but at 50Hz had quite a marked impact on tone (similar to the GEQ at 50Hz), but the impact on tone was reduced at lower Hz and LoEQ Shelf 30Hz works well. I wonder @Opticaleye if you were referring to the 'Shelf' setting when you were talking about "dropping off sharply to nothing".
  • Stacking up two or more of the same effect for all the above increases the effectiveness in terms of reducing speaker cone excursion, whilst having a correspondingly greater impact on tone.  

=> key conclusion for me is that there is very adequate HPF protection against speaker cone excursion (and protecting my cabs is my main priority in all of this) on my B3n so I don't need to spend ££'s on a dedicated HPF pedal. Job done. Thanks fellow BCers for your input and educating me!

6 hours ago, dannybuoy said:

But how are you measuring your scale of pants? Your mentioned previously your marker for whether it was doing its job or not was reducing air movement. Did you stand in front of the cab and measure how much your pants flapped?

My point is that with a HPF designed for speaker protection like the Thumpinator it's really hard to tell is having an effect. When it's on you still hear and feel deep bass, and feel air movement from your cab. But you do notice the cones lurching around less which ultimately gives you more headroom and definition. Less steep HPFs with a variable frequency like the Broughton are more about reducing sub frequencies on stage and tightening up your low end. Especially handy playing through your rig at home!

Actually DB, the impact on air movement can definitely be felt - depends on the power output, right? With the single 150W rated speaker which you are using at home the impact will, for sure, be less noticeable than through the 600W 2x12 Mesa Rig I had fired up in my basement with my Alesis SR18 drums going through the bass amp to give me a repetitive constant low end to compare, and family members complaining that I was shaking the whole house! "Turn the noise down, dad..." That just seems conceptually so wrong, I thought that was something only parents said to their kids...

Edited by Al Krow

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26 minutes ago, Al Krow said:

So I said I would try out the (new) LoEQ effect on the B3n, which is not available on the earlier Zoom pedals.

The LoEQ has two settings 'HPF' and 'Shelf'. What I found was as follows:

  • LoEQ on HPF at 50Hz was very comparable to the PEQ patch at 20Hz both in terms of reducing speaker cone excursion with relatively small impact on tone - One to (rather than in) the Opticaleye 
  • The LoEQ 'Shelf' setting was, however, definitely more effective than the HPF setting, but at 50Hz had quite a marked impact on tone (similar to the GEQ at 50Hz), but the impact on tone was reduced at lower Hz and LoEQ Shelf 30Hz works well. I wonder @Opticaleye if you were referring to the 'Shelf' setting when you were talking about "dropping off sharply to nothing".
  • Stacking up two or more of the same effect for all the above increases the effectiveness in terms of reducing speaker cone excursion, whilst having a correspondingly greater impact on tone.  

=> key conclusion for me is that there is very adequate HPF protection against speaker cone excursion (and protecting my cabs is my main priority in all of this) on my B3n so I don't need to spend ££'s on a dedicated pedal. Job done. Thanks fellow BCers for your input and educating me!

Actually DB, the impact on air movement can definitely be felt - depends on the power output, right? With the single 150W rated speaker which you are using at home the impact will, for sure, be less noticeable than through the 600W 2x12 Mesa Rig I had fired up in my basement with my Alesis SR18 drums going through the bass amp to give me a repetitive constant low end to compare, and family members complaining that I was shaking the whole house! "Turn the noise down, dad..." That just seems conceptually so wrong, I thought that was something only parents said...

As I understand it (and I'm far from an expert), the Shelf will just reduce by -12db and stay there. There will still be lower level audio (like a shelf in the frequency graph)  underneath the shelf frequency. With an HPF it is the slope that is being referred to in the "-12db/oct" and this means that the slope will continue downwards past the first octave at the same rate until zero audio content. 

 

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1 hour ago, Al Krow said:

Actually DB, the impact on air movement can definitely be felt - depends on the power output, right? With the single 150W rated speaker which you are using at home the impact will, for sure, be less noticeable than through the 600W 2x12 Mesa Rig I had fired up in my basement with my Alesis SR18 drums going through the bass amp to give me a repetitive constant low end to compare, and family members complaining that I was shaking the whole house! "Turn the noise down, dad..." That just seems conceptually so wrong, I thought that was something only parents said to their kids...

For sure, I wasn't disagreeing there. My point was though, similar to what is often said about compressors - "if you can hear it working, you're probably compressing too much". If you can hear the HPF working you might be chopping off more low end than you need to. Rather than just rolling off the frequencies that a speaker can't reproduce, you are in the territory of rolling off frequencies that your cab is fine to handle, but you're doing it for reasons other than speaker protection. That's where adjustability is a very handy thing to have to reign in sub-bass at home and on less than ideal stages.

My Orange Terror has no HPF built in as far as I know (they are in the school of thought that less is more in terms of components I think!) and my poor little sealed Ampegs need all the protection they can get so a Thumpinator lives on my board. My wife would probably prefer I swap it for a Broughton and rolled off everything under 120 Hz though!

Edited by dannybuoy

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Al, I'd recommend doing some reading on the different types of filter, their shapes on a graph, and their uses.

With respect you seem to be grasping about in the dark a bit, and knowing the theory would save you a lot of time here. High pass filters are the most effective way of removing subsonic content in a signal, and neither shelves or notches are high pass filters. Very useful, but not HPFs!

I don't have any decent graphs to hand, but Google will quickly give you a visual reference of what each filter is doing. While your testing method does make sense for practical use, listening for subsonic effects is obviously not the best approach! Cutting into the audible range is a good use of a variable HPF too, but why do it with a shelf when you can be removing a greater degree of the inaudible signal with a HPF?

The reason for the usual 20-20,000hz range for audio applications is that it is the generally accepted maximum range of human hearing. Occasionally manufacturers will quote outside of this, but it is not usually relevant to the use.

Home cinema is often more interested in frequencies below 20hz, as the feeling of explosions, large vehicles passing close to the camera, or that ultra-low rumble erroneously used to give a sense of being located in deep-space are goals in the setup. Of course, a piece of audio equipment rated between 20 and 20k may well still produce signal outside of that range, hence the main use of the HPF in the first place.

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Like Al Krow I'm on the same learning curve, eager to broaden my knowledge and open to receive guidance from the more experienced and knowledgeable amongst us!

So the optimum HPF settings on MS-60 B & B3 / B3n winner is------?

 

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I wish it were so simple!

As far as I have gathered the only HPF on the earlier Zooms is in the Ac Bs Pre. The B3n also has the LoEQ, which sounds to be far superior, but I've not had the chance to try it! Notches might sound effective, but for protection from VLF content they aren't actually much cop- in fact if they clear the really deep sounds from the signal they may encourage you to turn up and therefore potentially hit the amp/speakers with even more subsonic goings on than you would have otherwise. Not advised, over all! A shelf at least will apply it's cut infinitely downwards in frequency- so a 6db cut at 30hz will also be -6db at 20hz, 10hz and so on.

For true high pass filtering though, there is no 'best' setting, or even fixed use, and that's just in a bass guitar context. For speaker protection/greater headroom, then a cut applied as high as you can go without hearing it is about as specific as one can be. This of course will depend on the entire rig, and primarily the speaker. Of course, affecting the audible range of the instrument is also very useful, but all the more subjective and dependent on the sound of your rig, and what you want to achieve. I have some patches on my MS-60b set just to cut a little below 40hz (give or take, based on the limitations of the Ac Bs Pre), but some are really tightening up the lows, either because of the sound I'm after, or just to reign in some big low end from a couple of basses. Getting a similar effect for different basses can require different settings, too. To throw another fly in the ointment, I recently changed my speakers, and some of the settings I had been using translated really well- some I will need to sit down with and completely re-jig to get back where I wanted.

As ostensibly simple as a HPF is, it can be compared to a compressor in that it is very useful, but very (very, VERY) subtle, and is best used with a bit of prior understanding. On either, twiddling knobs til it sounds good is not likely to get the best results.

I'm not an expert, and certainly not trained in this stuff. I do have a bit of help in that I am an utter nerd about sound, and therefore have quite a high tolerance for reading through dull technical stuff for the sake of finding out, but I am really just relaying what I've learnt elsewhere, and some of my experience with fairly extensive use of these things. If you can bear to invest some time dredging through the info I would recommend reading up on HPFs and EQ in general, particularly from the perspectives of mixing both in the studio and live, setting up PAs, and audio installation for cinema, both home and commercial. They will be far more in depth than many bass related sources.

It's also worth trying to stick to articles rather than forums, as the AV world can be full of just as much guessing and supposition as anywhere else on the matter! I'm not suggesting it's the most fun you'll ever have, but as with comps, there is a bit of science that needs to go into proper use, unlike, say a drive pedal, which you can generally get the measure of just by plugging in and tweaking about!

If you have any specific questions feel free to ask and I'll try to be as helpful as I can (I rather enjoy getting stuck into this thread actually!) but I wouldn't want to be considered any kind of authority on the matter. There are far more reliable and knowledgeable sources out there. xD

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4 hours ago, Jus Lukin said:

...There are far more reliable and knowledgeable sources out there. xD

Well probably (at most) about 3 nationally who are on BC, so we'll make do and mend with you for now if that's ok? :D

23 hours ago, Jus Lukin said:

Al, I'd recommend doing some reading on the different types of filter, their shapes on a graph, and their uses.

Ah more gear related manuals to read... I really can't wait! xD 

But more seriously, just picking up on a couple of your other points to do with shelfs providing a consistent -12db cut for everything below vs the -12db / octave cut for an HPF and partly trying to give @JohnDaBass a practical answer to one of his Qs...having been nudged in the right direction by Opticaleye (for which many thanks for bearing with me), I've had a bit more of a play with with the LoEQ effect on the B3n and the following triple-effect combination works a treat as an HPF effects patch:

LoEQ shelf set at -12db at 20Hz [x2]

LoEQ HPF set at -12db/octave at 50Hz [x1] 

That works very well - and will be what I use on the B3n going forward; I'm no longer thinking I will need to get a dedicated HPF pedal to protect my cabs at home. Hopefully the AcBsPre can do something similarly effective on the MS-60B for a compact, pedal board solution.

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I'm sure it's been mentioned here before but just a reminder how Fishman recommend  setting up the Platinum Pro Eq depth control. This of course applies to the AcBsPre sim on the Ms60b and the B3.

Depth

Tighten up your sound, or dial out deep-bass feedback with the Depth control. The Depth control works hand in hand with the Bass control to bring out tight and articulate lows:

1. Start with the Depth turned up full (5:00) with the EQ set flat on your bass amp and/or PA.

2. Set the Bass control to full boost.

3. Play the bass and back off the Depth (counter-clockwise) until you hear the sound tighten up, usually between 9:00 and 12:00.

4. Re-set the Bass slider to taste.

I've always found this method to be really effective.

 

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Also :D

Given the fact that the HPF frequency  is the point where the signal is -3db, I'm not sure how necessary two shelving filters @20hz actually are (or even 1!) if you also have a HPF at 50hz. 

If you google images of "12db hpf at 50hz" it would give you some idea why.

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9 minutes ago, Opticaleye said:

Also :D

Given the fact that the HPF frequency  is the point where the signal is -3db, I'm not sure how necessary two shelving filters @20hz actually are (or even 1!) if you also have a HPF at 50hz. 

If you google images of "12db hpf at 50hz" it would give you some idea why.

Well it's because it's cumulative and I think you're maybe assuming that the HPF on the LoEQ on the B3n is as effective as a standalone dedicated HPF pedal and will have the same curve? I'd be very surprised if it was - as mentioned above, I've already found a single LoEQ shelf filter at 30Hz to be better than using the HPF mode at 50Hz. 

My turn to politely suggest you try the suggested combination with the two shelving filters @ 20Hz and let me know if don't find any difference to just the 50Hz HPF :) 

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Just now, Al Krow said:

Well it's because it's cumulative and I think you're maybe assuming that the HPF on the LoEQ on the B3n is as effective as a standalone dedicated HPF pedal and will have the same curve? I'd be very surprised if it was - as mentioned above, I've already found a single LoEQ shelf filter at 30Hz to be better than using the HPF mode at 50Hz. 

My turn to politely suggest you try the suggested combination with the two shelving filters @ 20Hz and let me know if don't find any difference to just the 50Hz HPF :) 

My preference is to boost the bass at 30-50hz and then HPF at 100hz or thereabouts. I doubt if I could hear 1 shelving filter at 20hz if I had a HPF at 50hz especially given the cumulative effect of the natural rolloff on the bass cab.

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11 minutes ago, Opticaleye said:

My preference is to boost the bass at 30-50hz and then HPF at 100hz or thereabouts. I doubt if I could hear 1 shelving filter at 20hz if I had a HPF at 50hz especially given the cumulative effect of the natural rolloff on the bass cab.

Ah, that's says to me we are trying to achieve different things (which is fair enough).

If I wanted to boost the 30 to 50Hz range, I can easily do that with my amp EQ. In practice, I find myself slightly cutting rather than increasing the bass EQ to prevent a muddy / boomy sound and the boost will, if anything be in the mids, to make sure I am cutting through in a live mix.

For HPF purposes, my goal is simply to eliminate the sub-sonic 'crud' below 20Hz (and nothing more or less) to protect my cabs and tighten up the low end. I'm actually hoping to 'hear' very little in terms of tonal change (the less the better!) but to see / feel quite a lot in terms of speaker excursion being reduced. With the B3n LoEQ combination patch I seem to be getting 90% of the way there, so that works for me.

Edited by Al Krow

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