Variable HPF/LPF on Q/Strip

[dave_bass5]

Just read his on TB. This was posted by Tech21.

This is news to me. Did anyone else know about this?

'The HPF/LPF is based on the unit set flat. If you adjust the mids above or below the flat setting it changes the set point for the filters. Try not to get bogged down in numbers as it's a waste of time. Just use your ears and set to what "sounds" good. Much of it depends on the final destination of your sound. Amp, direct, powered monitor full PA system etc. Be judicious with EQ as they also change the phase of the signal.'

[Jack]

All filters work that way. You can affect the -3dB point by using a shelving control. Here's a post with Charlie doing the opposite, boosting the bass and leaving it there whilst changing the hpf control, but of course the opposite to that opposite (which is what you're talking about) would also occur.

 

If you have a fixed high pass filter that's say -3dB at 100Hz then a flat shelving boost in the bass of +5dB would move all of that curve up and now your -3dB point would be something like 80Hz or so.

[dave_bass5]

I thought a HPF was something you set to a certain freq. In the manual it says its preset at 45hz.

Sorry, i don’t understand why it would be designed to move in an uncontrollable way. 

[Jack]

No, the hpf is fixed but all eq is cumulative. Lets say you were to have an amp with a treble control which is 5kHz and up shelving, and also a presence control which is 7KHz shelving. If you turn both up 5dB then they add right, so you've got +5dB from 5KHz to 7KHz and then a total of +10dB from 7KHz up. You could also turn the treble up +5dB and the presence DOWN *7dB. That way you've got a hump of +5dB from 5 to 7KHz and then after 7KHz you're back to 'flat'.

 

You can do whatever you want with the eq, and a lot of the controls will affect other controls. The HPF is no different and can be affected with the bass eq (if it's shelving) or a parametric band if that will go low enough.

[dave_bass5]

41 minutes ago, Jack said:

No, the hpf is fixed but all eq is cumulative. Lets say you were to have an amp with a treble control which is 5kHz and up shelving, and also a presence control which is 7KHz shelving. If you turn both up 5dB then they add right, so you've got +5dB from 5KHz to 7KHz and then a total of +10dB from 7KHz up. You could also turn the treble up +5dB and the presence DOWN *7dB. That way you've got a hump of +5dB from 5 to 7KHz and then after 7KHz you're back to 'flat'.

 

You can do whatever you want with the eq, and a lot of the controls will affect other controls. The HPF is no different and can be affected with the bass eq (if it's shelving) or a parametric band if that will go low enough.

Ah yes, i understand that EQ settings will have a knock on effect with others, but im only talking about the preset freq that the HPF is set to, which T21 said moves. I understand the effectiveness of it will change, depending on what its fed, but surely the set freq doesn't change as such?

[Jack]

Filters are described by their 3dB point. Even though it's mechanically doing the same thing, you can move the 3dB point by feeding it more or less 45Hz using the shelving bass control.

[dave_bass5]

1 minute ago, Jack said:

Filters are described by their 3dB point. Even though it's mechanically doing the same thing, you can move the 3dB point by feeding it more or less 45Hz using the shelving bass control.

But T21 said its linked to the Mid controls. I realise the Mid sweep goes down to 40hz though.

[Jack]

4 minutes ago, dave_bass5 said:

But T21 said its linked to the Mid controls. I realise the Mid sweep goes down to 40hz though.

Well the center point does yes, so obviously if the center is set below 45Hz then it will affect the LPF but don't forget that it will also affect frequencies to either side of the center. Tech 21 don't seem to quote the q, which is the width of the filter, but let's take a look.

 

Here's a 10dB boost at 143Hz but you can see that even there it's having a slight affect on 45Hz (the pale blue '1' line). This is with a q of 2, which is half an octave.

 

So here's a 45Hz high pass filter. With another eq boost miles away at 1200Hz they aren't affecting each other.

 

But move that same boost down to the 40Hz that your Qstrip is capable of and you can see how that's massively affected the filter. It is the same 45Hz high pass filter but if I had to eyeball guess I'd say the new -3dB point is about 33Hz.

 

Of course, we don't know how wide the Q is on the Q strip. Choice of filter width is what separates a semi-parametric eq like the q-strip from a fully-parametric eq. The q-strip is fixed (as there's no bandwith control) but we don't know what it's fixed at. it may actually vary depending on where the other controls are set. Generally in eqing we want narrow cuts to get rid of unwanted boom or feedback and broad boosts to add in things we want more of, but this is just a huge generalisation. All of this has been done assuming a q of 2, what happens if we widen that? If your q-strip has a q of 0.5 on the mid controls then we can move that control all the way up to 150Hz or so and it's still BOOSTING at 45Hz, despite the hpf.

 

It's even having a tiny effect at 863Hz!

 

 

I know I'm not making this simpler, but that's because it's not simple. Tech21 were right, twiddle until it sounds good.

[dave_bass5]

Thanks for taking the trouble to explain all that. I follow some, phase out at other bits, but seem to have my answer.

I was thinking it was more variable in a controlled way. 

[Tech21NYC]

8 hours ago, dave_bass5 said:

But T21 said its linked to the Mid controls. I realise the Mid sweep goes down to 40hz though.

 

I didn't really say it was linked but more that all the controls interact with one another which is true of most EQ. If you want to do more surgical EQ's like a notch filter, that is a very steep curve which is good for dealing with a node or problem frequency or feedback. Those types of EQ's aren't really musical they are for solving very specific problems.

It's always a bit puzzling to me that over the years many players want "full range" preamps and speakers etc and then have to use HPF/LPF to get back to where the

[Tech21NYC]

8 hours ago, Jack said:

Tech 21 don't seem to quote the q, which is the width of the filter, but let's take a look.

We use a mid bandwidth Q on the pedal which is more musical. The narrow Q is great for "fixing" things and a wide Q can sometimes be too subtle. It really depends on your application.

[dave_bass5]

11 minutes ago, Tech21NYC said:

 

I didn't really say it was linked but more that all the controls interact with one another which is true of most EQ. If you want to do more surgical EQ's like a notch filter, that is a very steep curve which is good for dealing with a node or problem frequency or feedback. Those types of EQ's aren't really musical they are for solving very specific problems.

It's always a bit puzzling to me that over the years many players want "full range" preamps and speakers etc and then have to use HPF/LPF to get back to where the

Maybe i just miss interpreted this statement

If you adjust the mids above or below the flat setting it changes the set point for the filters.

[Jack]

2 hours ago, Tech21NYC said:

We use a mid bandwidth Q on the pedal which is more musical. The narrow Q is great for "fixing" things and a wide Q can sometimes be too subtle. It really depends on your application.

I'm the kind of person that'll geek out over the details and in the past six months or so I've taken to scoping pretty much every piece of gear I've got.

 

I do totally understand why one would keep specifics like that close to one's chest. Not only would it hinder people copying or cloning but often specs hinder rather than help. You need only only look at amps and their power ratings.

[Tech21NYC]

There was really nothing hidden from anyone. All EQ's work in the same manner. Before the age of the internet, players just bought gear turned some knobs and used it. There was no need to become an engineer to use a piece of gear. In the end it should still be that way. Let the engineers do the geeky stuff and let the musicians do what they do  best which is play. Time is better spent playing than taking electronic measurements. How a waveform looks on an FFT or scope doesn't help the average player using a pedal or amp on a gig. I have no idea how the various systems in my car work. I get in, turn it on and drive...

When I'm on a gig and my vocal wedge has too much low end I know to use the HPF. That works. What works better is more low tech. I place the wedge on a milk crate which decouples it from the floor and also gets it a bit higher so I don't need to run it as loud. I figured that out long before I knew what a HPF was.

[Al Krow]

36 minutes ago, Tech21NYC said:

There was really nothing hidden from anyone. All EQ's work in the same manner. Before the age of the internet, players just bought gear turned some knobs and used it. There was no need to become an engineer to use a piece of gear. In the end it should still be that way. Let the engineers do the geeky stuff and let the musicians do what they do  best which is play. Time is better spent playing than taking electronic measurements. How a waveform looks on an FFT or scope doesn't help the average player using a pedal or amp on a gig. I have no idea how the various systems in my car work. I get in, turn it on and drive...

When I'm on a gig and my vocal wedge has too much low end I know to use the HPF. That works. What works better is more low tech. I place the wedge on a milk crate which decouples it from the floor and also gets it a bit higher so I don't need to run it as loud. I figured that out long before I knew what a HPF was.

Part of me completely agrees with what you're saying. But it doesn't have to be either or does it?

Alex Claber was a bass player before he started making Barefaced Cabs so was Doug at Darkglass and the list goes on...

Bass is our passion and making great music has gotta be right at the top of what's great about it. Many folk simply drive cars, but car enthusiasts often love understanding the intricacies of what makes a car engine tick. And similarly getting into the detail of sound, frequencies, power, how it all comes to be produced and interacts in making for great tone even if it's only us bassists who can hear it or care about it and even then sometimes only at home and not in a band mix with ear plugs in!

If someone finds enjoyment in taking electronic measurements and getting a deeper understanding of their kit that way, it's certainly not for me to tell them that their time could be better spent playing. Why seek to limit how far any of us take our passion for bass and what direction that might take?

[Tech21NYC]

If you have an interest in the technical side of things there is absolutely nothing wrong with learning about it. Our designer and owner as well as our chief engineer are both guitar and bass players. As someone that deals with the end user on a regular basis, my point is about the internet in general where people with little understanding of the science read some information (many times misinformation) and have no idea what it really means or how it applies. They go down this rabbit hole of research and analysis, taking measurements etc. only to get to a gig and struggle with the physics of the environment and wonder why the aforementioned seemed to fail them.

 

 

 

 

[Gareth Hughes]

Thanks to everyone above here for taking the time to explain things. I have a Q-Strip, and absolutely love it - placed in the effects loop of a Genz-Benz Streamliner has given me such happiness. I initially thought the hpf wasn’t high enough - I’ve gotten used to a variable one - but the pedal is so responsive to small adjustments that I’ve gotten everything I need from it. Thanks again everyone.

[itu]

On 18/03/2020 at 19:49, Tech21NYC said:

...my point is about the internet in general where people with little understanding of the science read some information (many times misinformation) and have no idea what it really means or how it applies. They go down this rabbit hole of research and analysis, taking measurements etc. only to get to a gig and struggle with the physics of the environment and wonder why the aforementioned seemed to fail them.

As this is very true, it is not too flattering to read specs from manufacturers' pages that has very little to do with real world. As an example: try to find max SPL, or sensitivity, or -3 dB freq range from cab makers? No chance. But you certainly get wattage! Thanks a lot.

[itu]

Yes, I studied acoustics in a university, music (electric bass) in a music school, and have been working with pro and consumer electronics for 30+ years. And while I play, I am also interested in the technology. True, I may not be your average customer, but we exist.