Truly Adjustable HPF?

[HolmeBass]

I am not a fan of DSP except for when I'm sitting down to mix. Perhaps I may convert at some point, but I don't belive the tech is quite there yet for live work, at least for the sounds I try to get.

I'm really curious what the technical hurdle is. I understand that electronics design is complex stuff, but I see some complex stuff out there. How is the slope of a cutoff attained, and is it possible to have a three-way switch that lets the user select 12/24/48db /octave? Is the problem that there aren't enough buyers out there to justify adding that feature?

I looked a little closer at your series 3, and noticed the "12 + 12" curve, which may actually solve my problem (for significantly less than $1000!). 24db/oct is usually what I've found works best while mixing to tame useless freqs while keeping the bass as powerful as possible, although it would be nice to be able to keep that slope while dialing the frequency. As I understand it: there's always a 12db/oct slope at <35Hz, and an additional 12db/oct at <the freq it's set at, resulting in 24db/oct <35 and 12db/oct between 35Hz and the selected freq.

The order form on your site shows up blank, likely due to a security issue, per your suggestion on the site. How might I go about ordering?

That seems like a very solid design to me, the 12 + 12. I wonder what Broughton uses? I also have to wonder whether 48 dB/octave is ever really needed instead of 24. Seems to me like 24dB/octave should always be steep enough, but am willing to listen to others who feel differently.

 

[Reuptake]

I used to do this regularly with my Rane PE51/PE15, an amazingly versatile EQ that made it ridiculously easy to tame the wool and mud out of my SWR rig (Henry 8x8, SM400S), regardless of the room.

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This is almost exactly what I have in mind. It doesn't allow the user to select the slope of the LF shelf, but the user can shelf at a higher frequency and then engage a narrow bass boost in the next eq to compensate. I do this in a DAW frequently. Thanks for the lead!

 

[Reuptake]

That seems like a very solid design to me, the 12 + 12. I wonder what Broughton uses? I also have to wonder whether 48 dB/octave is ever really needed instead of 24. Seems to me like 24dB/octave should always be steep enough, but am willing to listen to others who feel differently.

Last I checked Broughton HPFs sit at 12db/oct. Another thread going on regarding cabinet design wandered into HPF land, which is what inspired this HPF thread for me, where D.A.R.K. reminded me of something that I take for granted when sitting behind a computer:

Agreed- I just see this automatic response of "high pass" all the time, without any real specifics. The Fdeck unit is well liked, but only a 12 db per octave cut with no alignment specified. It really is going to depend on what your port tuning is, coupled with what frequencies you will be feeding the cab and the amount of power you will be using. For sub tuned instruments you may want to go as far as a 48db per octave slope around the port tuning frequency. It takes some experimentation based on the specs to get it right, especially if you are using heavy handed eq to bring forth those sub tunings.

The reason why I usually avoid an HPF with live/rehearsal sound is because it makes my bass sound weak. But that never happens in a DAW, because I always use a steeper than 12db/oct slope.

Combining HPFs in series, like with Fdeck's 12 + 12, makes sense. If one were to use two of Fdeck's 3rd gen boxes, then the 48db slope is theoretically possible, per D.A.R.K.'s suggestion, without getting into super spendy gear.

 

[Ben B]

Cutting bass using the 10-band eq carves too much out of adjacent freqs, as far as I can tell.

That makes sense. I think something like the fdeck HPF + your 10 band graphic equalizer would be all you need to solve the problem. I use fdeck HPF + 7 band GEQ with my double bass and they work well together. If I used the GEQ alone and lowered the left-most slider to get rid of boom, yes it would cut the fat sound of my DB. But the HPF reacts much differently than simply lowering a slider on a GEQ. It cuts the boom, but not the fat bass sound. Once the boom is cut, then the GEQ can be used to boost or lower other frequencies as needed.

I find bass guitar much simpler to EQ than my DB. I plug into an Ampeg. Done.

 

[PraiseBassing]

"The importance of an HPF could not be overstated..."

I don't know,.. in terms of bass guitar stage amplification I think that very often pedal hpf's are redundant. I'm pretty sure I've read on these very pages that virtually every amplifier built in the last few decades has high pass filtering built in. No doubt there's a huge trend on talkbass the last few years, but I wonder.... (Amplifier engineers, please correct me if I'm wrong here!)

As far as the signal that hits the front-of-house desk, yeah- there's extra hpf going on! However, every engineer I have ever worked with likes to have that control themselves.

Maybe I'm way off base in this, and I'm in no way trying to be "snarky", but I rarely see a pedal hpf used by an experienced touring professional. That doesn't necessarily mean it's a bad idea to use one, but I do wonder if this is an internet forum-nursed "necessity".

***All of the above does NOT apply to amplifying an upright bass! That is an entirely different animal!***


Expecting some arrows, but just trying to have an honest (and respectful) relevant discussion.

Following this philosophy, wouldn’t a pre-amp(on-board, pedal, or amplifier) before the mixer preamp be redundant also?

 

[PraiseBassing]

Last I checked Broughton HPFs sit at 12db/oct. Another thread going on regarding cabinet design wandered into HPF land, which is what inspired this HPF thread for me, where D.A.R.K. reminded me of something that I take for granted when sitting behind a computer:



The reason why I usually avoid an HPF with live/rehearsal sound is because it makes my bass sound weak. But that never happens in a DAW, because I always use a steeper than 12db/oct slope.

Combining HPFs in series, like with Fdeck's 12 + 12, makes sense. If one were to use two of Fdeck's 3rd gen boxes, then the 48db slope is theoretically possible, per D.A.R.K.'s suggestion, without getting into super spendy gear.

What gear and tone settings are you using? Needing a 48db slope sounds like some things are “extreme”.

 

[scotch]

Following this philosophy, wouldn’t a pre-amp(on-board, pedal, or amplifier) before the mixer preamp be redundant also?

By "mixer preamp" do you mean the foh board preamp? If so, then no, I wouldn't necessarily call that scenario redundant although there are multiple pre's involved. I imagine you're also thinking more of equalization rather than gain staging? Still, I wouldn't call that scenario redundant.

Equalization/tonal needs are often different at foh than on-stage. That's one of the reasons why you *generally* see foh engineers that want a clean, unprocessed feed straight from your instrument. But this is all getting away from the op's topic a little.

 

[scotch]

Part of this is my fault, since I didn't really go into detail about my situation and goals. I've found that the less I put between my bass and my power amp (GX7), the better. The only problems I've run into is that the preamp gain in my bass is insufficient, so I need some kind of preamp, I do need better eq control than the knobs on my bass, and I crank out noise and destruction-producing frequencies down to negative infinity. I like the sound of my MXR bass DI, and I have an MXR 10-band eq pedal that gives me a little more control, but I want to both boost the bass and at the same time cut bass below a certain level. Cutting bass using the 10-band eq carves too much out of adjacent freqs, as far as I can tell.

When playing live, I don't really worry about FOH, because either they know what they are doing, or they don't, and either way all I can really control is the sound and safety of my own rig. I just point to the direct out on my pedal. Really, I'm either looking for a stand-alone HPF, or a replacement for my preamp that offers control over where and how much I cut bass frequencies.

To belabor the point a little (sorry), take for example how compression is built into many preamps at this point. However, compression is usually relegated to one knob called "Amount". Sure, mabe in all reality this works just fine, but dammit I want to fiddle with the threshold, attack, release, input gain, output gain, and knee separately! I would rather have a preamp with only one knob called "Gain", outsourcing eq and compression. I feel the same way about HPF/LPF, although I do feel someone should be able to squeeze this into a nice parametric eq.

Understood. You seem to have a need for a very specific amplification solution. This is indeed a little different from the "hpf-osis" I'm noticing on talkbass! ;-)

 

[Reuptake]

What gear and tone settings are you using? Needing a 48db slope sounds like some things are “extreme”.

Using a variety of basses, some 5-string, lowest tuned down to Ab, running into a MXR m80 bass DI and an MXR 10 band eq pedal, feeding one channel of a QSC GX7 which powers a 2x15 cab with Emminence Kappa Pro 15As. I like to push the lower end of the eq as much as I can, depending on what's appropriate for the song, while still being able to tell what note I'm playing.

I think the idea behind the 48db/oct below the tuning of the cab is that we just don't want to hear that sound at all. I like the sound clarity/simplicity of my soundchain (but am not married to it), so I don't feel like spending loads of cash on a nice bass head. Everything about the band sounds better when I turn down, except that nobody can hear the bass. If I try to carve out the low freqs with the eq, I sound like I'm spanking a cardboard box. My experience mixing tells me that the solution is HPF. Whether 48db/oct is really necessary is clearly debatable. I am physically incapable of being happy with a new feature that can not be tweaked.

 

[Wasnex]

Using a variety of basses, some 5-string, lowest tuned down to Ab, running into a MXR m80 bass DI and an MXR 10 band eq pedal, feeding one channel of a QSC GX7 which powers a 2x15 cab with Emminence Kappa Pro 15As. I like to push the lower end of the eq as much as I can, depending on what's appropriate for the song, while still being able to tell what note I'm playing.

I think the idea behind the 48db/oct below the tuning of the cab is that we just don't want to hear that sound at all. I like the sound clarity/simplicity of my soundchain (but am not married to it), so I don't feel like spending loads of cash on a nice bass head. Everything about the band sounds better when I turn down, except that nobody can hear the bass. If I try to carve out the low freqs with the eq, I sound like I'm spanking a cardboard box. My experience mixing tells me that the solution is HPF. Whether 48db/oct is really necessary is clearly debatable. I am physically incapable of being happy with a new feature that can not be tweaked.

IMHO 48db/oct is great if the idea is to set the HPF just below the cab tuning. Below the port frequency the driver unloads and doesn't produce much SPL despite the massive excursion. I suggest hooking up your amp to a tone generator and performing a frequency sweep to get an idea how the low end response of your cab rolls off and the excursion picks up. The driver should be at minimum excursion at the port tuning frequency. Plenty of online tone generator are available.

 

[PraiseBassing]

Using a variety of basses, some 5-string, lowest tuned down to Ab, running into a MXR m80 bass DI and an MXR 10 band eq pedal, feeding one channel of a QSC GX7 which powers a 2x15 cab with Emminence Kappa Pro 15As. I like to push the lower end of the eq as much as I can, depending on what's appropriate for the song, while still being able to tell what note I'm playing.

I think the idea behind the 48db/oct below the tuning of the cab is that we just don't want to hear that sound at all. I like the sound clarity/simplicity of my soundchain (but am not married to it), so I don't feel like spending loads of cash on a nice bass head. Everything about the band sounds better when I turn down, except that nobody can hear the bass. If I try to carve out the low freqs with the eq, I sound like I'm spanking a cardboard box. My experience mixing tells me that the solution is HPF. Whether 48db/oct is really necessary is clearly debatable. I am physically incapable of being happy with a new feature that can not be tweaked.

IMHO 48db/oct is great if the idea is to set the HPF just below the cab tuning. Below the port frequency the driver unloads and doesn't produce much SPL despite the massive excursion. I suggest hooking up your amp to a tone generator and performing a frequency sweep to get an idea how the low end response of your cab rolls off and the excursion picks up. The driver should be at minimum excursion at the port tuning frequency. Plenty of online tone generator are available.

Completely agree with @Wasnex here.

Also, multiple filters will probably be your best bet since you are trying to use it for both purposes. One set just below the cab tuning, and another set where you need it to clean up any mud.

It is especially useful with large boosts to the bass frequencies of most amps. While the bass control is usually centered at a good frequency, it usually boosts low frequencies that are unneccessary along with it.

 

[PraiseBassing]

By "mixer preamp" do you mean the foh board preamp? If so, then no, I wouldn't necessarily call that scenario redundant although there are multiple pre's involved. I imagine you're also thinking more of equalization rather than gain staging? Still, I wouldn't call that scenario redundant.

Equalization/tonal needs are often different at foh than on-stage. That's one of the reasons why you *generally* see foh engineers that want a clean, unprocessed feed straight from your instrument. But this is all getting away from the op's topic a little.

I will not go much deeper in this conversation in an attempt to keep this thread on track; however, a HPF before the board is as redundant as any cut or boost in eq. There are many ways to use a HPF. Every situation is different and needs to be looked at carefully to find the best solution. I will not advise letting general practices of sound engineers dictate those decisions since they are not paying for your time or equipment.

If there is any concern of how your HPF will affect your signal to the board, there are more involved send methods that can be used to seperate what is sent to the board and what is sent to an amp on-stage.

 

[aprod]

I have been playing for 30 plus years and have never heard of a HPF applied to a bass rig. What am I missing?

 

[Stumbo]

I will not go much deeper in this conversation in an attempt to keep this thread on track; however, a HPF before the board is as redundant as any cut or boost in eq. There are many ways to use a HPF. Every situation is different and needs to be looked at carefully to find the best solution. I will not advise letting general practices of sound engineers dictate those decisions since they are not paying for your time or equipment.

If there is any concern of how your HPF will affect your signal to the board, there are more involved send methods that can be used to seperate what is sent to the board and what is sent to an amp on-stage.

Maybe @JimmyM will stop by and comment.

 

[Stumbo]

I have been playing for 30 plus years and have never heard of a HPF applied to a bass rig. What am I missing?

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

 

[Ben B]

I have been playing for 30 plus years and have never heard of a HPF applied to a bass rig. What am I missing?

Maybe nothing. I don't use a HPF for electric bass, but find it's very useful for double bass. But even for electric bass, it could help remove any undesirable boom you hear and it can give you some degree of speaker protection. If you are not having issues with boom or speaker failure, you may not need a HPF. Your choice of amps and cabinets are a big factor.

 

[Wasnex]

I have been playing for 30 plus years and have never heard of a HPF applied to a bass rig. What am I missing?

IMHO, an HPF is most useful (or perhaps essential) with bass reflex speakers. See my post #50 this thread. Basically an HPF limits unmusical garbage that wastes energy and muddies up your sound. By cutting subsonics, you increase headroom, protect your speakers, and tighten up your tone...and if you do it right you can still have a deep, thick, fat bass. Keep in mind electric basses don't typically put out a strong fundamental to begin with, so what you hear is primarily to first 1st overtone/second harmonic. I.E. open E is about 40Hz, but you hear mainly 80Hz.

I used to run huge levels of boost centered at 40Hz (18dB) on my Ampeg 810E and I thought it sounded great. I used one parametric filter with 12dB of boost that impacted the range of about a 4th, and a second filter with 6dB of boost that covered the range of about an octave. To find 40Hz I set the filters to a notch and peaked the fundamental of my open E string. I am sure the rolloff below 40hz was pretty steep. You could feel the impact of every pluck standing next to that rig and the notes were tight and focused.

 

[monkeyland]

Except that most rack mount graphic eq's do not have adjustable frequency HPFs and LPFs, and none that I know of that do have slopes greater than 12dB/octave.

If you go back to the earlier Yamaha products like the GEQ1231, they have an adjustable HPF but no LPF. A couple of Behringer models have 12dB/octave HPF and LPF, as does a BBE model, but generally they are not all that common. Most pro level products by DBX, KT, Ashley, etc. do not have both HPF and LPF that are adjustable as this is (was) usually done within the speaker processing system.

I still have 3 of the Peavey EQ31FX, which had variable HP/LP, sitting on a shelf in my garage. They were very useful to me back when they were in use. I wonder if they were one of Frank Appletons creations?

 

[Stumbo]

I will not go much deeper in this conversation in an attempt to keep this thread on track; however, a HPF before the board is as redundant as any cut or boost in eq. There are many ways to use a HPF. Every situation is different and needs to be looked at carefully to find the best solution. I will not advise letting general practices of sound engineers dictate those decisions since they are not paying for your time or equipment.

If there is any concern of how your HPF will affect your signal to the board, there are more involved send methods that can be used to seperate what is sent to the board and what is sent to an amp on-stage.

Unless you WANT/NEED to control what is sent to the board for your tone purposes. @JimmyM wrote the book on this.

 

[PraiseBassing]

Unless you WANT/NEED to control what is sent to the board for your tone purposes.

100% agree with you. But there are schools of thought that it is taboo to send a processed signal to the board. I was offering the idea that you are able to patch your foh send into a part of your board that doesn't have the HPF affecting it.