High Pass Filters

[Jus Lukin]

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Edited March 1, 2022 by Jus Lukin

[fretmeister]

I use them in my Helix all the time.

Very useful kit.

[funkydoug]

Yeah 

4 hours ago, PaulWarning said:

Trace Elliot GP12 does the job for me, or any parametric EQ should do it

This was what I used to do with the trusty red slider. My ABM doesn't really do it. 

 

I've ended up going for a Broughton. I get the feeling it'll become more and more common on new amp and pedal designs but for now the options are relatively limited. 

Cheers, Doug

[Al Krow]

Cheers guys - LOTS of helpful comments, appreciated - thanks!

@Jus LukinSounds from what you're saying that the Zoom MS-60B ain't going to cut the mustard as an HPF? If I'm looking to take out the high energy sub audio range, I presume I need to pretty much get everything below around 20Hz (which is where sub audio begins is generally accepted as starting) and if the Zoom only kicks in at 40Hz it's already missed the boat?  cutting stuff in the 20Hz to 40Hz range (in particular low B string notes) that I'd want to keep.

Here's my bit of online research to put into the mix:

Thumpinator - cuts off everything under 30Hz - starting to creep into the audio range, but not by too much: a low open B is 31 Hz; you can obviously get lower than this with an octaver and in fact the E below the open E string is 20Hz - partly I guess why I bang on about wanting octavers to be able to track down to the open E / E on the B string without glitching**.

The Broughton HPF / LPF - 'The high pass filter is a 12 dB per octave low frequency filter. The HPF knob controls the cutoff frequency and ranges from 25 Hz to 190 Hz'. Ok if that is getting everything below 25 Hz, that sounds like it could work really well?

I also really like the flexibility of having a LPF 330 Hz to 20 kHz in one compact package. If I set the LPF to (say) 12 kHz, that should also deal with all that annoying high end hiss that pedals / amps / tweeters can produce?

Given the limited options available which DB has pointed out and the fact that, as Jus Lukin says, a PEQ is no HPF, I think the Broughton is looking like a strong contender.

 

**Apparently the newly released Broughton Synth Voice is one of the very few analog octavers that can do this. Looks like I've got a potential bulk order going out shortly Josh Broughton! (and a separate one for a larger pedal board, lol!) - maybe Josh will cut me a deal on the shipping costs?

 

1 hour ago, funkydoug said:

I've ended up going for a Broughton. I get the feeling it'll become more and more common on new amp and pedal designs but for now the options are relatively limited. 

Cheers, Doug

Just seen your post - looks like you and me both!

Edited January 30, 2018 by Al Krow

[Jus Lukin]

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Edited February 25, 2022 by Jus Lukin

[Bigwan]

Unless you're spending super coupons on reproducing the fundamental a 40Hz roll off vs anything lower won't really be audible on a 5 string IME

[Al Krow]

12 minutes ago, Jus Lukin said:

Other way round, old boy!

If the Zoom does start cutting at 40hz (which is only what I read so far, but does tally with my experience) then it begins to cut at that frequency, and the attenuation continues from there down.  It gets very complicated with the shape of the corner and stuff, but for our purposes, the slope of -12db/oct will leave 40hz basically untouched. Everything from there on down will be increasingly attenuated, so by an octave down (20hz) any signal will have been reduced by 12db. By the time you get to 10hz, another octave down, any signal there will be reduceded by 24db.

The Thumpinator kicks in lower, at 30hz so actually affects a smaller portion of the frequency spectrum. Beginning at 30hz, it won't touch the lowest fundamentals of a standard tuned 5-string, but only attenuate signal below that point. However, at a steeper slope (I forget if the Thumpinator is -24 or -36db/oct, but lets say 24...) at one octave down, 15hz will have been attenuated by 24db. By the next octave, 7.5hz, it will have been attenuated by 48db.

So, roughly speaking and bearing in mind that these are 'guestimate' specs, the Zoom should leave a four-string intact and by 20hz be reducing the signal by 12db. The Thumpinator will leave a five-string intact, and by 20hz be reducing the signal by something like 18 or 20db.

No, I think we are saying (or at least intending) the same thing i.e. the Zoom is starting the attenuation at a higher point than I'd like and cutting everything below that so, as you say, it's attenuating a 5 string bass. The low B string is already typically the least 'present' of the strings audibly, that's why for me the Zoom is not going to 'cut the mustard' as an HPF.

The Broughton is leaving the B string entirely unattenuated by getting down as low as 25Hz and only cutting below that; which is why it wins over the Zoom in my reckoning. The Zoom patch however has zero incremental costs, given I have the pedal already...

 

[Jus Lukin]

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Edited February 25, 2022 by Jus Lukin

[Al Krow]

2 minutes ago, Jus Lukin said:

Ah, I see. There is a tiny chance I misinterpreted your post! 

Yes, but my fault - I could have expressed it a lot more clearly. Now edited!  

[Mottlefeeder]

8 hours ago, BigRedX said:

There are HPFs and there are HPFs.

The OP is asking about devices like the Thumpinator which are designed to remove sub-audible frequencies from your signal path which are below normal human hearing and therefore don't contribute in any way to the sound of the bass. These devices all have a fixed cut-off frequency (around 30Hz) and slope of at least 24dB/oct. You can't hear them working because you can't hear the frequencies they are removing, but your amp will have been wasting power trying to reproduce them, and they are potentially damaging to your speakers. This has nothing to do with corrective EQ for taming excessive audible low frequency boom.

The OP asks about protecting speakers "etc" so I do not think that excludes variable frequency high pass filters, which I agree only cut at 12dB/octave, but are much more versatile than a fixed frequency device cutting at 36dB/octave.

In my case, my reflex cabs were designed using WinISD, and the ports are tuned in the low 50s, although I play a 5-string. According to WinISD, the speakers could be damaged by a strong 30Hz signal,  but adding a 12dB/octave filter tuned to 40Hz removes that risk, so I use an FDeck clone for speaker protection, and where necessary, I increase the turnover frequency to get rid of boominess. In my experience, using a pair of Jack 10s, or a pair of reflex 10s, you can take out most of the bottom octave before the sound starts to get 'bass-lite'.

David

[obbm]

Just out of interest which bass heads actually incorporate a High Pass Filter.  I know that the Mesa D800+ does, so who else? 

[redbandit599]

I've been thinking about this too, but just contacted GK re my MB500 Fusion.

They say this amp has a roll off beginning between 40 and 50 hz. So definitely worth a check before ordering.

 

[Dood]

46 minutes ago, obbm said:

Just out of interest which bass heads actually incorporate a High Pass Filter.  I know that the Mesa D800+ does, so who else? 

The Bergantino B|Amp has an adjustable HPF! It also has a feedback filter for those playing double bass as well as a full parametric 4 band EQ which in itself would allow for low end roll off too. 

[dannybuoy]

15 minutes ago, redbandit599 said:

I've been thinking about this too, but just contacted GK re my MB500 Fusion.

They say this amp has a roll off beginning between 40 and 50 hz. So definitely worth a check before ordering.

 

Indeed a lot of amps feature one but just don't mention it, as some designers consider it a standard thing rather than a selling point! Hence @Al Krow might not need one at all with the Darkglass head! Same goes for anything Genz Benz / Genzler, not sure about other makes.

[redbandit599]

Yep, the guy from GK actually said "most amps have this" so " you don't need an HPF"

[Al Krow]

53 minutes ago, dannybuoy said:

Indeed a lot of amps feature one but just don't mention it, as some designers consider it a standard thing rather than a selling point! Hence @Al Krow might not need one at all with the Darkglass head! Same goes for anything Genz Benz / Genzler, not sure about other makes.

Ok so here's my issue. Just bought an end-of-line Yammy BB1025. Loving it. Dialled the tone completely back on the bass to get a more 'sub-by' vibe and been playing a couple of reggae riffs for a bit of fun. Now the Yammy P-pups, although they are passive, can hold their own with the best of the active pups IMO; and I'm finding all of a sudden that both my VK210 (with DG head) and Mesa 212 (with M6) cabs are physically rattling! Not massively but noticeably. The gain and volume dials are all set pretty modestly - well below rehearsal or gig volumes.

No similar rattle with my Warwick, Sandberg or Ibanez basses.

Now the rattling disappears, for sure, if I dial the bass EQ back; but for reggae, techno etc actually it's all about the bass (excuse the pun!) at every level (oh ok that and the groove).

So it got me thinking: if I could eliminate the high energy sub audio frequencies (20Hz and below) with an HPF that should allow me to dial back in the audio bass frequencies but still get rid of the shake rattle and roll on my cabs, and I can then get a full on sub-by bass sound?

Does that sound about right?

Edited January 30, 2018 by Al Krow

[dannybuoy]

As I said, check with Dougie Darkglass but I think the M900 is already rolling off those subsonics. You probably want to roll off a bit higher than you think, which makes the Broughton a good candidate with its adjustable frequency.

But also try some other solutions. How and where are the cabs situated? If you’re getting this at home and haven’t tried it out at a rehearsal or gig yet, are you sure there’s not something else in the room resonating that sounds like it’s coming from the cab? Try repositioning the cab or putting some isolation under it (a pillow will do if you don’t have a gramma pad to hand!).

[lee650]

I've always wondered if a thumpinator to would benefit me! I use a GK 100 rbs 2 which I've read is notorious for blowing up speakers, I wondered whether it would help protect my Bergantino AE 210

Edited January 30, 2018 by lee650

[funkydoug]

4 hours ago, obbm said:

Just out of interest which bass heads actually incorporate a High Pass Filter.  I know that the Mesa D800+ does, so who else? 

ABM 500 / 600 / Neo etc definitely don't have one as standard. The ABM 1000 does though (and maybe the 1200?), they made a decision to protect speakers from peaks of 2kW. Got a great email from Ashdown today about it.

[BigRedX]

18 hours ago, Al Krow said:

Cheers guys - LOTS of helpful comments, appreciated - thanks!

@Jus LukinSounds from what you're saying that the Zoom MS-60B ain't going to cut the mustard as an HPF? If I'm looking to take out the high energy sub audio range, I presume I need to pretty much get everything below around 20Hz (which is where sub audio begins is generally accepted as starting) and if the Zoom only kicks in at 40Hz it's already missed the boat?  cutting stuff in the 20Hz to 40Hz range (in particular low B string notes) that I'd want to keep.

Here's my bit of online research to put into the mix:

Thumpinator - cuts off everything under 30Hz - starting to creep into the audio range, but not by too much: a low open B is 31 Hz; you can obviously get lower than this with an octaver and in fact the E below the open E string is 20Hz - partly I guess why I bang on about wanting octavers to be able to track down to the open E / E on the B string without glitching**.

The Broughton HPF / LPF - 'The high pass filter is a 12 dB per octave low frequency filter. The HPF knob controls the cutoff frequency and ranges from 25 Hz to 190 Hz'. Ok if that is getting everything below 25 Hz, that sounds like it could work really well?

I also really like the flexibility of having a LPF 330 Hz to 20 kHz in one compact package. If I set the LPF to (say) 12 kHz, that should also deal with all that annoying high end hiss that pedals / amps / tweeters can produce?

Given the limited options available which DB has pointed out and the fact that, as Jus Lukin says, a PEQ is no HPF, I think the Broughton is looking like a strong contender.

 

**Apparently the newly released Broughton Synth Voice is one of the very few analog octavers that can do this. Looks like I've got a potential bulk order going out shortly Josh Broughton! (and a separate one for a larger pedal board, lol!) - maybe Josh will cut me a deal on the shipping costs?

Your research has missed some very important points.

1. No HPF will "cut off everything" below a certain frequency. What they do is progressively attenuate frequencies from the cut off point downwards according to the filter slope. Those frequencies will still be present but they are reduced in level more as you go further down from the cut off frequency. SFX have a frequency plot which shows the effect of the Thumpinator on their web site.

2. You have ignored everything else in the signal path including the human ear. While normal human hearing goes down to 20Hz, if you look at any frequency plots you will see that sensitivity drops off significantly from 160Hz downwards, so most of what you are hearing with your octaver on the open E string are the harmonics rather than the 20Hz fundamental - the brain is very good at filling in this missing frequency information for you. Also unless your rig includes PA style cabs specifically designed to reproduce signifiant levels of sub bass ( which case you should be using an active crossover and you won't need a HPF) your cabs will struggling to project these low frequencies at the same level as the higher ones.

3. Finally the design of the HPF itself is very important. IME a higher cut off frequency with a steeper slope (24dB/oct rather than 12dB/oct) is going to be far more effective at removing the potentially speaker damaging frequencies. Go too low with too gentle a slope and it won't be removing enough to be doing a worthwhile job of protecting your speakers. Also as has already been said many filter designs will as a by-product of the way they work add a slight peak to the signal at the cut off point - which is something you really want to avoid on one aimed at removing sub-audible frequencies. AFAIK only the Thumpinator is designed specifically to minimise this peak.

Edited January 31, 2018 by BigRedX

[CameronJ]

This thread is the sole reason for me withdrawing my Micro Thumpinator from sale...

[Osiris]

21 hours ago, Jus Lukin said:

The problem with using a parametric EQ is that it will cut around a certain frequency- as you get further away from that (it's often called a centre frequency, if that helps) the signal level rises again. Or to put it another way, signal above and below your chosen frequency is allowed to pass. Set to 20hz, with a Q to avoid affecting 30hz for a five string, will also be leaving 10hz and below untouched. A parametric is no HPF unfortunately.

While this may be true (I'm no expert on these things so I'm quite happy to accept what you say  ) I have had some great results using the Ba PEQ model on my Zoom MS-60B for reducing the lowest of the lows with my little 1x12 cab that I use for rehearsals. I use it with my Genzler Magellan 350 which has excellent built in HPF'ing, so it may well be due to the diminutive dimensions of the cab that is the limiting factor, but the speaker seems to 'breathe' more easily, for want of a better description. There isn't a massive impact on the low frequencies other than a subtle tightening up of the low end. It may not be a true HPF but it certainly helps for what I use it for. 

[Bigwan]

31 minutes ago, BigRedX said:

Also as has already been said many filter designs will as a by-product of the way they work add a slight peak to the signal at the cut off point - which is something you really want to avoid on one aimed at removing sub-audible frequencies. AFAIK only the Thumpinator is designed specifically to minimise this peak.

This effect is mostly down to design compromises made to allow the filter to be variable. The filter is, as a result, not ideal. The Thumpinator isn't specifically designed to minimise this peak, per se, but the filter doesn't have to be compromised in the same way. The filter design used in the thumpinator has been around for donkey's years, it's a standard electronic building block (see any active analogue filter design textbook for a 4th order Sallen Key filter).

Edited January 31, 2018 by Bigwan

[BigRedX]

7 minutes ago, Osiris said:

While this may be true (I'm no expert on these things so I'm quite happy to accept what you say  ) I have had some great results using the Ba PEQ model on my Zoom MS-60B for reducing the lowest of the lows with my little 1x12 cab that I use for rehearsals. I use it with my Genzler Magellan 350 which has excellent built in HPF'ing, so it may well be due to the diminutive dimensions of the cab that is the limiting factor, but the speaker seems to 'breathe' more easily, for want of a better description. There isn't a massive impact on the low frequencies other than a subtle tightening up of the low end. It may not be a true HPF but it certainly helps for what I use it for. 

Some digital parametric EQs are intelligent enough to go into HPF/LPF mode as they approach the the lower and upper limits of their frequency range. The EQ on my Tascam digital desk certainly worked in that way.

[BigRedX]

3 minutes ago, Bigwan said:

This effect is mostly down to design compromises made to allow the filter to be variable. The filter is, as a result, not ideal. The Thumpinator isn't specifically designed to minimise this peak, per se, but the filter doesn't have to be compromised in the same way. The filter design used in the thumpinator has been around for donkey's years, it's a standard electronic building block (see any active analogue filter design textbook).

Thanks for the info. Nearly all of my working experience with filters been variable designs in synthesisers, so I wasn't aware that by removing the variable aspect it would be easier to reduce the cut off frequency hump.