In praise of the HPF

[Doner Designs]

I had never heard of such a thing until I got my Noble DI/Pre which has a passive HPF built in. I use it a lot since I'm feeding a fairly crappy PA.

 

[radioface]

High Pass Filter

Is this something we need?

 

[cheapbasslovin]

Is this something we need?

Yes. Pretty much all speakers have a minimum effective frequency. Filtering out those that come in below those specs gives your entire rig more headroom and tightens up your sound.

 

[Al Kraft]

Is this something we need?

It was an especially useful device for folks (like me) who owned SWR amps back in the day. My SM400S could put out sub frequencies that weren't really useful or healthy for many cabs.

 

[blubass]

Is this something we need?

Yes, sometimes. Just as the OP gushed, an HPF or LPF can do wonders in cleaning up the bass frequencies. I find it much more useful on live recordings, myself, but is applicable everywhere.

For my applications, this is something much better served as stand-alone gear, instead of being incorporated into every amplifier. Nonetheless, a very important piece of gear at times.

 

[Latitude94941]

I just did a gig where I got stuck in a really awful bass trap. No definition from a rig I know sounds fine. But being of the "I'd rather be prepared than surprised" school I always carry an HPF and even if I rarely use it tonight it saved my ass.

So my question (and the reason this is posted in amps not effects) is why do you see HPF's onboard so few bass amps when it's something that should be built into every professional quality bass amp?

Hi, Jeff,

No disrespect intended but I'd like to set the record straight since you're not the first person here on TB to use the term "bass trap" incorrectly. Bass traps are actually a good thing in terms of room acoustics. I think you're referring to room modes/standing waves which are not good things.

Auralex Acoustics | Bass Traps

BTW, I agree with you re adjustable HPFs--I try to never leave home without my Fdeck.

 

[beans-on-toast]

Fixed high pass filters are in the power amp section of amps. Manufacturers want them in place to avoid low frequency excursion that blows speakers. It avoids warranty repairs.

 

[Gizmot]

If you cab is 10dB+ down at 29Hz (like most are) you'd not hear any difference with it in or out except for the increased definition.

Two things -#1 a - 10 dB spec isn't anything but marketing fantasy. It certainly isn't usable response. #2 - I doubt that very many bass cabs will actually deliver what response is claimed. A low B is 34 Hz and very few things will play that.

 

[Bass'd on a true story]

Just please don't use a HPF if you are playing on a 5er. Playing a note that essentially doesn't have a fundamental always sounds terrible. I used to hate it when one of the engineers in my studio would put an HPF on basically every track at 40hz. It ruins good bass tone. On a 4 string, go for. If your HPF is adjustable, go for it.

 

[kleinenenten]

My HPF cleaned up my amp. My amp wasn't trying produce sub lows it couldn't handle anyway and waste energy on the effort, so I got more usable and cleaner headroom. Not tonal differences at all, I still have crushing lows and can not tell the difference sonically. However, my speakers do not move anywhere near as much.

 

[Brad Johnson]

Still one of the more amusing things on TB is the demand for typically unusable low frequency specs on cabs and the recommendations by the same folks for a HPF to cut them off.

 

[Brad Johnson]

Just please don't use a HPF if you are playing on a 5er. Playing a note that essentially doesn't have a fundamental always sounds terrible. I used to hate it when one of the engineers in my studio would put an HPF on basically every track at 40hz. It ruins good bass tone. On a 4 string, go for. If your HPF is adjustable, go for it.

Interesting.

 

[Brad Johnson]

Is this something we need?

Maybe. Maybe not. I've never used a standalone one and the vast majority of my gigging basses have a nice low B.

 

[eyeballkid]

If you cab is 10dB+ down at 29Hz (like most are) you'd not hear any difference with it in or out except for the increased definition.

I would disagree. As someone who has had cabs (and maybe still does) with that kind of roll off i hear and experience a distinct difference. With both my fdeck and a friend i regularly see gig i find that it keeps the preamp from being bombarded with lows so there is more headroom in the preamp giving a nicer transition to overdrive and reduces the "flub". Also it means that the speakers, while unable to reproduce sub lows, arent having to even try to. This gives more volume potential before overexcursion. It also gives more dynamics and clarity to your playing subtleties. Plus it really does make you more authoritative in the mix....that may be all linked to "increased definition " but its alot happening. Also the whole amp doesnt have to work as hard for your volume and the headroom increase overall is significant.

 

[JimmyM]

Just please don't use a HPF if you are playing on a 5er. Playing a note that essentially doesn't have a fundamental always sounds terrible. I used to hate it when one of the engineers in my studio would put an HPF on basically every track at 40hz. It ruins good bass tone. On a 4 string, go for. If your HPF is adjustable, go for it.

I don't see it that way at all. I think it sounds even more muddy on those low notes myself. Granted, there are types of music where that kind of super low end on bass sounds great, but I don't play those types of music much, and most of the time it just adds extra woof that I don't want.

 

[Downunderwonder]

I would disagree. As someone who has had cabs (and maybe still does) with that kind of roll off i hear and experience a distinct difference. With both my fdeck and a friend i regularly see gig i find that it keeps the preamp from being bombarded with lows so there is more headroom in the preamp giving a nicer transition to overdrive and reduces the "flub". Also it means that the speakers, while unable to reproduce sub lows, arent having to even try to. This gives more volume potential before overexcursion. It also gives more dynamics and clarity to your playing subtleties. Plus it really does make you more authoritative in the mix....that may be all linked to "increased definition " but its alot happening. Also the whole amp doesnt have to work as hard for your volume and the headroom increase overall is significant.

I get all those advantages with a low B too.

But I think the guy you quoted meant the difference between the audible amount of 29Hz would be insignificant after highpassing, yet bestow the advantages.

 

[Bass'd on a true story]

I don't see it that way at all. I think it sounds even more muddy on those low notes myself. Granted, there are types of music where that kind of super low end on bass sounds great, but I don't play those types of music much, and most of the time it just adds extra woof that I don't want.

B strings already sound out of tune about 90% of the time. Many tuners, especially clip-ons, don't accurately pick up the low b. As I am sure we all already know, they are very hard to intonate, and many amps/cabs don't seem to reproduce their sound well to begin. Adding a cut anywhere above 29-30hz reduces their apparent intonation even more to my ears. Maybe it's just me?

 

[Jeff Bonny]

Hi, Jeff,

No disrespect intended but I'd like to set the record straight since you're not the first person here on TB to use the term "bass trap" incorrectly. Bass traps are actually a good thing in terms of room acoustics. I think you're referring to room modes/standing waves which are not good things.

Auralex Acoustics | Bass Traps

BTW, I agree with you re adjustable HPFs--I try to never leave home without my Fdeck.

When you corrected me I realized that even as I typed it I knew bass trap was wrong. What I didn't know was how to describe it in terms of room modes/standing waves. OP edited. Thanks!

 

[JimmyM]

B strings already sound out of tune about 90% of the time. Many tuners, especially clip-ons, don't accurately pick up the low b. As I am sure we all already know, they are very hard to intonate, and many amps/cabs don't seem to reproduce their sound well to begin. Adding a cut anywhere above 29-30hz reduces their apparent intonation even more to my ears. Maybe it's just me?

I use a tuner that picks up my low B on the rare times I use a 5 (and I have actually picked it up more than a few times lately). Can't say I ever found that intonation was much of an issue, but if that makes your sound pop for you, I'm all for it. Just isn't my thang.

 

[bdplaid]

Professionals are probably 5% of the total bassist population. Also, we don't have Government regulations that mandate minimum requirements for amplifier features, past electrical interference.

At what frequency/ies would a built-in HPF be set to accommodate every different style of cab and instrument? There's way too many variables that make mandated features a no-go.

I'd like to see built-in quality tuners, with tuner-mute and more comprehensive mid controls on every amp as a standard features, but it's an illogical pipe dream.

I don't know where you get "mandated." HPFs are more than useful for every player, especially those with sub-par cabs. Not mandated, but highly regarded and desired. Dialing out some low end can really tighten up a cab that can't keep up with the bass being fed to it.

The way this works is the filter has a fixed slope, but the frequency is settable, say from 20Hz up to about 180 Hz, give or take. and 180 is rather high, but I've seem go that high. What I'm talking about is not preset within the amp, but rather part of the tone envelope.

Further, more than several Class D amps have HPFs built into them. Cutting out the super low that the speaker can't reproduce anyway is a good way to focus the power available to audible frequencies without distortion. Having no HPF can muddy the hell out of everything.

There's was a good discussion about this over on the Mesa Subway D800 board a couple of weeks back.