High pass filter : frequency?

[jnewmark]

Just a caveat I always post in these threads about HPF's: Depending on your amp's design, it may already have an HPF built in ! For example, the Genz Benz Shuttlemax amps all have built in HPF's, set around 30-35 hz. When you add an outboard HPF, you get what's called a "cascading effect". Some of the more technical guys here can explain this effect better than me.

 

[HolmeBass]

I have one on my Mesa amp. I do not know what the filter's slope is, I was surprised to see many with only 12dB/octave roll-offs. I always figured it was at least 24dB/octave on the Mesa.

So I set mine to taste somewhere between 35 and 45 Hz. I play a 4 string in standard tuning.

 

[Stevorebob]

Around 60-70Hz, sometimes 80Hz, with the bass boosted some.

 

[JimmyM]

Motown bass was high passed at 70. Sounds good to me.

 

[Clark W]

I start at about the mid 40's Hz. Then adjust more to the room if needed.

I dont pay attention to what Freq I'm setting it to. I use my ears and listen to how it tightens the bass response. When it starts to get thin sounding then I back off a little bit.

Plus I have two HPFs.

One is built into my Mesa head. Then I have a Broughton that I use when I'm playing through an older GK head that doesn't have an HPF built in it.

 

[Gorilla Monsoon]

I play in our living room, where we have a picture of my mother in law on the hutch by the foyer. I start @100 hz, and start turning it down in 10hz increments until it falls onto the floor. Then I drop it another 10…just to be sure…

 

[J.Wolf]

fdeck S3, which IIRC is 24db/octave . start at the lowest (low 35hz), start rolling it up just until I hear it begin to affect the low lows, then back it off a tad, and leave it there.

Or if the room just sucks, roll it up just until the net effect in the room seems usable.

Always with my ears, and never by some math about the cab tuning, or the fundamental of the E or B string. That seems to work for me.

 

[dbsfgyd1]

If the HPF is variable it's generally adjusted to taste. That means the frequency can change depending on the room and you tone goals.

However, an HPF does have an important role in protecting your woofers from overexcursion, especially in ported designs.

The excursion plot of a woofer in a ported design has sort of an S shape. The precise shape of this curve is determine by the Thiele Small characteristics of the driver and how the box is tuned. In other words, put the same driver in different boxes and you get a different a different excursion plot and also a different frequency response.

These cone excursion and frequency response plots are for an Eminence 2512 II in a larger ported cabinet:
View attachment 5091993

Ref: 290-593--eminence-deltalite-2512-cabinet-design.pdf (parts-express.com)

In general: Starting around 500hz, as the frequency goes lower, cone excursion increases. The excursion continues increasing until a bit under 100hz, and then it starts to decrease. The reason this reversal occurs is because the port is starting to become active.

The port tuning frequency (Fb) for this design is 44hz. You can clearly see this in the excursion plot; it's where the excursion dips. At 44hz, the port is providing maximum suppression of cone excursion and also producing most of the sound.

Below Fb cone excursion increase dramatically and acoustic output of the system drops (typically) by 24dB per octave. Because of this it does not make much sense to feed the system power very far below Fb. Doing so does not produce any usable output, and it puts the woofers at risk from over excursion.

For context, the 2512 is rated for 250W RMS / 500W Program and has an Xmax of 4.9mm. But in this box the 2512 is mechanically limited to 125W and requires a steep HPF set no lower than 35hz.

Ref: 290-593--eminence-deltalite-2512-spec-sheet.pdf (parts-express.com)

If you look at the cone displacement chart, you will notice the driver exceeds Xmax at about 35hz. This is where the trace turns from black to gray.

If you adjust the HPF to 35 hz, it means it is reducing power by 3dB at 35hz. So if you are feeding the speaker 125W at 35hz and apply a 35hz HPF, the power drops by 3dB to 62.5W.

Keep in mind that an HPF is not a limiter. So if you crank up the gain by 6dB, the power level will rise to 250W.

You wouldn't happen to know where the optimal HPF setting for an Eden D-210-XST is? The reason I ask is A PB has a predictable low end that gradually increases as the notes go lower. It blooms. But when I set the HPF on my Eden WD-800 at about 85 HZ, From A on down that bloom goes away. It get real flat. Is that my imagination?

 

[Medicine Man]

Somewhere between 55 and 80, and I play low b and sub octave effects all the time. It seems counterintuitive, but you actually can get bigger bottom end by high passing. Some rooms just bounce those low frequencies around and they don't help anyone sound better.

 

[Obese Chess]

I also have the Broughton Always-On, and depending on the room/stage I tend to roll it almost all the way down to 25Hz and then slightly nudge it up. Just cleans up the mud when my 5 is tuned to Bb or lower.

 

[Bassmike62]

Very interesting thread, lots to be learned !

I have a Broughton single knob HPF first in chain, right after wireless and set a hair above the 40hz mark, which makes sense to me for 2 reasons: (1) Low E fundamental on a bass guitar is just above 40 Hz and (2) I use Traynor DNB115 and the freq response is 40-18k. My ears also tell me it sounds right, because when set below there not enough focus and when set higher, I feel I lose too much dynamics. It might vary a bit from room to room, but that's pretty much it. But after reading this thread, I'll experiment some more, for sure.

 

[Wasnex]

You wouldn't happen to know where the optimal HPF setting for an Eden D-210-XST is? The reason I ask is A PB has a predictable low end that gradually increases as the notes go lower. It blooms. But when I set the HPF on my Eden WD-800 at about 85 HZ, From A on down that bloom goes away. It get real flat. Is that my imagination?

I don't know a specific frequency for that cab, but I would try lowering the HPF cutoff a bit, unless you are pushing the cab super hard.

 

[dbsfgyd1]

I don't think I am pushing it hard. WD-800 puts out 400 watts. The Eden 210XST is rated @ 500, and I play reasonably flat with a slight boost around 165 hz. I'm in a vocal band with PA support. I'll certainly try your suggestion.

Thanks much for your time and response.

 

[dbsfgyd1]

I don't think I am pushing it hard. WD-800 puts out 400 watts. The Eden 210XST is rated @ 500, and I play reasonably flat with a slight boost around 165 hz. I'm in a vocal band with PA support. I'll certainly try your suggestion.

Thanks much for your time and response.

 

[DrThumpenstein]

properly set HPF can actually give you more headroom and also make the low end sound fuller and tighter.

Couldn't agree more. I just posted the other day on a different thread that I think the built-in variable HPF is the most useful control on my amp when trying to dial in an aggressive tone. I'm playing in a metal-flavored party rock band, and the HPF lets me push the gain and mids without getting boomy or muddy from any low-end distortion. The lows can get pretty woolly without it, which robs note definition.

 

[Kindness]

I run two HPFs. A fixed 18 dB/octave at 20 Hz at the front of my signal chain and a variable 12 dB/octave at the end, which I tweak between 40-80 Hz depending on bass/cab/room/desired tone.

Front of signal path:
[URL]https://www.broughtonaudio.com/product-page/bba[/URL]
End of signal path:
https://www.broughtonaudio.com/product-page/low-high-pass-filter

 

[cymbop]

I set my Broughton as low as 40 and as high as 65, depending on the variables of room and bass.

 

[logdrum]

Higher than what you think it should be. 60-80 Hz. Even 120

 

[HolmeBass]

I have found that when I set the HPF at 50 or higher, sometimes all the way up to 75 to tame a very boomy room, I have to turn my shelving bass control up or it sounds much too thin for my taste.

Personally I prefer the deeper extension and less bass boost in the EQ.

 

[sunbeast]

For my big rock rig (Mesa Prodigy into Berg NV610) I would often use my FDeck HPF set up as high as 100hz or so depending on the room and it was perfect with my flatwound-equipped bass to give me plenty of punchy firepower and headroom without flub in a dense loud band. With roundwounds I might drop the frequency a bit. The NV610 doesn't have a deep low extension as it is, and the HPF noticeably helped tighten up the sound from the relatively limited power available from the Prodigy when pushed. The FDeck was really a key part of that rig for me. I really dig the integrated HPF in the Mesa Subway amps too and tend to use it as more of a tonal tool to shape the bass response from the amp on my TT800.