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HPF Options?

Discussion in 'Amps and Cabs [BG]' started by Warpeg, Apr 20, 2019.


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  1. SwitchGear

    SwitchGear Supporting Member

    Mar 23, 2005
    Sunny Beach
  2. Balog

    Balog

    Mar 19, 2009
    Everett, WA

    And the Schalltechnik Vong Filterung is a full kit ready to assemble. Has a LPF too.
     
    dabis, Zbysek, sears and 1 other person like this.
  3. @ThisBass might have some spare time to draw you a graphic of what you should be able to hear differently between the fdeck and Broughton.

    Fdeck has dual filters one fixed 12dB/octave below 30 hz and the adjustable kicks in another 12dB/ octave at the knee for 24dB/octave.

    Iirc the Broughton is a single 12dB filter with variable kickoff. If I understand it that would mean you would need to start the filter an octave lower to get the same cut at any given frequency as the fdeck does.

    I would have thought that would be plenty audible.
     
    Stumbo likes this.
  4. Balog

    Balog

    Mar 19, 2009
    Everett, WA

    I’d think the 12db at 30hz would be inaudible (since the speakers won’t put out audible levels at that frequency anyway) so it’s essentially just the same sweepable 12db on everything you can hear with both of them.
     
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The 12dB refers to the slope not the level of attenuation. HPF frequency is stated at the point that the signal falls 3dB from its initial value.
     
    Sascha Erni, dabis, Zbysek and 4 others like this.
  6. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    if you play nothing but some walking bass tunes it may happen that you don't notice any difference anyway.
    In this case it depends pretty much on your total sound setting on the EQ if you hear a difference with a HPF present to the signal path.
    The more you dig in lowish content with the EQ then the more you might notice a difference if a HPF is present within the system.

    If you enrich your playing style with rather percussive stuff and also quick notes, and if you dig in some lowish content with the EQ as well, its more likely that you'll notice a more clean sound with the HPF that cuts more of the lowish transient (sub) harmonics.
     
    Bboopbennie and sears like this.
  7. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    I notice a huge difference with either brand HPF especially with the SWR.
    I was surprised that I didn't hear a difference between the two especially considering the SWR produces very low freqs.
    In other words, does the second filter of the f'Deck offer more flexibility for the average owner or is it a rare moment to need this?
     
  8. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    Massachusetts, USA
    What are you using for a cab?

    My guess would be, your cab doesn't go down below 30hz, and that's why you can't hear a difference with the 30hz HPF.

    Maybe if you were listening through a powerful PA with subwoofers, or with excellent headphones, you could hear the difference.

    I doubt, it though. Perceiving a -3db difference at 30hz is very close to the limit of human hearing. An HPF set to 30hz is getting into "placebo" territory, IMHO. Try setting the HPF up around 80-100hz, if you really want to hear an audible difference in your tone.

    In conclusion, while your SWR has the reputation as an amp head that "produces very low freqs" in the subsonic spectrum, your cabinet probably doesn't have that reputation.
     
    agedhorse and Zbysek like this.
  9. Balog

    Balog

    Mar 19, 2009
    Everett, WA

    I think calling it a placebo is inaccurate. The cab may not be able to produce usable volume at 30hz, but it’ll still try if that’s what you feed it. Speaker protection and preserving amp power for audible frequencies is an extremely real and useful effect of high passing. Saying that it’s not there just because you can’t hear it is wrong.
     
  10. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    Massachusetts, USA
    To clarify, I don't think HPF's generally speaking are useless placebos! They are valuable tools for studio and stage alike. I own 3 of them (not counting cab sims).

    I do however think there are a lot of TalkBassers wasting their money on HPF's they don't need, for their specific use cases. One example of that is all the 4 string EADG players flocking to use 30hz HPF's with cabinets that roll off below 80hz. IMHO that is venturing into "placebo snake oil" territory.

    (And again, that is an educated opinion from an HPF lover who owns 3 HPFs. I'm really not trying to be a naysayer here. :))
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Removing the sub-audible information improves a speaker's power handling, decreases IM distortions, and generally improves performance.

    For a cabinet with a -3dB point of 80Hz (not a great choice for bass get.) a HPF set for ~60-70Hz imo
     
    Zbysek, dabis, Balog and 2 others like this.
  12. Don't forget the distortion created by a speaker trying to produce too low is twice the frequency or more. You might well not hear the offending low that causes it but easier to hear the lack of murk after the invisible hand does its thing.
     
    Zbysek, Balog, Mushroo and 1 other person like this.
  13. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    Massachusetts, USA
    Which people are now spending hundreds of dollars on Cab Sim pedals to achieve this effect deliberately. ;)
     
  14. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    The cabinet is a GB 2x12 NeoX; 72' fender P bass; SWR SM400
    This rig without an HPF is unusable at any real volume.
    You can pull down the slider at 30 Hz. and lower the bass EQ and still watch the speaker look like piston by just pushing the strings toward the pickup let alone aggressive playing.

    Either HPF sounded fine during the demo.
    I usually set the f'Deck at somewhere between 60-70 Hz.
    I set the Broughton the same way.
    Even thought the f'Deck has 2 filters, it sounded the same.

    Perhaps I can't hear the difference.
    Maybe the cabinet doesn't need the extra filtering.

    Are two filters more dramatic if the adjustable filter was set considerably higher (assuming you need the extreme low freq. protection)?
    Why have two filters?
    Love the product just trying to learn more about HPF's.
     
    Zbysek and Btbp like this.
  15. Mushroo

    Mushroo Supporting Member

    Apr 2, 2007
    Massachusetts, USA
    I misunderstood the situation and apologize if my earlier comments were off the mark.

    If I understand correctly: You have two HPFs, you've tried them both at 60-70hz, and they more or less sound the same at those settings. You're wondering why is that, why do they sound the same? Shouldn't the FDeck HPF sound different from the Broughton HPF?

    My simple layman's understanding is that, with the dial at 70hz, the FDeck cuts -18db at 35hz and the Broughton cuts -15db at 35hz. (That's just around the low B on a 5 string bass.) I think what is happening is that your ear can't tell the difference between -15db at 35hz and -18db at 35hz. Those are both significantly steep cuts. It's like, can you feel the difference between falling off a 15 story building vs. falling off an 18 story building?

    I owned a SWR back in the day and always wondered why it didn't seem as loud as my Peavey of the same wattage. Sounds like the explanation could be as simple as, the Peavey had a better HPF. :)
     
    Last edited: Jan 13, 2020
    Sascha Erni and Jim C like this.
  16. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Thanks for this; great analogy.
     
    Mushroo likes this.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I would expect the SWR amp to work better with those cabinets using a 4th order HPF set around 40-45Hz
     
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  18. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    But I just wanted to play some bass and not have another fabrication project (as I don't think this is a buyable product).
    I don't know of another HPF for the MI industry other than those listed above and some rack mount EQ's with a HPF.
    Of course, not a big deal with good amp design.
    I've tried the f"Deck with an SVT-CL and SVP-CL pre amp, GK MBF800 and 1001RB and it really wasn't needed for my application.
    It did help tighten up an ABM 500 though.
     
  19. The 1001RB has blown many a fridge with 5 stringers.
     
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Sure it is, Fdeck, Braughton will both do this.
     
    Jim C likes this.
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