Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

QSC 30 Hz Filter and the Low B

Discussion in 'Amps and Cabs [BG]' started by Masher88, Sep 24, 2005.


Thread Status:
Not open for further replies.
  1. Masher88

    Masher88 Believe in absurdities and you commit atrocities

    May 7, 2005
    Cleveland, OH
    I've read that the Low B frequency is at 30.9 Hz...should I take off the filter of 30 Hz on my QSC PLX amp? Are there overtones or harmonics that extend further down that are being filtered out by the amp?
     
  2. I don't know about the Schroeder cab, but the other cabs can't produce any useable sound below 30 hz (I don't think they'll even come close). So I'd leave the filter on.
     
  3. Masher88

    Masher88 Believe in absurdities and you commit atrocities

    May 7, 2005
    Cleveland, OH
    Yeah...I'm not sure what the low frequency limit is on the 310212 Schroeder, but it goes pretty low. Maybe I should do some detective work!
     
  4. Also... having a big low B string fundamental is not necessarily a good thing. Some cabs that roll of much higher (like the Eden410XLT) have the best B string sound I've ever heard (IMO). Sometimes rolling those deep lows off a little actually results in a tighter, more defined B string than having the huge boom. To me, that second harmonic (or whatever it is) makes the B string sound more like 'the E string lower' than the sometimes huge 'he's playing on the B string' sort of phenomenon.

    So, use your ears, but I'd keep that filter on in a big way!
     
  5. Masher88

    Masher88 Believe in absurdities and you commit atrocities

    May 7, 2005
    Cleveland, OH
    Thanks for the tips! :)
     
  6. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    I leave my 30 hz filters on. It protects your cabs from low frequency transients that could quickly damage them. This is especially important in PA systems.
     
  7. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    I also leave the filter on. NO lack of bottom on my B.
     
  8. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Dose anyone find the 30Hz filter to have any impact on the sound/tone when playing BEADG bass (positive or negative)?

    [Seems like it might actually tighten up the low notes a little.]

    I plan to check it out at practice tonight (I haven't been using it).
     
  9. Chef

    Chef Moderator Staff Member Supporting Member

    May 23, 2004
    Columbia MO
    Staff Reviewer; Bass Gear Magazine
    On my qsc/pplx 1602, I leave the *50 hz* filters on.
    I play BEADG 5 string a lot.
    I'm running an Eden Navigator pre into the qsc, and then into a Schroeder 410.
    You can argue that the 50hz filters cut too much, but it does not seem so either to me, or sound guys ro bass players that have heard this rig. I don't even have to roll inordinate amounts of bass back in on the Nav.
    I don't think reproducing the 30hz fundamental of your B string is either what you want, or what will sound good. It's mostly mud down there. The low B contains many harmonics and to my ear, the 50hz filter, along with adding some eq in at ~80-120 works out really well.

    Just me though.
     
  10. Leave the filter on. I noticed a large drop in cone excursion with no difference in tone. I think fingers on strings/handling noise produces a lot of subsonics that waste amp power and damage speakers.

    The 30 Hz filter doesn't cut off everything below 30 Hz, it rolls it off a bit gradually. Think hill rather than cliff. And I heard that low B is more like 27 Hz, but even then its still not going to be significantly cut by a 30Hz filter.

    Randy
     

  11. Low B fundamental is 31hz.... +1 on everything else :)
     
  12. What's low E, 40 Hz? I worked down from there 5 half steps (12th root of 2) and got 29.9. Not sure where I heard the 27 Hz from... 41Hz for E gives you 31Hz for B.

    Answered my own question, 440Hz for A gives 329.6 Hz for E, /2= 164.8 Hz/2=82 Hz /2=41Hz for low E.

    So yup, 31Hz is defintely low B.

    Randy
     
  13. Yes... E fundamental is 41. Good meeting you the other day at the GTG!

    Ken
     
  14. Same here! I always remembered 40Hz for E, just an old wives tale as well.... or an approximation. Looks like you have to go to the A below low B, that would be about 27.5 Hz...

    Randy
     
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The 30 Hz rating of the filter is either the corner frequency or the -3dB frequency, in either case it won't appreciably affect a 31 Hz tone. High pass filters don't do an awful lot until you get a half an octave or so down. Ideally you want the filter frequency the same as the tuning frequency of your cab if it's a reflex, to reduce the input below that frequency in compensation for the unloading of the driver.
     
  16. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    The graph in the user guide for my PLX shows it to be the -3dB point.

    Thanks for the info, Bill.
     
  17. Chef

    Chef Moderator Staff Member Supporting Member

    May 23, 2004
    Columbia MO
    Staff Reviewer; Bass Gear Magazine
    My Schroeder 410 is tuned for 40hz, so the 50 hz filter is as close as the 30hz...Bill, would one be better than the other in this case? Thanks, I always look forward to reading your opinions....

    chef
     
  18. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    If you look at the curve, there is significant bass-cut *above* the "frequency" of the filter. The 50hz filter was a little too booty-free for me, but not by much.
     
  19. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Use what works. If you're not getting farting with the 30 Hz filter then don't worry about it. Kick it to 50 Hz if you exceed the TOF.
     
  20. DEVILMAN

    DEVILMAN

    Nov 24, 2001
    New York,NY
    ...if you want REAL low-end(with the price of a few lbs.), go for a Crest or Crown...

    ~S~

    PS: They DON'T have "limiters" & are widely used in bass AND PA applications, how could all those people be wrong?...
     



Thread Status:
Not open for further replies.