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Semi-Parametric Help!

Discussion in 'Amps and Cabs [BG]' started by KeithBMI, Aug 10, 2005.

  1. [​IMG]

    I have a Fender BassMan 150 and I have no idea what to do with the Semi-Parametric EQ. Is there a "standard" freq. I can turn both to? Just something that works for jazz would be fine...

    The first goes from 150-1.5k (the middle is 700)
    The second goes from 800-4k (the middle is 2k)

    Thank you for your help! :smug:
  2. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    Your settings are going to be a matter of taste. Only thing you can do is to give it a whack and decide what you like and don't like. One concrete item I can offer is that your amp is going to sound different in every room you play in. If you are using extrme EQ settings to achieve your sound, that can become problematic because of the room variations.

    I guess the other thing I should mention is that if the bass sonds good and full to you when you are right by your cabinet, then it's going to sound muddy 20 feet away.
  3. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Go to the Euphonic Audio site and download one of the iAmp manuals. They have a great section on tone shaping with semi-parametric eq. Just remember that you don't have a slider for frequency but a pot.
  4. Alright, I'll just noodle around with it and visit that site. Thank you both for the help! :smug:
  5. Petebass


    Dec 22, 2002
    QLD Australia
    Try to think of it this way.

    The "Bass" knob on your amp is a single knob, and you turn it up or down to taste, correct? What's happening here is that the amp's manufacturer has chosen your "Centre frequency" for you. Lets pretend it's set at say 80Hz. As you turn the knob up, 80Hz bets boosted, as does the frequencies surrounding it. The reverse happens when you turn that knob down. Imagine a bell shaped curve. 80Hz sits right at the top of that curve.

    The only difference between this and your semi parametric is that instead of the manufacturer choosing the centre frequency, it is variable. You get to chose it via the knob at the top. Then you cut or boost that frequency with the knob at the bottom.

    Semi paramtric EQ can be approached the same way as a graphic EQ. I guess Graphics are easier because they're more visual. You can boost one slider at a time and hear what it does, and if it sounds better, you just leave it up. If it made everything sound worse, you put it back to it's original spot.

    You can do the same with a parametric, by boosting the knob at the bottom to about 3/4 from full. Set the top knob as far to to the left as it can go (in your case 150Hz). So at the moment, we've got 150Hz boosted. Now play something on you bass and while you're doing so, slowly turn the frequency knob to the right. You will hear the sound changing. There will be moments when things sound better, and there will be moments where you cringe. (For fun turn it back and forth really fast. Sound familiar? It should, this is how Wha effects work).

    If after all that you're still unsure, and you're happy enough with your sound anyway, just leave everything set in the middle. With no boost or cut on the bottom knob, turning the top knob should make no audible difference to your sound.

    I hope that all makes sense.
  6. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    try this link from IvanMike.


    he explains everything you'll need to know. course, use your ears as well, and listen how each twist of the knob works.

    also, try the recent august '05 issue of BP w/ Darryl Jones on the cover. there's a nice little article discussing para EQ's.

    but easy way,

    while leaving all of your EQ knobs flat, boost one of the parametric knobs, and then simply twist the "frequency" knob until you hear something interesting or that catches your ear. then try cutting that same knob, while twisting thru the frequencies. then do the same with the other knob, while setting the former flat. then try a combo of either one.

    also, this works best when you're in your band situation. helpful in finding those frequencies that work best and are most useful for your style of music.
  7. Ozzyman


    Jul 21, 2004
    Well actually it's more like half of a bell shaped curve. The left of 80hz (below) it's a straight line. So if you boost it 6dB at 80hz then it will be 6 at 40 or 50 or 70. But it does drop down to the right of 80hz like a bell curve.
  8. Petebass


    Dec 22, 2002
    QLD Australia
    I didn't really want to talk about Q curves etc because we'd be delving into the full-parametric world. But lets just say we're both right, depending on the amp. Again the characteristics of the EQ knob's Q is determined by the manufacturer for both a plain ol' eq knob, and for a semi-parametric. On a fully parametric EQ, you get to chose the Q curve.
  9. Keith, I own the Fender Bassman 250/115. Same semi-parametric EQ. I used to get lost in that thing, but now I just leave it flat. IMO the new Fender Bassman combo series sounds best flat.

    But, to try to help you out I say do this. Set both flat, (the boost). While the 'high-mids' are flat, bump the 'low mids' by say... 3-4db. Then rotate the freqency selector knob, then play, then rotate it again, then play and so on. You will see the more counter clockwise it is, the more it will boost deeper/lower mid frequencies. The more clockwise it is, the more you will boost higher mid frequencies.

    Then once you'v found the frequencie you'v decieded to zero in on, then bump more, or cut more to your taste.

    I say just leave em' flat though. I ABSOLUTLY LOVE MY FENDER BASSMAN 250/115 SET FLAT!!! Fender really voiced these things well.
  10. Cool, I have all the info I need/want :smug: Thank You!