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graphic and parametric

Discussion in 'Amps and Cabs [BG]' started by K Dubbs, Apr 30, 2002.

  1. K Dubbs

    K Dubbs Just graduated from OSU, Go Bucks!

    Mar 16, 2002
    Toledo, Ohio
    I know visually what the difference is and how they work...i think anyway...but why do people seem to prefer parametric eq over graphic eq. Without extensive experience with good versions of each, i should think say a 31 band graphic EQ would be much more attractive than a 5 band parametric, simply because the 31 band seems to give more control than up or down this much at this frequency in only 5 spots. Maybe someone can educate me
  2. Brad Johnson

    Brad Johnson Supporting Member

    Mar 8, 2000
    Gaithersburg, Md
    DR Strings
    Do you really understand how parametric works? Most people don't.

    While 31 bands seem like a lot of control it's still possible to have a frequency between the bands that you need to tweak while the majority of the rest don't need tweaking at all. Each band is set on a specific frequency and that frequency is not adjustable.

    A parametric EQ allows you to dial in the exact frequency you want to cut or boost... not close like the 31 band, the exact frequency. For the sake of this discussion we'll leave out semi-parametric vs. full parametric ;)

    On a bass rig IMO a parametric EQ is much more usable... unless you just like 31 band graphic EQ more. Then again, with the right bass and right amp you might not need either. That's my situation:)
  3. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    What Brad said, but also, with a fully parametric EQ, you not only get to select the exact frequency you want to diddle, but you get to diddle the Q (bandwidth), too. The Q is the width of the frequency band, centered on the selected frequency, that is affected by your gain adjustment. Full parametric EQ, then, allows adjustment of three parameters: frequency center, bandwidth, and gain. Graphic EQ's allow only gain adjustments at selected frequency centers. The bandwidths are constant and are built in to the unit. Semi-parametric EQ allows adjustment of only two parameters: frequency center and gain. The Q is again constant. Steve Rabe's (Raven Labs) True Blue EQ looks like a cool tool, although I've never diddled one. It's semi-parametric in five adjustable frequency bands.
  4. PICK


    Jan 27, 2002
    Sydney, Australia
    IMO a 31 band graphic may be too daunting and confusing. I have a 9 band on my amp and i dont use. I dont need to. Also i think that 31 bands is probably too much control.
  5. K Dubbs

    K Dubbs Just graduated from OSU, Go Bucks!

    Mar 16, 2002
    Toledo, Ohio
    ok so the bandwidth part means "centered at 37.5hz i want the gain to be upped a few db's for 3 hz in each direction" type of thing?
  6. No. Bandwidth is not centre frequency.

    Your example of 37.5 Hz is the centre frequency. The bandwidth is the the frequencies either side of centre that the filter will pass, usually quoted at the point 3dB down or -3dB assuming the centre frequency is at 0dB.

    Assume the 3dB down points are at 27.5 Hz and 47.5 Hz (not realistic numbers but multiples of 10 are easier to understand). You can decrease the bandwidth by increasing the Q of the filter by making the -3dB points (say) 32.5 Hz and 42.5 Hz.

    If you want to mess with the frequencies the filter will pass before they drop to half their original value (-3dB) you alter the Q: if you want to alter the main frequency the filter is set to, you alter the centre frequency.

    Hope that makes sense.

  7. I gave up my Rane PE17 which was a 5-band overlapping parametric. It was replaced by a Rane GE30 31-band interpolating graphic.

    I couldn't "see" the pattern.

    Also, I have an RA27 real time analyzer that has LEDs in exactly the same frequencies as the 31-band EQ. It is very easy to dial in the EQ when it has a 1:1 relationship with each analyzer LED.
  8. KlarkKent


    Dec 17, 2001
    Los Angeles
    I just aquired an Ashley Bp-41.....I am very ignorant about the parametric myself...from what I have read in this post and other posts, magazines,.....see if my example is Kosher.

    Ok...I have set my regular eq how I like it, but given that, I play with a pick, have an agressive attack and play fast single note punk lines, (Early Police tunes like Fallout and So Lonely), my e-string is very muddy, boomy and hard to distinguish between each note. Given that, I've read, the open E-string on a bass is at 41hz, I dial in 41hz on my parametric, punch in "narrow" ,(I have two options "in"-narrow, or "out"-wide), and bring the level down. That way my bass lines on the e-string are a little tamed/thinned.

    Is there any truth to my scenario or .."This guys got it all wrong"?

    Klark Kent
  9. Brad Johnson

    Brad Johnson Supporting Member

    Mar 8, 2000
    Gaithersburg, Md
    DR Strings
    What you've done is pinpointed a frequency and cut it. This is a common way to deal with resonance in a room or undesirable sound at a particular point. I had the same Ashley preamp back when I ran a stereo triamp rig*... in bars and clubs alike. Talk about overkill ;)

    Graphic EQ's are definitely easier to "see". Full parametric (I know, I said I'd leave these out... blame Munji;)) not only give you the ability to dial in the exact point you want to cut or boost, you also get to choose how much or how little of the frequencies on either side of that point are affected. Semi-parametric loses the Q function as Munji mentioned and allows setting a center frequency and cut/boost.

    I got away from this for live gigging... I just got an amp that sounds great flat, speakers that sound great with that amp and basses that sound great through this rig... without tweaking. My life is very simple now. Plug and play.

    *2 JBL 4530 scoop cabs, 2 custom 2-12 cabs, 2 horns. Ashley preamp, Biamp 3 way active crossover, Carver PM 1.5 amp, Crown DC300 amp, AB amp. If those folks back then could only see me with my B-100R now:D
  10. Nick man

    Nick man

    Apr 7, 2002
    Tampa Bay
    I would be great if a parametric eq was developed that had a display similar to a graphic eq. It would probably be largely digital.

    Do you understand what I'm saying?

    Something where you could adjust the frequency affected and the gain at that frequency, as in a parametric eq, but with a digital display that would "graph" out a visual image of your settings that would resemble a graphic eq.

    Could anyone give me their opinion on the Raven Labs True Blue EQ?


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