BFD and Parametric EQ: noob questions

Discussion in 'Speakers' started by cacu, Nov 7, 2003.

  1. cacu

    cacu Stunt Coordinator

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    I have Tempest sealed mid-Q with a Rythmik amp feeding from a Pioneer Elete 45tx. I've heard alot about how BFD and Parametric EQ can improve sound quality of my bass. Being a newbie that I am, I'd like to know if and how it can help me with my setup. I've notice the BFD sells for around $120 and the Art 351 P-EQ sell for about the same.

    Please lecture me.

    Thanks
     
  2. Tuan Le

    Tuan Le Agent

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  3. ThomasW

    ThomasW Cinematographer

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    The ART unit is 'graphic' EQ, not parametic.

    A graphic EQ unit has fixed EQ bands usually only 1/3rd octave wide. These control the cut and boost.

    The BFD is parametric EQ. This means that user can define different bandwidths. So the user isn't limited to to only 1/3rd octave EQ

    Graphic EQ's are easier to use, but not nearly as flexible/useful as parametric units.

    My suggestion is buy the Behringer
     
  4. Wayne A. Pflughaupt

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  5. Thomas J. Coyle III

    Thomas J. Coyle III Stunt Coordinator

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    Hi Cacu

    I own both the Behringer BFD and the Rane PE17 parametric equalizer. The BFD is a digitizing equalizer while the Rane parametric equalizer is strictly analog. With the BFD you can digitally adjust and modify the selected bands. With the Rane unit, you had better have a RTA available as the band center frequency, boost/cut and Q markings are not very accurate and you will need the RTA to set up each band you select after you have done your frequency survey. You can probably get close by using the dial indicators on the front panel of the analog equalizer, but you will not be able to get as close as you can with the BFD.
    Regards,
    TCIII
     
  6. Tuan Le

    Tuan Le Agent

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    I just ordered the BFD today, it will be here next Thursday. [​IMG]

    One question for Wayne.....What tool did you use to measure and graph the 2 pictures above? Thanks. [​IMG]
     
  7. MichaelDDD

    MichaelDDD Supporting Actor

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    Wayne,

    The BFD seriously ironed out your response curve! Looks great...bet your sub sounds smooooooth.

    Got a question for you.

    Have you noticed any "adverse effects" from having the BFD inline? Such as delay, distortion, etc? Anything there or missing that was/wasn't there before? How "transparent" is the BFD?

    How's it sounds with music? I use the sub with both movies and music.

    I am seriously contemplating the BFD purchase. The benefits to cost ratio is quite high. [​IMG] I'd just hate to introduce anything bad into the signal chain.

    Thanks much. [​IMG]
     
  8. Wayne A. Pflughaupt

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    :b Uh-oh! I didn’t mean to mislead anyone, but I don’t have a BFD, and this isn’t my curve (wish it was - mine’s not nearly this good!).

    I lifted the charts from a “BFD help” thread that was running here about a year ago at this time, driven by a Forum member named Warner. For those not faint-of-heart, you can see the whole thing Here.

    For some reason he has left them up, which is great for me, because I reference them regularly for the benefit of BFD doubters (and those poor guys that think bass traps are better than an equalizer – I’ve yet to see anyone brave enough to post readings from their bass-trapped room!).

    I will say, however, that Warner’s post BFD curve is one of the best I’ve seen. As you can see, it was pretty bad going in; it took him something like 11 filters to get it looking this good. Usually the results don’t look this good on paper, but fortunately they don’t have to look this good for the sub to sound great.

    I think the charts can be created with an Excell file you can download at Sonnie Parker’s BFD Comprehensive Set-Up Guide site.

    Michael, Are you sure your wife will let you have that BFD? Just kidding (yes, I saw that thread). [​IMG] It’s generally accepted that the BFD is not nearly transparent enough to use for the mains, but I’ve never heard anyone complain that they did anything detrimental to their subs. Everyone pretty much concurs that when you get your sub properly EQ’d (and this includes dialing in a correct house curve), you’ll see a significant improvement with both music and movies. In fact, Warner says as much in his lost post on that thread.

    Regards,
    Wayne A. Pflughaupt
     
  9. MichaelDDD

    MichaelDDD Supporting Actor

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    Thanks Wayne. [​IMG]

    I have actually DL'd the Excel spreadsheet..just in case I buy the thing. I also DL'd the "BFD Instructions Bible" put up by Sonnie.

    What is a "house curve?" I know every room will have it's peaks and valleys; is the curve dialing in the EQ to compensate for the room?
     
  10. GeorgeJM

    GeorgeJM Agent

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    Yes, your house curve will be different from mine, even if we use identical equipment.
     
  11. Wayne A. Pflughaupt

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    Michael,

    People that EQ their subs for ruler-flat response usually end up being very dissatisfied with the way it sounds. “Flat” response is typically characterized as sounding ”weak” or ”thin.” Play a coupe of sine-wave test tones at say, 100Hz and 30Hz and you can see why: The 100Hz tone will sound much louder, even though it measures the same as the 30Hz tone.

    Basically, a “house curve” is a response curve that slopes upward as the frequencies go lower. The “house” designation comes from the fact that the amount of slope needed will depend on the room, as George indicated. Thus when the curve is dialed in right, those two tones at 30Hz and 100Hz will sound the same, irrespective of how they measure.

    For more information, see these two posts:

    http://www.hometheaterforum.com/htfo...918#post499918

    http://www.hometheaterforum.com/htfo...014#post530014

    Regards,
    Wayne A. Pflughaupt
     
  12. GeorgeJM

    GeorgeJM Agent

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    The idea of a non-flat response was borne out of psycho-acoustic testing. In other words, even though a sound setup may *measure* flat, it *sounds* different to us because of the way we perceive sound. As Wayne points out, when speaking of subwoofers, the general idea is to give more boost as frequency drops.

    The reason behind it is that we are less sensitive to low frequencies and more sensitive to higher frequencies. That's why many HT receivers (5.1, 6.1, 7.1) have an EQ switch that rolls off high frequencies -- we are more sensitive to them and we percieve a *flat* response as being too bright. Rolling off the high frequencies can make lower frequencies sound louder, or you can do the opposite and boost lower frequencies.

    Additionally, our perception of how loud certain frequencies sound relative to other frequencies depends on the overall volume. That's why Dolby and DTS wants us, the home user, to calibrate our systems to reference level. Otherwise the sound mix at home will sound much different than they intended.

    Personally, I think we have tended to add more and more bass as time goes on because that's what we are exposed to at the movie theaters, so we expect it at home too.
     
  13. Bill Polley

    Bill Polley Second Unit

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    I respectfully disagree with the house curve statement. Yes, we are less sensitive to lower frequencies, but if the recording is done correctly (recorded taking into account any FR rolloff in the microphones) everything should work out with a flat response. Loud, deep bass should be recorded as such, and if it is, a ruler flat system should play it back perfectly. A house curve is needed if the owner WANTS the bass overemphasized, or if the recording has bass that is rolled off from the original sound (not correcting the recording mic's rolloff).

    What I am trying to say (and not doing a very good job at!), is that the original recording needs to capture the bass energy accurately. If a live performance is recorded accurately, dynamic bass should be recorded at the same energy level as it is heard live. When played back on a flat system, it should retain that energy, and our ears should perceive it as having the same energy and impact. Our ears naturally roll off bass frequencies, but ALL bass including live music, thunder, etc, not just bass from our speakers.
     
  14. GeorgeJM

    GeorgeJM Agent

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    Bill, you're right. Everything *should* work out with a flat response. Just like receiver A *should* sound exactly like receiver B, since neither *should* add or subtract anything from the original source. But unfortunately, it all too often doesn't work the way it should.

    For instance, are you certain that the subwoofer should be at 0dB relative to the main and surrounds? Or do they need to be +2dB? Or -2dB? Is that for Dolby Digital and DTS, or just DD? Personally I am not at all certain exactly how it should be, so what it boils down to is I have my system set up the way *I* want to hear it, thus, it's my house curve [​IMG]
     
  15. Bill Polley

    Bill Polley Second Unit

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    I agree George. We all hear differently. I also understand that each component adds coloration, some audible to all, some only to a select few and their pets. I also believe that anyone who desires the sound of a house curve can have it. But as far as accuracy is concerned, a truly flat response with low distortion and acceptable room reflections and absorptions should reveal the bad in poor recordings and the beauty in great recordings. That being said, a house curve, while desired a a large amount of people, is not a neccessity. With a well set up system and an excellent recording, it should not even be a consideration. Just my opinion and I will leave it at that, as I was for several years (a long time ago) a fan of house curves.
     
  16. Wayne A. Pflughaupt

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    Bill, to you have a SPL meter and a broad-band pink noise source?
     
  17. Christopher E

    Christopher E Stunt Coordinator

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    I was under the impression that a house curve would compensate for the fact that movies are recorded and mixed to be played back at reference level. Since most of us don't listen at that loud a level, we are not hearing what the mixer intended. At a lower volume the bass and treble frequencies drop off at a different rates than the mids due to the human ear. So these have to be corrected for to create an accurate presentation of the soundtrack at a lower volume.

    Please correct me if I'm wrong.
     
  18. GeorgeJM

    GeorgeJM Agent

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    That sounds more like the "Loudness" button on many car stereos, and what used to be popular on home stereos, but it's essentially the same thing. I don't think there's any official defintion of a house curve. It is subjective in nature, and is quite literally what sounds good in *your* house, using your equipment.

    You're quite right that at lower volume levels we simply don't hear the same thing the mixer intended, so we compensate with boosted bass. Measured on instruments, it would not be a flat response, but we perceive it as flat. Granted some people go too far and it sounds boomy, like those cars that we've all heard driving down the street, but I dont' think that's what most people are talking about when the say house curve.

    Do I watch DVD's with the sound at reference level? Nope, so I have bass response boosted to compensate. It doesn't sound boomy at that level, but if I then went back to reference level, it would (and does) sound like it has too much bass. I think everyone here is pretty much saying the same thing.
     
  19. Bill Polley

    Bill Polley Second Unit

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    Wayne, yes I do have an SPL meter and a broadband pink noise source. Rat Shack SPL meter, Stereophile test CDs, and a 31 band/channel digital EQ with an additional 5 band parametric EQ/channel, plus the BFD.
     
  20. Bill Polley

    Bill Polley Second Unit

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    and I almost forgat, a calibrated microphone for the 31 band eq (with RTA)
     

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