My BFD

Discussion in 'Archived Threads 2001-2004' started by Harold Leroy, Feb 27, 2002.

  1. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Here are my readings with BFD in by-pass. These are raw and comped. I sure would appreciate some input on BFD settings.

    Thanks

    FREQRAW SPLSPL (comp)

    168091.5

    189098.0

    209299.5

    229399.5

    259196.0

    289296.0

    31.58790.0

    369193.5

    408890.5

    457981.0

    508687.5

    569192.5

    639293.5

    719293.5

    808788.5

    898788.5

    1008284.0

    1118485.0

    1258181.5

    142.57777.5

    1608079.5

    MEASUREMENTSWITHOUT BFD
     
  2. Harold Leroy

    Harold Leroy Stunt Coordinator

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    I should have added that my room is 5,500 cu ft and I'd like about an 8 db steady rise from 100hz to 32hz.
     
  3. Steve Morgan

    Steve Morgan Second Unit

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    Those that downloaed the sine waves off Sonnies site how do you convert the MP# to wave files on the computer? I have Adaptec easy CD creator on my PC.

    Thanks,

    Steve m.
     
  4. Oscar_R

    Oscar_R Second Unit

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    n00b question here, but what are these readings off?

    is this from a test DVD?
     
  5. Harold Leroy

    Harold Leroy Stunt Coordinator

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    I took readings from my receiver which generates tones at all even hz (20, 22, 24, 24 26, etc). I also downloaded the the 1/6 octave test tones recommended by Sonnie and burned a CD. I then set the volume on my receiver so that the CD test dbs were very close to random frequencies, then I took all the 1/6 octave test tone readings (this allowed me to get 18hz and 16hz which my receiver doesn't generate). In some cases the various frequency db readings differed a couple dbs between my receiver tones and the CD test tones.
     
  6. brucek

    brucek Second Unit

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    Harold,
    Well, there's been a lot of "boost or cut" debates around here lately, so I guess you could take your pick.
    You've got a fairly nice curve with a smooth drop that you indicated that you want.
    I suspect you've used Sonnie's Excel graphs at http://www.troycable.net/~snap/bfdinfo.htm . These will give you a good visual of what to do.
    You're only real problem is between 40Hz and 50Hz. Personally I would try and boost this up a little and then lower from 56Hz to 71Hz a bit and then remeasure and see what it looks like. The little dip at 31Hz would be very easy also. My best advice is to keep your bandwidths small. Start with 5/60th to 10/60th and see how it goes.
    brucek
     
  7. Sonnie Parker

    Sonnie Parker Second Unit

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    Harold, if you don't have webspace I can post you a graph so you can eyeball it.
    Ken, if I could bother you and Wayne over on this thread:
    http://www.hometheaterforum.com/htfo...847#post485481
    Ari and I would appreciate it when you get the time.
    Steve, I think I sent you an e-mail about that but Easy CD Creator converts those mp3 files to wave (cda) when you drag and drop them in the recording window. No conversion is necessary.....unless you have an really old version of ECDC. If you must have a converter then here is a link to Cdex.
     
  8. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Sonnie,

    Thanks, I have been using your graph and your instructions....very helpful.

    I have not been able to boost a nasty null I have at 45hz.
     
  9. Bob Christensen

    Bob Christensen Stunt Coordinator

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    You may want to play around with the phase a bit. You may be encountering a room interaction node that is very difficult to EQ out without some fairly dramatic cuts across vast frequency spectrums. Also, some (even very small) changes in the sub position, and even orientation can sometimes make some noticeable differences in such nulls. Worth a try!
     
  10. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Both SVS 20-39+ subs are in my right front corner (that's the corner with the longest uninterupted walls). I have moved them in various places in that corner with only a 1db change at best. I think I will have to bring everything down to the null and increase Samson 1000 gain.

    Last night I tried boosting the 44hz null (8 hz wide) as much as +12db with no change whatsoever. I also narrowed and widen the bandwidth, also no change at all. I have taken out a couple peaks and boosted 3dbs at 31.5, so the curve is a fairly flat house curve, except the the null in the mid 40hz range.

    I have the eq input levels set to the level determined by U-571 depth charge scene. The yellow light blinks occassionally and saw the red flicker once, so I think I'm giving the eq enough signal to work with.

    Tonight I will try bringing the rest of the curve down to the null--that's like using the eq as a volume control and I don't like that thought, but maybe the only course of action. A 45hz note tends to disappear with the existing set up--really noticable on a MOBY CD I played around with last night. The "Play" CD song 4, nice base to test set up. Listen first with just my ears and then with Radio Shack meter--you see hear and see the null on certain base notes.
     
  11. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Here are my results after a few days of tweaking. This is really flat!!

    FREQRAW SPLSPL(comp)RAW SPL BFD SPL (comp)

    168091.57081.5

    189098.07886.0

    209097.57885.5

    229197.57985.5

    258994.07984.0

    288993.08185.0

    31.58487.07982.0

    368991.58082.5

    408486.57981.5

    457577.07981.0

    508182.58182.5

    568485.58182.5

    638384.58081.5

    718384.58081.5

    808283.57980.5

    898283.58182.5

    1007880.07981.0

    1118283.07980.0

    1257979.57878.5

    142.57171.57575.5

    1607776.57675.5

    MEASUREMENTSWITHOUT BFDMEASUREMENTS WITH BFD
     
  12. Wayne A. Pflughaupt

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    Nicely done, Harold! Typically only 1-2dB difference from one reading to the next – excellent.

    It is pretty flat, though, and that might not sound good.

    Try this little test: Ditch the meter and play a tone at 32Hz and 100Hz. I know there is only a 1dB mesaured difference between the two, but it 100Hz sounds louder, you might want to introduce a house curve to achieve true spectral balance.

    Regards,

    Wayne A. Pflughaupt
     
  13. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Wayne,

    Is it possible to do that with a couple of additional filters?
     
  14. Nick P

    Nick P Second Unit

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    Harold,

    I dunno, I have to agree with Bruce. I like your unequalized numbers better. I hate to see you give up the gain you had at 28-16hz. Maybe try boosting a little in the other areas to bring them up some to curve into your great looking 28-16hz readings. If you've pumped 12db into 44hz with no change then it's probably best to leave it alone as a lost cause. Just curious, after reducing the peaks did you remember to recalibrate your sub level back up to your mains?
     
  15. Wayne A. Pflughaupt

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  16. Harold Leroy

    Harold Leroy Stunt Coordinator

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    Wayne,

    100hz did sound louder to my ears, so I have added a nice house curve for my 5,500 cu ft room. Here are my numbers.

    FREQSPL (comp)

    1691.5

    1891.0

    2090.5

    2291.5

    2590.0

    2889.0

    31.590.0

    3689.5

    4088.5

    4587.0

    5086.5

    5685.5

    6382.5

    7181.5

    8081.5

    8981.5

    10080.0

    11178.0

    12576.5

    142.576.5

    16075.5
     
  17. Harold Leroy

    Harold Leroy Stunt Coordinator

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    BUMP...come on guys, at least say good job Harold. By the way, how do you post a copy of the graph, it looks impressive.

    Thanks
     
  18. brucek

    brucek Second Unit

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    Harold,
    I suspect you had a lot of playing around with your filters to get that nice house curve you have now.
    Nice job Harold........ [​IMG]
    I have an interesting way of introducing a house curve from a flat response that may have worked in your case.
    You simply add a single wide bandwidth filter outside the subs frequency range that will evenly slope all the way down to 30Hz.
    I had a very flat response set in my filters that sounded - well, flat... I added a 120/60 BW filter at 366Hz with a cut of -15dB. This massive filter has an effect all the way down to about 30Hz that decreases obviously with frequency. This introduced a nice slope on my flat response. I then wholesale compensated by increasing the overall gain of my sub a bit. You need a little headroom to do this depending on how aggressive your curve is.
    This is a lot easier than adjusting many filters to achieve a slope.
    It's easy to pick a value for this filter by downloading the BFD FEEDBACK DESTROYER DSP1100P Design software and play with a few filter values and you'll be able to visually come up with a single filter that will slope all the way back to 30Hz with the house curve you want.
    You can play with this software yourself and see what I'm talking about. The web site is below:
    http://www.behringer.com/05_support/...mid=4&lang=eng
    Select FEEDBACK DESTROYER DSP1100P Design and download the zip file.
    This ends up acting a bit like a shelf filter that the BFD doesn't have..
    brucek
     

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