BFD's highpass filter

Discussion in 'Archived Threads 2001-2004' started by Kevin_W, Jul 27, 2001.

  1. Kevin_W

    Kevin_W Second Unit

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    I currently have an ART 351, however I have in my room HUGE humps in the 42-52hz range (ranging from 7db to in excess of 15db) but the 30hz range is relatively ok. These are tough frequencies to adjust without lowing frequencies I don't want lowered. I am looking into the BFD since you can assign a filter to any freq, but what is also as important is a high pass filter. The art will let you start a -12db slope (correct term?) as low as 15hz... I only need to have this at the 20hz tuning point of my SVS's... will the BFD accommodate that? And will it do a -12db slope?
    I dont know if this is important to me, I remember threads going about the BFD in regards to whether or not it can truly pass a freq lower than 20hz (or something like that I didn't pay too close attention at the time). Is there anything about that I should know about?
    Thanks in advance, any advice will be greatly appreciated.
    Kevin
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  2. BruceD

    BruceD Screenwriter

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    I just bought a BFD to do what you talk about.
    Except, I already have a Marchand XM9L electronic xover for my low-pass and high-pass between my mains and my sub. This way I can put the BFD ONLY in the low pass (60Hz xover) signal chain. The reason you don't want to use it as a high pass, is because it puts the signal through an additional A/D and D/A signal processing step which degrades the signal going to your main speakers.
    BruceD
     
  3. Kevin_W

    Kevin_W Second Unit

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    Hi Bruce,
    I've read the threads about analog-digital conversions it does, but is this degregation in signal really as noticable for LFE signals?
    How about the high pass filter on it? Do you know how low you can make the starting point and how much you can set the slope? The ART I have does -6 and -12. The -12 does a decent job, though I'd even like it more if its possible.
    Thanks
    Kevin
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  4. Deane Johnson

    Deane Johnson Supporting Actor

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    Kevin:
    I'm not sure I understand your question completely, but I don't believe the BFD has any kind of a high pass filter.
    Deane
     
  5. Kevin_W

    Kevin_W Second Unit

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    Deane,
    I'm sorry.. I think I am mixing my high/low pass filters around... I am referring to the subsonic filter.
    Kevin
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    [Edited last by Kevin_W on July 27, 2001 at 02:13 PM]
     
  6. Deane Johnson

    Deane Johnson Supporting Actor

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    My understanding is that the BFD does not have a sub-sonic filter. I looked through my instruction book, including the specs, and find no mention of one.
    Hope this helps.
    Deane
     
  7. Kevin_W

    Kevin_W Second Unit

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    Thanks Deane,
    I have another question, is it true that the BFD only passes freq down to 20hz? What happens to signals under 20hz? Are they cut completely, or just attenuated at a configurable level?
    My problem is that I dont run my mains at reference, but I like to run my subs pretty hot. Without a subsonic filter I am hitting bottom on the SVs with bass heavy material. The ART has helped immensly with its subsonic filter, but I sure would like the flexibility of a parametric EQ so I can dial in specific frequencies... I am almost thinking that if the BFD can't pass a sub 20hz signal, is that so bad in my system since I set my ART to cut anything under 20hz (the tuning point of my subs).
    Thanks again for your time.
    Kevin
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  8. Deane Johnson

    Deane Johnson Supporting Actor

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    I don't know if this helps you or not, but I just ran some tones through mine, using a Velodyne FSR-18 (HGS-18), one of the more capable low end subs around.
    Using the Radio Shack meter and the Stryke disc I got a meter reading of 0 level at 20 Hz and -9 db at 17.5 Hz. These are uncorrected (RS chart). The meter correction charts lead me to believe the meter looses about 3 db between 20 Hz and 17.5, so I could be down about 6 db at 17.5 from where I am at 20 Hz. I have some boost dialed into the BFD at 20Hz, so it is affecting something, I just don't know what.
    I guess what I am leading to is that in my system, something is dropping the low end below 20 Hz about 6 db at 17.5 Hz. Could be the BFD, could be the sub, could be the receiver, could be a little of everything.
    Deane
     
  9. Shade Watson

    Shade Watson Stunt Coordinator

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    I am thinking about buying the BFD for my two Shiva subs. The only knowledge I have about the BFD is what I have read on this and other forums.
    I have read that the BFD does indeed pass sgnals below 20Hz wothout any problems. I belive that the issue with the BFD and the 20Hz figure, is just that 20Hz is the lowest frequency that you can dial in. I have also read that any filters that you set up, will affect sub 20Hz frequencies just as you would expect them to affect all other frequencies.
    All this is hear say, however the person who posted this info seemed to put a lot of time and effort into checking out the BFD.
    Check out this link: www.avsforum.com/ubb/Forum3/HTML/005017.html
     

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