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Thinking of a BFD is it worth it......Graph

Discussion in 'Subwoofers' started by FazerThou, Jun 16, 2005.

  1. FazerThou

    FazerThou
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    HI all,

    Been looking at the BFD now the price is so good so I did a test tone CD and have my results, see attached excel file.

    To me the results look pretty good without any dips or peaks compared to the link from the header. So will i get much benifit from said BFD or am i just looking for another toy?

    The levels were taken at -10db not - 15db.

    Look forward to your responses.

    Paul
     

    Attached Files:

  2. eviljohn2

    eviljohn2
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    You'd definitely notice a difference if you used a BFD although you would almost certainly notice a reduction in the "kick" bass that hits you in the chest if you reduced the peaks at ~42Hz and ~32Hz. It depends what's important to you but you should get a far more balanced sound after EQ.

    As a quick aside, traditionally the x-axis on graphs increases in value to the right rather than vice versa. :)
     
  3. FazerThou

    FazerThou
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    So would I be right in trying to level of the graph at around 80 and then increasing the gain to get the level back up.
     
  4. eviljohn2

    eviljohn2
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    I don't quite understand what you mean. :confused:

    You would use 1 of the filters available in the BFD to reduce each of the peaks so that you have something approaching a flat line. So in your case only a total of 2 filters would really be necessary with no need to touch the sub controls (there is more to it than that if you want to delve really deeply but it would certainly be a good start). :)
     
  5. FazerThou

    FazerThou
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    Thanks for the nudge. Got one on order.
     
  6. stevej

    stevej
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    Sorry to come to this a bit late.

    You may want to look at the Room EQ software, found here http://homepage.ntlworld.com/john.mulcahy/roomeq/ (for some reason I can't paste links:().

    It can give you a good idea of what can be achieved with the BFD.

    Steve
     
  7. FazerThou

    FazerThou
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    Have looked at that but i dont have the necessary bits & pieces to coneect it to laptop or pc.
     
  8. stevej

    stevej
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    You don't need to take measurements using your pc, you can import your readings via a text file, then let the software work out any filters. I've said it before, but it really makes setting up a BFD a piece of cake.
     
  9. FazerThou

    FazerThou
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    Okay then have had a play with the software, do i need a midi lead to do it all or can i just manually input the figures that the software gives me?
     
  10. stevej

    stevej
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    You save your measured data (spreadsheet used to create graph - the raw readings w/o compensation) as a text file. Then import it to the software. You can only save two columns of data (frequency and measurement), as a text file.
     
  11. bob1

    bob1
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    Could you give us an example of the text file please.
     
  12. stevej

    stevej
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    Here's a copy, and here's how you do it.

    1. Open the spreadasheet with your measurements.
    2. Copy the column with the frequency data to a new spreadsheet; not a new worksheet as you can only save one lot of data.
    3. Copy your readings to the new spreadsheet and save the file. See attached Frequency file.
    4. Next, save the new spreadsheet as a text file. Go to save as and select .txt.
    5. you can now import this to the RoomEQ software and start having a play around - with the software that is!

    Unless you're some kind of bassfreak!

    Hope this helps.

    One word though. If you want to be really pedantic you can't beat completeing the whole measurement through your pc. I was surprised how far out my manual readings were. Also, once you have calibrated your soundcard and meter, you can use it to set up all of your speakers; it's much easier and accurate looking at the reading on a screen rather than the tiny needle on the spl meter.

    Steve:thumbsup:
     
  13. stevej

    stevej
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    Here's a copy, and here's how you do it.

    1. Open the spreadsheet with your measurements.
    2. Copy the column with the frequency data to a new spreadsheet; not a new worksheet as you can only save one lot of data.
    3. Copy your readings to the new spreadsheet and save the file. See attached Frequency file.
    4. Next, save the new spreadsheet as a text file. Go to save as and select .text.
    5. you can now import this to the RoomEQ software and start having a play around - with the software that is! Unless you're some kind of bassfreak!

    One word of warning though. If you're a pedantic so and so, I'd dive in and complete the whole measurement with the software. I was quite surprised how far out my manual readings were. Also, once you've got the calibration/connection of your soundcard and spl meter, you can use it to set up all of your speakers. It's much easier looking at the reading on a screen than the tiny neddle on the meter.

    Hope this helps.

    Steve:thumbsup:
     
  14. stevej

    stevej
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    Sorry for the double post, I can't upload any attachments.

    Steve
     
  15. bob1

    bob1
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    Thanks for that Stevej but i'm still a little confused whats the spead sheet i need? Is it the xsl one on the snapbug site.
    Did you mean to put a sample up ?
    I must be thick :( :confused: .
    What does the saved text file look like. :rolleyes: ,I don't mind inputing the data. :suicide:
     
  16. stevej

    stevej
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    bob1,

    That's right, use the snapbug spreadsheet. The text file open's in Notepad and looks like this:

    16 0
    18 50
    20 54
    22 58
    25 63
    28 68
    31.5 63
    36 95
    40 90
    45 95
    50 92
    56 97
    63 93
    71 87
    80 94
    89 93
    100 90
    111 91
    125 85
    142.5 67
    160 68

    Steve
     
  17. eviljohn2

    eviljohn2
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    Steve, are you talking about the official BFD software or the Java based Room EQ Wizard?
     
  18. stevej

    stevej
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    The RoomEQ software.

    I feel like a salesman, but I'd say it's as invaluable as the Snapbug site when it comes to getting a result form a bfd.
     
  19. eviljohn2

    eviljohn2
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  20. stevej

    stevej
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    That's a shame eviljohn2, I think you'd find that the RoomEq software takes some beating when it comes to setting up the bfd. The hard part is the connecting and calibrating of your soundcard and spl meter. But, once you've done this it's easy.
     
  21. FazerThou

    FazerThou
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    Thanx for all your help fellas, will let you know how it goes when the bits arrive.

    Paul
     
  22. eviljohn2

    eviljohn2
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    I've done it the long winded way using TrueRTA so I don't think I'm missing out too much Steve - I can certainly appreciate the power available in that software and have difficulty believing that it's free! :)
     
  23. bob1

    bob1
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    :D Thanks for making it simple ,just like me. :oops:
     
  24. stevej

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    It's good to see that the high end technology really is filtering down, as we discussed before eviljohn2. I'm starting to save my pennies for a 2805, as my kit rack has started to expand again. I want less boxes, not more! But for now the bfd works - with whatever software you use to make your measurements.
     
  25. FazerThou

    FazerThou
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    In theory then if using a pre - power combination could you not use 3 BFD's, 1 for L & R, 1 for rears and 1 for centre and sub...extreme, i know and no i don't intend to. But in theory.....
     
  26. eviljohn2

    eviljohn2
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    In theory you could but the BFD has a comparatively low SNR and introduces a number of phase shifts depending on which filter combinations you use. Whilst this is fine for low frequency use I would expect it to cause all number of problems if used across the whole range in a hifi system - there are better equalisers available but they're very expensive. :)
     
  27. oconnpad

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    John

    What do you reckon is the max range you should filter on a BFD, if you've your crossover set higher than lets say 80Hz.

    Is there a point where the BFD is no longer effective, i know you probably wouldn't have the crossover that high but just wondering.
     
  28. eviljohn2

    eviljohn2
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    I'm happy to use the filters on my BFD across the entire operating range of my subs whilst they're only connected via the LFE output from my AV receiver. If it was necessary to use filters much above about 110Hz you'd still be having serious problems with the outputs from your main speakers.

    In summary, up to about 120Hz would be fine but there's nothing stopping you going higher as the unit is designed to be effective across the whole audio range. :)
     
  29. bob1

    bob1
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    This is off the snapbug site, i have tried it but could not tell any difference.



    "If you have the filters available, you may wish to add the following filters:
    -48db @ 1.0 khz, -48db @ 1.25 khz, -48db @ 1.63 khz, -48dB @ 2.0 khz... all at a very narrow bandwidth of 1/60. It has been suggested that these filters supposedly eliminate the harmonic distortion and/or buzzing that often occur with some subs. I have not experienced these noises that I can determine and can not verify if this tweak actually works, but I can not see how it would hurt."
     

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