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Do I need a BFD for my SVS 20-39i?

Discussion in 'Subwoofers' started by BrianC, Oct 7, 2004.

  1. BrianC

    BrianC
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    Right, I sat down this morning and plotted the response of my sub and while it doesn't look too bad I'm not that impressed with the hump between 35Hz and 50Hz. I'm not able to move the sub to another location without getting bits chopped off by the wife, so is a BFD the answer, or is my hump too big?
     

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  2. recruit

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    Brian that is quite a good response that you have, no troughs so if you added a BFD you would be able to flatten it out and get a much smoother response across your lower frequencies :cool:

    John :)
     
  3. owain_thomas

    owain_thomas
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    Brian,

    CanI just step in and hijack your thread a second? Can you explain how you made the plot? There was a q on here recntly about it but I dn't remember seeing an answer, do you have a special mic or is it done manually with an SPL meter?

    Ta,
    Owain
     
  4. lmccauley

    lmccauley
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    Yes - what John said. Don't worry too much about getting a completely flat response. Just dropping that hump centred at 40Hz by 15dB will make a tremendous difference.

    Cheers,
    Liam
     
  5. lmccauley

    lmccauley
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    It looks like the snapbug spreadsheet, which you can find here.

    Cheers,
    Liam
     
  6. BrianC

    BrianC
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    Thats right, I burnt the sign waves onto a CD and played them back using my DVD player, measuring the response with my radio shack SPL Meter.

    So a 15 DB cut isn't to much for a BFD?
     
  7. recruit

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    No Brian a 15db cut is ok it's not going to damage anything it is only when you start adding +db's then you could maybe do some damage if played at Ref levels.
    I had one nasty peaky at about 36hz and corrected it with a 16db cut and bass just tightens up and i also had a slight dip at 63hz so added a +3db increase to level it out.

    John :)
     
  8. BrianC

    BrianC
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    Thanks for the advice John! :)

    I've gone ahead and ordered my BFD, I'll post the results when I've got it setup.
     
  9. owain_thomas

    owain_thomas
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    Thanks for the link, easy when you know how, eh?

    Has anyone else found that the mp3s on that sitehave interference when they are ramping up and down to/from full volume (ie the first and last 2 seconds)? The middle 8 seconds are fine, crystal clear but the begining and end sound bad, or is this a problem with my HCPC?

    Owain
     
  10. karkus30

    karkus30
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    I think thats exactly right, but Im not going to have another listen to those waves to find out. 4hrs calibrating my sub gave me a Pavlovian response to sine waves.
     
  11. lmccauley

    lmccauley
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    LOL! Yeah, there's only so long you can spend listening to sine waves before you just say "f*** it, it sounds good enough!".

    Cheers,
    Liam
     
  12. BrianC

    BrianC
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    I took delivery of my BFD on Friday, but I didn't get to play with it till this morning :( Cause I was too busy playing with my new Denon 3910

    I've attached my first pass at tweaking the output, the blue line was the very first stab at it while the pink is what its set to at the moment. I realise that I've got a fair old drop off at 89Hz, this is because I've changed the cross over for the sub to 80Hz from 90Hz, I'm probably going to set this back at some point.

    Any other suggestions?
     

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  13. recruit

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    Hello Brian,

    I have been looking at your graph and you have it slightly riseing from 22hz up to 45hz how does it sound to you?
    I have found that the sound i most prefer is a house curve and it is explained on the snapbug site, so i have a decrease from 20hz down to 80hz Xover point of about 10db so you end up with a slope.
    The most important thing is though to have a sound that you like so this may not work for you but it is just a suggestion.

    John :)
     
  14. BrianC

    BrianC
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    Its certainly sounding alot less boomy than before I had the BFD cutting the big peak between 28 and 50 Hz, but I think I have lost some of the output below 20 Hz - I guess the BFD is clipping this.

    Although it doesn't look like it on the graph, there is actually only 0.5 db between 20 and 40 Hz, but there is a jump of 1.5 db between 40 and 45Hz (I guess this needs smoothing a little more), but after 45 Hz I'm back to 0.5 db.

    I'm not sure I fully understand what a house curve does and why its potentially better than a flat curve, assuming that I've understood how to implement it - 85 dbs at 20Hz down to 75 dbs at 80 Hz?
     
  15. recruit

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    Hi Brian,

    I am no expert with a BFD but i must say i have enjoyed useing it and i feel it has given me a great improvement in sound quality ref bass :thumbsup:
    But it also does depend on the room aswell as this can affect the quality that you get.
    With regards to the House curve i can only give an opinion for what has worked for me but i would say by giveing higher output at the lower end say 20hz it does give the sound a fuller feeling and it is alot nicer to listen too, rather than being dead flat as i have tried that and it seemed to be misssing something.
    Again i think it is down to experimenting and finding a response that you like :smashin:

    John :)
     

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