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BFDing ASW 850 - advice required on my charts.

Discussion in 'Subwoofers' started by rags, Sep 11, 2004.

  1. rags

    rags
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    Hi all,

    I have done some tests for frequency response (crossover at 100hz, PLII
    mode, all speakers off) on my ASW850 in a couple of positions in the room.

    The graphs are attached below. They look seriously bad ! The blue one is my preferred
    location (in between the left and right fronts) and the purple one is where my
    wife would like the sub to be in the room (side postion in the room).

    Not sure which one to work with to be honest ? The blue one seems to have a nasty and wide peak around 31hz but the red one seems to have some troughs which I understand are harder to get rid of.

    Also any advice on filters and anythng else would be appreciated.

    Thanks
    Rags
     

    Attached Files:

  2. Daneel

    Daneel
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    Go with the blue. When EQing you want to be applying cuts to peaks not boosts to troughs.

    That peak doesn't surprise me at all, that's probably the punch you love about your system, removing it might not be to your liking. :)

    BTW, why are you crossing at 100Hz with those speakers? I've be inclined to use between 50 and 80 for the front two and 60-80 (I'm not sure what your surround are capable of but the HTM1 goes down low enough) for the others if you can set them separately. Otherwise 80 for everything.

    Here is the standard BFD setup guide:

    http://www.snapbug.ws/bfd.htm
     
  3. rags

    rags
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    Thanks Daneel - I normally cross over at 70hz however just increased it for the purposes of this test.

    That peak isnt the punch I dont think - im getting a slight boominess with the sub in the front position and not in my wifes preferred location (didnt happen with the ASW750) and I think that may be it. Not sure to be honest. Punch is louder than ever.

    I havent even opened the BFD up yet but any ideas on filters ?
     
  4. tk2001

    tk2001
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    Hi Rags,

    I've also recently purchased a BFD and but haven't used it yet due certain things in my set-up I need to sort out first.

    I have however taken a reading of the frequency-response to my sub and I have also got a nasty peak at around 40hz which is around 30dB higher than 80hz!

    I have downloaded a program called 'Excel Viewer' but I can't seem to plot in my SPL figures into the 'Subtestmodel' spreadsheet. Any ideas what additional software I need?
     
  5. rags

    rags
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    tk2001 - from that link that Daneel has given you can download a preprepared excel spreadsheet that does it all for you. It even automatically compensates for deficiencies in the Radioshack SPL metre that I am using. Sounds like a serious peak mate !!
     
  6. rags

    rags
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    Ok I have been mucking around with the filters and have got the following result on my first attempt (I didnt set each filter and test the frequency response after each one but just plonked them all in as I saw fit). Please see the files attached below. Its looking much better but am wondering if there is anything else I need to do.

    The Positive gain adjustments I have had to make are concerning me (especially when I read the bit about doubling power requirement for a 3db boost). I know they are at higher frequencies which may mitigate the risk slightly but do I need to worry about them ? I would appreciate it if you BFD experts out there can review my adjusmtents on the second page and give me your opinion - I have set up a 1db boost at 63Hz and a 3db boost at 80Hz.

    I just took a punt on the bandwidth - should I be running more frequencies to get a more accurate picture or will these suffice (21 frequencies used only as per the chart) ?

    Thanks
     

    Attached Files:

  7. Daneel

    Daneel
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    How does it sound? I think I would find base response very hard to judge on movies alone. Give me some music with a good bass line and things become much easier.

    Your curve looks quite reasonable now so i suggest you let your ears manage any further tweaking.
     
  8. rags

    rags
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    All I have tried so far is Monsters Inc and Chicago and they sound just fine to me. Still have the punch but lost that slight boom. Running the sub a little hot as I normally do (2-3db - just my taste) and Monsters Inc was lovely. Im going to try and experiment with the house curve thing tomorrow. Worried about the postive boosts through the BFD though.
     
  9. Daneel

    Daneel
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    It's only 1 of 3 dB. It will be fine. Is there much improvement over your 750?

    I'm going to have to get my hands on Monsters Inc (up in scotland atm) and a BFD. There are a couple of peaks that I have been unable to tame. My neighbours must love me when I watch a film. :)
     
  10. rags

    rags
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    Oh yeah definately - the 850 is in another league bass wise to the 750.
     
  11. Stellavision

    Stellavision
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    Looking good Rags. :thumbsup:
    Your trough looks very small and possibly not woth worrying about. If you haven't done any lfe sweeps yet, then i would reccommend you do, which will give you a better representation on how smooth your response really sounds.
     
  12. rags

    rags
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    Thanks Barrie - How many filters are you using in the BFD and and what kind of bandwidths ? I am using mainly around the 4/60 mark and am concerned that I am flattening just the test frequencies and not any peaks around them. Sounds good though. Ill do the sweep as you suggest.

    After recieving some very useful advice from Recruit and Smurfin I have managed to achieve a slightly sloping curve. Other positive news is that I am using one less filter (9 instead of 10) and only one positive gain (3db at 80hz). I have a slight bump at 22Hz which I cant shift.

    Tried a couple of discs and this sounds slightly better to my ears. What do you lads think of the graph below ?
     

    Attached Files:

  13. Stellavision

    Stellavision
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    Hi Rags
    I actually have all 12 filters in use on the bfd, but I did not intentially set all of them up my self. I my self made adjustments using 6 filters then I realized there were already filters programmed in there from the previous owner, probably cwick who I bought it from on the classifieds. I left the remainder on there as they were obviously helping.
    The main ones I worked on were:
    40hz, 45hz and 50hz as these were my big hot spot areas. I had quite a wide peak at 45hz so I used a band width of 10. My other bandwidths were as low as one but never exceded 10. I will fill in the filter correction chart and post it sometime if I get chance.
     
  14. recruit

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    Rags that looks good i don't think you need to improve on anything else ;)

    John :)
     
  15. avanzato

    avanzato
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    I will first admit that I'm not a fan of BFD Eq'ing but I'd be interested as to how y'all feel in a few weeks time about the sound. The BFD comes up for sale regularly and just wonder if it's complexity or sound issues as to why some people give it up.

    FWIW I'd have used one filter on your plot rags, to drop the 35hz peak.
     
  16. rags

    rags
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    Thanks Recruit

    Avanzato - I have already done that - on the second engine ! Just one filter at -7db and 10/60 bandwidth. I will do a head to head between the engines later on to see which one I prefer. Why arent you a fan by the way ? What are the negatives ?
     
  17. avanzato

    avanzato
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    I like to keep things simple if I can. Most BFD'ers seem to go for lots of filters and a flat line. I've tried the flat line in the past, admitedly well before the BFD was around and I thought the sound lost something but the BFD might be different. Just interested what it is that makes some people give up the Eq. when most say it's brilliant.

    Also I'm surprised that people don't measure several positions and average the result as the flat line is only accurate for the position of the Mic. To much effort I suppose.

    BTW I'm not anti Eq as I have an SOS but it's automatic so I don't have to plot anything just trust the designers did a good job. :suicide:
     
  18. rags

    rags
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    Avanzato - I achieved a reasonable flat line but I prefer the slght drop off I have now. I like to run the sub 3db hot (I know I know but its just the way I like the sound) and I can do so now without any problems whatsoever. Overall I prefer the sound post BFD to what I had earlier although it certainly was a bit more exciting with that big peak kicking in. I am not going to tweek it anymore as tbh a 2-3db change at any given frequency will not be noticeable in the thick of an action movie.

    What I have discovered was that my room response wasnt a disaster to start with with no big troughs and only one significant peak.
     

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