My BFD results

Discussion in 'Archived Threads 2001-2004' started by John Vo, Feb 13, 2002.

  1. John Vo

    John Vo Agent

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    Thanks to all of the information I was able to gather from this board, I had the confidence to purchase a BFD and tweak my SVS20-39CS.
    I am using an Outlaw Audio 1050 receiver and have my X-Over set at 80hz. The only problem I see is that I have a big dip at 80hz and it just goes downhill from there. Do any of you have any suggestions or do you think it is fine where it is? My mains are Diva 6.1s and all my speakers are set to small. Thank you in advance.
    Graph:
    [​IMG]
    SPL Chart:
    [​IMG]
    BFD Filters:
    [​IMG]
     
  2. jeff lam

    jeff lam Screenwriter

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    It looks exactly like you and I have the same room. I have a huge peek at 40 Hz too. I measure about 10dB higher at 40Hz than any other frequency. Its horrible. I'll have to get a BFD too so I can smooth out the response. But not until I get a new Amp.
     
  3. John Vo

    John Vo Agent

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    Let's just say that this has allowed me to up the output on my subwoofer by about 5 notches. And the only thing that bottoms it out now is that darn Phantom Menace THX intro. That thing is tough.
     
  4. Pete Mazz

    Pete Mazz Supporting Actor

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    Was that measurement taken with just the sub hooked up?

    Pete
     
  5. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Try run a curve with the mains on. As Pete points out, its looks like these curves are sub only. If your lucky, the mains might just fill in that little dip at 80 Hz.

    Also, are these pure tones or narrow band noise or warbles ? If those are pure tones, then your pre BFD curve is pretty good already. Pure tones will reveal room modes that are covered up by narrow band noise or warbles.
     
  6. John Vo

    John Vo Agent

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    These measurements were with only the sub. Was I supposed to do it with the mains as well?

    I used a CD I burned myself with pure sine test tones I generated from my computer. Is this not good enough? I did order the Stryke CD but will not receive it till next week. I was planning on measuring again when I get the CD just to double check.

    Is there anything I should look out for when I measure with my mains on? Should I expect drastic changes?

    Thank you in advance.

    -John
     
  7. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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  8. brucek

    brucek Second Unit

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    John,

    You've done everything correctly and your results look excellent. The dropoff after 80Hz is the bass management of your receiver reducing the level of the sub properly. You had a peak at 40Hz and it has been corrected allowing you to better set the overall level of your sub.

    Yes, you should carry out the equalization (as you have done) with the sub only. Once that has been done, it is then nice to repeat the readings with your mains on also, so you can get a look at how well they integrate with the sub.

    Looks good - in fact, looks amazingly good. Wish my room was as easy.

    brucek
     
  9. JerryW

    JerryW Supporting Actor

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    John, your results look great. Now you need to test with your mains and blend them in with the sub at the crossover point. Again, you ain't done nothin' wrong. Awesome work. [​IMG]
     
  10. Pete Mazz

    Pete Mazz Supporting Actor

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    Actually, with just the sub playing, I would have expected a faster roll off. Seems like it's only dropping off at ~12dB/octave. I thought most processors use 24dB/octave.

    Did you try it with different Xover points?

    Pete
     
  11. John Vo

    John Vo Agent

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    I haven't tried it with any other xovers yet. Tomorrow, I will take measurements again with my mains on. I should do that with only my towers and subwoofers connected and in stereo mode correct?

    After that, I am unsure as to why I would try different crossovers. If with my mains on, I see that I get a flat response up to 80hz without that dip, should I just leave it at that? Should I try to equalize anything above 80hz where my towers would be handling the bass? What would be the purpose in trying different crossovers?

    Thank you in advance,

    John.

    Also, thanks to everyone for the support and supportive comments. I too am surprised my results came out this well as I have never touched an equalizer before and never knew that I needed one until I learned about it here. That one FAQ by Sonny on how to use the BFD is terrific.
     
  12. Rick Radford

    Rick Radford Supporting Actor

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    >Try run a curve with the mains on<

    Here is where I ran into a limitation of ETF. ETF requires the use of one output channel for soundcard error correction purposes. Consequently, you are limited to running only one channel of output when you try to measure both the mains and the sub, or Y out and run one channel through both mains.

    I'm not sure how that would affect the readings/outcome.

    How do you guys with ETF measure your mains? Perhaps I have not stumbled into the right way to do this.
     
  13. Pete Mazz

    Pete Mazz Supporting Actor

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    Rick,

    I run the output from the soundcard to a single input ooon my receiver and either disconnect the sub out, or set the sub to "no" on the receiver, depending on what I want to test on the mains.

    John,

    I found a 90 Hz Xover gives me a much smoother transition than 80, in my room. YMMV. If you've got the tim, give different settings a try. That's when software like ETF comes in handy. You can prettymuch change settings and get instant feedback.

    Pete
     
  14. Rick Radford

    Rick Radford Supporting Actor

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    Pete,

    >either disconnect the sub out, or set the sub to "no"<

    I want to see how the mains blend *with* the sub at the xover (80Hz). When I take my sub + one channel readings, I get some crazy looking info... especially with the left main.
     
  15. Pete Mazz

    Pete Mazz Supporting Actor

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    You probably need to look at what's causing your left and right readings to be so different (if that's what "crazy looking" means). Is the left main close to a side wall? That type of thing.

    Sub integration with the mains usually only has to be done with a single channel running with the sub. I would guess that with both channels running a mono signal, you'd get too much comb filtering for the test to be of any real use.

    Pete
     
  16. Rick Radford

    Rick Radford Supporting Actor

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    Pete,
    Check this link for a layout of my first floor including my HT room. Bear in mind that I've moved the sub from the LF to the RF corner (not as depicted).
    This link is a graph of my EQ response:
    sub only
    sub + right main
    sub + left main
    I think you'll see what I mean!
    (be advised: when I use IE 5.0/6.0, Opera 6.01 or Netscape 4.79 to click the above links, I get the Page Not Available screen. However, with Opera or Netscape, just clicking the Go button beside the Address window takes me to the url. OTOH, IE will not go there.)
    Edit: I upgraded (?) to IE 6.0 and made sure all my MS stuff was up-to-date from the Windows update site.. and I still have the same problems with GeoCities and IE.
     
  17. Ken Woodrow

    Ken Woodrow Stunt Coordinator

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    Rick:
    Your "sub + LM" looks like my sub readouts! I find it strange that there would be such radical fluctuations in one front speaker, but not the other. Hopefully someone out there can shed some light on this. Perhaps it is due to the phase of the sub relative to the speaker?
    Edit: I forgot to ask -- do the spikes in frequency response correspond to projected room modes?
    As for your room layout, I really think you ought to move your HT into your living room. That big LR is just a waste of space without a projector and sound system! What WERE you thinking? [​IMG]
    - Ken
    Windows IE users can copy the links and paste them into a separate webpage to get them to come up.
     
  18. BruceD

    BruceD Screenwriter

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    Rick,
    Using IE 5.5 and clicking on your links brings up the page not available (don't know why it won't display the jpg).
    But, going to your "directory" and selecting from the files there works just fine.
    your directory
    Must be a geocities quirk with jpg files.
     
  19. Pete Mazz

    Pete Mazz Supporting Actor

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    My guess would be cancellation of those freqs from the distance of the LM to the sub. Seems to occur at 70, 105, 140...but someone else will have to give you the whys and wherefors.

    Pete
     
  20. Rick Radford

    Rick Radford Supporting Actor

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    >do the spikes in frequency response correspond to projected room modes?<
    I dunno Ken. I never ran any s/w to project anything. If you're referring to CARA, I haven't jumped into that yet. I'd sorta like to see some feedback here on that s/w before I plop down $50. [​IMG]
    >I really think you ought to move your HT into your living room... What WERE you thinking?<
    Heheheh. Well, as you also have a WAF involved, you do the math. [​IMG] Also, some idiot put a fireplace in the middle of the long wall . [​IMG][​IMG]
    Windows are on both 12' walls and a sofa sits in the center of the other long wall opposite the f/p.
    I think the HT will eventually move to the bonus room. I'll get a diagram of that posted sometime and y'all can help me figure out a best placement scenario.
    And that reminded me that I already had that worked up.. but just needed to convert it to a jpg file. Look here.
    BruceD:
    >Must be a geocities quirk with jpg files.<
    I think you're right.. and I think this is also why I've had problems showing images in msgs here. I need to become more html educated and put a page up on my roadrunner site. That should work better.
    Hey Bruce, haven't you run tests of your mains with the full range signal/ETF? How did you do it with both mains? Just one at a time?
    While you guys are in my Ht directory, look at the file named: 0207xls.jpg. (this link) I did that with the Excel worksheet from Sonnie's site. Compare the yellow and cyan lines (raw baseline and EQ measurements). Then compare the dark blue and magenta lines (RS comp'd baseline and EQ'd numbers).
    I just grabbed the dB numbers at the indicated freq from the ETF LF response graph (which is normalized to 100 dB max). So the dB's are not necessarily representative, but the curves should be.
     

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