An SVS, a BFD and 4 hours...

Discussion in 'Speakers' started by Robert*S, Feb 21, 2005.

  1. Robert*S

    Robert*S Stunt Coordinator

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    This is what I ended up with: Sub curve
    I never realized how good this sub could truly sound until I eq'd it with the BFD. I must admit that I would not have gotten anywhere without Sonnie Parker's BFD setup guide (or as I call it, the BFD bible).
    Now I have a good amount of rumble, my mains actually sound better not being obscured by the bloated bass and my wife no longer asks me to turn it down during a heavy bass scenes!
    We watched I,Robot last night and, man alive, does it have some good bass! Now I am going through all my dvd's to check out all the bass I missed the first time around. Can't wait to watch the LOTR trilogy again!
    Big thanks to Sonnie Parker for his excellent BFD guide(www.snapbug.ws/bfd.htm), Wayne P and Bruce K for all their posts, I must have read thousands of posts from them on how to use a BFD, and Tom at SVS for heading me towards the BFD.
    Now that I am done tweaking I can sit back and enjoy the films. But then again are we really ever done tweaking?

    Note: this is crossposted over at the Home Theater Spot.
     
  2. Kenneth Harden

    Kenneth Harden Screenwriter

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    So a pretty good $100 mod, huh?
     
  3. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Looks like an almost perfect house curve! How many filters did you use?
     
  4. Robert*S

    Robert*S Stunt Coordinator

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    A very good $100 mod!!

    I used 10 filters to get that curve. A lot of trial and error, but it was a lot of fun. [​IMG]
     
  5. Garrett Lundy

    Garrett Lundy Producer

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    Which model SVS is that?
     
  6. Robert*S

    Robert*S Stunt Coordinator

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    It is a 22-31PCi.
     
  7. JasonCI

    JasonCI Stunt Coordinator

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    Nice work Robert, but where did the dip at 111 Hz come from? Perhaps you used too many filters?
     
  8. qualen

    qualen Agent

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    Wouldn't that dip be insignificant once you crossover at 80Hz?
     
  9. David Bikeman

    David Bikeman Stunt Coordinator

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    If Robert used Sonny's Excel program, that dip at 111 is built in. When I ran my numbers on that program, it did the same thing. There was no dip by the numbers but it put a big dip in nonetheless.

    David
     
  10. JasonCI

    JasonCI Stunt Coordinator

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    Bass is output from both your mains and your sub just below and just above the LFE crossover frequency. In other words, with an 80 Hz crossover setting your AVR will still send out an LFE signal even if it's playing a 100 Hz frequency.

    That's why phase is so important. The proper blending of the LFE channel and main speakers near the crossover frequency is crucial.
     
  11. Robert*S

    Robert*S Stunt Coordinator

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    I have always had that dip at 111Hz. Maybe it is Sonnie's software. I added a filter at 111Hz and there was no change so I figured it was a null. I will do a measurement this weekend and manually add the correction to see what I come up compared to Sonnie's spreadsheet.
     
  12. Ryan Tsang

    Ryan Tsang Second Unit

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    That's awesome! Your experience with clean bass echoes mine exactly when I got a servo-15.

    Makes me want to go back and redo it since I got new towers. I'd love to score a curve like yours.
     
  13. Robert*S

    Robert*S Stunt Coordinator

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    Thanks Ryan! The hardest part about that curve was getting some quiet time away from the wife and kids!
    Go for it (you know you want to![​IMG] ) and make sure you post your curve!!
     
  14. Ryan Tsang

    Ryan Tsang Second Unit

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    Robert, help me out here..

    Okay....this calibration/EQ stuff is harder than I thought. Every time I do it, I learn something different and realized what I had done in the past might be wrong.

    Let start with basics: I use Sonny's website, and used NCH tone generator to create a test disc of 1/6 oct tones from 16 to 160hz. Set all channels to small. X-over 80hz. Sub is Paradigm Servo15, no internal xover. All xover done in AVM20.

    Questions:

    #1: Do you eq with mains disconnected, sub only?
    #2: Do you eq the mains only (no sub) to find out what their output is like? I did and still found sizeable output at 40hz even when x off at 80hz.

    I tried eq with mains + sub and learned that to get it flat, my sub only needs to start playing below 40hz. Then I threw in Avia and the sub signal is super quiet, eventhough it was fine on the test disc. I reckon it is because the output of the towers was too great such that the sub didn't add much to get it flat. So when I played the sub by itself, it is too quiet. Result: Haunting DTS.....lifeless. Correction: Used internal test tones from prepro, calibrate all channels to 75hz which meant boosting sub output 9db. Result: back to normal, what I was used to before. Only now, I don't know if it's flat anymore.

    #3: How do you get the test tones to sub only? Plug left channel out into sub?

    Sorry for this long post. For those who can make sense of this, I would appreciate help. Or just tell me how you EQ your sub.
     
  15. Ryan Tsang

    Ryan Tsang Second Unit

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    I just read the snapbug website in greater detail and it says to unplugged the amp while EQ the sub. maybe this is my answer. But then doesn't the "below-xover output" of the mains add to the already flat sub? What if your mains peak at 45hz like mine? Eq those too?
     
  16. Robert*S

    Robert*S Stunt Coordinator

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    Hey Ryan, lets see what we can do for you.

    Okay....this calibration/EQ stuff is harder than I thought. Every time I do it, I learn something different and realized what I had done in the past might be wrong.

    Not neccesarily wrong, there are many ways of doing the same thing. Are you using the excel spreadsheet to calculate the SPL sub corrections? I can be done by hand but the excel spreadsheet makes it a little easier to plot a graph.

    Let start with basics: I use Sonny's website, and used NCH tone generator to create a test disc of 1/6 oct tones from 16 to 160hz. Set all channels to small. X-over 80hz. Sub is Paradigm Servo15, no internal xover. All xover done in AVM20.
    So far so good.
    Questions:

    #1: Do you eq with mains disconnected, sub only?
    #2: Do you eq the mains only (no sub) to find out what their output is like? I did and still found sizeable output at 40hz even when x off at 80hz.

    So with the crossover set to 80hz you are still getting usable output down to 40hz from the mains? My speakers, JBL N24's only go down to about 77hz according to the manual. I have never measured how low they could go but I suspect not much lower. You can't ask for much from a 4 inch woofer! From what I have read people have done it that way with the mains unplugged and as you mentioned in your next post, that is what Sonny did. I eq'd my sub with the mains on. I figured that there is some interaction between the mains and the sub so I wanted the curve to blend with the mains. Does that make sense?

    I tried eq with mains + sub and learned that to get it flat, my sub only needs to start playing below 40hz. Then I threw in Avia and the sub signal is super quiet, eventhough it was fine on the test disc. I reckon it is because the output of the towers was too great such that the sub didn't add much to get it flat. So when I played the sub by itself, it is too quiet. Result: Haunting DTS.....lifeless. Correction: Used internal test tones from prepro, calibrate all channels to 75hz which meant boosting sub output 9db. Result: back to normal, what I was used to before. Only now, I don't know if it's flat anymore.

    Take another measurement and plot another chart. I took me something like 18-20 measurements when trying to eq flat. Then I went from flat and layed another filter down to get the house curve. It takes time but it is worth it. I found that I had to raise the volume on my sub by almost a quarter turn to equal the mains after eq'ing.

    #3: How do you get the test tones to sub only? Plug left channel out into sub?

    One way to get the tones to the sub only would be to disconnect all speakers except for the sub. I'm guessing the signal would still be sent to the mains but since they are unplugged all you would get is sub info.

    Sorry for this long post. For those who can make sense of this, I would appreciate help. Or just tell me how you EQ your sub.

    What I did was play the test tones with mains on and took readings from 16-125hz. From there I plugged the numbers into the spreadsheet and saw where my peaks were. My goal was to tames the peaks and raise a dip or two. Lay down one filter and take a measurement and see how it effects the rest of the curve. Then add another filter, take another measurement, and so on until you have a somewhat flat cuve (+/-5db). I would try to eq the sub with the mains on I would guess (and I have been wrong when guessing) that the mains are adding to the flat response but the sub should be outputting something as well and maybe you are hearing the mains more because they are louder.
    I hope this helps! Keep us posted. [​IMG]
     
  17. Ryan Tsang

    Ryan Tsang Second Unit

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    You know what, I don't know if my measurements are representative or not. But if you could read my the graph, I get as much output from 80hz as I do from 45hz, both are peaks. It finally falls below avg at 36hz.



    Thanks for you help. I hope I don't add more confusion. Let's just enjoy! Cheers!
     
  18. Max F

    Max F Second Unit

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    I would say that if you mainly watch movies, just EQ the sub alone since you don't want to screw up the sound that is LFE only. For music, though, you would want to EQ with mains and sub so that there is smooth integration.

    Or best of all, do it both ways. The BFD has two channels to do parametric EQ (channels 4 and 5). Use one for movies and one for music.[​IMG]
     
  19. JasonCI

    JasonCI Stunt Coordinator

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    Just to clarify, the BFD comes pre-configured with presets 4 and 5 in parametric mode. You can use any of the 10 presets in parametric mode if you choose to.

    I have a question though about using one preset for movies and one for music.

    For those of us with smaller HT rooms (
     
  20. Max F

    Max F Second Unit

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    I think most, including me, have the gain (from the receiver) higher for movies than music anyway. The only way i'm going to bottom out the sub is by watching movies. Music won't even be that close (at least for my music). If you boost down low you just have to be careful.
     

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