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  • Greg Y
    Junior Member
    • May 2002
    • 15

    BFD results

    I finally purchased a BFD DB4 is the latest set of measurements from my sub when equalized with a Behringer Feedback Destroyer DSP1124P. I am now a true believer. The only problem I really have is that to tame the peak at 45 hertz (its still really hot at that frequency) had to apply an 18 db cut at 45 hertz. I did this using a 1/6 octave bandwidth. Not only was the 45 hertz fully affected, neither were the frequencies around 45 hertz.

    My measurements are plus or minus 1.5 db from 19 hertz to 63 hertz. Plus or minus 3 db from 18 hertz to 71 hertz. The reason the measurement drops above around 70 hertz is that my sub is at a higher level than my mains and the crossover is bringing the level down.

    Fr DB1 DB3 DB4
    16 92.5 85.5 85.5
    18 90 88 88
    20 89.5 92.5 93.5
    22 87.5 92.5 93.5
    25 88 93 93
    28 87 90 91
    32 91 92 93
    36 84.5 88.5 90.5
    40 90.5 91.5 91.5
    45 100 94 94
    50 101.5 90.5 93.5
    56 97.5 89.5 92.5
    63 95.5 93.5 91.5
    71 85.5 73.5 88
    80 83.5 81.5 86.5
    89 81.5 90.5 89.5
    100 81 84 85

    The sub can hit 110 db peaks on the pod race (the explosion in the tunnel) on the Star Wars Episode I The Phantom Menace with no audible distortion (that I can hear). The part I really like about the eq is that during the pod race I can now hear individual pulses when the racers come by instead of a bloated amorphous drone.

    My sub is a DIY using a Dayton 12" DVC in a 3ft3 box with a 15" Adire Audio PR using about 500 grams of mass.

    For music the sub is almost too clean. I really can't tell its there. I guess this is how it should be when your bass is well integrated. I am thinking about applying a "house curve" to my eq to get a little excitement back.
  • Lex
    Moderator Emeritus
    • Apr 2001
    • 27461

    #2
    ay' not to bad mate! Glad you got positive results with the feedback destroyer.

    BTW, I posted a message in the chalet about your username woes, basically, you have 2 usernames now Greg, if you need passwords, email me, but I admit I had a problem trying to email you. So, email me your phone number and I can call if necessary to straighten you out.

    Lex
    Doug
    "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

    Comment

    • Sonnie Parker
      • Jan 2002
      • 2858

      #3



      Greg, I'd say that looks very dadgum good. Is DB1 your initial measurements without the BFD?






      SONNIE

      Cedar Creek Cinema

      DVD Collection

      BFD Comprehensive Setup Guide

      Comment

      • Greg Y
        Junior Member
        • May 2002
        • 15

        #4
        Thanks Sonnie. DB1 are my initial measurements. Still unsure about the 45 hertz cut. To attenuate 45 hertz by about 7.5 db I had to cut about 15 db on the BFD. I tried moving the center frequency, using multiple bands, overlaping bands, everything. This is the most cut I could get. Is this unusual?

        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15209

          #5
          Was this measured nearfield, or at a typical listening position? If nearfield, that would be unusual, to have such a pronouned output at 45. If farfield, it suggests the confluence of room modes; (two or more axial modes), which suggestes relocating the sub and or the listening position.

          I generally favor acoustical solutions to acoustical problems, then do minor clean up with the EQ, and compensate for minor driver shortcomings. That's what we did with the AS-15 sub; worked like a charm.





          -Jon




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          Comment

          • Burke Strickland
            Moderator
            • Sep 2001
            • 3161

            #6
            Greg -

            Impressive results -- looks like the Behringer was a worthwhile investment. And here I thought "BFD" meant something else besides "Behringer Feedback Destroyer". :>)

            However, it appears that the "original" meaning of "BFD" kind of applies to your reaction to music with the Behringer engaged. :>) But you are right -- when properly calibrated and balanced with the rest of the system, (which is the goal of using the Behringer), a sub should NOT call attention to itself with music, but should deliver the deepest bass as a seamless extension of the other speakers.

            If you take it out of the system and play music with very deep bass content, then the lack of a sub should then be apparent. A "stealth sub" does take some getting used to, though, if you are accustomed to more bloated and boomy "in-your-face" bass. So I'd recommend trying it a while "as is" and get acclimated to the ultimately more enjoyable and satisfying "natural-sounding" bass that enhances music rather than overpowering it. (Too much "excitement" can be fatiguing after a while in music as in other things.) :>)

            Enjoy!

            Burke

            What you DON'T say may be held against you...

            Comment

            • Greg Y
              Junior Member
              • May 2002
              • 15

              #7
              Jon,

              The measurements were taken from the listening position which is about midway down a 23" wall. The dimensions of the room are 13X23. The sub is in a front corner of the room. I am really limited in my sub placement. I may be able to get it about 6 feet from the back corner of the room. This is about 5 feet from the listening position. The 23X13 room connects to a 14X22 room with an open double doorway. Not ideal.

              Burke.

              The BFD is a "bfd". Now that I've got it I can never go back. The sub is very musical and unobtrusive when listening to musical selections. Play a movie with some good LFE and the floor shakes big time. My sub would just drone before the BFD. I hooked.

              Comment

              • Sonnie Parker
                • Jan 2002
                • 2858

                #8
                I'd say the front corner is by far the best location. Jam it as far up in the corner as possible. I have mine about 2 inches from the corner (back and side). This will give you the best chance of eliminating nulls. Which it appears you only had one low spot at around 36hz. I'm assuming you boosted that area a tad. Also moving it to the rear can create phase problems.

                I would not suggest that 15db cut is unusual. I've seen several that use more than one cut of 16-18db. Remember you can cut up to 48db. I'd say that would be unusual.

                I am curious about one area. At 16hz and 18hz it looks like you may have filtered those a little. I'm not familiar with your sub, but if it can handle it, why did you filter those areas.

                I've re-created the chart above to show you the before and after.






                SONNIE

                Cedar Creek Cinema

                DVD Collection

                BFD Comprehensive Setup Guide

                Comment

                • Sonnie Parker
                  • Jan 2002
                  • 2858

                  #9
                  Hmmmm.... now that I visualize the before and after, it appears you've boosted quite a wide area between 20hz and 36hz. Typically I suggest don't boost too much in the low area but if your amp can handle it and you like it then there should be no problem.

                  Maybe you can post your filters. I'd be interested in seeing them.

                  If you are looking for a house curve you might use another preset and leave that one as is since you seem to like it for movies. I have about 4 presets on my BFD. Although I only really use 1 of them. I have 1 set up that is softer for week night viewing (when our daughter is asleep). The boom does travel through the house fairly noticeable. Kind of like a night theater mode except not as dramatic a cut in dynamic range as the night theater mode on my pre/pro. Then I have a couple of house curves with 1 flat filter. Or I should say as flat as I can get it. I have a serious room induced null around 50hz. It doesn't hurt me with the house curve as much but on the flat line it is noticeable.

                  A house curve might be a challenge for you. It's gonna mean more cut at that 40hz to 63hz range.

                  Typically I see BFD users stating the movies are right on with a house curve but too much on the music side. Of course only you can decide what you really like.






                  SONNIE

                  Cedar Creek Cinema

                  DVD Collection

                  BFD Comprehensive Setup Guide

                  Comment

                  • Greg Y
                    Junior Member
                    • May 2002
                    • 15

                    #10
                    Hi Sonnie,

                    There is a big difference from 16-30 hertz but it is not from EQ. I have a passive radiator sub. When I was getting mundo bass down to 16 hertz, I had too much weight on my passive radiator. It was killing my efficiency from 20-30 hertz. When I reduced the weight on the passive, 15-18 hertz really dropped, but 20-30 hertz improved quite a bit. I have added +2 db at 28 hertz. From my car audio days, I used to add only 2 db (more than that just kills your headroom) but cut as much as you need. Even with a passive, you can only add so much mass to the PR until you kill the efficiency in some other part of the low-end.

                    I have a 3ft3 box tuned to about 21 hetz. I am running a Dayton 12" DVC. It sounds very good now.

                    Comment

                    • Sonnie Parker
                      • Jan 2002
                      • 2858

                      #11
                      Ahhh, I see. I'm not much up on passive radiators but that's understandable and makes sense.

                      I agree on the boost, especially below 50hz or so.

                      You got a good looking curve. Glad it sounds good. That's what it's all about. :T

                      ;x( to the BFD!!!!






                      SONNIE

                      Cedar Creek Cinema

                      DVD Collection

                      BFD Comprehensive Setup Guide

                      Comment

                      • Greg Y
                        Junior Member
                        • May 2002
                        • 15

                        #12
                        Test

                        Comment

                        • Greg Y
                          Junior Member
                          • May 2002
                          • 15

                          #13
                          Sonnie,

                          A PR is equivelent to a port. A 15" PR has an effective cone area of about 12.8". It is = to a 12.8" port. The mass of the PR = the mass of air in a port. So my 15" PR is equivelent to a 12.8" port about 211" long. That is why you can tune a PR cabinet so low.

                          As the above illustrates, even though you can tune it low, you lose some snap at the higher frequencies to get the low tuning.

                          Everybody,

                          Also, I was playing the frequency sweeps on the Avia Guide to Home Theather DVD. I noticed that all of the cutting I did at 45 hertz resulted in a dip at 45 hertz on the sweeps.

                          It seems the sine waves I tested with really energized the modes in the room at the listening position. The sweeps, being more transient in nature, failed to excite the room modes like the sine waves I measured with.

                          What this is leading to is since we don't listen sine waves, I think I will back off on my cut at 45 hertz to about 6db. It may not measure quite as well, but I bet it will sound better with music.

                          Comment

                          • Sonnie Parker
                            • Jan 2002
                            • 2858

                            #14
                            Similar situation here Greg. When I boosted my dip at 50hz I found it was really noticeably louder even though some of the dip was still there. I backed off the boost a little and it blended much better.

                            Interesting info on the PR.






                            SONNIE

                            Cedar Creek Cinema

                            DVD Collection

                            BFD Comprehensive Setup Guide

                            Comment

                            • ThomasW
                              Moderator Emeritus
                              • Aug 2000
                              • 10934

                              #15
                              A PR is equivelent to a port. A 15" PR has an effective cone area of about 12.8". It is = to a 12.8" port. The mass of the PR = the mass of air in a port. So my 15" PR is equivelent to a 12.8" port about 211" long. That is why you can tune a PR cabinet so low.

                              As the above illustrates, even though you can tune it low, you lose some snap at the higher frequencies to get the low tuning.
                              Well sort of.......

                              IMO PR designs do suffer from a loss of definition when compared to ported ones. But they offer a way to make smaller cabinets since port length and displacement aren't issues. Ported and PR designs can be tuned equally low.

                              There should be no loss of 'snap' at higher frequencies with low tuning of either a port or PR. Changes in spectral balance (increased LFE) can 'fool' the brain into thinking there is less higher frequency info, when that isn't really what's occurring. Measurements will prove this out.

                              EQing 'flat' won't always provde the best sound. When possible acoustic problems should have acoustic solutions (bass traps/sound absorbing panels are the first choice). These impact the performance in the whole room.

                              Electronic room Tx= EQ can only be maximized for one specific listening position. And therefore should be used sparingly




                              theAudioWorx
                              Klone-Audio

                              IB subwoofer FAQ page


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