BFD Gurus - Need pointers

Discussion in 'Archived Threads 2001-2004' started by Sundar Prasad, Feb 6, 2001.

  1. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    I just got myself one of the Behringer units which a lot of members on HTF have been talking about. I want to smooth out a 100 litre sealed Shiva sub in my smallish room. The Shiva is very good above 35 Hz, but drops off fairly steeply below that. By the time I get to 20 Hz, I am about 14 dB down. In addition, there are a couple of room mode humps at 40 and 60 Hz (about 5 dB over) that I would like to tame. I also want to use the BFD to boost at a 25 Hz centre frequency by about 8 to 9 dB to compensate for some of the subwoofer's roll off.
    Amplification is being provided by my old NAD 7240PE receiver which is being used in stereo - each channel driving one voice coil of the Shiva. The NAD goes plenty loud for my listening levels and I am quite pleased with the low end support that the subwoofer had brought to my existing setup of PSB 500 speakers that are no slouches in the bass department either.
    First - some advice for potential BFD buyers. Get a cheater plug if you don't want hum. I always read about others getting hum on their systems and was sure I was immune. The BFD changed all that when I plugged it in yesterday. I was getting hum not only from the NAD amp that the BFD was connected to, but also from my Marantz MA700 monoblocks which are connected to my Denon 3300 receiver. I am hoping that the cheater plug fixes that issue today.
    My main problem however, with the BFD is the signal input level needed for this unit. I am using the subwoofer out jack on the Denon 3300 and connect this to the channel 1 input on the BFD using a mono 1/4" jack. The input level switch on the back of the BFD is set to -10dbV (for lower level home signals). I have a self-made test CD with 2 Hz increment tones from 14 Hz to 100 Hz recorded at -6 dBFS (very loud). A 40 Hz tone from the Denon's SW out jack that registers 80 dB on my RS meter barely shows as -40 dB on the input level meter of the Behringer. Now I know I can't compare a dB value on the BFD LED display to the SPL reading from the RS meter, but I wasn't expecting to see such a low input level on the BFD. Boosting the Denon's subwoofer output level doesn't make much of a difference to this situation (of course the sub gets louder). I ideally want to operate with the Denon's SW out level set at -6 dB or so, but this seems to be a very low level to drive the Behringer.
    Are existing BFD users seeing something similar? How have you hooked up your BFD in your system? Directly between the receiver's SW out and the sub amp or some other way? Are you able to get the level meters on the BFD moving up to -10 dB or so?
    I also tried to use just one filter (to begin with) to see if I could get any boost at 25 Hz. After getting to Preset 9 on the BFD, I switched off all the filters on both L and R channels. I then set 1 filter on the L channel with the required centre frequency, bandwidth and gain parameters and saved it. The BFD display showed one red LED switched on for the L channel and all other LEDs off - which I assumed meant that the filter was active. I also made sure that the In/Out switch on the BFD was in the off position (all filters active). When I run the test tones through my system, (albeit with some background hum), I don't see any sign of the requested boost when I check the RS meter. The subwoofer still rolls off in the same way. But then, the input level meter LED on the BFD only went up to -40 dB when I ran the tones. This is too low a signal for the AD converter in the BFD to do a good job with in the first place.
    Any pointers and advice on using the BFD properly will be most welcome.
    Thanks,
    Sundar
     
  2. Deane Johnson

    Deane Johnson Supporting Actor

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    Sundar:
    The first thing I would do would be to get your system playing properly through the Behringer without setting any of the filters. This way, you can make sure all is operating well before you start introducing variables.
    I feed my sub out to the Behringer as you do. On normal sound at normal listening levels the bottom green level light blinks much of the time. On a little heavier material the second one up blinks. On real heavy bass material maybe as many as four blink. I run my Marantz sub output at +/- 0, which means I might be putting out more from my receiver and turning my sub input down more than you do. My sub input is only about 15% open. If that is the case you're going to get even less indication on the Behringer input level meter. I feel I'm going to be less suseptible to hum and noise if I send out a bit hotter signal.
    Other than indicating a sub signal, I wouldn't worry about what the level indicated next to the LED says.
    The next thing I would do is determine what filters are to be assigned to what frequency and make notes. Don't try to boost your bottom end with one filter. Spread it over several. I wanted to boost from 35 Hz down to 20 Hz about 2 db. I spread that over three filters. When assigning filters, they don't all have to be active. You can skip any of them you want to if no boost or cut is needed.
    BUT, before boosting, get rid of your spikes. Then adjust your sub with something like VE to it's proper operating level. Perhaps you can do it by ear. Whatever you usually do will work.
    Run the sweeps and see what it looks like. You should not have much in the way of spikes since you've taken them out. But you will have room nulls. You can boost small ones 2 db to maybe 4 db, but not much more. Room induced nulls just don't move much and if you try to correct them you're shoving so much signal at that frequency into your sub it just over drives and ruins the performance.
    Once you have some confidence you have the spikes tamed and any small nulls improved you can work on the bottom end. Again, you're not going to gain very much with boost. Maybe 2db to 4 db. Maybe more, but that means you're making your sub work very hard for not much more output.
    I would tend to think about placement if you're having that much drop on the bottom end. Is your sub in a corner? That can make a huge difference. Boosts in low frequency obtained through room placement are the best way to go. It lets the room do the work, not the sub. Also, I don't know what you should expect from your Shiva, since I have no experience with it. Mine is a Velodyne FSR-18 (HGS18)so the bottom end is not a great challenge.
    I have no way of knowing about the accuracy of your test disk. If it's not feeding a perfectly flat signal into your receiver, your results will be tainted to that degree. I use the 200 Hz down to 20 Hz sweeps on AVIA, but they certainly have their drawbacks also. They go by too fast.
    I hope this helps you a little further along. Let us know how it is going, as I'm sure these discussions help others with their installations.
     
  3. Sankar

    Sankar Second Unit

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    I too am eagerly following these threads! My BFD is due sometime next week in the mail and by then I hope to have an arsenal of "theoretical" knowledge !
    I was hoping to use a pink noise signal (and an RTA program) to do the analysis and cleanup .. do you find that using individual notes to be easier ?
     
  4. Deane Johnson

    Deane Johnson Supporting Actor

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    Sankar:
    I don't know the answer. I think it would be great if you tried it and posted your results for us to learn from.
    Thanks.
    Deane
     
  5. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Deane has raised many useful points and I thank him for the prompt feedback. The BFD as it is presently hooked up in my system is definitely passing the subwoofer out signal from the receiver to the subwoofer amp. I am able to put the unit in bypass mode (flashing In/Out LED) and get the subwoofer to produce the test tones properly. However, when I engage the filter that I have programmed (as a test case), I do not see any difference in the performance of the subwoofer.
    My concern is that the AD converter in the BFD is not going to do a great job of digitizing the low level signal from the SW out of the Denon 3300 especially if the level meter on the BFD barely shows -40 dB. I see that Deane's BFD does not seem to indicate that the SW out signal from his Marantz receiver is at any higher level either - so that puts one of my concerns to rest - my unit is not faulty.
    That then leaves me with trying to find the best way to hook up the BFD so that its input level meter goes up to at least -15 dB peaks for regular listening and -6 dB peaks for the loud and heavy stuff. I will have to try to insert the BFD after the preamp output of the NAD receiver (so that it sees a boosted subwoofer signal) and before the inputs to the NAD power amps (the 7240PE can be uncoupled so that effects devices such as equalizers can be inserted between its preamp and amp sections). Maybe this might solve the low input level problem with the BFD.
    Deane, which preset number on the BFD did you program your filters into? Also, what position do you leave your In/Out switch at? LED on or LED off. The manual seems to indicate LED off for normal operation, but I want to see what others are doing.
    Also, the test tone CD I use was made by me using CoolEdit. I generated .wav files at several frequencies with the same amplitude (-6 dB with reference to the 16 bit full scale for CD), and so the levels of all the test tones are exactly the same. CoolEdit also allows generation of warbles and sweeps. My test CD works very well for the purpose of determining room spikes and nulls. Luckily, there are no nulls in my listening position for frequencies under 100 Hz - measured in 2 Hz decrements. The situation when I get up to 1 kHz or so is another matter. I can get the RS meter to swing by +- 6 dB if I move the meter around my listening position by a few inches. Maybe pure sine tones are not the best way to go for higher frequencies - I will have to check with the warble tones on my Stereophile CD.
    I hope other BFD users can contribute to this thread. I really need to nail this input level issue down.
    Sundar
     
  6. Deane Johnson

    Deane Johnson Supporting Actor

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    My in/out led is steady green. My Engine L and Engine R LEDs are both steady green. I seem to have filters on both sides locked together and so when any filter LED is lit, the other is also, even thought there is nothing going through the right side. I considered this harmless.
    The instruction book is a little unclear, but I think when the in/out LED is off, you may have the filters out of the circuit. Also, you indicated you weren't seeing a boost when you tested one filter. Be sure you have that filter set to PA. Also, keep in mind that boosts are very difficult to acheive. For testing, try a temporary deep cut somewhere and see if you get a corresponding dip.
    I used memory position 5 at first, decided start over the next day with a new curve and used memory postion 4. That's the one that is on all the time now. I don't think it makes a bit of difference which number you use.
    On your level problem, you indicated you had your receiver sub out level at -6 db. How about just turning it up to +2 or something, lowering the level on the sub to correspond, of course.
    I have to admit the instruction book confused me. I just started messing, refering to it as necessary, and stumbled into what worked. I accidently figured out that to "store" a change, I needed to hit the store button twice.
    Deane
     
  7. Sankar

    Sankar Second Unit

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    Deane:
    I was hoping that someone had tried .. it will be at least 10 days defore I can start playing with the BFD (will be out of town).
    If I were to do it, I would have to use the Avia sweep .. I do have a CDR with test tones, but my dvd will not read it
    [​IMG] ..
    I'll let you know what I find.
    Sankar
     
  8. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Deane - I have to try leaving the In/Out switch with the green LED on and check to see what happens. The manual is very unclear on this issue. My unit also has a mechanical transformer hum (the case vibrates and I can hear it), and so I have to open up this baby tonight and check on the transformer mounting. I will also simply disable the ground lead internally and then check if the 60 Hz electrical hum disappears.
    I was hoping to see other BFD users respond to the input level issue, but am surprised that no one seems to have additional data.
    Sundar
     
  9. TerryC

    TerryC Stunt Coordinator

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    Sundar,
    Where the LEDs lite up to is really of no interest unless you are clipping them.
    Try playing the Haunting DTS or Matrix or Lost in Space at reference levels and see how high it lights. I can clip mine if I set my sub out on the receiver too high. Currently it is -10 or -12 I forgot.
    When playing bassy rap music at up to 103db at my seat I am only getting up to the -30 light to light up. But If I play a DVD such as lost in space at reference volume I can go all the way up to the -6 and -3db lights. So in otherwords be careful what signal you use to determine the optimum input level. The lights on the front aren't the way!
    You need to have the in/out light on for the filters to be active or at least that is the way on my unit. You can only use filters 4 and up for Parametric use.
    Hope that helps.
    Terry
     
  10. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    Thanks for the note Terry. When you say that only Filters 5 and above can be used for Parametric duty, I am a little confused. I thought I could use all 12 for equalization purposes. Perhaps you mean the BFDs preset programs. The input level thing is a relief however: if your unit's meters only get up to -30 dB when getting 103 dB at your listening position, I am going to barely light the -40 dB LED when I calibrate for 80 dB at listening position.
    Tonight, I will be running more tests and will update this thread with my results. BTW, Behringer's little DSP1100 application is very useful to determine filter settings if you have an equalization curve in mind. It can be downloaded it from their web site.
    Sundar
     
  11. Deane Johnson

    Deane Johnson Supporting Actor

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    Terry:
    I'm puzzled by your post that you can only use filters 4 and up for parametric use. I have PA available on all of them. Are there different BFD units?
    Deane
     
  12. Deane Johnson

    Deane Johnson Supporting Actor

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    After making that last post, I got the instruction book out and looked at the pre-sets. I had spaced that before. There is a difference in them. I had stumbled onto the two that work by accident.
    It appears the 4 and 5 both allow PA on all channels. I really haven't figured out what this means, but for some reason using number 4 allows me to have things working.
    More research seems necessary. I think I have blundered into correct us for my system.
    Deane
     
  13. TerryC

    TerryC Stunt Coordinator

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    My Bad guys, finger slipped was supposed to be 4 and up. The very first time I set up one of these we where trying to use Filter #1 but had nothing but problems. We switched to one of the ones 4 and higher and everything worked smoothly. So I have never tried using the ones below 4 since. If they work then its news to me, but I wouldn't be surprised if I'm wrong as I've never tried them since.
    Sundar,
    "If your unit's meters only get up to -30 dB when getting 103 dB at your listening position, I am going to barely light the -40 dB LED when I calibrate for 80 dB at listening position."
    Remember you calibrate with pink noise recorded at either -20db or -30db. So in reality if you keep the volume setting the same and throw in a DVD with lots of bass such as the Haunting your system will be trying to reproduce 115db levels.
    Terry
     
  14. Deane Johnson

    Deane Johnson Supporting Actor

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    Terry:
    Are you intending to say pre-set position #4 rather than filter #4. If so, that would match with what I have discovered.
    Putting it another way, when you turn the unit on, you use the jog wheel to go to position #4, then you can re-program all 12 filters as you wish as parametrics.
    The unit then remembers that you were on pre-set #4 when you turn it off and that's where it returns to when you turn it on next time.
    Deane
     
  15. Deane Johnson

    Deane Johnson Supporting Actor

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    On levels, I just watched the 5.1 version of Manhunter at reference level. The heaviest bass ran the bar graph up about 4 lights, possible breifly to 5 once.
    Deane
     
  16. Patrick Sun

    Patrick Sun Studio Mogul

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  17. Julian Data

    Julian Data Second Unit

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    Hmm.. I have been able to program all 10 presets as a PA Eq with 12 Filters saved.. thus 10 PA EQ settings.
    Julian
     
  18. Geoff L

    Geoff L Screenwriter

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    Hey all,
    Been following this thread eagerly as very interested in the BFD that you all speak of.
    Am I to understand that the manual that comes with the unit is this unclear. Certianly expermentation is to be assumed but one must have a starting point of reference,basic operation. Hence, a manual that will clear some things up.
    Clearly BFD is a steal at it price and not probley for the novice, but sounds like you guys are starting a class for the BFD basics!
    So is the manual and other info that comes with the unit that unclear?
    ------------------
    Smoothe
     
  19. TerryC

    TerryC Stunt Coordinator

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    Sundar,
    I noticed you have buzzing. Louis had buzzing on his as well and had to send it back for replacement. The trasformer was faulty on his. hope you can find the problem on yours.
    Terry
     
  20. Deane Johnson

    Deane Johnson Supporting Actor

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    I'm inclinded to agree with Julian that you can program all 10 presets with 12 filters each set to parametrics. I just messed with mine and it seems to work that way. Probably no need to though, since I can't imagine anyone needing more than a couple of pre-set memory position. I only use one.
    Geoff:
    I wouldn't let the talk of a unclear manual deter me from acquiring the unit if I wanted it. Lot's of manuals are unclear. This one appears to have been translated from German and sometimes the wording in translating is a little different than if it had been written in English to begin with.
    Part of the issue is that the machine really does a lot of things and is rather amazing in it's capablility for what it costs.
    Deane
     

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