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Who uses a Behringer Feedback Destroyer?

Discussion in 'Subwoofers' started by Stellavision, Apr 4, 2004.

?
  1. Yes

    27 vote(s)
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  2. No

    20 vote(s)
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  1. Stellavision

    Stellavision
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    I am interested to know how many people are actually using a Behringer Feedback Destroyer.
    I am considering buying one but I would like to justify if shelling out £100 on one of these things is really worth while.

    If you bought one was it worth it or do you find it caused more problems?

    I'd apreciate your thoughts guys.
     
  2. Gary Lightfoot

    Gary Lightfoot
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    I bought one more out of curiosity because a friend used his to flatten out the subs response, and to eliminate a rattling radiator he had at 42hz. It worked well on both counts apparently!

    I did a sweep using an SPL meter and a test CD, and although my sub sounds fine to me, there were dips and peaks. I used the BFD to flatten them out, and to reduce a couple of frequencies that I thought were a little 'fuzzy' perhaps, but you don't normaly notice that because the sub rarely produces just that one frequency for any length of time.

    I then checked the subs overall volume just in case the adjustments had increased or reduced it.

    I've now added a second sub, and I think all I need to do is use the SPL to reduce the volume. I've just downloaded a load of frequencies to HDD, and I'll make a test CD so that I can use them to check all frequencies. I might plot a graph to post here if I do. What's the best program to do that? Excell??

    Gary.
     
  3. Smurfin

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    Wouldn't be without one.
     
  4. OldEngland

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    Fantastic bit of kit.

    I think in 5 years time, every new sub will include some form of EQ
     
  5. chrisgeary

    chrisgeary
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    i do use one, but i also believe there are other solutions to a given problem. i actually use three solutions for my bass management:

    - i use the REL's ABC so it doesn't output bass above frequencies i dont need (i have large main speakers, so the REL is augmentation)
    - i use another REL at the back of the room for resonance control
    - i use the BFD to control which frequencies the rear sub outputs and to bring down the output of the front sub to reduce how much it excites modes.

    i dont believe a BFD is the answer to everything, but part (and a very useful part it is!) of a carefully thought out bass managed room.
     
  6. eviljohn2

    eviljohn2
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  7. Ed Selley

    Ed Selley
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    We're five years ahead of schedule then :D
    Seriously though, we have a BFD for the dem room and I think it is very fine piece of equipment but the intergrated notch filter we build into three of our products can do many of the things the BFD can and its free. Couldn't imagine running two unfiltered subs in my room :rolleyes:.
     
  8. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Chris:
    Do you use the BFD to reduce the output level of frequencies that excite the modes of your room?

    Are you saying you have each sub doing different frequency ranges?

    How does the sub at back of room do resonance control?

    Gordon

    Just asking these questions to better understand how folk think through these LF issues.
     
  9. deckard

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    Tried it, but sold it on.

    My room is a devil in terms of it's frequency response (nearly a half-cube). I had to use some ridiculously big filters (both gain and bandwidth) to attenuate the response so that the volume on the sub had to be increased from just below 1 to nearly 6 (out of ten, Velo CHT-15). Even then I had to use positive filters if I wanted a flat response.

    This meant the sub was trying to work on a weedy output from the BFD and frankly I wasn't impressed overall. The bass was certainly more even but 'something' wasn't right.

    Not for me then. Others do very well, but it's not necessarily a panacea.
     
  10. Relay

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    I bought one this weekend and its definitely the best £95 spent.

    I've owned a number of subs ranging from M&K VX100, REL 201, REL Strata III and finally my current sub a B&W ASW CDM. If I'd bought one earlier I probably would have stopped at the first!

    The problem is that there's a pronounced peak at around 40Hz in my listening room which means that I previously couldn't make full use of the 20 - 40 Hz range without suffering boom and rattle at 40Hz or so, hence the sub volume had to be kept relatively low. Just a few hours tinkering this Sunday has evened out the response, though still far from flat, the spread between the highest peak and lowest trough has about halved. I now get the 'where did that come from ?!!' feeling when the sub bass hits. With a bit more experimenting things will improve further. I would recommed anyone dissapointed with their quality sub to consider trying one before they make an expensive mistake and potentially needless change.
     
  11. Stellavision

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    Thanks guys.
    I'll decide tomorrow whether to buy one or not.
    I don't feel I have a significant problem because I only notice a couple of dramatic volume increases while I'm doing a sweep.
    I suppose this could by why I have to suddenly reach for the remote control while watching a film late at night.
     
  12. avanzato

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    I consider Eq to be something that's used sparingly if you have to and none at all is best.
     
  13. chrisgeary

    chrisgeary
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    Yes and No. I don't believe you can't just reduce the output level, you still have waves building in the room, thus you still have resonance which results in poor timing. See below.

    kind of...

    ok, you know about standing waves. so i have a sub generating them at one end of the room. it obviously takes time to get to the other end of the room and at modal frequencies, this bounces back and forth along the room causing either a resonant peak or a cancellation. i get the sub at the back generating the same frequency as the sub at the front, but out of phase - so it helps stop the wave from building in the case of the peak, or it helps stop the wave from cancelling, in the case of a dip. thus it acts as a sort of 'stopper' reducing the resonance you get with standing waves. but you don't want it cancelling all frequencies, otherwise you would be losing out on the good stuff that doesn't excite the room.

    however, its quite hard to integrate two subs in this way with a BFD due to phase shifts. i have done some tests with and without the BFD - i have come to the conclusion that too many filters introduce too many phase shifts which become unmanagable.

    in my case, i have large speakers up front which means i can use my front sub to augment them. so what does work is using the front sub without a BFD (thus avoiding nasty phase shifts) and using its crossover control to bring it in below the rolloff freqs of the mains. so i end up with extended bass but even more nasty peaks and troughs than without the front sub. this 'resultant' response is then controlled by a lightly BFD'd sub at the back of the room. before i had the BFD, i just used the rear sub's crossover control to get it to operate around the main room mode. however it had enough extension to also cancel out the nice frequencies below that mode too (as the crossover control doesn't work below its value!). so i bought the BFD to stop it outputting below the main mode frequency. interestingly, above the main mode, where there were mostly dips, these have been restored a little. it does not give me a totally flat room response though, my room is way too peaky/troughy for that. when i finally actually own a house, i will invest in some room treatment and only use BFD where absolutely necessary.

    if i had small speakers and had to use lots of filters on the sub, i would be unable to use a rear sub - i believe there are too many phase shifts to make it work effectively.

    my condundrum is this:
    LFE are output to the sub channel only. now allegedly, my meridian 561 will duplicate the sub information across large speakers and subs in certain operating modes. however, it is my experience that this is only partially true. some movies contain LFE in the LR channels only. this does not get duplicated. so why not just have LFE information sent to the large speakers and use high level to my subs? well then there goes the BFD option and the use of the rear sub.

    there is no perfect solution, as far as I can see. what i want is a bass managed system which is the same for 2 channel music as it is for movies. i can accept peaks and troughs in movies, so i worry less about that - but what about DTS music? I was listening to tubular bells the other night, and noticed some higher bass notes were missing. i turned off the ABC on my front sub, and there it was. So the meridian is clearly not duplicating LFE information as it should. Thus using the front sub to augment the mains isnt going to work either.

    The only other choice left, is to turn off the sub output, use high level for the mains and augment them, and then split out the line level feed to the main power amps to supply a BFD'd rear sub for resonance control. I have yet to try this out. This is where i start to realise that treating the room (the cause) is probably a much better starting point than using electronics.

    This is my thinking on bass management... *phew*
     
  14. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Interseting thought process Chris. I think some of your issues are that you have so many sources of bass energy in your system.

    Gordon
     
  15. selexus

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    Behringer are currently producing some very interesting products at a price that i find very appealing.
    Having read what Branxx and others have to say about the RME range of soundcards, i've decided to move over to a complete HTPC set up, using the HTPC to decode the DD or DTS stream and the RME to do the DAC bit with the Behringer DCX2496 to filter and eq the front L&R channels and the sub. The DCX has 3 inputs that i'm planning to use for L/R and LFE. Summing all 3 to feed 2 subs with an EQ'ed signal. I'll use the remaining 4 outputs to bi amp some seas odins that i'm saving for, the rear and centre being fed direct from the RME to the power amps.
    The only reservation i have with the behringer is a possiblity that it will run out of steam with all the work i'll be asking of it.

    Lots of work, but a possiblity of a very rewarding system for a bargain price.:smashin:

    Cheers
     
  16. avanzato

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    Similar thoughts to mine there Selexus but I wasn't going to use a HTPC. I was thinking of doing a fully active system with two DCX2496 and the Seas Coaxial drivers. After downloaded the DCX manual and realising what a flexible but complex thing it was I have postponed the idea for now. When I get the spare cash I'll probably get one to try and was thinking of it being a bass manager for my front channels, with the option of sub Eq should my plans go horribly wrong. ;)
     
  17. chrisgeary

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    gordon: yes, that may well be true. i have also tried setting all speakers to small and letting the subs do the work - but there really isn't much output at all compared to having the mains in the equation. it could be that i've outgrown my subs now!?
     
  18. chrisgeary

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    gordon et al: just for completeness, i have reverted back to large mains and LFE duplicated between them and the subs. it makes for a much more even response through the room with the rear sub controlling resonance. and i do use the BFD now to reduce the output of the front sub at the main room mode. would struggle to achieve all this without a BFD in a rented house that i cannot room treat.
     
  19. IronGiant

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    I set up a near perfect curve with a BFD using an SPL meter at a single spot (where I wanted to sit) but there are so many different nodes in my room it wasn't appropriate. 2 people sitting side by side on the 2 seater sofa in front of the screen either get massive bass or barely any. I've compromised by reducing all settings by a half until I can resite the subwoofer/ seating area. The BFD is incredibly helpful, but it doesn't overcome the problem with the room ie dead/hot spots of bass.
     
  20. Ettepet

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    Just ordered one three hours ago, for 140 euro (incl. p&p).
     
  21. Nic Rhodes

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    I have the 'other' Behringer box that can do this. I would always treat this approach to 'acoustics' as the last resort and would use a BFD as the final thing. I feel there are much better ways of doing this but.......BFD is easy. Use with caution and know it limitations, it is not a bee all and end all solution
     
  22. Stellavision

    Stellavision
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    Which 'other' Behringer box are you refering to?
     
  23. eviljohn2

    eviljohn2
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  24. Nic Rhodes

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    Mine is the Ultra curve pro 2496 which also does MUCH more besides. The Behringer boxes does much for little money but you are far better off trying to solve the 'issues' first, a bit like KEYSTONE CORRECTION in projectors.

    Must admit a sneakying admiration for what Behringer give you for so little money however, my box has two of the SHARCS my Tag AV32R uses!
     
  25. Ettepet

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    Today it arrived. I didn't know what the large and heavy box was for, until I opened it. Man, that BFD is BIG!! :eek:

    I haven't got an SPL-meter yet, nor a proper RTA setup, so I guesstimated the settings of the 6 PEQ's now in service. The sound has improved a lot! (I must have "absolute" hearing :D)
     
  26. mw3cdj

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    It's not big :confused:

    Anyway i use mine in combination with Auralex Bass traps and further room treatments.
    Made a hell of a difference

    Daran
    :smashin:
     
  27. Ettepet

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    It's Pro-audio rack size, the box alone is over half a meter long!
     
  28. rob_w

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    Hey Mr Beekeeper,

    My Ultracurve pro 2496 uses AKM delta sigma stuff - is this the same as the sharc stuff ? - Would be nice to know my xo(ultradrive) uses the same stuff as Tag.:D

    Cheers

    Rob
     
  29. Stellavision

    Stellavision
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    The actual bfd may be nearly half a metre wide at 48 cm, but that includes rack mounting brackets on the end and the whole thing is only 4 centimetres high! Hardly the size of a 7.1 multi-channel amp!!!
    Its shipping weight is only 3 KG.
    Add another 20 and you will be near the weight of an SVS PB2+!
     
  30. Ettepet

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    Stellavision, and there you see that going from a BFD to a 7.1 multi-channel amp and then on to a full-blown SVS PB2+ is really only a matter of added weight! :D ;) But that reminds me that I can pro'lly get those brackets off... :smoke:
     

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