Brian Fellmeth
Supporting Actor
- Joined
- Jul 30, 2000
- Messages
- 789
What does a BFD do and do I need one?
BFD stands for Behringer Feedback Destroyer.
One of the goals in setting up your audio system is a relatively flat frequency response. This means that all frequencies in the audio spectrum are neither enhanced nor attenuated by your system. Thus, what strikes your ears is exactly what the musician or sound engineer mastered into the source.
Designing the electronic components to have a flat frequency response is relatively easy, and virtually all currently available electronic components do not introduce significant varations.
Speakers, on the other hand, are tougher to achieve flat response, and the manufacturers go to great lengths to get within a few dB of perfectly flat in an anechoic environment (which basically means that aside from the interactions you'll find in the room- the speaker is "flat").
Unfortunately, when a speaker is placed in a real room, the room becomes part of the sound generating system, and the manufacturer’s best efforts are undone. The problem is by far at its worst in the deep bass area- frequencies below 150 Hz. It is not uncommon at all for a room to boost frequency X by 15 dB and reduce frequency Y 15 dB even though the sub is putting out exactly the same overall sound pressure level (SPL).
The effect on what you hear is that the deep bass becomes boomy and dominated by the boosted frequencies. The problem is most apparent with bassy music where some notes will jump out of the music and other recede into the background as if the bass player was playing some notes very hard and barely hitting others.
There are two methods of attacking this problem : room treatments and equalization. Room treatments involve installing sound absorbing panels and boxes in strategic locations such as corners and along long uninterrupted walls- trying to get the room to behave more like the ideal echo free chamber that the manufacturer used to design the speaker. This is expensive, time consuming and has a horrid SAF (Spouse Approval Factor). The alternative is equalization, and this is where the BFD comes in.
The Behringer Feedback Destroyer (BFD) is a $140 piece of pro audio gear that was designed and marketed for an entirely different purpose from improving the bass response of home theaters. The BFD is supposed to be used to monitor the amplified signals in live music performances (mostly microphone channels) and snuff out feedback by blocking (or filtering) the specific frequency that is generating the feedback.
As a secondary, almost throwaway feature, the Behringer engineers decided to allow the user to control the 24 available EQ filters by specifying a filter frequency, the degree of boost or attenuation at that frequency, and the degree to which neighboring frequencies are affected (or the “bandwidth” of the filter). By applying combinations of these bell shaped filters to the signal sent to the subwoofer amp, it is possible to very precisely shape the frequency response curve-- effectively counteracting the peaks and valleys introduced by the room.
Understand the the BFD is not really a unique item in that it is an equalizer. There are several thousand EQ products on the market, and any one of them - in theory- could be used to tame peaks and valleys in the subwoofer signal. However, what the BFD does offer that is lacking in any unit even remotely in this price range is a great number of filter points and full frequency control. Where other Eqs may only have 2-3 filters positioned to control bass frequencies (and others which are assigned to midrange and treble)-- the BFD can use all 24 filters in the "bass" range- making it specifically well suited to use with subwoofer- offering ultimate level of control.
So, the BFD is used to equalize the signal sent to the sub in such a way that is a reverse of what the room is doing to mangle the response curve. The frequencies that the room makes too loud are quieted down, and those that the room sucks out are boosted. The only equipment required to program the BFD filters are a radioshack SPL meter and a CD with low frequency test tones. There are several expert BFD gurus at HTF that are very generous with offering assistance via the board. The archives are loaded with threads where most of the common problems are discussed.
There is also a comprehensive tutorial published by Sonnie Parker here :
Link Removed
So, if your bass is boomy and uneven, this $140 upgrade may have much more impact than a $1000 sub upgrade. Room effects do not discriminate. A top of the line SVS, Rel or Velodyne is just as susceptible as a Bose bass module.
BFD stands for Behringer Feedback Destroyer.
One of the goals in setting up your audio system is a relatively flat frequency response. This means that all frequencies in the audio spectrum are neither enhanced nor attenuated by your system. Thus, what strikes your ears is exactly what the musician or sound engineer mastered into the source.
Designing the electronic components to have a flat frequency response is relatively easy, and virtually all currently available electronic components do not introduce significant varations.
Speakers, on the other hand, are tougher to achieve flat response, and the manufacturers go to great lengths to get within a few dB of perfectly flat in an anechoic environment (which basically means that aside from the interactions you'll find in the room- the speaker is "flat").
Unfortunately, when a speaker is placed in a real room, the room becomes part of the sound generating system, and the manufacturer’s best efforts are undone. The problem is by far at its worst in the deep bass area- frequencies below 150 Hz. It is not uncommon at all for a room to boost frequency X by 15 dB and reduce frequency Y 15 dB even though the sub is putting out exactly the same overall sound pressure level (SPL).
The effect on what you hear is that the deep bass becomes boomy and dominated by the boosted frequencies. The problem is most apparent with bassy music where some notes will jump out of the music and other recede into the background as if the bass player was playing some notes very hard and barely hitting others.
There are two methods of attacking this problem : room treatments and equalization. Room treatments involve installing sound absorbing panels and boxes in strategic locations such as corners and along long uninterrupted walls- trying to get the room to behave more like the ideal echo free chamber that the manufacturer used to design the speaker. This is expensive, time consuming and has a horrid SAF (Spouse Approval Factor). The alternative is equalization, and this is where the BFD comes in.
The Behringer Feedback Destroyer (BFD) is a $140 piece of pro audio gear that was designed and marketed for an entirely different purpose from improving the bass response of home theaters. The BFD is supposed to be used to monitor the amplified signals in live music performances (mostly microphone channels) and snuff out feedback by blocking (or filtering) the specific frequency that is generating the feedback.
As a secondary, almost throwaway feature, the Behringer engineers decided to allow the user to control the 24 available EQ filters by specifying a filter frequency, the degree of boost or attenuation at that frequency, and the degree to which neighboring frequencies are affected (or the “bandwidth” of the filter). By applying combinations of these bell shaped filters to the signal sent to the subwoofer amp, it is possible to very precisely shape the frequency response curve-- effectively counteracting the peaks and valleys introduced by the room.
Understand the the BFD is not really a unique item in that it is an equalizer. There are several thousand EQ products on the market, and any one of them - in theory- could be used to tame peaks and valleys in the subwoofer signal. However, what the BFD does offer that is lacking in any unit even remotely in this price range is a great number of filter points and full frequency control. Where other Eqs may only have 2-3 filters positioned to control bass frequencies (and others which are assigned to midrange and treble)-- the BFD can use all 24 filters in the "bass" range- making it specifically well suited to use with subwoofer- offering ultimate level of control.
So, the BFD is used to equalize the signal sent to the sub in such a way that is a reverse of what the room is doing to mangle the response curve. The frequencies that the room makes too loud are quieted down, and those that the room sucks out are boosted. The only equipment required to program the BFD filters are a radioshack SPL meter and a CD with low frequency test tones. There are several expert BFD gurus at HTF that are very generous with offering assistance via the board. The archives are loaded with threads where most of the common problems are discussed.
There is also a comprehensive tutorial published by Sonnie Parker here :
Link Removed
So, if your bass is boomy and uneven, this $140 upgrade may have much more impact than a $1000 sub upgrade. Room effects do not discriminate. A top of the line SVS, Rel or Velodyne is just as susceptible as a Bose bass module.