What is the BFD?
The BFD is a Parametric Equalizer used to equalize the frequency response of any home theater or home audio subwoofer in home audio or home theater systems. The model that most people have been using is the Behringer Feedback Destroyer Pro DSP1124P and is currently priced at around 90-100 bucks at several online stores. There is an older DSP1100P model and a newer FBQ2496, but stick with the 1124... it's really the best of the three anyway. This is also the model for which the BFD Guide is written.
What is the BFD used for?
Originally the BFD was designed for the performance/entertainment industry. Think about its name "feedback destroyer". It is used in recording studios and concerts. The unit is wired into the system, set on auto-pilot, and then it searches out feedback and kills it. However, its functionality and design allows it to be used in the home theater system as one of the most flexible parametric equalizers for a home audio subwoofer available... and the least expensive by far. With the BFD you can pick up to 24 frequencies (1 combined channel X 24 or 2 separate channels X 12), adjust the bandwidth as narrow or wide as you wish (from 1/60 of an octave to 120/60 or 2 full octaves), and either boost them as much as 16db or cut them by as much as a whopping 48db. How many parametric equalizers do know of that can do that for 100 bucks or less? Pretty impressive if you ask me.
Why do I need a BFD?
As stated above, the BFD can be used as a parametric subwoofer eq. Subs are professionally measured and tested in either a wide open space or an anechoic chamber/room and the mic is usually placed 1 meter out from the center of the sub speaker cone. How many of us set up our sub in the perfect room and have our listening position with our ears centered 1 meter in front of the sub? When you see the frequency response of a sub measured by the manufacturer you see this:
The manufacturer rates the frequency response as 22hz - 200hz (+/-3db). When we place that sub in our homes there will be two things for certain and one thing for sure… if we measure the frequency response at our listening position, it will not be the same as the manufacturers response. It will look something like this:
This is actually the pre-BFD response of a former sub I owned and is measured from my main listening position. Obviously yours may look different... the point is that it will not be nearly as flat as the manufacturers rated response. This is not the sub manufacturers fault... they did what they were suppose to do. Our room size, shape, construction, and things we place inside such as cabinets and chairs, as well as the location of our sub, will all have an effect on our sub response. This means what we are hearing from our sub is not what the manufacturer intends for us to hear and it will probably not sound as good as it should. What we can do with the BFD is at least get the response better for the main listening position, and many times it will make it better for those near that main listening position. What we would like to do is get our response to look something like this:
No... this is not a perfectly flat line, it is somewhat of what we call a house curve. The image above is the post BFD response of my former sub from my main listening position. The house curve is what many enthusiasts like for movie watching, while critical music listeners might prefer a flatter response. The house curve generally rises about 10-12db from about 100hz to somewhere aroud 30-40hz and then flattens out. It all depends on what kind of response you like. There really isn't a chiseled in stone rule for the house curve. In my case it’s the best I could do since I had a nasty dip at 40hz. So... if we take those two graphs, the pre-BFD response and post-BFD response, we can get a really good picture of what the BFD can do:
Not bad, huh? I wonder what your response looks like.
How complicated is it to setup and use the BFD?
When I first learned of the BFD I was challenged mentally trying to figure it out. To me it was intimidating and humbling. The manual is just not that specific with regards to using it as a parametric equalizer for home audio subwoofers, since that is not its original intended use. I searched the forums and found bits and pieces of info, but I could never find one place that had it all put together and easily understandable. Many of those bits and pieces I found were written by the technical savvy and most of what I was reading flew right over my head. Not to mention I couldn’t find everything I needed to know... I had lots of unanswered questions. Yeah it was frustrating. So I challenged myself again. I decided I’d put together a comprehensive guide dedicated to the setup and use of the BFD that would contain all these bits and pieces of information in an easy to understand language. With the help of mainly brucek and a couple of other forum buddy’s (I could not have done this without everyones help), I was able to put together the BFD Guide. brucek was a major contributor in much of what is written in the Guide and in helping me understand all the technical stuff, while the others had various inputs of importance to it's accomplishment as well.
Links related to the BFD that may be of interest to you:
Official REW Support Forum
brucek BFD Review
brucek on Bandwidth
brucek on House Curves
Wayne Pflughaupt on House Curves (excerpt from forum thread)