Another BFD success story...

Discussion in 'Archived Threads 2001-2004' started by John Sully, Apr 12, 2002.

  1. John Sully

    John Sully Stunt Coordinator

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    But I just had to do it differently from everyone else...
    Being a basically lazy type of guy I didn't want to burn a CD with test tones and make 1/6 octave measurements over and over, aka "the manual method". So I went looking for something better.
    I started out trying to use ETF with my RS SPL meter, but found no joy here since my laptop only has a mic level input. I also found that the demo version of ETF was really too crippled to make multiple measurements -- you can only initiate two measurements each time you start up the program -- and that it was, in general, difficult to use. So I decided to hunt for a decent piece of software to handle the RTA duties. I looked at several and settled on the demo version of Praxis. The demo version of this program provides a very capable RTA.
    Next I needed to find a microphone which I could use for my measurements. Once again Behringer came to the rescue with the ECM 8000 a very flat omnidirectional mic intended for just such use. It is pretty cheap, I got mine at my local music store for $45. It also needs a phantom power source which was another $45. A cheap tabletop mic stand and a couple of cables and I was ready to roll.
    My first look at my room response was rather disappointing -- Praxis had a brickwall with no response below 90Hz. Ugh. RTFM. Adjust FFT size up until I get response down to 10Hz. Much better. However the response graphs keep jumping around. Praxis has an averaging function, I set it to 5 and things settled down quite a bit. Finally, I decided to set the resolution to 1/20th of an octave which required another increase of the FFT size.
    Once I had figured out how to set up Praxis, EQ'ing the sub was easy. Time to disconnect the mains and see what we can do. Choose a center frequency, bandwidth and gain. See what it does on the laptop. Too much bandwidth? Cut it down a bit and see what happens. Not enough gain? Adjust and see. It took me about 1/2 hour to get the sub +/- 5db from 20Hz to 100Hz. After the sub EQ was done I plugged the mains back in and took a look at the splice between the mains and sub. The sub seemed to be running a bit hot compared to the mains level, so I cut down on the sub level a hair. Time to give a listen...
    Oh my god! This is easily the best change I have made to my system in a long time. The bass from my HGS-15 was smooth, tight and fast. Kick drums had kick. Basses were bassier. It just sounded right. It also got rid of some of the localization problems which had been plauging me for years. I always knew in my heart that equalizing a sub is really quite essential for good bass response but units such as the AudioControl Richter Scale were always too expensive. The BFD, at $125, provides *more* control than the Richter Scale. Thank you fellow HTF members for introducing me to this piece of equipment.
     
  2. Sonnie Parker

    Sonnie Parker Second Unit

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    Sounds familiar, HGS-15 and a BFD. Good selection!
    [​IMG]
     
  3. Rick Radford

    Rick Radford Supporting Actor

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    Sounds like you did nice work, John.
    OOC, did you investigate :
    http://purebits.com/ (Purebits RTA)
    or
    http://www.trueaudio.com/truerta.htm (True audio RTA)?
    I haven't looked into them for a long time and am curious if they work well and are a comparable option for ETF/Praxis/Spectra.
     
  4. John Sully

    John Sully Stunt Coordinator

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    Yes I looked into both Purebits and True Audio. One of the requirements is that an RTA had to be useful in the demo version. Purebits had some silly limitations on the demo version which made me shy away from it, and True's free version was limited to 1 octave resolution, which is not enough for anything but looking at the pretty lines jump around. Finally, SpectraPlus does some evil things to your hard disk, so that I immediately ruled it out.

    In the end the only one which offered a free and fully functional RTA was Praxis, which is why I chose it.
     

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