BFD House Curves and Calibration

Discussion in 'Speakers & Subwoofers' started by ChuckRG, Feb 13, 2004.

  1. ChuckRG

    ChuckRG Agent

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    I was experimenting with using what would be equivalent to a BFD house curve last night. But when performing the channel calibration, because the response is so different than NOT using a house curve, I was wondering if I need to set the gain of the subs slightly higher than normal. What I mean is that if I set the level to match the other speakers according to what the processor generates as sub noise, will the sub output be too low. (I finished this at 2AM this morning so did not have a change to listen)

    Based upon the slope of the curve, my cross over point (80Hz) is about 7 db's down from 30Hz.

    PS: I am actually using at Tact Audio Room Correction device instead of a BFD to accomplish the house curve

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  2. Keith M.

    Keith M. Second Unit

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    Im using a BFD also, and have heard of "house curve" but each time I search the forum for a clear definition or example I get nothing...

    Could you please explain what a "house curve" actually is? Is this just a set of filters that accentuate certain freqs. based on what the listener likes rather than truely flat response?
     
  3. ChuckRG

    ChuckRG Agent

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    A house curve is just that--taking your flat response and turning into something else. If you read the documents that explain it, it suggest that from 30Hz to about 100Hz, the curve slope down about 5 to 10 db's. I assume that the reason for doing so is to take into a account the Fletcher-Musnon effect of the way the ear/brain deals with low frequencies.

    On a BFD, you can obtain kind of curve this by creating a filter that starts at about 366Hz, is two octaves wide and has a gain of minus about 15db. Try it and if you don't like it, turn that filter off or modify it until you do like (change the gain, Frequency or width)
     
  4. Wayne A. Pflughaupt

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  5. Wayne A. Pflughaupt

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    Chuck,

    Personally I set my subs by ear. The calibration procedures are a good starting point, but they cannot take into account the size of your room. Smaller rooms will require that the sub measure higher than larger rooms.

    I’d say go ahead and set it for the “correct” calibration, but if you think it needs further tweaking, feel free.

    Regards,
    Wayne A. Pflughaupt
     
  6. BruceD

    BruceD Screenwriter

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    As a kinda short-hand description, I'd say a house curve tends to make the bass frequencies Sound like they are at the same SPL level as the higher frequencies rather than Measuring the same SPL level as the higher frequencies.

    Yes, this has everything to do with the Fletchur-Munson curve (our ears less sensitive response to bass frequency SPL) and the automatic cabin-gain boost of bass frequencies in small rooms.
     
  7. Steve_Ma

    Steve_Ma Second Unit

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    I understand the Fletcher-Munson curve, but I never quite undertood the reason for the house curve or how it relates to accuracy (if we assume accuracy as a goal). Or does it relate at all?

    OK, humans are less sensitive to the lower freqs. Fine, that makes sense to me.

    But then why wouldn't the artists and sound engineers take that into account during the performance and/or recording of the material and automatically compensate? Surely they also must abide by the Fletcher-Munson principal as well?

    Did that even make sense? I'm not trying to be a smart-a#%, but I don't get it. Are we to assume that the artist or engineer actually meant to have more OOMMPH in the recording, but they were unable to do it so the consumer/end user should compensate?

    I'm not trying to start a flame war, but I really want to understand this better. [​IMG]
    --Steve
     
  8. Wayne A. Pflughaupt

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    You can find a discussion on the topic at this thread. It’s pretty long, so get a cup of coffee and a jelly roll. [​IMG]

    Regards,
    Wayne A. Pflughaupt
     
  9. Steve_Ma

    Steve_Ma Second Unit

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    Wayne,

    Thanks for the link. That is more than enough info for me to chew on for awhile.

    I really liked the discussion on cabin gain in various rooms vs the nearfield environments of a recording studio. It's certainly a place for me to start to get my hands around this....but I still feel like I'm missing something. My gut reaction still wants to say that when I calibrate my system, am I not (to a limited extent) compensating for that difference? Anyway, I'm gonna do more research, but thanks again for the link. Great thread.

    --Steve
     

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