Bass Responce / Room EQ / House or Room Curve

Discussion in 'Archived Threads 2001-2004' started by Kirk Mango, Jan 17, 2003.

  1. Kirk Mango

    Kirk Mango Stunt Coordinator

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    I took the time a while back to measure my bass room response using my Ref 30 room eq mode. (These numbers do not include the adjustments due to the inacuracy of the Rat Schack SPL meter. They came straight off the meter.) I used the -42dB test tone available in the Ref 30 for my test. Here is what I got.

    HZ dB
    20 63
    22 66
    24 70.5
    26 70
    28 72
    30 71
    32 70
    34 70
    36 71
    38 72
    40 76
    42 79
    44 80
    46 81
    48 81
    50 80
    52 76
    54 74
    56 73
    58 74
    60 76
    62 76
    64 76
    66 77
    68 77
    70 76
    72 76
    74 76
    76 76
    78 74
    80 72
    82 70
    84 67
    86 62
    88 63
    90 63

    What would this look like with the Rat Schack Meter Adjustments added in? Is this a normal room response with the test tone I am using? I know there is always going to be a room boost around 40-50hz, is it worth trying to eleviate this? (I have been told that this boost is important for movies because alot of information from special effects is in this range and this is what helps give them their effect.) Any suggestions?

    KM
     
  2. Ned

    Ned Supporting Actor

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    bleh
     
  3. Frank Carter

    Frank Carter Screenwriter

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    What subwoofer is this?
     
  4. Kirk Mango

    Kirk Mango Stunt Coordinator

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    It is a Rel Storm III. Keep in mind I am only applying a -42dB test tone to it. There is also a test tone in the -30's and one in the -20's (to loud to effectively use).

    Any other responses on whether I should knock the peak down in the 40-50hz range? Does this scale represent a normal house curve? Should I apply the midrange test tone and see if the increase volume level shows as much of a difference through these ranges?

    KM
     
  5. Wayne A. Pflughaupt

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    Succinct answers to specific questions:

     
  6. Kirk Mango

    Kirk Mango Stunt Coordinator

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    Wayne,

    When you say better, in what way. What will my efforts give me. If I knock this down, won't I need to increase the sub volume in order to get it balanced with my other speakers when calibrating? I am not sure but the test tone for calibration from my Ref 30 may fall within the hz range I am talking about knocking down. If I do this won't all other hz ranges increase because I will need to increase the signal level to the sub to reach proper calibration at 75db for reference levels?

    Do you know the Increase &/or Decrease of adjustments which is needed to be added to my meter readings from 20hz - 80hz going up 2hz at a time. I have only found one such table and it does not give adjustments for every 2 hz (20,22,24,26,28,etc.) Once I have done this how do I apply a house curve to it? Based on my readings I would assume that I would want all measurments to read around 74 - 75 on my dB meter, is that correct (of course that would be after adding in the calibration adjustments for the Rat Schack Meter)?
     
  7. Edward J M

    Edward J M Cinematographer

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    Kirk:
    This is the best chart I have seen. I would simply extrapolate between any numbers you don't have a value for. At worst you will be off a dB or so, but overall you will be much closer to your actual FR than without any correction value at all.
    http://members.tripod.com/~terrycthe...um/page11.html
    Of course, after you EQ, you will have to regraph your results and recalibrate. Yes, the sub test tone is typically around 40 Hz, and knocking down that huge hump at 50 Hz will affect your calibration level.
    This looks like a room-induced peak. You might want to experiment with placement before you apply any EQ. If EQ fails, try a feedback destroyer.
    Without hearing it, I'd predict this sub is rather boomy sounding right now. Special FX on LFE are often more in the 25-35 Hz range, rather than the 50-60 Hz range.
    Tame that hump, flatten out the curve, and recalibrate and you will realize a much more realistic bass presentation with the low end stuff feeling a bunch stronger in comparison. The sub hangs in there pretty well down to about 25 Hz (corrected curve), as compared to the 80 Hz level, so I think there's hope for a decent in-room FR.
     
  8. Wayne A. Pflughaupt

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  9. Edward J M

    Edward J M Cinematographer

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  10. Kirk Mango

    Kirk Mango Stunt Coordinator

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    I cannot really move it around. It is behind a 61" RPTV which is placed in a corner. The sub is corner loaded, by rels instructions, and is set up perfectly, again per rels instructions. Two more questions. First, it seems to me that this -42dB test tone gives me around a 74-75dB reading on average, after corrections factored in, when you look at the readings I took. Most of my hz readings are close to this. Now I know there is no way to get it all exact, however, should I be knocking that hump down from the 81db high to 75dB? Then put my normal preamps LFE test tone on and then increase level till I hit 72dB for the sub(+2-3 for correction factor bringing it to 75dB).

    Second, The Rel Storm (as are all REl subs) are suppose to be way overengineered. Their subs are also protected with special circuitry to keep them from bottoming out. If I do this will this sub be able to handle what LOTR, Titan A&E, and ATOC will dish out? I normally listen at -15dB below Reference and I get a lot of shaking already. I can feel my couch and floor rumble in the intense scenes of the above DVD's. To just give you one example, when I play the beginning fly by sequence in Star Wars ATOC, I get meter readings of areound 99dB when the ship comes through the clouds and that is with a volume setting -15dB below reference. I do not know what I sould get at reference.

    Lastly, Im I correct in assuming that this will only effect my LFE settings and will have no bearing on the settings for my highlevel connections which run directly to my amplifier (connected to right and left mains for support of their bass)?

    KM
     
  11. Wayne A. Pflughaupt

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    Kirk,

     
  12. Kirk Mango

    Kirk Mango Stunt Coordinator

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    Wayne,

    Thanks, great response. I am not using a seperate equalizer. My Ref 30 Preamp has a notch filter in it, however, I have not yet discovered how I can knock down a specific hz level without it knocking down all the others. When I changed one hz setting say by 2 db the whole hz range changed by the same amount. This is not what I would want or expected. I will have to call B&K for an explanation on how it works. As far as my room goes, It is a rectangle that is 24 feet long by 14 feet wide with an 8foot ceiling. The back wall opens completely into the kitchen, only 3 walls. The wall where the RPTV and the sub are at is full of california sandstone, the other two long walls are drywall. My sub volume setting on the LFE side is 1/2, however, my preamp setting for the sub is at -3.0. 0 is aproximately the middle setting for the pramp, I assume. Thanks for your posts, very helpful. Anything else you can tell me based on the above info would also be helpful.

    KM
     
  13. BruceD

    BruceD Screenwriter

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    Kirk,

    That gives you a volume of 2688 ft3 with the addition of an open wall to the kithchen (which means you need to add all of the volume of space on the other side of that open wall).

    Depending on the size of the other open areas, this means your sub might be trying to load >5000 ft3 area, maybe too much area for the REL at reference volume.

    Then again it could be just fine, experimentation on your part will tell you more. The notch filter (a parametric EQ)on your Ref30 may help you knock down the 50Hz peak if you are not using the high-level (speaker wire) connection method for the REL.

    You just need to set the "Q" or width of the notch filter to it's minimum value, which narrows the effect of the filter. Otherwise it can be too wide and will work on a full octave of frequencies around the notch frequency (50Hz) selected.
     

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