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Recent content by Richard Greene

  1. Richard Greene

    Room response time and TrueRTA

    It is said that it takes about 250ms signal to get those room modes ringing. RG: That's much too long! The correct time for a front wall to back wall standing wave to start would be the time it takes sound to go from your speaker to the back wall, bounce off the back wall, and then...
  2. Richard Greene

    Setting Up Multiple Subs - An interesting read...

    The white paper appears to be based on scientific principles but the science is faulty and the conclusions almost worthless to the average home theater owner. The paper should be deleted from the Harman website because it detracts from the excellent Floyd Toole papers at that website. The...
  3. Richard Greene

    Using the crossovers in your sub AS WELL AS in your receiver?

    A 24dB/octave filter is nothing more than two 12dB/octave filters cascaded. A 12dB/octave low pass filter in the receiver cascaded with a 12dB/octave low pass filter in the subwoofer is the cheapskate's 24dB/octave low pass filter. Two common subwoofer problems: (1) Too much output over...
  4. Richard Greene

    BFD EQ Help

    I'm not sure why you would not be able to reduce the peak at 111Hz. unless your bandwidth is too narrow and the center frequency is wrong. Most peaks are addressed with 1/6 octave (10/60) to 1/4 octave (15/60) bandwidths. Once in a while there are two adjacent peaks that need 1/3...
  5. Richard Greene

    BFD EQ Help

    The goal with a BFD should be bass in a +/-5dB range. Sometimes the best you can do is +/-6dB You seem to be close to +/-5dB. The major problem getting to +/-5dB is not the peaks (the BFD can handle them) -- it's one or two nulls. You can't affect standing wave nulls with an equalizer...
  6. Richard Greene

    Will adding more subs really improve bass response in a properly calibrated setup?

    The article you referenced is misleading because its goal is not the smoothest possible bass frequency response for a single listener, which most of us want. The goal of the experiment was the most consistent (not smooth) bass frequency response from seat-to-seat within a fairly large area of...
  7. Richard Greene

    Will adding more subs really improve bass response in a properly calibrated setup?

    In a rectangular room (and most common room shapes) using two subs on opposite sides of the room will prevent odd-order standing waves from forming between two opposing surfaces. The common left-right subwoofer set-up places the two subwoofers out-of-polarity for the first-order axial room...
  8. Richard Greene

    BFD Boost Question

    Wayne is correct that one can't EQ nulls. However you don't have nulls, you have what I like to call "partial nulls" ... and in addition, it's very likely your ears are not located at the deepest portion (weakest bass) of any of these partial nulls. A true null would have no output at all...
  9. Richard Greene

    Stereo Subwoofers

    "I have used my subwoofers in "stereo" for years." RG I used "stereo" subwoofers from 1980 to 1994, and a mono subwoofer since 1994. If one sharply limits output above 70-80Hz. a subwoofer becomes sonically invisible almost 100% of the time while listening to music. When a subwoofer is...
  10. Richard Greene

    Suggest some appropriate BFD filters...

    What signals were used and where were you measuring from? The measurements are so good they suggest you were using pink noise or warble tones, measuring outdoors where there are no standing waves, or you placed the microphone a few inches from the subwoofer to eliminate room effects rather...
  11. Richard Greene

    how much does it take to blow out speakers?

    I noticed the usual misunderstanding of clipping distortion and the misconceptions about square waves / DC (there are no square waves and there is no DC current caused by amplifier clipping). Clipping distortion has only a very small effect on drivers (related to too much power going to the...
  12. Richard Greene

    Can A Sub Damage Your Home?

    If you excite the wall's resonant frequency long enough and hard enough you may get some "nail pops". When I had my Tempest tube sub in a room corner a 20Hz. sine wave at about 100dB caused some nail pops near the subwoofer. The wall was rattling very loudly at that frequency ... but a sine...
  13. Richard Greene

    Question about equlizing with a BFD

    Cabin Gain is an approximately 12dB/octave bass ramp up starting below the lowest frequency room mode whose center frequency in Hz. for a rectangular room would be approximately: 565/room length (largest room dimension) in feet. Cabin Gain will be less than 12db/octave if there are open...
  14. Richard Greene

    Sub placement and standing wave help please.

    Subwoofer position is an interesting topic because everyone seems to have a strong opinion, seems to believe there is one right answer for every room, and almost nobody makes measurements to collect data that would lead to at least a Rule-of-Thumb for rectangular rooms. The first goal should...
  15. Richard Greene

    Sub too big for a room?!?!?!?!?!?!?!?!?

    I originally designed a low Qtc (6.5 cubic foot tube filled with 8 lbs. polyester stuffing) sealed Tempest subwoofer for a 13' x 12' bedroom. It sounded fine although that use was a waste of displacement. I later moved the subwoofer to an 800 square foot living room where it gets some exercise...
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