主题：常见电声设计软件

 QB3 VENTED-BOX ALIGNMENTS

                 +----------------------------------------------+

                 | QL=7 |  Qts |  h   |   a   | f3/fs | Peak-dB |

                 |------+------+------+-------+-------+---------|

                 |      | 0.10 | 3.84 | 34.39 |  5.22 |   0.00  |

                 |      | 0.12 | 3.21 | 23.55 |  4.33 |   0.00  |

                 |      | 0.14 | 2.75 | 17.02 |  3.70 |   0.00  |

                 |      | 0.16 | 2.41 | 12.77 |  3.21 |   0.00  |

                 |      | 0.18 | 2.15 |  9.86 |  2.83 |   0.00  |

                 |      | 0.20 | 1.94 |  7.78 |  2.53 |   0.00  |

                 |      | 0.22 | 1.77 |  6.24 |  2.28 |   0.00  |

                 | QB3  | 0.24 | 1.63 |  5.07 |  2.06 |   0.00  |

                 |      | 0.26 | 1.51 |  4.15 |  1.88 |   0.00  |

                 |      | 0.28 | 1.40 |  3.43 |  1.72 |   0.00  |

                 |      | 0.30 | 1.31 |  2.84 |  1.57 |   0.00  |

                 |      | 0.32 | 1.24 |  2.37 |  1.44 |   0.00  |

                 |      | 0.34 | 1.17 |  1.97 |  1.33 |   0.00  |

                 |      | 0.36 | 1.11 |  1.64 |  1.22 |   0.00  |

                 |      | 0.38 | 1.06 |  1.36 |  1.12 |   0.00  |

                 |      | 0.40 | 1.01 |  1.11 |  1.02 |   0.00  |

                 |------+------+------+-------+-------+---------|

                 |      | 0.42 | 0.97 |  0.91 |  0.94 |   0.01  |

                 |      | 0.44 | 0.93 |  0.73 |  0.86 |   0.14  |

                 |      | 0.46 | 0.90 |  0.57 |  0.80 |   0.56  |

                 | SQB3 | 0.48 | 0.87 |  0.43 |  0.75 |   1.32  |

                 |      | 0.50 | 0.83 |  0.31 |  0.71 |   2.46  |

                 |      | 0.52 | 0.81 |  0.20 |  0.68 |   4.01  |

                 |      | 0.54 | 0.79 |  0.10 |  0.66 |   6.08  |

                 |      | 0.56 | 0.77 |  0.01 |  0.64 |   8.87  |

                 +----------------------------------------------+

C4 VENTED-BOX ALIGNMENTS

                 +----------------------------------------------+

                 | QL=7 |  Qts |  h   |   a   | f3/fs |Ripple-dB|

                 |------+------+------+-------+-------+---------|

                 |      | 0.26 | 1.05 |  3.68 |  2.23 |   0.00  |

                 |      | 0.28 | 1.08 |  3.24 |  1.94 |   0.00  |

                 |      | 0.30 | 1.10 |  2.80 |  1.71 |   0.00  |

                 |      | 0.32 | 1.11 |  2.40 |  1.53 |   0.00  |

                 | SC4  | 0.34 | 1.10 |  2.01 |  1.37 |   0.00  |

                 |      | 0.36 | 1.08 |  1.67 |  1.23 |   0.00  |

                 |      | 0.38 | 1.05 |  1.37 |  1.12 |   0.00  |

                 |      | 0.40 | 1.01 |  1.11 |  1.02 |   0.00  |

                 |      | 0.42 | 0.97 |  0.91 |  0.94 |   0.00  |

                 |      | 0.44 | 0.92 |  0.75 |  0.87 |   0.00  |

                 |------+------+------+-------+-------+---------|

                 |      | 0.46 | 0.88 |  0.63 |  0.81 |   0.01  |

                 |      | 0.48 | 0.84 |  0.54 |  0.76 |   0.03  |

                 |      | 0.50 | 0.80 |  0.46 |  0.72 |   0.07  |

                 |      | 0.52 | 0.77 |  0.41 |  0.68 |   0.12  |

                 |      | 0.54 | 0.74 |  0.36 |  0.65 |   0.19  |

                 |      | 0.56 | 0.72 |  0.33 |  0.63 |   0.27  |

                 |  C4  | 0.58 | 0.70 |  0.30 |  0.61 |   0.36  |

                 |      | 0.60 | 0.68 |  0.27 |  0.59 |   0.46  |

                 |      | 0.62 | 0.66 |  0.25 |  0.57 |   0.57  |

                 |      | 0.64 | 0.65 |  0.24 |  0.56 |   0.68  |

                 |      | 0.66 | 0.64 |  0.22 |  0.55 |   0.80  |

                 |      | 0.68 | 0.62 |  0.21 |  0.54 |   0.92  |

                 |      | 0.70 | 0.61 |  0.19 |  0.53 |   1.05  |

                 |      | 0.72 | 0.60 |  0.18 |  0.52 |   1.17  |

                 +----------------------------------------------+

 BB4 VENTED-BOX ALIGNMENTS

                 +----------------------------------------------+

                 | QL=7 |  Qts |  h   |   a   | f3/fs | Peak-dB |

                 |------+------+------+-------+-------+---------|

                 |      | 0.20 | 1.00 |  5.90 |  3.37 |   0.00  |

                 |      | 0.22 | 1.00 |  4.85 |  2.95 |   0.00  |

                 |      | 0.24 | 1.00 |  4.05 |  2.60 |   0.00  |

                 |      | 0.26 | 1.00 |  3.43 |  2.29 |   0.00  |

                 | SBB4 | 0.28 | 1.00 |  2.94 |  2.02 |   0.00  |

                 |      | 0.30 | 1.00 |  2.54 |  1.79 |   0.00  |

                 |      | 0.32 | 1.00 |  2.22 |  1.60 |   0.00  |

                 |      | 0.34 | 1.00 |  1.96 |  1.44 |   0.00  |

                 |      | 0.36 | 1.00 |  1.74 |  1.31 |   0.00  |

                 |------+------+------+-------+-------+---------|

                 |      | 0.38 | 1.00 |  1.54 |  1.21 |   0.01  |

                 |      | 0.40 | 1.00 |  1.39 |  1.13 |   0.14  |

                 |      | 0.42 | 1.00 |  1.25 |  1.07 |   0.37  |

                 |      | 0.44 | 1.00 |  1.13 |  1.02 |   0.66  |

                 |      | 0.46 | 1.00 |  1.03 |  0.98 |   1.00  |

                 |      | 0.48 | 1.00 |  0.94 |  0.94 |   1.36  |

                 |      | 0.50 | 1.00 |  0.86 |  0.91 |   1.74  |

                 |  BB4 | 0.52 | 1.00 |  0.79 |  0.89 |   2.13  |

                 |      | 0.54 | 1.00 |  0.73 |  0.87 |   2.53  |

                 |      | 0.56 | 1.00 |  0.67 |  0.85 |   2.93  |

                 |      | 0.58 | 1.00 |  0.63 |  0.84 |   3.33  |

                 |      | 0.60 | 1.00 |  0.58 |  0.83 |   3.73  |

                 |      | 0.62 | 1.00 |  0.54 |  0.82 |   4.12  |

                 |      | 0.64 | 1.00 |  0.50 |  0.81 |   4.51  |

                 |      | 0.66 | 1.00 |  0.47 |  0.80 |   4.90  |

                 |      | 0.68 | 1.00 |  0.44 |  0.79 |   5.27  |

                 |      | 0.70 | 1.00 |  0.41 |  0.78 |   5.65  |

                 +----------------------------------------------+

 DESIGN TABLES FOR VENTED-BOX ALIGNMENTS

      When designing  a vented-box  system, it  should be  kept in  mind that

      there are  many combinations  of h  and a  that can  be used  to obtain

      different low-frequency  response characteristics  for a  given  driver

      Qts. Various  compromises exist as to low-frequency extension, response

      flatness, box size, and transient response.

      There are  a number  of commonly  used alignments,  and  these  can  be

      subdivided into  those that  are flat or non-flat. Flat alignments will

      have a  better transient  performance than the non-flat alignments, and

      can be obtained by using drivers with low values of Qts. Note, however,

      that the "better" transient performance of some alignments results from

      the reduced  output that  is obtained  in the transition band above the

      cutoff frequency.  We will  now proceed  to describe  some of  the more

      popular alignments that have been mentioned in the literature.

      There are  three main  flat alignments. The Super Fourth-Order Boom Box

      alignment (SBB4)  is characterized by a large box, low tuning frequency

      and good transient response, albeit with less bass response through the

      transition band  just  above  cutoff.  The  Fourth-Order  Sub-Chebychev

      alignment (SC4) has a degraded transient response compared to the SBB4.

      The Quasi Third-Order Butterworth alignment (QB3) is popular because it

      results in  a smaller box and lower cutoff frequency for a given driver

      Qts. Its  transient response  is not as good as that of the SBB4 or SC4

      alignments.

      Corresponding to  the above,  there are  three non-flat alignments. The

      Fourth-Order Chebychev  alignment  (C4)  has  an  equi-ripple  response

      characteristic, and  can be  useful for  low values of ripple less than

      1 dB. The  Fourth-Order Boom  Box alignment  (BB4) has  a peak  in  the

      response near  cutoff, which  can prove  undesirable if  too large. The

      Super Third-Order Quasi-Butterworth alignment (SQB3) is a high value of

      Qts extension of the QB3 alignment.

      The following  three sets of tables describe the values of h and a that

      are required  to tune  a vented-box enclosure to a particular alignment

      for a driver of given Qts. Also shown are the ratio of cutoff frequency

      to driver  resonance f3/fs,  and the  peak or  ripple in  the  response

      characteristic. The  values of  h and  a were calculated for an assumed

      leakage loss factor of QL = 7. It should be kept in mind that there are

      many other  possible sets  of values of h and a that yield satisfactory

      low-frequency response  characteristics, particularly  when the effects

      of room  loading are  included. The  tabulated values  should provide a

      good starting point for an alignment to be used in the SVB submodule.

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