Akabak simulation of large BR

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This Akabak script simulates a tall BR with a RCF L18P400 at the bottom of the box and ports above. The hight of the box is just enough to stack the 18", a 10" midrange and a horn on top. I wanted to simulate a good port placement.

I started off by doing a WinISD simulation, a -3 dB bass shelf, giving about 280 liter volume.

Taking all the parameters to Hornresp, I could almost simulate the box using a stub. Anyway, exporting to akabak gave me a quick start into akabak.

I made a few mistakes. Shorting a vent to 0 is the trick for ending a section.

Hopefully this code can be reused

|COMMENT: RCF L18P400 akabak

|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

|REQUIRED AKABAK SETTINGS:

|File > Preferences > Physical system constants:

|Sound velocity c = 344m/s
|Medium density rho = 1.205kg/m3

|Sum > Acoustic power:

|Frequency range = 10Hz to 20kHz
|Points = 533
|Input voltage = 40.00V rms
|Integration = 2Pi-sr
|Integration steps = 1 degree ... 1 degree
|Integration method = Cross

|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Def_Const |Hornresp Input Parameter Values
{
|Length, area and volume values converted to metres, square metres and cubic metres:

S1  =  3060.00e-4;  |Horn segment 1 throat area (sq m)
S2  =  3060.00e-4;  |Horn segment 1 mouth area and horn segment 2 throat area (sq m)
S3  =  3060.00e-4;  |Horn segment 2 mouth area and horn segment 3 throat area (sq m)
S4  =  325.00e-4;   |Port area

L12 =    23.00e-2;  |Horn segment 1 axial length (m)
L23 =    36.00e-2;  |Horn segment 2 axial length (m)
L34 =    28.00e-2;  |Horn segment 3 axial length (m)
L36 =    28.50e-2;  |Port axial length (m)

QdFo1 =	1.0;
QdFo2 =	1.0;
QdFo3 =	1.0;

|Parameter Conversions:

Sd  = 1200.00e-4;  |Diaphragm area (sq m)
}

Def_Driver 'Driver'

  Sd=1200.00cm2
  Bl=24.60Tm
  Cms=1.66E-04m/N
  Rms=4.35Ns/m
  fs=29.00Hz  |Mmd = 157.52g not recognised by AkAbak, fs calculated and used instead
  Le=1.20mH
  Re=5.10ohm
  ExpoLe=1

System 'System'

  Driver Def='Driver''Driver'
    Node=1=0=9=5

  Radiator 'Diaphragm'
    Node=5
    SD={Sd}
    Label=1

  Duct 'Below driver'
    Node=0=9
    SD={S1}
    Len={L12}
    Visc=0
    QD/fo={QdFo1}

  Duct 'Driver 2 port'
    Node=9=10
    SD={S2}
    Len={L23}
    Visc=0
    QD/fo={QdFo2}

  Duct 'Port'
    Node=10=12
    SD={S4}
    Len={L36}
    Visc=1

  Radiator 'Port mouth'
    Node=12
    Def='Port'
    Label=2

  Duct 'Above port'
    Node=10=0
    SD={S3}
    Len={L34}
    Visc=0
    QD/fo={QdFo3}

 

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Simulation result with no damping

 

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The same simulation done in the new version of Hornresp.

Akabak shows a dip at 200 Hz, but Hornresp shows amplification above 200.

 

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Setting "path length" in Hornresp to 0 shows the same response as in Akabak.