Akabak for beginers

Im going to try and explane how Akabak works.... Now we all know horn resp is very good at modeling low freq but is not acurate at high freq this is one reason i turned to akabak. Please feel free to correct me if i make a mistake as i have only used this software for 2 months. Before i ever installed a copy on my pc there was a myth surrounding Akabak about how un-user friendly it is and the need to know a basic level of programming, this is not true. The guides and examples supplied are a waste of time (well to me) if you are a first time user they wont make sense. The first job is to ignore the manual put it to one side, we will need it, but only as a guide. To try and learn by reading the manuel is very hard going and after a few pages you will keep re-reading the pages hoping it will make sense to me at first it did not.

There are 3 ways of designing a cab in akabak.

1. inport data from horn resp
2. using the forms based wizards
3. and writing a script

The basic scrip works by linking all the aspects of a speaker together these are called nodes. We will start with a speaker driver, each driver has a positive terminal and negative terminal, now instead of calling them positive and negative we need to call them, node 0 and node 1,

node 0 = negative
node 1 = positive

Hope you are keeping up........

All nodes in a script link together for example, you would define a driver nodes 0 and 1, the rear chamber node 2, and then a series of waveguides, or acoustic horns nodes 3 and 4. The difference between a waveguide and a horn is that a horn is an output of sound, and a waveguide will be connected to another acoustic element in your design.

node 0 = negative
node 1 = positive
node 2 = rear chamber
node 3 = Wave guide
node 4 = horn mouth

Hope you get the idea. By using the node method you have an unlimited amout of modeling can be done covering all acoustic systems.

So lets get started writing your first script we will name this script mt121.

1. launch akabak

2. left mouse click 'file' (top left)

3. from drop down menu select 'new script'

4. a blank script page will open on the first line you will see a line of code (System 'S1'), This tells us the name of the script. Now change
the 's1' part to mt121. It should look like this on the


System 'mt121'

5. The next part is to assign the nodes to each other, to design the mt121 in akabak it uses 4 nodes from 0 to 3. nodes 0 and 1 are
the driver, node 2 is the rear chamber and node 3 is the horn, the next line defines the drive change the dr1 bit to the name of the
driver you want to sim.

System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

6. Now we need to define the driver, for this you will need the driver thiel small parameters at hand, and to name the driver. to define the
driver the code needed is Def_Driver 'Dr1' def= define, driver = driver, 'dr1' = name of driver, now change the dr1 bit to the driver
you want to sim in akabak.

Def_Driver 'Dr1'

The scrip should now look like this....


System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'

('Dr1' would be the name or make of the driver you are siming)

7. The next step is to input the thiel-small parameters used, below is the parameters im using (can you guess what make and driver it is..).


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

please note not all the parameters supplied for the driver are needed. the script should look like my example below, (apart from your driver parameters)


System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

8. now the speaker has been designed we need to connect it to the rear chamber. this is on node 2 the script for this is below.

Enclosure 'rear chamber' Node=2

Now the rear chamber has a volume of 19 liters (vb) and has a baffle, the baffle is 400m2 (sb). the next line is the script for this.

Vb=19L Sb=400m2

just to round up your script should now look like this.


System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

Enclosure 'rear chamber' Node=2

Vb=19L Sb=400m2


Thats all for tonight guys tomorrow we will design the wave guides and horn........ Thanks for reading.

Part 2......

9. To sim the horn in Akabak we need to break it down into 2 sections, the first section will be the waveguide and the second will be the
horn. The next step in the design is the waveguide.The waveguide will be called node 3 and the horn will be called node 4. The next line
of text shown below tells us the this section is a waveguide the name of the wave guide and the node number, it also tells us the wave
guide is connected to the horn. The 'wave1' can be re-named to anthing you want..

Waveguide 'wave1' Node=3=4

10. This is where the horn will start to take shape. The throat of the speaker can be square or round, as the mt12 section is square this next
line of code tells us the height and width of the throat.

WTh=16.4cm HTh=22cm

(wth = the width and hth = the height)

11. We now need to let akabak know the size of the end of the wave guide, in horn resp each wave guide is known as s1, s2, s3 etc.

WMo=32.4cm HMo=27.2cm

(WMo = width of the mouth wave guide, HMo = the height of the mouth wave guide)

12. The last part we need is the size of the pressure chamber volume at the inlet to the duct, length of the horn and the the type of horn.

Vf=1L Len=25.3cm Conical

(vf = the size of the pressure chamber, Len = length of horn, and conical = type of horn)

Your sim should now look like this....



System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

Enclosure 'rear chamber' Node=2

Vb=19L Sb=400m2

Waveguide 'wave1' Node=3=4

WTh=16.4cm HTh=22cm WMo=32.4cm HMo=27.2cm

Vf=1L Len=25.3cm Conical

We are know in to the final stages of your first ever sim using akabak....

13. The last stage is to design the horn it's self the following text below is the text needed.

Horn 'horn1' Node=4

This text lets akabak now its a horn the horn name 'horn1' this can be any name you want it to be and the node number of the
horn (node 4).

14. The horn uses very simular code to the wave guide but differant measurments.

WTh=32.4cm HTh=27.2cm

WMo=51.6cm HMo=36cm

Len=20.5cm Conical

(wth = the width of the start of the horn, hth = height of the start of the horn)
(wmo = the width of the horn mouth, hmo = height of the mouth of the horn)
(len = length of the horn, conical = shape)

15. The total script should now look like this.....


System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

Enclosure 'rear chamber' Node=2

Vb=19L Sb=400m2

Waveguide 'wave1' Node=3=4

WTh=16.4cm HTh=22cm WMo=32.4cm HMo=27.2cm

Vf=1L Len=25.3cm Conical

Horn 'horn1' Node=4

WTh=32.4cm HTh=27.2cm WMo=51.6cm HMo=36cm

Len=20.5cm Conical

16. The final thing to do is plot your sim and see what it looks like. On the shortcut bar at the top of the akabak main page press the
SPL tab button. An acoustic pressure window opens. Now change the input voltage to 2.83v and press the ok button. There you have it
your first sim If you are using the same driver as me it should look like this......





I hope this guide is helpfull in getting you started with Akabak in part 3 i will show you how to re-design this horn and try and improve it........

Part 3.

In part three we are going to change a few parts of the code to try and make this horn better.The first thing we are going to do is make the throat round. The original code we wrote for the throat was.

Waveguide 'wave1' Node=3=4

WTh=16.4cm HTh=22cm WMo=32.4cm HMo=27.2cm

now if we delete WTh and Hth and in its place type Dth=20cm, we tell Akabak that the horn throat is round and it is 20cm in diameter. The code will now look like this.....

Waveguide 'wave1' Node=3=4

dth=20cm WMo=32.4cm HMo=27.2cm

If you re-run the script you will notice the horn is now louder..... The next step is to delete The waveguide section of the programe see below.

Waveguide 'wave1' Node=3=4

WTh=16.4cm HTh=22cm WMo=32.4cm HMo=27.2cm

Vf=1L Len=25.3cm Conical

Now delete wth and hth from the horn section and replace with dth=20cm see below.


Horn 'horn1' Node=4

Dth=20cm WMo=51.6cm HMo=36cm

Len=20.5cm Conical

We now need to change the len to 45.6cm and add vf=1L see below

Horn 'horn1' Node=4

Dth=20cm WMo=51.6cm HMo=36cm

Vf=1L Len=45.6cm Conical

If we were to run this sim it would not work as there is less sections now (nodes) to the original sim. node numbers need to be changed to
node 0 and 1 driver, node 2 rear chamber, node 3 horn. The new script is below...


System 'mt121'

Driver Def='Dr1' Node=1=0=2=3

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

Enclosure 'rear chamber' Node=2

Vb=19L Sb=400m2

Horn 'horn1' Node=3

Dth=20cm WMo=51.6cm HMo=36cm

Vf=1L Len=45.6cm Conical

Now if you re run the sim you will notice the plot is not as good as the original plot. This is the sim for the simplefied version of the
mt121 horn. An mt121 horn with only 1 section to the horn, less volume and a sharper drop off around 9k.

The next part of this progect is to add some shape to the horn below is a section from the akabak manual which explanes how we do this,




By adding rw, wc, rh, and hc this will add a curve to your horn. now re-run the plot below...

Def_Driver 'Dr1'


SD=530cm2
fs=50Hz
Mms=47.83g
Qms=4.32
Qes=0.17
Re=5.4ohm
Cms=0.20625mm/N
Vas=82.27L
Bl=21.86Tm

Enclosure 'rear chamber' Node=2

Vb=19L Sb=400m2

Horn 'horn1' Node=3

Dth=20cm WMo=51.6cm HMo=36cm

Vf=1L Len=45.6cm Conical

Rw=29.8cm Wc=31.2cm Rh=29.8cm Hc=31.2cm

By playing around with rw, wc, rh and hc you can improve on this design but ill let you have fun playing around. please post you
plots up it would be good to see what results you can come up with. Also vf is set to high now as the horn throat has changed by
lowering vf you will increase high end. Below is my effort......




In part 4 i will try and sim another cabinet please post what cabinet you would like me to sim and ill try to show you...

Yes this is great work bee.

For so long I need to use akabak.

So can you show how to sim a sealed box, a reflex box, a 4th order bp and 6th order bp.

Can you sim the sealed box with def driver as node 0 and 1, then node 2 as sealed box, like in the sim above but without waveguide or horn.

Thanks for the help you have given.

Chana

Amazing tutorial, thank you.
smiley32

yes chana no probs what size do you want the sealed box to be.... and what driver would you like me to sim for you in this box. The main thing to remember with akabak is nodes 0 and 1 are the driver all other nodes conect to this.

regards

Ben

so helpful at all! thanks Bee

Cheers guys im glad i can give back and not just take tips and advice.

Part 4

Creating a sealed sub box is a very common need, so for this exersize we are going to creat it using the forms wizard option in Akabak.

1. From the top menu bar select the def tab then select the def bass unit option.

2. In the window that opens up imput all the parameters for the driver you want to use im going to use the 12inch B&C speaker 12pe32
just cos i had the parameters sitting on my desk whilst writing this.If you dont have all the parameters leave them blank. Now
right mouse click on one of the parameters you dont have, for me this was dd, A new window appears try and enter the info needed
here or you can change the value types needed (i.e. mms to vas).DD is commonly known as SD.For some of the parameters its best to
type the measurement of unit symbal as well.You will need to enter the box volume as well, the box volume is up to you.

3. Now press the evaluate button on the bottom of this screen. If you have filled in this screen correctly then Akabat will calculate
the box for you. If it wont calculate then look what box the curser has jumped to and ammend this field, usualy this is because you
didnt specify the unit type liters for example.

4. When all is ok you can press the diagram button to generate a graph or the alignments button to generate a list of possible boxes
that will work with your driver.

5. The last step is to press the copy to clipboard option. Then open a new script from the file menu and press right mouse button
paste. The script for your new enclosure is now pasted so you can same the data.

Hope this helps chana....

Ok bee, thanks for the help.

I can press evaluate in the def driver window and it works, I can also press diagram and I get a plot, but alignments does not work.

I then press copy to script and paste into a new script.

I get this

System 'S1'

Def_BassUnit 'BU1'
SD=683cm2 |Piston
fs=35.97Hz Mms=153.6g Qms=6.835
Qes=0.289 Re=5.8ohm Le=1.5H ExpoLe=0
Vb=80L fb=42.0Hz Qb/fo=0.1
|Performance in vented enclosure:
| fsb Qtr fD f3
| 36.0Hz 0.277 370.6Hz 43.3Hz
| Lwmax Pelmax UoRms t60 Ripple
| 0 0 0 98.46ms 0

This was for a vented box.

I can't get a SPL plot to open as there looks like a problem with the first line of the script.

Any ideas as to what I did wrong.

Chana.

hi chana,

sorry for not getting back to you, but i have been moving house this week. Ill take a look at your sim in detail later and get back to you.

regards

ben