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Which loudspeaker software do you use/recommend?

It’s difficult to recommend just one loudspeaker software program because of the varying nature of the drivers parameters under different conditions and the level and ability of the operator to input all the data required. If you put the same box details into 5 different programs you would get 5 different plots that all look slightly different. This is not due to some programs being more accurate, but down to the better programs needing more details and taking more parameters into account to come up with there output. The better programs can also start to predict, and that’s all it is a prediction, what changes will take place with higher levels of input power. All programs derive there output from the drivers T/S parameters and these are measured at very small signal levels, usually less than 1 watt, and so when you hook the cabinet up to your 500 watt amp and start feeding it some real world power most of the T/S parameters change considerably. The fs will rise due to voice coil heating effects and so will the Re. Vas is also temperature and humidity controlled and so even if the driver is not connected to an amp will change from day to day quite significantly. All this makes it impossible to predict what will happen accurately. The simple programs like Win ISD and Bass Box Pro just take into account the most basic parameters needed to give an output. They use a set of calculations derived by T/S to calculate what the optimum box size should be and will also let you suggest the box size with the program showing you what the plot would look like. They will also come up with the recommended port sizes and port lengths. Again you can enter your own port sizes and the program will work out the length needed and also the air speed within the port to make sure you will not get port noises. Out of the two Bass Box Pro is the better program, but Win ISD is free and because both these programs take the same parameters into account the resulting plots look quite similar. There will be one difference in the output plot between the two programs and this is due to the internal box lining. Win ISD does not take the box lining into account and so its output is only a rough guide. Bass Box Pro does take the amount of lining into account and you enter whether you have minimal, normal or maximum amounts of lining or fill. It should also give this as percentages, so it would allow you to enter 10% (minimal fill, just the rear wall lined), 50% (normal fill, opposing walls lined), or 100% (maximum fill, all surfaces covered). This is an important parameter for a program to take into account as the more fill you use the bigger the chamber appears, which in turn effects the port length. These two programs also allow you to use the golden ratio to derive the optimum box shape. While this is a good feature as it stops you making overly short and deep cabinets, they don’t take driver size into account. So it might suggest you make the cabinet 400 mm wide when you driver is 450 mm wide. But used as a rough guide it’s quite a good feature. While were on box shape, don’t get overly concerned about making the optimum shape box. If a box has the right and correct amount of fill and is braced well then the box shape is a secondary thing. Its good if you can get the shape near to optimum but fill and bracing will make a lot more difference to the result than the shape of the cabinet. Try to avoid making a box with the exact dimensions in height, width and depth as this could have a problem with standing waves.

The next program up from Bass Box Pro and similar programs is something like Leap. This does all the simpler programs do but tries to give a more accurate result by attempting to calculate the effects of box losses, port non-linearity and effects due to the coil heating up. You don’t have to enter too many more parameters than you would have to for the simpler programs, it’s just that the program has a better understanding of the real world. You do need to have a good understanding of speaker design though to be able to interpret the results. Leap also has a really good frequency measurement section. So you can make frequency, dispersion, impedance and other time related plots from the cabinets you have just built. All this comes at a price though and if your not going to use the measurement side of the program, which is the best part of the program, you might want to consider something else. As mentioned Leap is very good at giving frequency and time dependent plots, but if you already have a system for doing this then it’s a lot to pay just to be able to calculate the optimum box size. I would be tempted to use something like Bass Box Pro instead to come up with the basic box size, port lengths and box shape and then tuning the cabinet by ear using the measuring equipment you already have. Why make the best prediction you can when you can actually measure the plot for real and then alter things like the amount of box fill and port lengths until you hear or see what you like. Its ok to make the best prediction you can about how a cabinet will behave, but it is a prediction and like fortune telling I don’t really buy into it. Leap might give you a realistic prediction, but it will not tell you how the cabinet will sound, so you might as well use a simple program and your ears.

One step up from Leap and probably as far as most mere mortals want to take it are modeling programs. These try to make a prediction by taking all the details you can throw at them and then using known mathematical models to calculate the behavior. One such program I use is called Akabak. This is not for the fainthearted, as it requires a level of knowledge from the person inputting the data that can only be gained from a life’s time of experience. So if you don’t think that you are going to give your life over to designing speaker systems all day long then look elsewhere. It’s a full time job this program, not a hobby. The set of parameters required are not like you find in programs like Bass Box Pro or Leap, you don’t even have to start with a speaker, you can define all the parameters of the voice coil and then go on to model a suspension system and cone assembly around the voice coil to end up with the definitive driver. You don’t enter values into defined boxes either, most data is inputted using scripts. These scripts are complicated, even for a single driver in a simple sealed box. Below is a simple script from Akabak showing a driver with impedance compensation firing into a horn.
Driver model with discrete elements

System  'Dis '|Voice coil iimpedance  'I1'  Node=1=2 

 Z={ Z=Ree + j*w*Le; } 

|Motor Gyrator 'G1'  Node=2=0=3=4 Bl={Bl}

|Mechanical part Impedance  'I2'  Node=3=5 

Z={ Z=Rms + j*(w*Mms - 1/(w*Cms)) }

|Reverse diaphragm Coupler  'C1'  Node=4=0=10 dD={dD|

Front diaphragm Coupler  'C2' Node=5=0=300 dD={dD} 

|Radiation Radiator   'R1'   Def='C2'  Node=300

WEdge=20cm  HEdge=50cm

Def_Driver   'D1' Meas_DoNotModify

dD=35cm  tD1=-50mm  |Concave dome 

fp=800Hz |Mass reduction frequency fs=60Hz  Mms=58g

Qms=3.41  Qes=0.32  Re=5.58ohm  Le=85mH

Inspect/Network Impedance

|Impedance compensation

Capacitor  Node=1=0  C=20uF  Rs=5ohm

BassUnit  'B11' Def='D1'  Node=1=0

x=0  y=-10cm  z=0  HAngle=0  VAngle=0

WEdge=20cm  HEdge=50cm

Filter  'F1' fo=300Hz {b0=1; a2=1;  a1=1.414214;  a0=1;  }

|Diffraction of finite baffle

System 'Bass'

BassUnit  'B11' Def='D1'  Node=1=0

x=0  y=-10cm  z=0  HAngle=0  VAngle=0

WEdge=40cm  HEdge=50cm

Filter  'F1' fo=300Hz {b0=1; a2=1;  a1=1.414214;  a0=1;  

System  'S1'

Horn driver

Driver 'D11'  Def='D1'  Node=1=0=20=0

Duct  'Du1' |sound path around the voice coil Node=20=0    

WD={pi*5e-2}  |Perimeter of magnet cap (formula parser)

HD=8mm |Width of magnet cap. Len=20cm |Depth of duct.

|Begin of funnel with a duct. Duct  'Du2' Node=20=30 

dD=10cm |duct diameter Len=10cm|duct len  Vf=1.8cm3

 |The mid section of horn is conical Waveguide 'W1'

 Node=30=40  Conical   dTh=10cm       |throat diameter

WMo=50cm      |mouth widthHMo=50cm      |mouth height

Len=20cm |funnel length Radiation part of horn exponential

Horn  'H1' Node=40 T=1     |simple exponential flare

WTh=20cm  HTh=10cm    |throat width/height

 WMo=50cm  HMo=20cm    |mouth width/height

Len=50cm Rw=50cm  Wc=20cm    

 |radiation cone (horizontal)

 Rh=20cm  Hc=10cm      |" (vertical)

 x=0  y=0  z=0        

|radiation position of horn HAngle=0  VAngle=0

Generate measured loudspeaker with menu point:

|  "Tools/Generate Def_MeasRadiator File" |from the files:

|  "\Import\Horn.spl"  and|  "\Import\Horn.imp"

|Input voltage: Uin=2.83V peak |Distance: r=1.m

|Cross section 10cm x 5cm

I did said it wasn’t simple. You even have to manufacture your own horn from conical sections, ducts and funnels. So there’s no easy asking what happens if use a certain driver with a horn this long with a throat this big and a mouth this big. It is actually quite simple to use, its just that it take a life time to know what to enter. Akabak will also help you to design active or passive crossovers, many of the other programs listed here will do the same but Akabak allows you to insert any amount of filters anywhere into the chain and see what result it has on the plot. You can also design 4 or 5 way systems on Akabak, with each band having its own driver, cabinet and filter network.

So that’s about it for speaker software. People often ask what program do I use. Well I use all of the ones listed above. You get to know how the results of all the different programs relate to how the product will sound when you build it. So for one project I might use all the programs to see what might happen. It kind of covers it from all angles then. If a friend of mine wants a simple sealed enclosure for the back of his car then I would use Bass Box Pro as there’s no point in looking into it any further. Bass Box Pro also has a nice feature that gives you the response for the back of a car, as it is very different form a cabinet in room response. If I’m asked to design a two way system with a 12” driver and a 1” horn in a trapezoidal box for a company then I would use Leap to derive the box volume and port sizes and then make the cabinet and continually make modifications and do listening tests until I was happy with the result. For horn cabs, be it bass or mid top designs I would use Akabak. I would also use David Mc Beans excellent Horn Response program. While it does not go into the depths that Akabak does it is really nice to use and you are able to see very quickly if a design is worth continuing with early on into the project. I like it for bass horns and it seems quite accurate at predicting what will happen when you finally listen and measure the design. Horn Response is a free program and I thank David very much for his input into making this planet a better place to be in with people such as himself giving so freely that which others would not. So as you can see there is no one program that does it all, I even have other programs (one by JBL) that fills the gaps that the other programs leave. I sometimes even resort to using a hand calculator and paper in making a design and then checking it in the software domain to see how accurate I was. I also use a 3D CAD modeling program to draw and plot the final plan of the design. All the plans on the speakerplans site were drawn by hand on a technical drawing board. One of my jobs in life is as a speaker and system designer, and so if I summit plans to a big company I always use the 3D computer CAD program as they are expecting it, I can also come up with a file that can be used by a CNC router for large scale manufacture. But for the simple plans on the speakerpalns site I like to resort to doing things by hand as I find it quite a relief from having to work with computers all day.

So which program for who? If you’re a novice then don’t Leap into Leap or Akabak. They will do your head in and you will forget about speaker designing forever. Start off with Win ISD, it’s free and will teach you most of the basics quickly. You will need to know that if you make the rear chamber of a ported box bigger you can then reduce the length of the port, or that if you make the port diameter larger you will have to increase its length to achieve the same tuning frequency. Things like this can be learnt in all the programs, with the exception of Akabak, which assumes you know everything about speaker design. Akabak is a bit like a mirror in that it doesn’t tell you anything more than you know already, it just shows you what you do know and how to better to apply it. So the basics can be learnt form Win ISD, but when you grow out of that then Bass Box Pro should keep you happy for years. It will never really push you as a designer but will give you the opportunity to design some good sounding sealed, reflex, 4th and 6th order bandpass enclosures and even passive radiators. It takes enough detail into account to be able to construct a cabinet that will sound a lot like its plot suggests. If you get bored by this program and want to take it further into the scientific realm then get Leap. The ability to be able to make measurements is one of its strongest features, but the fact it takes a lot more parameters into account make it more suitable for the pro designer or very serious hobbyist. And finally if you are a nutter and your every waking and sleeping thought is about speaker designing then you should get Akabak. If you are not mad before you use this program you will be afterwards, its just really good that it makes you go mad in a way that wants to make other people on this planet have a good time and enjoy themselves though being better able to hear music reproduced more accurately.

To finalize I would not jump into an advanced program like Leap without some kind of prior training. You could gain your training in that program but it would be slower doing it in a program that assumes you know what you are doing that in a simpler program that is there to help you. I know you want to do the best job you can quickly, but in the end of the day it’s all about having something to listen to. Starting off on an easier program will enable you to have a working cabinet that will sound really good in weeks.  To do the same thing in Leap will take months and probably years. And then as you might have missed something you should have already known, your end product might be not as good as if you had designed it in a simpler program that made sure you understood what you needed to know. If you seriously want to change the world and come up with groundbreaking designs that have multiple patents applied to them like many of the systems I design for Big Mouth Speaker Systems then use Akabak. But be sure this is the direction you want your life to go in, as there’s no turning back.

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