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Old 29th March 2013, 02:54 PM   #1
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Default Help with ltspice, total newbie

So I wanted to play around with various crossover simulations in LTSpice. I tried to do a 1st order crossover at 2kHz - not to actually build one, just trying to learn LTSpice.

I used the calculator at '' to find I need a 19.88 uF cap and .32 mH coil. Adding these, the wires was easy and grounds was easy. It took me longer to find I needed to add 'voltage' under components and run a "AC Analysis". This gives me a some output, but I messed up somewhere, as I am crossing over closer to 200Hz if I am reading the output correctly (solid lines are response).

I used resistors for my drivers. Is that correct?

How do I get the "Edit Simulation Command" window back after running this the first time, if I want to change my starting or stopping frequencies or points per octave?

This is a pretty cool program if I can get my mind around it.
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Old 29th March 2013, 03:25 PM   #2
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I was using a 32 mH coil! Changing that to .32 works as expected, but I still want to know if there is a better way of modeling speaker impedance than just a nominal 4 ohms resister.
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Old 29th March 2013, 03:37 PM   #3
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Why not try google?

1st hit: Loudspeakers

2nd hit:

3rd hit: Spice speaker models

The question has been asked before, see 3rd link!

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Old 29th March 2013, 04:28 PM   #4
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I will play around with this, but are those links really where you'd recommend someone start if they've never used SPICE before and just want to model a 1st order crossover?
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Old 29th March 2013, 04:35 PM   #5
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If you want to model a speaker, it will probably help reading about modeling a speaker, won't it?

The third link starts with the following:

Could you guys please explain to me how to create a spice model for a speaker driver? "
That is exactly what you were asking. Where is the use in trying to repeat everything that has been written in another thread?

Even a 'total newbie' will gain more from reading about the basics and trying to understand them than just playing around without an idea of what is happening. If questions arise, and they probably will, there will surely be someone here willing to help.

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Old 29th March 2013, 04:57 PM   #6
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I was asking if there was a simple way to play around with simple low pass and high pass filters without creating a detailed spice model of a speaker driver, but I guess the answer was "No".

These links all point to .asc and .inc files.

I am not sure what an .inc file is exactly, but saw a tutorial on how to include one that tells me to add by using 'S' on my keyboard. This gives me a large block of text that says ".inc" but it doesn't appear to do anything.

I understand .asc is a schematic, and there might be a way to make it into a modular component. Trying to include spice-tsp.asc with the .inc command (as above) gives me an error about multiple 'Flag' objects.

I am trying to find a modular way of including a component or something similar as a driver. Is that the correct way to go about this? Will it be easier with .inc files or .asc files or does this matter?

spice-tsp.asc gives me something that runs and lets me plug in Thiele/small parameters. I can probably simulate a 3-way speaker just by duplicating it 3 times. This seems more like a hack to build a speaker for someone who doesn't understand spice than a good solution.
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Old 29th March 2013, 05:38 PM   #7
Elvee is offline Elvee  Belgium
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Did you study the tutorials available for LTspice, they should get you going.
One or two examples (there are many more):
LT SPICE Instructions and Support Files
LTSpice and What the New User Should Know - diyAudio
LTspice Tutorial

You can post your asc file directly on the forum, this will allow other members to correct or improve what needs to be
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Old 29th March 2013, 05:41 PM   #8
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To understand about .asc and .inc files, you need some LTSpice basics...

Found them out myself by trial-and-error, but there are good tutorials out there...

The .inc file contains information about the behaviour of a sub-circuit. A sub-circuit is almost anything you want to use in your schematics besides simple stuff like resistors, capacitors and inductances. Any transistor, IC, tube or whatever is a subcircuit and usually comes with an .inc file.

Including the .inc file creates just a text block telling Spice what to do. For the schematic, the .asc file is needed, it creates the 'face' for the subcircuit: Usually a symbol with connectors you can use in your circuit.

LTSpice has quite a number of symbols in its gallery, but most of them have no model provided with them, you have to find your own.

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