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The Kfilter Handbook
from Martin Erdtmann Version 0.5 , Son July 15 22:29:16 CEST 2001

1. Introduction

KFilter is an application to test the parameters of an acoustic loudspeaker design. It is not intended to provide a complete design framework. It is more a possiblity for testing system parameters, providing frequency responses to changes in filter and driver network designs. The general problem while making a loudspeaker design is that there is a non-linear impedance where the crossover network is connected to. This makes it very difficult to estimate the influence of simple changes to the dimensions of capacitor and/or coils. Using simple formulas will not be a good solution because they will only work under the circumstances that the loudspeaker has a linear and non-complex impedance. This will cause very bad and faulty results in most cases. KFilter is able to show what happens when a standart filter crossover network is connected to a complex impedance and gives you the opportunity to get a optimized version of the crossover network. Another problem is the interactive influence of different box types both to loudspeaker devices and the behavior of the crossover network. This is a very important aspect: Simulating the behavior of the volume you can create adaptable crossover network furthermore e. g. with optimized performance. KFilter is able to include all this simulation parameters in a summarized output graph of the acoustic magnitude.

1.1 Changes

Version 0.4
Added a filterwizard. Bugfixes

Version 0.5
Added a color selection dialog. Improved performance for the impedance calculation.
Made bugfixes.

2. Installation

2.1 How to obtain Kfilter

To obtain the latest version of Kfilter go to the application's website here and download the source.

2.2 Requirements

The only requirement as of this writing is a working Qt install, 2.0 > version >= 1.44. Qt can be obtained from TrollTech's website here. KFilter Version >= 0.6 will need Qt version 2.x

2.3 Compilation and installation

In order to compile and install Kfilter on your system, untar and unzip the source tarball and build Kfilter. Type the following at your command prompt:

    % tar xzf kfilter-{rev}.tar.gz
    % cd kfilter-{rev}
    % ./configure
    % make
    % make install
Be sure to replace {rev} with the revision number of the tarball you downloaded. Since Kfilter uses autoconf you should have no trouble building it. Always remember you can type
    % ./configure --help
to see the full list of configuration options. Should you run into problems please report them to the the author, Martin Erdtmann

3. Usage

3.1 General Usage

The first step creating a new KFilter project is to make shure the Thiele-Small parameters of the loudspeaker devices you have. These data should be inserted in the Driver -> Parameters dialog at first. If you already have an existing loudspeaker system which should be optimized you can insert the current crossover topologie in the Driver -> Network dialog and the box parameters in the Driver -> Volume dialog. Dependent of the check boxes you have enabled in the parameter dialog you will already see the results of the magnitude, impedance and/or the summary of different drivers. The funktion of each dialogs will be explained in the following topics.

3.2 Driver Parameter Dialog

This dialog can be reached over Driver - Parameters. The main purpose is to specify the Thiele Small parameters. There is an exception which should be mentioned here:

In normal cases the "f0" parameter which describes the resonance frequency has a value > 0. f0 = 0 cannot occour in the real world. But anyway, inserting a 0 value for f0 is possible. In this case KFilter assumes that you do not want to calculate the full equivalent circuit design. Instead of this, KFilter will take care of the voice coil inducance and resistance and not more. The rest of the analogue circuit design will be ignored. This can make sence it you have special speakers where the resonance frequency is not visible in the impedance magnitude. For example this can be a horn speaker or something else.

The slider at the right border gives you the opportunity to adjust the performance in the simulation. Since KFilter gives a relative performance output and not the absolute pressure of the different drivers you need to adjust the slider to find out how the different drivers work together. In the real world the performance of the different drivers should be adjusted be try and error or measurement.

Now you can decide what graph should be shown in the output window by using the check boxes in the options field. The summary lines will be merged with the summary lines from the other drivers, that means if you only have specified one summary checkbox this will be identical with the single magnitude/impedance graph.

3.3 Driver Network Dialog

You can specify the network topology of the crossover network here.
(Will be updated)

4. Theoretical basics

Will be updated

5. Questions and Answers

Will be updated

6. Copyright

Kfilter Copyright 2000 Martin Erdtmann , martin.erdtmann@gmx.de

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

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