QLoud 1.0

An Open Source app to measure step responses, loudspeaker frequency and distortions

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What's new in QLoud 1.0:

  • Compatible with QWT v.6.1. For earlier QWT use earlier QLoud.
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GPL (GNU General Public License) 
Andrew Gaydenko
ROOT \ Multimedia \ Audio
2 QLoud Screenshots:
QLoud - An overview of the QLoud application and how it works!QLoud
QLoud is an open source graphical software implemented in C++/Qt and designed from the offset to be used for measuring loudspeaker frequencies, as well as step distortions and responses, under any GNU/Linux operating system.

The main emphasis is on xovers tuning

Being inspired by several applications designed to manipulate audio, created by Fons Adriaensen, QLoud is a small utility that will also allow you to test sound cards and audio amplifiers. The main emphasis is on xovers tuning, also known as DIY (Do It Yourself) loudspeakers.

How the program works

The application will generate an excitation signal, also known as logarithmic sine sweep, to the sound card line out, which goes to the power amplifier and then to the loudspeaker under testing using a measurement microphone with a preamplifier, then back to the sound card line into the application, which will capture loudspeaker response.

When the audio system response capturing process finished, the application will calculate the Impulse Response (IR), supporting plotting of the SPL (Sound Pressure Level), IR-power, Step Response, and harmonics IR-aware analysis outcomes.

Getting started with QLoud

Its graphical user interface is pretty intuitive and easy-to-use, especially because it uses a single window design with no tabs or menus. To get started, select the working directory, set the parameters for the excitation signal, such as length (in seconds), sample rate, bit depth, minimum and maximum frequency, and configure the playback level and the delay before capture starts.

Under the hood

A quick look under the hood of the QLoud software will tell us that it is written entirely in the C++ programming language, uses the cross-platform Qt GUI toolkit for its graphical user interface, and requires the Qwt, JACK Audio Connection Kit, sndfile and fftw software packages. It has been successfully tested on 32 and 64-bit computer platforms.

QLoud was reviewed by , last updated on January 15th, 2015


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