About:

QLoud is a tool to measure a loudspeaker frequency response and distortions. 
The app page is here: 

http://gaydenko.com/qloud/

Writing this app is inspired by excellent applications written
by Fons Adriaensen:

http://users.skynet.be/solaris/linuxaudio/

Theoretical background belongs to Angelo Farina:

http://pcfarina.eng.unipr.it/

In particular, this method was used:

http://pcfarina.eng.unipr.it/Public/Papers/134-AES00.PDF


Target use:

- loudspeakers DIY-ing (xovers tuning).


Measurement chain:

- the app, generating excitation signal,
- sound card line out,
- power amplifier,
- loudspeaker under testing,
- measurement microphone (with mic preamp),
- sound card line in,
- the app, capturing loudspeaker response.


Result:

After audio system response capturing is done, IR (Impulse Response)
is calculated. Currently these IR-aware analysis outcomes are available:
 
- plotting of SPL (Sound Pressure Level) as function of frequency (db/Hz scale),
- plotting of IR-power as function of time (db/sec),
- plotting of Step Response as function of time (amp/sec),
- plotting of harmonics (2d - green, 3d - red, 4th - light green, 5th - light red)
  as function of frequency (db/Hz scale).

IR-power plot is useful to see a room reflections behaviour.
Step Response plot is useful for speakers time alignment in multiway loudspeakers.
All plots support zooming with history and panning.  


Few hints:

- move mouse above "?" sign at plot window and wait,
- to change a measurement description double-click it,
- to delete a measurement, use context menu on measurements table,
- to see what the app do, just connect app's JACK ports directly and try,
- to see what your sound card do, use loopback for line in/out,
- take into account your measurement mic slope at high frequencies when
  observing harmonics plot.


Feedback:

Please, add "QLoud" to your message subject. My email is: a@gaydenko.com


Regards!
Andrew Gaydenko
