QLoud is a tool to measure a loudspeaker frequency response and distortions. This is just an attempt of porting it to QT5. The original app page is here:
Writing this app was inspired by excellent applications written by Fons Adriaensen:
Theoretical background belongs to Angelo Farina:
In particular, this method was used:
- loudspeakers DIY-ing (xover tuning).
- 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.
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/s),
- plotting of Step Response as function of time (amp/s),
- plotting of harmonics as function of frequency (dB/Hz scale):
- 2nd – green
- 3rd – red
- 4th – light green
- 5th – light red
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.
A 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.