THD measurement method

[mike.e]

Hi all
Topic i havent seen much solid info on
Im keen on measuring woofer distortion both baffled and unbaffled.-linkwitzlabs style,steady state sine and impulse.

Mainly consisting of THD and IMD measurements
Ive seen the site listed below-but its not highly useful due to different drive voltages used!

Questions
1-Is the FFT in cooledit accurate enough?Can do quite high FFT size,ive heard of people using it for specialist uses.

2-If i was to keep one thing constant-should it be drive voltage/power OR SPL

3-program to use hobbybox4/praxis demo/winmls etc

4-Baffle size when used? IEC size? Im only considering the bass frequencies so i think this isnt such an issue at all

RS SPL meter->cooledit recording line in-inspection of wave files with FFT tool

Il only consider outside measurements to keep it simple and not get into MLS/gated stuff.

Im keen on seeing the resonant effects of ported box vs horn vs IB etc!

-Hopefully my eyes will show what i hear

Apparently the TCsounds 2+ matches the XLS12 driver distortionwise!

When i overlay the two graphs to have the same fundamental amplitude-
xls seems to have more distortions(+10db) at 4th and 5th harmonic.

Cheers!
Mike.e



tc2+ vs xls www.mfk-projects.com

[till]

did you try http://www.cetaceanresearch.com/analysis.html spectralab?

[mike.e]

No,ive vaguely heard of that one il check it out!

Im mainly looking for something thats user friendly but still pretty accurate and can compensate for nonlinear soundcards

Thanks!

[mike.e]

Ok ive got a list of software now

Speaker workshop(especially since its free)
Winmls
Clio
Praxis ...
Spectralab

What il do is download all of those-Do the measurements all at once,and see what i get!Compare results and see what works and whats hard to use...

And once chosen i could jump in and buy the one most suitable + a better mic than RS spl meter

Cheers!

[jdybnis]

let us know what you decide on

[DSP_Geek]

Originally posted by mike.e
Hi all
Topic i havent seen much solid info on
Im keen on measuring woofer distortion both baffled and unbaffled.-linkwitzlabs style,steady state sine and impulse.

Mainly consisting of THD and IMD measurements
Ive seen the site listed below-but its not highly useful due to different drive voltages used!

Questions
1-Is the FFT in cooledit accurate enough?Can do quite high FFT size,ive heard of people using it for specialist uses.
[....]

The FFT in CoolEdit is quite accurate, far better than any sound card out there. I used it recently to debug a nasty aliasing problem for $DAYJOB.


Francois.

[mike.e]

My dad even used the FFT in cooledit2000 for Radio repeater fault diagnosis once! i told him it had a good looking FFT function,and he found a problem and solved it hehe

Il tell you guys what happens! Cheers