Good way to measure transient distorsion ??

[youyoung21147]

Hello,

As far as I don't have Praxis or Clio, I figured I could measure transcients linear distorsion just with a function generator and a soundcard scope.

I generate a burst that stops and go suddenly from -0 to -144dB, and observe the response at the microhpone on the scope.

It gives me the kind of result attached.

Do you think it is a good way to compare drivers performances ?

[youyoung21147]

Is nobody using this method ???

[Juergen Knoop]

I think sine bursts, google says tone bursts?, are something oldfashioned.
Everyone is fixed on flat amplitude response.
Regards

[joe carrow]

These may interest you:

http://www.markk.claub.net/linear_distortion.htm

http://www.linkwitzlab.com/x-mid_dist.htm

[youyoung21147]

Thanks for your answers !

I've already read those two very interesting articles, that's why I'm trying to reproduce this kind of measurement myself.

Unfortunately, my measurement software (Loudspeaker lab 3) has no function to draw the "enveloppe" for the cosine burst, so I'm restricted to using oscilloscope.

Do you know a soft that could do that ??

[joe carrow]

You could check out Arta, it does cumulative spectral decay:

http://www.fesb.hr/~mateljan/arta/links.htm

It's not precisely the same as what you're asking for, but I think it will get you the information you want in a form that's useful.

[youyoung21147]

Loudspeaker Lab 3 also does Cumulative Spectral Decay.

But I've figured that CSD graphs were less precise than tone bursts, that's why I would like to be able to capture tone bursts with the cosine enveloppe when I need a more precise measurement.

[Svante]

No, I don't think it is a good method.

The reason is that the behaviour of any linear device is completely described by the impulse response, and if a spectrum is derived from the impulse response (via FFT) the display is probably the most relevant for how we perceive it.

The burst response will contain similar information, but is far more complicated to interpret. The risk is that the system gets optimsed towards something that is very visible for the eye, but not for the ear.

I see methods like these pop up every now and then, and people seem to think that they measure something that the impulse response or frequency response fail to detect, but that is hardly the case. They just provide the same information, more or less obscured.

As for nonlinearities; they will make a change in the response, but at normal levels they will be hard to spot. But this is a differnt issue.

Just my 2 öre...

[youyoung21147]

OK, thanks very much for your enlightement.

What kind of graph would you recommend me to evaluate linear distorsion performance (apart from frequency response) ?

Is the impulse response an intepretable graph "as-is" ?

Also, I don't understand how a whole frequency response can be guessed from just one spike. Seems like magic to me lol. Could you explain me ?


Thx !

[freddi]

I'm curious as to how real speaker systems deal with large-signal transients with music passages such as well-recorded drum and why they often fail to convey much sense of realism. What needs to be analyzed? Is there anything missing from how loudspeakers are measured?