[LAU] speaker frequency response measurement and display

Fons Adriaensen fons at linuxaudio.org
Fri Jun 24 18:31:36 UTC 2016

On Fri, Jun 24, 2016 at 01:33:03PM +0200, Michael Jarosch wrote:

> Am Freitag, den 24.06.2016, 12:17 +0200 schrieb Ffanci Silvain:
> > Just a starting point, Michael, and I'm not sure how much help it
> > will be. There is Aliki, which can record frequency responses and, of
> > course, there are other graphical analyser tools, whose screen you
> > might capture. Then there is DRC, digital room correction. Maybe DRC
> > has everything in it, that you need. Just thinking aloud...
> As long as I know, the tools you mentioned are not made for my purposes
> as the room is explicitly included in the measurement, because in the
> end speaker AND room is what to be linearized, frequency wise. I need
> something different: The speaker itself, in the best case without the
> influence of a room surrounded.

Whether the room is included or not doesn't depend on the tools,
but only on how you use them. If you don't want to include the
room, you need a measurement setup that avoids room reflections
during the valid part of the impulse response. For speakers, one
method (already mentioned) is to do the measurent outdoors, with
the speaker on the ground and mic suspended above it. The 'ground
effect' can be accounted for later, and anyway most speakers are
use close to a wall anyway so it's not entirely wrong.

I have some reason to suspect that the plot you referred to
was actually based on a measurement using Aliki.

To measure impedance you need to capture speaker voltage and
current at the same time. This can be done with any good stereo
soundcard and some simple electronics (a few resistors is all
that's required).

An alternative to using Aliki is pyjacktools, in particular
if want to process the data using python/numpy/matplotlib.



A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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