From: James Cameron <quozl@laptop.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Wed, 18 Mar 2020 22:16:54 -0700
Subject: Re: [EE] Measuring speaker impedance
Thread-Topic: [EE] Measuring speaker impedance
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Problem foreseen is that the impedance you measure will then depend on
a set of simultaneous frequencies rather than a signal of just one
frequency, so using the impedance meaningfully is limited.

The other thing is that the starting position of the cone would
matter; a low frequency signal within the mix of signals could cause
the cone to be in a position that may beat with the sampling.  So
despite doing it rapidly you could have the low frequency signal
imposed on the results.

On Thu, Mar 19, 2020 at 01:02:18AM -0400, Neil wrote:
> Hi,
>=20
> I'm working on a project for a friend, which will measure speaker=20
> impedance over a given frequency range.  I'm thinking I'd use a function=
=20
> generator sweeping across frequency range, then measure current (prob=20
> with a clamp sensor) and voltage across the speaker and do the math from=
=20
> there.  No prob so far.
>=20
> But can how about doing this dynamically?  IE: play music and=20
> dynamically figure out speaker impedance from there.  He believes=20
> commercial devices do this.  So far, all I can think of is measuring the=
=20
> voltage and current as before, but dynamically FFT-ing both and=20
> (rapidly) doing the math from there.  Does this seem workable?
>=20
> Cheers,
> -Neil.
>=20
>=20
> --=20
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--=20
James Cameron
http://quozl.netrek.org/
--=20
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