Does impedance matter?


In all my post readings, the #1 question category is the 'Does It Match' question. This is usually addressed as a speaker / amp question.
Most responders start with impedance.
Of all the things to look for in a speaker impedance is down the list. I have looked at at many speakers measured by reputable testers. 8ohm 'nominal'? These guys are all over the place from 3ohm in mid frequencies to 20 ohms+ at resonance. Some are 4 or 5 ohms from 200hz to 1khz...prime musical turf.
Is it easy to drive? Well, it's an 8 ohm speaker, so it should be. Not so fast, there. This is only part of the story.
Please check out this link::http://www.hometheaterhifi.com/technical-articles/228-a-secrets-technical-article.html?start=1

The Smith Chart is a fine way to visualize the quality of load a speaker may actually represent.

When looking at a speaker then, it is important in evaluating the load it represents by not only the impedance, but the inductance and capacitance as well. As voltage leads or lags current, the strain goes back to the amp.
Please see this link for an explanation / details.
http://sound.westhost.com/patd.htm

Just watching Diana Krall in Paris on the TIVO.

magfan

Showing 1 response by almarg

Has anyone looked at the link to the Smith Chart....
It is a VERY interesting way to view the impedance curve of a speaker VS phase angles, which is really a much better way to evaluate 'is it a good or bad load?'

I read the article, and it is indeed somewhat interesting, and I don't see anything wrong in it technically. The article does a good job of emphasizing that the magnitude and the phase angle of the speaker impedance, as functions of frequency, must both be taken into account in assessing how difficult a load it represents.

I see two basic problems, though. First, it is difficult to interpret due to the lack of frequency information on the plot. The author himself acknowledges this:

The main drawback compared to the normal, two-plot method is that we lose the frequency dependence of the impedance.

The second problem is general lack of availability of this kind of plot across a wide range of speakers. I think that being able to meaningfully utilize this kind of plot for a specific speaker would require prior familiarity with what the plots look like for a large number of other speakers, of various types.

Thanks for the interesting read!

Regards,
-- Al