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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
unsound
7,327 posts
 
A speaker with a higher impedance might theoreticaly sound better, and even then within some limits, but in practice that isn't always the case. I have yet to hear speakers with a "high" impedance load that I would care to own.
almarg's avatar
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almarg
9,670 posts
 
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
magfan OP
1,583 posts
 
Agreed on both points....But, nobody ever said it was supposed to be easy. Also, once you are accostumed to this presentation of phase/impedance it is fairly easily seen.
Frequency data would be Very helpful.
bombaywalla's avatar
bombaywalla
1,958 posts
 
Hi Ralph,
all your points on impedance are well taken.

IMHO Magfan's original post did not imply that impedance was not a useful number; in reality it is! I quote from Magfan's thread-starting post:
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.
I believe that point that he wanted to highlight was that we need to look @ impedance using BOTH the impedance & phase plots as a duo. All what you wrote in your post applies.
Most people just blow off the phase plot because they do not understand how to use it & they think that the impedance plot is it. Wrong!
I think that you understand this (& I'm sure, besides Magfan, Almarg & a few others out there do as well).
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