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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

Showing 2 responses by bombaywalla

bombaywalla's avatar
bombaywalla
1,958 posts
 
You said it Magfan! Speaker impedance should be studied/viewed uisng *both* the impedance & phase curves. The phase angle lets the user know what sort of real-time strain will be put on the amp.

If users do not like passive x-overs, they are free to try active x-overs. There are many examples in the market + many more from various speaker manuf.
If you choose to stick with passive x-overs, then, large L & C values are needed. Just the physics of the matter!
Boothroyd-Stuart Meridian's method for active speakers using digital technology is supposed to be the best-in-class tho' I have not heard any of their speakers.
ATC's method of active speakers is your other choice. Many people like their sound (implying they like their design & the sound of their in-built amps). Maybe you will like them too?
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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