Understanding impedence matching

Chuck --
investing a little time in understanding Ohm's law will take you a long way towards understanding these issues. It's a bit like learning a language: in the beginning it feels daunting and impossible and then, suddenly, you loosen up & speak the language... you've acquired the "knowledge" as it were.

OK, you may not be ready to design your own amps, etc -- but, as Clueless (and not a physicist:)) notes,

if folks understood ...(that)... (and a little RLC) about 3/4 of the magic and synergy would disappear from the wires used in audio

However, the magic of matching devices into a system would appear.

Try this link, too. It's a short introduction to electricity & components.
It can be fascinating!

A couple of practical points specific to your components: since your pre has an output impedence of 800 ohms, using the 1:10 rule your power amp should have an input impedence of at least 8k, which is easy to find. (My Alephs, for example, have an unusually very low input impedence of 10k ohms.) Secondly, and perhaps more importantly, use of a tube amp with a high output impedence (let's say above 1 ohm) WILL couple with your speakers' variable impedence differently as a function of frequency, resulting in the somewhat unpredictable trampolining of its freq response that can make tube amps so much fun (!?). However, a 6ohm speaker load min is pretty high, so MOST tube amps will show minimal timbral distortion. Again, think of the varying load response the amp sees as it's 1 ohm impedence meets a 6-20 ohm load across 30-20kHz window. (Yes, study ohm's law.) Then imagine what happens with a more common lower impedence load, often varying down to impedence minima of 2-3 ohms!
There can then easily be a 10x change in "load" across the frequency band, severely modulating the response. Usually the upper bass and mids get plumped up, the highs rolled off. Only works well a small percentage of the time since it's such a wild crapshoot. So even though your speaker is relatively amp friendly I'd chase an amp with a low output impedence to maximize your odds of a reasonably flat frequency response without having to tweak the hell out of your room, or other consequent bandaids. Good luck.

If the circuitry is stable and well designed, the source output impedance should match that of the load input impedance. If the load contains a high level of reactance, especially at sharp phase angles, the source output impedance should be measurably lower than that of the load input impedance. If our audio gear was designed properly, we wouldn't be using a 1 / 10 ratio or anything close to that.

The only company that i've ever seen that offers a product line that takes advantage of such design features would be Sierra Audio ( i "think" it was them ). Jud Barber of Joule Electra has also made comments similar to this, but not to the point of promoting matching input / output impedances. Sean
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Thanks everyone. I have begun my inquiry into Ohm's law and its implications. I've gotten the E=IR concept down, but as to the implications, well I gotta keep studying. But since there is some conviction from you that understanding this does, in fact, help demystify the process, I am eager to learn.

Again, my thanks. The more I explore the web, the more amazed I am by its power to connect strangers.

Clueless,

I'm sorry - you are misusing the term "impedance matching".

When you have tranmission lines - and you do "impedance
matching" - you make the impedance of one element exactly
the SAME as the upstream components.

For example, if you have a transmission line with twin-lead -
the type that's used for antenna connections to TVs - that's
a 75 ohm transmission line. When you want to terminate the
transmission line - you use a 75 ohm resistor. That's
because a 75 ohm resistor looks to a twin-lead transmission
line like an infinite length of twin-lead transmission line.

THAT is impedance matching - making the impedances the SAME
hence the term "matching".

I would use the term "coupling" not "matching" in the example
you give with the tube amp. Even with the transformer -
the output impedance of the tube amp is not 2-8 ohms.

In fact, the ratio of the output impedance of the amp to
the load impedance of the speaker is called the "damping
factor" and it is not unity [ 1.0 ] in a good stereo setup.

For the amp to exert good control on the speaker - the
damping factor is usually a few hundred. That is the
output impedance of the amp is around a few thousand ohms.

In an audio system - the interconnects ARE transmission
lines - typically 47k ohm transmission lines.

I believe we have a semantics problem here. You evidently
well understand how amps and speakers work. However, you're
evidently unfamiliar with the terms "transmission lines"
and "impedance matching". These are well defined terms in
science and electrical engineering.

Courtesy of the Institute for Telecommunication Sciences:

Transmission line definition:

http://www.its.bldrdoc.gov/fs-1037/dir-038/_5565.htm

Impedance matching definition:

http://www.its.bldrdoc.gov/fs-1037/dir-018/_2679.htm

Dr.Gregory Greenman
Physicist