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Speaker impedance patterns - how to read them?

I know this has probably been discussed ad nauseam, but here's my question. I'm grateful for any sensible opinion.

Premise.
A speaker system may have a complex impedance pattern that can vary from 3-ohms to 30-ohms depending on frequency. Some speaker systems with similar impedance patterns may be stated as being 8-ohm loads because the speaker is 8 ohm in an important part of its frequency response, but only there.
A tube amp, as a voltage amplifier, likes a regular impedance pattern. Almost no speaker system has a constant, regular impedance pattern. I am aware that solid state, powerful amps are built to compensate for modern speakers' complex impedance patterns, but there are tube amps around and people who love them. It's difficult to understand what average load a given speaker system will present to the amp.

Question.
When looking for suitable speakers for a tube amp - mine is a PrimaLuna EVO 100, 40w x 2 from EL34s - what must be looked at? How to best interpret the impedance pattern, whenever available? Assuming that one listens at normal levels in a medium-sized room, what are the criteria for matching speaker and amp?

Thanks for your views. M.
martinguitars
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russ69's avatar
russ69
3,427 posts
 
"...My 20wpc Raven Blackhawk not only had no problem driving them to a nice loud level, it made them sound a helluva lot better than a 100wpc ss amp that was also used. Enormously better. So ”
How entirely errrrr ....... Believable ... Not..."

I believe it. Tube amps generally have good power supplies and generous capacitors and they often play much better than the WPC rating suggests. The WPC rating is a guide but it's not the whole story. Yes I know, a watt is a watt but test out enough gear over a lifetime and you will find out that perceived power is not just about watts. 
millercarbon's avatar
millercarbon
12,531 posts
 
Thanks russ69. Anyone experienced will know what you are talking about. Not to mention there was about a half a dozen here who heard it. But we are talking Asperger’s-level MDS here. Oh well at least you tried. Thanks again.
ghdprentice
6,831 posts
 
I listen to speakers or read reviews of what they sound like and ignore all but a quick look at a couple parameters. I was a former scientist and analytical person who has spent his career doing highly analytical work. I found most the analytical stuff just leads me away from sonic truth. Not wrong to be interested in it… but for me life is too short.
russ69's avatar
russ69
3,427 posts
 
"...Not wrong to be interested in it… but for me life is too short.."

Exactly this. Impedance matching the speakers and amp is more about how they sound rather than having a perfect impedance match on paper.
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