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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
russ69's avatar
russ69
3,427 posts
 
More important is finding a pair of loudspeakers that is relatively efficient due to having 40 wpc. 
millercarbon's avatar
millercarbon
12,531 posts
 
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? 
Look at speaker sensitivity. Even this is a gray area. My cutoff is 92dB. I simply will not consider any speaker with sensitivity below 92. However, a lot of that is because I enjoy a nice high volume level without having to buy amp with 100-200 or more watts. One time recently we had some really inefficient little speakers in here, 87dB I think they were. 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 again, gray area, rough guide. 

I have for nearly 20 years now used all tube integrated amps, 20-60 watts, and just like your Prima Luna. Currently using Tekton Moab, and if you go with any Tekton speaker you will be fine. Better than fine. Before this I used Talon Khorus which were right at my cutoff 91-92dB and they were fine. Impedance? Who cares?    

So brief as it was russ69 totally answered your question. Beware the people who recommend paying a lot of attention to technical specifications, because there is no end to it. Next you will have to learn to read waterfall charts, dispersion patters, obsessing about front vs rear firing ports, cabinets vs open baffle, dipole, planar, on and endlessly on.   
Instead of what actually works: filter inefficient speakers out, then focus on finding the best sounding from whatever is left. Yes it really is that simple.
twoleftears's avatar
twoleftears
5,315 posts
 
As usual, it's more complicated than that.

https://forum.audiogon.com/discussions/high-sensitivity-low-impedance-vs-low-sensitivity-high-impedance

https://forum.audiogon.com/discussions/epdr-more-important-than-impedance-alone

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