Speaker impedance patterns - how to read them?

One other thing needs to be stated: don't match/buy a speaker for a certain amplifier based solely on the published specs that come from the manufacturer.  This applies to nominal impedance (a real moving target), sensitivity, whatever. Notice, too, that sensitivity can be expressed in different ways.  When magazines with the technical wherewithal measure speakers, the results are very frequently different, and when they are different they are almost always less favorable to the speaker (i.e. it will be harder to drive for one or other reason).  

Learning more about technical specs is always helpful, but since what matters is they sound good to your ears. I'd put emphasis on simply trying different speakers and not get caught up in tech talk. Graphs won't guarantee them pleasing your ears. That amp is small enough to take to a dealer for  demo.

I've used a PL Prlogue, which is the forerunner to your EVO 100. Most of the popular brands are 87-89 db, and will work fine-for "normal listening."  As the manual suggests, try both 4/8 ohm taps.

I used a sealed cabinet, 89 db speaker with good results. 

 

Hi all,

thanks very much for the several interesting and useful replies. And for the kind welcome, I am new to this forum.
I've bookmarked a few links and will read the pages carefully; on the other hand, I am well aware of what some, like tablejockey, have said - it's not a good idea to rely entirely on specs, and that's what I am not going to do. My starting point with this thread was to take advantage of the solid background of many to bypass, for once, the usual criterium of just listening and to try and find a bunch of speaker systems that match well my amp on an electrical basis. To do that, I needed to learn how to correctly interpret an impedance graph.

I think that with an amp like mine - which I am keeping because I like it, sonically and visually - it may be better to use a speaker system with not necessarily an extremely high sensitivity - which in my experience is often paired with low impedance, at least in critical points on the FR - but with a regular, highish impedance pattern. I too think that 87/88dB or so and a minimum 6ohms should be good companions for my tubes.

Earlier this afternoon I listened again to a pair of Naim n-Sats, which I used to have; they are not at all of anyone's taste, but have some nice qualities. They are a sealed box and the 'woofer' is about six inches. I am not saying that I like them more than anything else, but they surely would be a sensible choice. Unfortunately, they have an idiosyncratic voicing and can only satisfy certain room acoustics. But I got a better impression of them from a more aware listening.

Thanks to the careful reading of a number of papers I didn't know, I now have a clearer idea of what to look for; one year ago I would have based my choice on brand, looks, number of drivers... Now I know better and I can demo speaker systems with a clearer idea of what can be ruled out soon and what can be tried at home.

Thanks for now for the precious help,
greetings from rainy Italy.
Max

@timlub

We are clearly talking past each other and it's unnecessary so I am stopping now. 

I've been looking at both impedance and phase angles, in certain instances speakers employing  
mid bass drivers with low impedance dips and 45 deg
or higher phase angle swings will overheat and stress
some amps.
In one of the previous links the example of a 100 wpc amp with 
 a 45 deg phase angle will produce 400 watt's heat. Unclear
if that incl a  matching dip in impedance.
As phase angle increases beyond 45 deg things can get serious.
depending naturally on the amplifier design.