I'm new to the fantastic world of speaker building.
I'm searching for an help in projecting a mini system 2Sat+sub that should be low cost, very efficient and the more little is possible.
Can you help me?
Unfortunately very efficient speakers are both large and expensive. But you can do something fairly efficient and fairly small by using an 8" Radian co-ax or 10" Eminence co-ax. These are drivers that use a high-efficiency compression driver mounted "piggy-back" to the rear of the woofer with the driver's horn firing through the center of the woofer and the woofer cone itself acting as the outer flare of the horn. Take a look at www.radianaudio.com
I agree with Tom. HE comes at a price of size and cost.
I think the 8"s were developed by Radian for the commercial install market (MUCH bigger than high-end audio), but an enterprising few have found them to work well as music speakers. The coax driver give a controlled dispersion that is much less frequency dependent than non-coincident speakers. This gives them increased intelligibility over a wider area, and a smaller space requirement than a similar 8" 2 way. Similar characteristics are also good for music speakers.
These Radians appear to be the same units as in the Galante Audio Rhapsody. You can get an idea of their performance from the Enjoy the Music <a href="http://www.enjoythemusic.com/magazine/equipment/1101/rhapsody.htm">review</a>. I don't know where they cross over in the GA's or the slopes, but research the Tannoy specs for similar sized drivers to get an idea.
They look really good, and if I didn't love me horns so much, I'd import a pair to play with.
Another 10" coax to look at is the <a href="http://www.paudio-europe.com">P.Audio</a> 10CXA. It looks like it uses their BM 740 compression driver which isn't bad. The bigger 15" coaxes I'll be playing with soon (for PA work), so I'll report on the quality.
The last couple of years it was in production the mighty Altec 604, the most popular studio monitor driver ever, was sold as a ceiling speaker!?! Radian makes some very interesting stuff, those 12" and 15" horn co-axes look good. I can attest that Radian compression drivers sound very good, when I heard Tom Danley's Unity horns at his house he was using the Radian 475. And their replacement diaphragms for Altec and JBL compression drivers are very good, I'm very pleased with them. EV now makes a 15" co-ax with a piggy-back compression driver too, as do JBL and Beyma. And Tannoy of course. I have a pair of 35 year old Altec 605A DuPlexes and the buggers really sing, there is much to be said for this kind of design. It was a good idea 60 years ago and a good idea now.