which speakers would recommend for rear & surround,electra 905 being front spkrs

Something of a similar efficiency would be my advice. Focal probably has a matching set for the 905s. It appears from your profile you already have some to try out.

thks xenonman. now dumb question from me but how do you measure the efficieny of speakers?

thks 4 the help xenonman, found info on the internet, will remove totem mites & add b/a a70s instead!!!!

The efficency is usually stated in the specs for the speakers and measures how much sound pressure is generated at 1 meter with a 1 watt input signal. The measurement is in db and is usually given as XX db at 1 watt or 2.83 volts. When the power to the speaker is doubled the spl increases by about 3 db so with a 7125 putting out 125 watts it is able to increase the spl above the rating by about 21 db. If the speaker is 88 db efficient then a spl of about 109 db can be generated at full power of 125 watts. Most people experience some pain at or near those levels and long term it can damage your hearing.

I know why the measurement is made at 1 meter, but I am sorta curious if there is good information what happens at "normal listening distances". Yes, I know the calculation for fall off of sound energy but that does not cover the fact that loudspeakers are NOT point sources. Quite the opposite I seem to recall (listening to the sales guy explain why we might use "constant bandwidth transducer" designs for the linear arrays in our PA system at church) that each driver does have a specific focus point that can be exploited in a Keele or Bessel style configuration to provide more uniform volume and frequency consistency. I think there are even firms that use digital delays to drive each speaker in planar configuration at a tiny phase difference so that the benefits of "steering" the sound can be achieved without the "rock concert" look of the traditional array hung from the rafters.

In theory one ought to be able to play around with the physical orientation and digital delay of multiple speakers to maximize listening levels. Of course the effects of room acoustics and what exactly each person's "normal listening position" equates to is going to have a huge effect on what is "too loud" vs "not enough power"...

The efficiency rating is a good way to compare speakers only from a power requirement angle. How the speakers sound in a real room is something that has to be experienced.