Beovox M70 "Normal"

Beovox M70 symmetry

from web (I haven't good condition for a good pic, and mines needs some refresh)

Regards

Maybe I can bring some shade of an answer but I don't have the whole story behind that change of the M70's.

The top picture is showing the "early" model whereas the bottom picture is the "late" model manufactured in 1979, last year of production.  I can confirm this because I actually bought the pair of speakers of the bottom picture and the woofers are stamped 79 for the year of manufacture.

The "early" and "late" not only differentiate as being left or right but also the woofers are different and the crossover network is also different.  Since I also own an "early" pair, I'm curious to know if the crossover network change is an actual "improvement" or something else.  The crossover looks like a mix of the S series and the old design.  I don't think the crossover change is due to the different woofer because I've the "late" style woofer matched with the old style crossover design.

I will conduct frequency response test between the two models and see how and why there was a crossover change somewhere towards the end of the product of the M70. 

I'm pretty sure that Martin (Dillen) has the answer to this enigma... 

Hi Jean,
despite of differences, there is only 10 of ecart in the serial number, and used with a Beomaster 6000 on a quad configuration
There seems to be buyed in the same lot (?)

Regards

Bruno