Originally Posted by BassmanPaul
this is a complete myth. The size of the cone is irrelevant to the lows it will produce.
Adding a 2x10 could work BUT it MUST be twice the impedance of the 4x10. This will balance out the power to each driver. So 8Ω 4x10 needs a 16Ω 2x10. 4Ω 4x10 needs an 8Ω 2x10 and your amp will have to be 2Ω stable.
I agree with the first statement!
But a 210 which works together with a 410 can have both - 8 or 16 Ohms. Okay; in an 8 Ohms cab the 210 speakers have to work "twice as hard" as the 410 speakers (or the 210 in a 16 Ohms cab). But that's no problem. Remember that the Backline 600 "only" gives 150 watts per cab.
For a 16 Ohms cab ...
The total impedance of a 8 Ohms 410 plus 16 Ohms 210 is 5.333 Ohms.
A 300w @ 4 Ohms would give about 270 watts max. (to make it easy) ...
This means that the 8 Ohms gets 2/3 and the 16 Ohms 1/3 (because of the higher impedance).
So, the 410 gets 180 watts, the 210 gets 90 watts - each 10" speaker 45 watts.
That's nice - but not neccessary ...