Summing up L & R line-level for dual subs

Probably too well. Combining the L/R out of the Lamm will probably sum the output to the main amp/speakers. Result: No stereo.

If your subs have L/R inputs, you should connect to them independently and let each sub do the summing. Otherwise, you need an isolated or buffered Y connection.

Why would you not want your subs to be in stereo as extensions of L/R main speakers?

If the second set of outputs on the Lamm LL2 are buffered than you can use a Y cord. If not you will have to add a small buffer stage.

You could always try a Y cord (as it will not hurt anything) and if the main system ends up in mono you will know that the Lamm does not have separate buffered outputs.

Thanks for the inputs. I'll ask Lamm if the outputs are buffered or not. Good tip!

Karl, you wrote "If your subs have L/R inputs, you should connect to them independently and let each sub do the summing". Yes, my subs have L & R inputs, but how should I connect them independently? From preamp left output #2 have a Y connector to go to sub # 1 and to sub #2 connecting to left input in each one, and do the same on the right?

Csontos, the reason being Mr Geddes has put much more time than me into this and that's his prescribed way...so if I want to give the approach a fair shot...it follows I should follow the prescription. It is indeed an intriguing approach.

Thanks all for the input!