Hi,

The easiest way would be to use the high level output from the Amp to the sub and then to the speakers.

If you don't have a sub out (or a seperate pair of pre-outs on the receiver) this is your only option without buying additional gear like an SMS-1 or ICBM.

I did this several years ago with a NAD 3240 PE powering Bose 6.2's and an Energy 8" sub before I picked up my first receiver with bass management ( a 1050). It worked fine, I could detect no difference in speaker response, just more bottom end when I powered up the sub.

The LFM series have only 1 line level input, so you could not use the receiver's pre-outs unless you also get a device that combines the signal of the 2 channels into 1, like the SMS. I don't believe you could use a Y connector in situations like this because the the signal will need to be be summed before going to the sub.

Using the high level inputs you will need to set the crossover in the sub to determine what gets passed to the sub driver. I'd start at the -3dB frequency on your mains and adjust from there.

An SPL meter and a CD with test tones can be helpful if you're interested in calibrating.

The full range signal gets passed through to your mains without modification.

The upside to this approach is that you don't have to go out and buy a bass management device like an ICBM or SMS-1.

The upside to using an SMS-1 is that you get to fine tune your sub's output for smoother response.