How to best connect active sub to int amp?

The REL system of connecting it to the speaker outs of the amp works great...positive left and right and one negative. It presents a very high impedance (100,000 ohms) to the amp so it doesn't disturb anything.

The best way to connect a sub to an integrated depends on the available I/Os on both units. The OP specified that his LFD integrated has no pre-outs or sub-out. However, he doesn't mention which sub he's using or what I/Os the sub has.

Some subs have a single mono LFE RCA input. Some have left and right RCA inputs. Some have speaker-level inputs, some have speaker-level inputs and outputs. Some have stereo pair RCA inputs and outputs, which are useful with a tape or effects loop.

If you have a stereo pre-out pair and the sub has a stereo RCA input, use that. If you have a stereo RCA output but the sub only has a single mono RCA input, you can't fix that with a Y-adapter. You'd need a stereo-to-mono mixer of some sort.

If your sub has speaker-level inputs, use those. IME they sound surprisingly good and you don't have to turn the sub up as much, which should keep noise level down as well. I have found that--like anything else--the sound quality improves with better speaker cables. In other words, use something better than lamp cord.

There are benefits to connecting your subwoofer to the speaker outputs on your integrated. With your integrated amp sending a sample signal to your subwoofer the subwoofer takes on the character of your integrated and the overall sound becomes more seamless.

I wish people stopped using abbreviation and answered in plain English. I do not know LFE is or LFD etc...

I have a kef active sub woofer that came with kef egg speakers and ran it from an av reciever.
I now own an onkyo 9010 amp with 1 pair of q acoustics 3020s.
I want to connect the amp to the sub woofer for more bass.
Like the above comment I don't want abbreviated terminology just plain English please.