Is there some reason that you can't use a line-out method of connecting the sub? Many subs have line level inputs where the speaker connections from your amp go to the sub and then from the sub to your monitors.

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Hello...new to this forum. I do have a question about adding an extra sub to supplement an existing 2 channel setup(preamp, amp, speakers). My preamp has a single output. I'm starting to call up modification services to add a sub-out. Is there an easy and safe alternative way on what I have right now? A friend of mine suggested to split the left channel output but I'm worried what it might do damage in the long run. I could sell the preamp and find a unit that will satisfy the purpose but I'm still going to buy the sub and cables. Can someone recommend a mod service if no way is possible? I live in SoCAL(WCovina area). Thanks.

Find a sub with 2 line-level (L/R) inputs and get two Y-cables.

Kal

No, it shouldn't make any difference as far as connectivity is concerned. I would opt for a powered sub with an adjustable output and frequency crossover if it is within your budget. If you go for a passive sub, try to match the ohm rating of the sub with that of your speakers.

If you look at the sub pictured above, you will notice that it has provisions for speaker level inputs and outputs as well as line level inputs. You could use the speaker level inputs by running from your amp to the sub and then the speaker level outputs from the sub to your monitors.