Some of the other replies to this thread seem to be over complicating matters, kinda like "paralysis by analysis".
Lee.
Here here Lee! I hooked the "line level" input to the sub to the right speaker output along with the speaker wires to the right speaker..I actually soldered them together. And it works great. I still can't get a straight answer on if this will damage the amp probably because nobody knows for sure..at least anybody who has replied to this thread.
Here is a private message scipt between me and TLS guy..
Me: Hi there..you replied to a post I put up and I needed some clarifying on what you said. Could you please revisit the thread and check it out?
TLS Guy: What are you confused about?
Me:OK, my first and main question is, if I just hook the sub-in wires to one channel of the amp along with the speaker wire will that blow the amp? That would be the easiest fix if that will not hurt the amp. The sub-in does not appear to be creating any resistance to the signal like if I hooked 2 speakers to the left channel and one speaker to the right channel. So the bottom line is, IF that will work, what is the advantage if any of going to all the trouble to build the opamp circuit?
TLS Guy: Using only one channel to power a sub is way less than ideal. It is also not optimal to power a line level output from a speaker output either.
The way I suggested is the correct way to do it.
..answers like "way less than ideal" and "not optimal" kind of dodge the direct questions like "will that blow the amp?" and "what is the advantage of doing the complicated if the easy will do?"
What I have learned so far is:
#1 The "line level" input or single rca jack input to a sub is not line level at all. It is not like a "line in" on a receiver. The signal from the amp feeding that line increases and decreases with the volume of the amplifier. If you try to feed a sub with a real "line level" source, you ain't getting much sound.
#2 There is always a more complicated and expensive way of doing things.
What I haven't learned and would like to:
#1 Will this blow the amp?
#2 Is bass typically, ever or never separated into two different stereo channels on recordings such as music and movies?