Hook up subwoofer to Integrated amp???

Since the integrated amp has no bass managment and the subwoofer doesn't seem to be able to do much to offload the main speakers, there is no "best way", just something that is highly compromised.

Been there done that and moving up to an AVR with bass management was a huge upgrade in terms of SQ.

Not a chance. No connection to the amp's volume control.

The best way to run a sub is with its own dedicated amp. If the sub has a 'plate amp' built into it, its best to run an interconnect to the plate amp from the preamp out. You can also run speaker level output, like you said from speaker B to some plate amps if they have the input for it. Record out on an amp is the same as a line level out. You could use that output to your plate amp via interconnects

Sorry, I just looked closer at your pics - you have both - line level and speaker level inputs on the Klipsh. Use the line level - any of the line outputs on the back of the amp will work

...but won't allow him to control the volume...as mentioned.

The output of a proper subwoofer crossover, the subwoofer output of an AVR, etc.

I am afraid that you have no good options.  What you state above will make sound from the main speakers and the sub but you do not appear to have any way to balance their relative output and no way to remove the lows from the main speakers nor to remove the highs from the sub.  Your amp has no provisions for a sub and your sub lacks all the features needed to work with an amp like that.

You've again missed an important point that many have been trying to get across:

One of the most important goals of adding a subwoofer is offloading your existing speakers and power amp.

That means that there has to be something that hooks between your existing equipment and your existing speakers that filters out the lows and routes them through the sub.

The sub you have can't possibly do it!

The integrated amp you have can't possibly do it.

Yes.

Finally! ;-)

Perhaps but there's no evidence of that in the picture you provided.  There is usually an adjustment knob or two.

Agreed. Here is the back panel of a fully-equipped subwoofer:



Note that there are inputs and outputs for both RCA jacks and speaker jacks.

I couldn't find the comparable picture online for the OP's sub. But, the portion of the back of the sub he shows seems to be a very stripped-down model. It is fine if you have an AVR but you are screwed if you don't.

Hey LS - is there a remote with the sub that allows you to control the crossover/volume? That would explain things a bit. Again, use the line level out from your amp, into your sub.

If you had an AVR this omission would be meaningless.

Since you don't have an AVR it is highly signficiant.

Lots.

Yes.

They were designed for use with AVRs.

From the subwoofer spec sheet found on the Klipsch web site:

the RW-12d features the DCS digital user-interface that includes three equalization modes (flat, depth and punch) and three useradjustable presets (music, movie and night) to create specific listening preferences

So as others have said: no crossover. This sub is clearly intended to be used with an AVR.

If you want to augment the bass of your main speakers with a subwoofer, the easiest solution would be to purchase an AVR.

If you really don't want an AVR then you'll want to find a powered subwoofer which has speaker level inputs. You will have two runs of speaker cable, one pair to the mains which will be running full range (far from ideal) and one pair to the sub. You will then attempt to blend the sub with the mains using the crossover and level control. REL subwoofers are designed specifically for this setup, so you might give them a look.