speakers and cables

Also when done, make sure the subs are in phase. That will kill this entire process.

@mswale , if OP hooked up to both of his subs from amp + to + and - to -, and then he went from his subs to his speakers in the same manner (+ to + and - to -) is there any reason that his subs (or speakers) would be out of phase with each other? That is a serious question; OP did report that he felt that things sounded "thinner."

On edit:  if OP uses 'Y' splitters from preamp and goes out to his subs via RCAs, there is no way the subs could wind up out of phase?

. . . @griz: I don’t know if you’ve happened upon it yet, but if not, at this very moment there is a thread/discussion on the amps/preamps forum (right here on A’gon) about merging the sound of subs with the main speakers. (This thread is NOT about how to connect the speaker wire.) You may find it an interesting read and helpful to you for dialing your own subs in with your speakers.

ongoing discussion

On edit:  you will probably also find the discussion interesting  that is going on here in the 'speakers' forum about which input to use hooking up REL subs.

@immathewj yes, that's a cool thread. The last two comments got me confused though (what doesn't) 

I am going to hook up my Y connectors in an hour and I hope I will like it :)

@immathewj I plugged in the splitters and rewired the speakers.

The speakers definitely "came forward". The subs seem to have a weaker signal - maybe because it's low level, but I can boost the gain for sure. I will listen now for a couple hours to my usual test CDs and albums

@grisly, this thread and the many replies to it left me with a few questions about my own system (which is actually a good thing--to be periodically evaluating your system and possible changes that could be made to setting up the existing components),

so I finally got around to re-reading the manual for my ancient M&K sub to see if I could answer some of my own questions. Which is NOT to say that what applies to my old M&K sub/system applies to other sub/systems.

However, M&K stated emphatically (in bold print) that their subs (at least at the time, which was ’93) have no high pass filter (meaning to me--no crossover).

M&K, at the time, recommended using RCA versus speaker wire connections and stated it would give better bass performance from the sub.

They also explicitly said it was okay to use ’Y’ splitters from the preamp but they also said that "in many cases, the slight improvement this makes in bass quality may be offset by slight degradation of sound quality through the satellite speakers." They go on to say that they do not recommend ’Y’ splitters,, but "feel free to experiment." (As I assume you are presently doing.)

M&K really did seem to like, at the time, the idea of putting a high pass filter between the preamp and the amp and running the RCAs out TO the sub from the HP filter. I suppose that is why I bought one and went that route for a while. However, it should be noted that M&K also manufactured the HP filter they suggested that I use. (I may try it again as a result of this discussion, but if I do I’ll configure things a tiny bit differently--I’ll go balanced from my CDP into preamp, and then I’ll have to go RCAs out of my preamp the rest of the way.)