Subwoofer

I do buy into the idea that subs aren't just for improving the bass but the overall experience of the music.  I played around tonight with an AR H6 sub (100W, 8" driver, ported) from our very modest home theatre that was on its way to Goodwill.  Stuck it midway between a pair of Prelude Plus speakers facing right at the listening position (not orthodox sub positioning at all) and approximately on the same "front" plane as the Preludes.  Found some old JPS Labs speaker cables and hooked the sub to mono block amps via speaker input terminals.  Started listening with level and crossover dialed all the way back; gradually increased things.  Found a combination that seemed to blend well...almost couldn't tell the sub was on but for the effect on music I knew well.  Dunno if it was power of suggestion/self-delusion but I'd swear imaging was clearer and sound stage bigger than without the sub.  A fun evening.  Definitely thinking now how nice things will sound with a pair of sealed, better quality subs that are properly positioned.

Amphion Argon 2s, JBL PSW 1000.
Couldn't get the sub dialed in for months. I Couldn't find the right place where the sound changed from hear to feel, base was either boomy or lacking, No external crossover, just trying to get the sub to roll in where the speakers rolled off.

Then My wife and I attended a Bach organ concert at a big, stone church (Univ of Chicago, Rockefeller Memorial Chapel). After hearing (and feeling!) what "live" sounded like it was just another hour of tweaking and all was good!

I am on my third setup with sub woofers.  I find you must have patience to get them properly integrated into your music system.  But once done, they add so much to the sound of the system, they take the great sound from the main speakers and make them sound awesome.

One of my audio "mentors" used to tell me that the best sub woofer was one that didn't sound like it was there, unless of course, you are a person whose pants hang down, exposing your undies.

This last go around was the most difficult integration of all, as the room had all sorts of resonances that interfered in a big way with the law bass.  It took the installation of 10 bass traps and tuning the crossover frequency, curve and volume using the Room EQ Wizard software and calibration microphone to get it sounding "just right".  Now that it does, it just sounds awesome!

tboooe,
I swear to you adding subs has "opened things up and expanded the soundstage." I don't know why, but it's easy to hear.
What has been difficult is blending them perfectly!

I sure hope so!  I am going to pull the trigger on a REL T-5i sub.  I think in my modest room and style of music  this sub should work for me.  

Where do you guys suggest I set the crossover point?   My speakers start to roll off at 72hz and its -6db point is 43hz.

My "main" speakers are -3dB around mid-40s with a fairly shallow rolloff.  I added subs below 25hz (72dB / oct) using an analog electronic crossover built by an audio designer who knows what they're doing.  Steep cutoff below 10hz.  I built a pair of 12 cu ft cabinets, each housing 1 x 18" Eminence Kilomax driver.  150 watt mono amp per sub.  Corner placement behind the mains. 

Crossover could be higher with a strong likelihood they would interfere with the mains (soundstage, image, details). 

Nice DIY subs.  But they do need a bit of extra power to compensate for their natural rolloff.  (Crossover has an additional response curve to counter the natural driver rolloff in that enclosure.) 

I try really hard to keep from "dropping the needle" when playing vinyl.