<font color='#000000'>Since that initial post I went ahead and purchased a Hsu STF-2 (nice piece of equipment). Want to report on all I've heard and learned.
Main conclusions -- based on personal preference, which I can't emphasize enough, since we all have different tastes -- is that with my floorstanders, I prefer using the sub only for HT, not for music. This may be because I have a fixed crossover, not a variable, but I suspect not. Once I got the placement and calibration of the sub to my liking, I found that it was awesome for HT but for music (my tastes run from Emmylou Harris to John Hiatt, Lyle Lovett to Stan Getz, occasional classical and classic Jazz) -- for music, the floorstanders gave a more coherent sound, regardless of the settings.
The three reasonable settings FOR MUSIC I could come up with in experimenting have been:
Option 1: Mains: "Large," Sub-out: "Both," Cross-over: around 50 Hz (with lots of experimentation) set at the sub.
Option 2: Mains: "Small," Sub-out: "SWFR," Cross-over: set so the sub uses the receiver's fixed cross-over, which in my case is 90 Hz.
Option 3: Mains: "Large," Sub-out: "Main" -- this is a no-sub setting, where I'm doing standard 2-channel stereo all through the mains.
I wish I could have used an option of Mains: "Large," sub-out: "SWFR," with a variable crossover within the receiver at 50 or 60 Hz, but that's not an option with my fixed crossover receiver (hence the source of this thread).
Option 1 yields more or less acceptable integration between the floorstanders and the sub, however, even at 60 Hz I hear problems of bass overlap between the floorstanders (which go down to 37 Hz +/- 3 Db) and the sub ... a pronounced sense of bass that is unpredictable and can overshadow the music. As a result I sometimes end up setting the sub-level xover so low (even as low as 43 Hz at times) that it begs the question -- why use this?
Option 2 works for some recordings, so long as the sub volume is set low ... but if the sub volume is the slightest bit too high, then the mains take on a tinny sound, coupled with a sluggish bass sound (even though the Hsu does well on music). I don't find that I notice the sub's location (or rather, the bass location), but I do find an awareness of a lack of overall coherence, and on certain recordings (ones with more pronounced bass beats) the bass can get very pronounced. This has been, therefore, the worst option. It works fine on some acoustics, but on any piece with well-orchestrated, well integrated bass lines, I find that I have to turn the bass down low to get a decent sound, but that it still not as good as the final option --
Option 3, using no sub for music, works great, all the time. My Axiom M60s have really nice, clean, fast and tight bass. If anything, all this experimenting made me realize how great they perform on the low end. If there's a drop-off below 37 Hz, and perhaps a tad of warm distortion in the 37 Hz range and sliightly above, it doesn't bother me -- rather, I get a coherent, in-phase sound that's great. No anxiety, no "should I tweak the xover" thoughts, no complaints from my wife. The overall improvement is such that at times, while experimenting, I felt physical relief when I switched from one of the sub-settings to this no-sub setting ... a sense of "Ahhh, that's how it sounds" as opposed to the puzzled, scrutinizing sense that sometimes came with using the sub. I don't think this was a matter of calibration, though I know sub-lovers everywhere will jump to this thought. I have the Hsu well-positioned, well-calibrated ... I just prefer the coherent sound from no-sub music -- perhaps, I freely admit, because I don't have a variable xover at the receiver level.
My experiments jibe with an interesting article I found which calls attention to some of the challenges of integrating a sub-woofer with 2-channel stereo. The link is below - basically it explains that our ears are great illusionists, and can fill in the missing bass information even from radio speakers, let alone floorstanders that get down to sub-40 ranges. Now, the real thing is better than an illusion, but problems can ensue with subs, because inevitably they will have timbre and PHASE differences that can jar the human ear. Many will disagree - I respect your opinion. But this held for me, and I've now sworn off using a sub for music. Maybe if I get really into the 1812 Overture I'll recant, but for now I'm sold on the no-sub / great mains route for stereo.
On HT, whole different deal of course, because there's discrete info designed for the LFE channel and the sub, AND you generally want a sub to pick up the bass info for your center and/or rears, which are usually not bass-capable speakers. (And of course many people don't have bass capable mains in their HT either, making a sub a necessity.) Probably because of the discrete sounds designed for HT, I don't find any problems with timbre jarring or phase. My own preference for HT is:
HT Setting: Mains: "small," even though they are floorstanders (also centers and rears set to small, but in my case they ARE small), Sub-out: "SWFR" (not "Both"
. By setting the sub-out to SWFR only I avoid an overlap with the mains, and avoid making my receiver drive the 5 channels PLUS bass info, letting the subs dedicated amp do that work. It's also easier to calibrate the bass volume if only the sub is doing this work.
In an ideal world, I would set my xover lower than the 90 Hz fixed level for the mains, but frankly, this setup works great, and with HT I have no complaints. If I get into Hi-Rez audio, well, then I'll just have to get better equipment.
Two articles that were helpful in all this experimentation:
Pitch Timbre and Quality vs. The Subwoofer by Jan Plummer, for Home Toys.
Miscellaneous Ramblings on Subwoofer Crossover Frequencies by Colin Miller and Brian Florian, for Secrets of Home Theater and High Fidelity.
Birdman</font>
