I was going to write this up as a full review ... it's that deserving of attention to this audience. But as there is this thread going (and others) I'll do a mini-review and setup guide here.
Background
I have used some of the very best subs for both music and HT over the past 10 years and have settled on the REL as being the most musical (and by far the easiest to dial-in without technical measuring equipment). Evolving my experience with both reference monitor systems and a dedicated $120K surround SACD system, I understand the importance of a well-designed and well-placed sub or pair. (yes, even an inch or two can make a difference in placement).
I've also learned the hard way: 90% of the subs available are not really fast enough for music, and unless matched to the specific speakers you are using, they do not integrate well or the sub takes inordinate tweaking. The exception are the RELs and some older Vandersteen subs, which do not use low-level outputs from either a home theater receiver or preamp, but rather take a tap directly off the main speaker outputs. These subs are not cheap (I use the Stadium III @ $2900, which is no longer made anymore) and there are very few of them ...most subs are optimized to move a lot of air for HT effects; music is a secondary consideration. The REL is designed from the opposite perspective of music first. A quick glance towards Audiogon at the many reference monitor systems and threads regarding music subs will confirm this.
Setup
So here's how it all works: I take the second preamp output from my Singlepower preamp to a low-cost Dared tube amp, which feeds the sub's on-board crossover and amp directly from the Dared's speaker outputs. The other output from the pre is to my Stax headphone amp.
Many headphone amps, or amps with a dedicated headphone output, will unfortunately, switch off the speaker outputs when the headphones are used. If you are using the amp to drive a main set of speakers; this is of course, desirable; but not so if you want to drive a REL by itself along with your headphones. Therefore, you need a second amp fed from another set of your preamp outputs (at least this amp does not need to be overly expensive). I use an old Dared integrated tube amp (because it too has a volume control)
So How Does it Sound?
With a family of 6, I rarely get to listen to my full-range speaker system, but the family doesn't seem to mind the sub on most music, except late a night (can I say compromise). And as my son is a rock drummer, the family cuts me slack, as they are used to bass from strange places at strange hours.
Another essentially is that the Stax are open, so they let the bass in; because bass is omni-directional and the REL is very fast, the illusion is that the sound is coming from the soundstage. It really works. Well.
But I doubt you'll be able to do this with closed cans.
Until you've heard the Eagles' Hell Freezes Over through this type of system, you have not experienced the ultimate in headphone listening; it moves the Stax to another level, with full-sized speaker "room loading" that any headphone, at every price level, lacks. Moreover, rock music that you may not necessarily enjoy on the Stax, now moves into the I'm there ... in the front row, category, especially some of high-rez DVD-A 24/96. (Yes, EL&P, Santana and Chicago DVD-A come to immediate mind.)
Jazz also takes on another dimension, with new life and presence injected into the bass of Blues in Orbit SACD now having the same impact through headphones as it does through full-range speakers.
Dropping in the Wilson Audio demonstration CD ...the opening of Copeland's Fanfare for the Common Man will wake the dead and make you appreciate that things need to be tied down during Richter Scale events. Track 8's It's Not Easy Being White spoof demonstrates how a well-integrated sub gives weight and presence to an otherwise relaxed presentation.
Quality not Quantity
The importance of picking the correct type of sub for this type of "far-field-near-field" listening cannot be underestimated ...I tried this with a servo driven $3K home theater sub (Velodyne HGS 18") and it did not work well. Too slow, even with that pricey servo drive.
The REL is minutely tunable to the exact frequency cutoff and volume (less is more), filling in the bottom octaves that the Stax system, as good as it is, simply cannot produce. And even if headphones could go that low, you still need a large room (and hence the sub reasonably far from you), to hear the wave of 20Hz note correctly. I re-emphasize that this is not overemphasized ... mindless, pumping bass, but rather the music that's in the original music ...nothing more.
The Stax now sound much closer to a reference speaker system, not only further drawing you into the music, but into the room the music was recorded in. With the tubes' midrange bloom (Stax and Singlepower) and the low-end impact of solid-state system loading the room, the illusion paints itself so well that I often play the opening track to the reunion Hotel California again and again and again.
Sanity Kicks In
There are of course many trade-offs, the words practicality and cost come to mind. You cannot make this system portable, you probably can't have it in your office and, your significant other will ask if you've taken your medication. That and a decent Rel is at least $1K on the used market make for considerable barriers to entry.
But if you're entrenched in the pursuit of the best, can't listen full range as often as you'd like, have the space and want to really reproduce the music as intended, there is no substitute. (sorry Porsche for stealing your line). The Stax/Rel combo is very close to a live performance and as revealing as my JM Mini Utopias were (which were far more expensive than the Stax).
And what of the cost? With some of the best electrostatic custom headphone amps now north of $5,000, spending $1,000 to $3,000 on a sub is not out of line.
I enjoy the Rel-augmented system so much, that when I can't use it and am forced to listen to my Stax with an octave or two missing, I feel deprived. So much so that I'm considering a second, smaller Rel for my home office to give me a near-field experience through headphones.
Am I bit eccentric in this? Perhaps. But every time I listen to the Stax/Rel system I come to the conclusion: this sounds better than any other headphone system that I have heard. Cost, eccentricity and political correctness aside, I stop thinking about my system, or the music ... and I just enjoy.
