In my post above I really didn't emphasize the raison d'etre for the Gammas. It goes back to the premise that the ideal in-room bass system is multiple subwoofers spread around the room.
The problem with trying to reproduce bass in our home listening rooms is that the room inevitably imposes a peak-and-dip pattern on the output of any bass source in the room. We can move our speakers and/or subwoofers around and re-arrange these peak and dip patterns, but we cannot make them go away. Moving the listening position likewise moves the peaks and dips but does not eliminate them.
Now peaks and dips from room reflections abound at midrange and treble frequencies too, so why do the ones in the bass region matter so much more? Two reasons:
First, if the peaks and dips are close together (like within 1/3 octave or so of one another), the ear/brain system averages them out and doesn't hear the individual peaks and dips. So unsmoothed in-room frequency response measurements typically look like total hash in the midrange and treble, but that's not how the ear interprets it. In the bass region, because the wavelengths are so long, the room-induced peaks and dips end up being too far apart for the ear to average them out.
The second reason has to do with how long it takes the ear to detect pitch. We cannot even detect the presence of less than one cycle of a bass frequency, and it takes many cycles for us to detect the pitch. So by the time we hear and begin to detect the pitch of bass energy, the room's effects are indelibly stamped on the woofer or subwoofer's output. In other words in the bass region, perceptually we cannot separate the woofer from the room. They form a system. At any distance beyond a few inches from the cone, we cannot hear the woofer apart from what the room is doing to it.
The solution offered by my Swarm system and Geddes' multisub systems is this: Take multiple subs and place them asymmetrically (Geddes recommends three with one near the ceiling, my systems use four and it's okay if they're all on the floor). Jim Romeyn uses four and advocates reversing the phase on one of them (which sounds like a good idea to me). Anyway, the point is, each sub will produce a unique peak-and-dip pattern at the listening position, and the sum of these dissimilar peak-and-dip patterns is significantly smoother than any one of then would have been. This improved smoothness applies to any listening location throughout the room, so there is significantly less variation from one location to another. And the peaks and dips that remain are not only smaller, but closer together - which gives the ear/brain system's averaging characteristic a chance to perceptually smoothe things even more.
There is one more thing that my Swarm systems address, and that is room gain. My more expensive vented model's anechoic response rolls off below 100 Hz by about 3 dB per octave, which is the approximate inverse of typical room gain. My less expensive sealed version uses Qtc = .50 sealed boxes which aren't as close an approximation as my vented boxes but still come pretty close, and are probably a better match for a smaller room that would normally have a bit more room gain.
One possible issue with a distributed multisub system is that subs which are far away from the main speakers can betray their presence by passing lower midrange energy loud enough to be heard as a separate source. The solution is a steep-slope lowpass filter, so the amp I use with the Swarm has a 24 dB per octave lowpass filter (variable frequency of course).
Why not just use one big sub and equalize it? Since the peak-and-dip pattern produced by a single bass source changes significantly with location, equalization has the tendency to actually make things worse outside the sweet spot. Also, there is anecdotal evidence from people who have tried it both ways that four small asymmetrically-scattered subs sound more natural than a single equalized ubersub even right smack in the sweet spot.
So if we want the best possible bass quality and have mancave priviliges, a multisub system makes a lot of sense. But then what do we do for the rest of the spectrum?
Well, it would be nice and convenient go have main speakers whose inherent rolloff characteristics allowed a good blend with the subs without any further filtering, and whose midbass driver wouldn't come anywhere near its linear limits without needing a protective high pass filter (the good ones are expensive). It would also be nice if such main speakers had good radiation pattern control, good dynamics, and low coloration.
The complete Planetarium Gamma system consists of the two Gamma satellite modules and a four-piece sealed Swarm multisub system with external kilowatt amplifier. The amp includes a single band of parametric equalization in case there is still a significant in-room problem, but so far to the best of my knowledge none of my Swarm or Planetarium customers are using the parametric equalization feature. Anyway, the Planetarium Gamma system offers all that for under four grand. For those in a position to deploy a multisub system, I think the Gamma system offers significant sonic advantages over conventional systems in the same price ballpark.
I'd like to mention a couple of other things:
Grilles. Wooden grilles with black fabric can be included, and they'd raise the price somewhat. How much I'm not sure, but as a ballpark estimate let's say $120 a pair. Or if the intention is just to protect the woofer against finger-pokes, round metal waffle-grilles can be installed for about $40 a pair.
Custom versions. If someone wants a custom system that involves a different configuration, such as a taller Gamma system with powered subs built into the bottom half of the cabinet (like the custom Planetarium Alpha system I linked to in the post above), contact me. As long as it doesn't involve a major revision (re-designing the crossover would fall into that category), it can probably be done at an attractive price.
Let me sign off with a couple of quotes from people who have heard and/or presently own systems that use a Swarm for the bottom end. The first one is taken from a post here in my circle:
"I’m 54, musician, assistant engineered & programmed synthesizer at the Sausalito Record Plant, been doing this since a teenager. Have auditioned the following among other speakers known for great bass: Infinity IRS III ($65k late-‘80s dollars, four 7’ tall rosewood towers) properly setup in the Tiburon home of the owner of Landmark Cards & Calendars. CES setup by the designers of many cost-no-object sub systems including humoungous stereo towers w/ four to eight drivers per side. Linkwitz’ $15-20k commercial dipole systems. VMPS discontinued SuperTower III SRE w/ stereo sub towers, each tower 400 lbs, 5x 12s w/ staggered resonance points. Owned the best 2006 Sunfire Signature sub w/ automated digital EQ & owned several VMPS subs & the VMPS SuperTower/R SE (dual 15s, 10 midbass). My last room had the equivalent of about $6k worth of acoustic soffit installed to tame bass modes. Also heard the superb $100k YG Acoustics Anat Reference system (Yoav is a great guy, very down-to-earth, worth hearing if setup correctly).
"
Duke’s latest SWARM v2.0 equals or exceeds the best sub performance I know of. You name the quality, it’s there in spades. Slam, low bass cutoff, power, etc. In pure musicality, pitch definition, transparency, realism, portraying differences in recording venues, this system probably sets the world standard. I’ve played electric bass; the acoustic guitar I sold last winter was a Martin HD-28LSV (purchased from Dave “The Ghost” Caspar of the Oakland Raiders at his home in his trophy room). There's a nice Chang grand upstairs. The capability of v2.0 to flatten the room’s bass modes blows away the above described soffit of my last room. I had to leave that soffit behind. I could pickup & carry the sum total five pieces of Duke’s v2.0 in two trips in my hands from Duke’s room to my car (wish I thought of that when he wasn’t looking!) Each of Duke’s subs is only about 1cf. The amp is of moderate size/weight.
"Duke’s subwoofer philosophy may seem strange to the uninitiated, who might view four subs as about three too many. To them I reply: “Oh, really?” Take a little peak over at the circle for room acoustic modifications & read the pages about people trying to control bass modes. Duke’s philosophy, IMO, completely eliminates the need for any other contraption to flatten your modes. The automated digital EQ of my [expensive competing model] sub was almost completely worthless (in performance) compared to Duke’s, which costs less." (emphasis mine)
And, this from a post over on AVGuide.com, which is associated with The Absolute Sound magazine:
"I recently took possession of a pair of Duke Lejeune's Planetarium Betas, which consist of a pair of main speakers with two 12" woofers, mounted front and back, and a pair of 1" compression, waveguide-loaded tweeters, also mounted front and back. The idea behind the design is to produce a "controlled-pattern bipolar configuration". The mains are specifically designed to roll off at, by my estimate, 65 Hz or so. Below that, music is handled by what I consider to be the truly innovative part of the system, the SWARM. The SWARM is a set of 4 small subwoofer units, each with an 11" X 11" footprint, and utilizing a ported 8" woofer (tuned to 25 Hz). The subs are driven by a very flexible 1000 watt amp. The idea behind the SWARM is to place them at locations at varying distances from room boundaries, with each sub having its own room response, and thereby producing a much smoother overall room response when output from all four is summed. In my own field of expertise (geophysics), this is known as minimizing constructive interference. Does it work? Boy, does it ever. I had thought that my previous speakers (SoundLab A-1PX) were relatively impervious to room effects. They are, actually, but not nearly to the degree that I had thought.
I am now enjoying the best bass, both in quality and quantity, that I've ever heard anytime, anywhere, in nearly 40 years of audio experience. Those looking to extend their bass response (Quad, Maggie, and high quality monitor speaker owners spring to mind) should definitely give the SWARM, which apparently is sold as a standalone system too, some serious thought." (emphasis mine)
* * * *
There's a rather interesting discussion of subs and multiple subs going on in
this thread, and a brief but educational post by Earl Geddes in
this thread.
