At the Rocky Mountain Audio Fest last weekend, our new Planetarium Sigma system made its debut. Here's a shot taken just before we hooked everything up on Thursday afternoon:
The Planetarium Sigma is an eight-piece system (ten if you count the stands), certainly going off in a different direction than most of the home audio world, but doing some things that a pair of regular stereo speakers really can't do as well.
Here are things this configuration does better than a conventional two-speaker system: Smoother (i.e. "faster") and more natural-sounding in-room bass, and more realistic overall presentation.
The smoother bass comes from the distributed multisub system. I'll go into detail for anyone who's interested, but briefly each sub will generate a unique in-room peak-and-dip pattern and the sum of these dissimilar peak-and-dip patterns is inevitably much smoother and more natural-sounding than a single ubersub.
The more realistic presentation comes from more closely approximating the sound field we find in a good live venue. Studies were done on what makes a good seat (as opposed to a lousy seat) in a concert hall. A critical factor is whether or not we have a clear differentiation between the direct sound and the reverberant sound. Let me quote David Griesinger on the subject, he uses the word "envelopment" to describe the experience of immersion in the soundfield that I'm aiming for:
"Envelopment is perceived when the ear and brain can detect TWO separate streams: A foreground stream of direct sound. And a background stream of reverberant sound. Both must be present if sound is to be perceived as enveloping."
When the direct and reverberant sound are run together (in the time domain) so that the one is not clearly differentiated from the other, we don't get this sense of envelopment, and that result in a poor seat in a concert hall. And that's usually what we have at home, because they usually do run together too much.
The Planetarium Sigma system is designed to provide these two distinct streams that Griesinger calls for, by using a highly directional main array and then supplementing it with a pair of dedicated reverberant-field-only speakers optimized and aimed so that their output arrives after a fairly long time delay (ten milliseconds constitutes a "fairly long time delay" in this context).
Conceptually, this is like the improvement you get when you position Maggies a good five feet out into the room, except that the angled/upfiring Space Generators allow you to get away with much closer-to-the-wall placement because they take advantage of the ceiling height to get the desired path-length-induced time delay for the "backwave" energy.
Another way of looking at it would be this: It's like we took the radiation pattern of a good conventional speaker and chopped it up into two parts, both spectrally correct. We fire one part at the listening area, and fire the other part off in a direction that results in a much more natural-sounding arrival time because it better mimics what happens in a good seat at a good hall.
The ear/brain system judges the size of an acoustic space largely by the time delay between the direct sound and the onset of significant reverberant energy (after the floor and ceiling bounces), and this surge of late-onset (and spectrally correct) reverberant energy from the Space Generators makes the room sound bigger than it is, and correspondingly expands the soundfield. So this system will make it sound like you have a significantly bigger room, all the way down into the bass region, where the Swarm does that as well!
Tube amp friendliness is retained (93 dB, 8 ohm load when the Sigma Mains and Space Generators are driven in parallel), and we have the dynamic liveliness of prosound drivers (negligible thermal compression on peaks). I've been told by many listeners, at this RMAF and at previous shows, that my speakers are a welcome break because they are so relaxing to listen to. I don't emphasize audiophile fireworks; I want something that you can leave on all day and never begin to get tired of (owning SoundLabs for many years ruined me as far as being able to tolerate fatiguing speakers).
I've been told that I need to spend more time emphasizing how user-adjustable my speakers are, because that seems to be a fairly unusual, perhaps even unique, attribute. So here goes:
The Swarm subwoofer modules can be used sealed, ported, or some of each. Many users get best results with reversing the polarity of one of the subs. Aside from the normal subwoofer controls (frequency, gain, and phase), the subwoofer amp has a single band of parametric EQ and a bass-boost switch (normally engaged for sealed box mode, and disengaged for ported box mode).
The top end of the Sigma main modules can be gently tilted up or down by changing the value of a high-quality resistor in an external terminal cup on the back of the cabinet. Sound too laid-back for you? Use a lower value resistor. Also we have four pluggable ports on the back, so we can fine-tune for how much boundary reinforcement the mains are getting (or not getting). Most stand-mount speakers are weak in the lower midrange/upper bass, but not these. And the midwoofers have enough excursion that you can run the mains fullrange (no protective highpass needed) with all four ports open (worst case scenario) and they won't be at risk going into over-excursion until you get to about 114 dB at one meter. So if you've agonized over trying to find a truly transparent highpass filter that is affordable, you can stop. You don't need one.
The Space Generators have a wider range of tonal adjustability as far as tilting the top end of the response goes, to accommodate a wide range of room acoustic situations, and to compensate for the typically dull off-axis spectral balance of most conventional speakers (when they're added to an existing system). They have a level control as well, and can generally be set to work well with main speakers having a 2.83-volt sensitivity ranging from the lower 80's to the lower 90's. They present a nominal 20 ohm load at their loudest setting (and a correspondingly higher impedance load at their lower settings), so the Space Generators can safely be run in parallel with most speakers. They can be connected in normal polarity, reverse polarity, or one of each, depending on what works best in your room. One of each seems counter-intuitive, but that introduces more de-correlation into the reverberant field, which is actually desirable.
The net result is, aside from getting the basics right (timbre, clarity, imaging, dynamics, lack of listening fatigue), the Planetarium Sigma system is more engaging because it recreates the cues that you would get at a live performance in a good seat at a good venue. The Planetarium Sigma brings what most systems are missing.
Main Modules: Two-way ported (but seal-able) MHM; 8" prosound woofers; 1" Beryllium-diaphragm compression driver on a waveguide-style horn; 65 Hz to 20 kHz; 16 ohms; 95 dB/watt and 92 dB/2.83 volts; 28" x 18" x 10"; 55 pounds. $6000/pair + shipping, not counting stands.
Space Generators: Two-way 10" sealed box coaxial; 60 Hz to 19 kHz; 20 ohms or more (depending on passive level setting); 78 - 88 dB sensitivity (2.83 volts); 12" x 12" x 19" tall; 35 pounds. $1800/pair + shipping (introductory price).
The Swarm: Four-piece 10" multi-sub system; typical in-room response -3 dB @ 18 Hz ported and -3 dB @ 23 Hz sealed (bass boost engaged on the amp for sealed mode); typical in-room smoothness (as reported by many customers) +/- 3 dB, 1/3 octave smoothing; each module 12" square by 23" tall and 44 pounds. $2800/set + shipping, kilowatt-class shelf-mount subwoofer amp included.