The Prisma (prounounced "PREEZE-ma") is my latest design, an obvious Rhythm Prism derivative that offers a few refinements: Bigger box for deeper bass; even greater adjustability for a wider range of room/amplifier compatibility (the bigger box translates to better performance in a large room); flush-mounted drivers for marginally better WAF; standard finish includes Walnut (depicted is a stained Walnut); and a rear-firing tweeter that's about 10 dB down relative to the front horn, which fills in a little bit of reverberant energy that is otherwise missing because of the horn's more limited vertical coverage.
I try to avoid waxing too poetic over my speakers because my opinion couldn't possibly be objective, but I think the Prisma is unusually natural-sounding on voices and instruments. It offers what I think is a unique combination of attributes that has shifted my "how to design good, reasonably-priced loudspeakers" paradigm. I'll go into more detail about the what, how, and why behind this after the secret weapon goes public.
On the back of the speaker are two ports, one high and one low. This is consistent with my philosophy of distributing the in-room basss sources as much as is practical. Two speakers inherently spreads out the bass sources in the side-to-side dimension, but we can do better than that; mounting the woofers on the front and ports on the rear gives us some separation in the front-to-back dimension, and then the woofer and both ports all being at different heights gives us some distribution in the vertical dimension. Thus we have our bass sources interacting with the room modes differently from one another, which results in some smoothing of the in-room bass. We don't get as much smoothing as with a distributed multisub system, but then we don't have four more boxes in the room either.
Also, having one port high and one port low results in a more symmetrical airload on the back of the cone. The ports can be lengthened enough that, even in a corner-loading situation, we can still keep both ports open and thus maintain that more symmetrical airload. This won't really matter at normal in-home levels, but if you really crank the speaker, it can help maintain linearity at high levels. Cooling is also facilitated, with hot air exiting the top port and cool air entering the bottom port - again not a factor in normal use, but not a bad feature to have if you ever really crank 'em.
There is a significant hidden savings that ought to be factored in when considering a system-on-a-budget: The Prisma sounds great driven by an inexpensive little Virtue Audio amp. In other words, your amplifier cost can come way down compared to what most speakers are looking for. And then if you later want to go with a specialty tube amp (OTL or SET), that will work just fine too because of the smooth impedance curve and adjustable port tuning.
I may offer a professional version with higher power handling crossover parts and maybe another tweak or two, as I think the Prisma has potential for studio use. As noted, the design includes features that contribute to good performance at high power levels. And the woofer has enough excursion that its high thermal power handling isn't wasted by xmax being exceeded at modest power levels.
Edit 6-12-11: Due to the rising price of neodymium, and the inclusion of a rear-firing tweeter as standard on the Prisma, the price has increased to $3300.
Here are specifications for the Prisma:
Type: Two-way controlled-pattern floor standing reflex system
Impedance: 8 ohms nominal, tube-friendly
Efficiency: 93 dB/1 watt
Recommended amplifier power: 5 to 300 watts
Thermal compression: Less than 1 dB at 50 watts (110 dB SPL)
Radiation pattern: 90 degres in the horizontal plane from about 1.4 kHz on up
Toe-in of front baffle: 45 degrees
Typical bandwidth, light boundary reinforcement: 41 Hz to 18 kHz
Typical bandwidth, moderate boundary reinforcement: 34 Hz to 18 kHz
Typical bandwidth, strong boundary reinforcement: 27 Hz to 18 kHz
User adjustable features: Port tuning and treble tilt
Dimensions: 44" tall by 14" wide; depth along long side = 24"
Weight: 95 pounds each; 125 pounds crated
Price: $3300.00 per pair plus shipping, Oak or Walnut veneer, natural or stained.
