High Performance Subwoofer Systems for Music and Home Theater Enthusiasts
 
After years of enjoyment and having sold off Ravens that I’ve built so that I could build more of them in different finishes, including cherry, mahogany, black laminate, maple, hickory and oak, I found a supplier that makes a unique product from bamboo (which is discussed in more detail on the Going Green page of this site). As I have always leaned toward buying products for my own use that are “environmentally friendly”, I began looking into that aspect of design more intently. The Raven, as a system I designed for my personal theoretical, industrial design and home theater application, was a no-holds-barred subwoofer  from the ground up. Since every Raven is a one-of-a-kind creation and was painstakingly built by hand, I was limited as to the number of Ravens I could build and so, because I received so much interest from people from around the world, I decided to design systems that retained the Ravens performance capability, yet were a bit more affordable as well as being a bit easier to build, package and ship. Extreme output, 18 preset user-selectable native frequency response curves, uncompromising attention to detail, the first and only active conduction/convection driver/enclosure cooling system, Raven was truly one-of-a-kind low frequency machinery. The successful outcome and years of enjoyment of Raven inspired me to design and build similar audio hardware to offer to others.
As the photo shows, I had already begun using the cylinder shape, using a 1/2” thick custom extruded PVC cylinder. I had also begun using the base plate with ball feet as well, which has come to be the signature base plate system for the Raven subwoofers. In the early days I had designed and built my own Linkwitz Transform (L/T) equalizing circuits from a spreadsheet that was available online. During a trip to CES, I met and befriended Phil Marchand of Marchand Electronics. He showed me his adjustable L/T which he calls the Bassis, and I immediately ordered one. It saved me a lot of time in calculations and soldering and is a tool that can instantly transform any sealed design, on the fly. Over the years, Phil has engineered and built various analog processors that I designed for my subwoofer systems, as they’ve evolved over the years, all of which have been superb products. After building many versions of the above illustrated subwoofer, looking at every conceivable facet of the design, I built what was to be at the time, the finest possible home theater subwoofer system I could build. Using the best parts I could find, and incorporating features that have never been available before, I had a system of which I was both very proud and extremely satisfied. I eventually named the subwoofer the Raven. Its features included a custom extruded hourglass-shaped PVC enclosure, dual-opposed 15” drivers, a 1/2” beveled glass top I call DriverVu, an active driver motor cooling system I call ThruVent Cooling, a custom Bassis signal shaper and a high powered class-H 95 pound amplifier. I built four of them for an 8x15” system with 2-5,000W amplifiers which resulted in a system that provided a ruler flat response at the listening position from 4 Hz to 120 Hz, takes up very little real estate and, if I may say so myself, looked like no other audio hardware in the world (to myself and, more importantly, my better half). Pictured, clockwise: ThruVent Cooling, Raven Executive in Mahogany, Hourglass enclosure and DriverVu glass tops.
Measured at the Primary Listening Position in a 3,500 cubic feet room that’s open to a stairwell and a hallway to the rest of the floor plan. 3 Parametric EQ filters with mild cuts were used to result in the frequency response shown.
Where it all began... Fifteen years ago, after the advent of the AC-3 format of discrete satellite channels with a discrete LFE +10dB channel, each having a response down to 3Hz, I began to search for a new preamplifier and subwoofer system to accommodate the new format. I had built a 2 subwoofer system of large 1x18” ported subwoofers for my initial HT, but looking realistically at a specification for possible content to 3Hz meant that my ported subs would not stand a chance of covering that bandwidth. After investigating the so-called high efficiency alignments (ported, passive radiator, transmission line, horn, bandpass, etc.), I began looking at the sealed alignment. Its shallower roll off appeared to be well suited to working with room gain to be able to reach much lower than any of the other alignments, which all have a practical limit well above 3 Hz. A sealed subwoofer system also afforded the opportunity for a much more compact system as I discovered with the other alignments the lower the tuning, the bigger the subwoofer... as in BIGGER. The more I searched, the more I found available subwoofers to be wanting, both in performance and appearance. So, I decided to build my own. I designed and built a subwoofer for a single 12” driver and began testing. Soon afterward I moved to 15” drivers as well. I ordered and tested some 50 drivers from around the world and, during that process, I got the idea to design a dual-driver subwoofer with the drivers facing out in opposite directions. It made sense that the opposing forces of the moving drivers would cancel the mechanical forces, which can be quite violent in such a design, adding unwanted noises to the presentation caused by extraneous vibrations. The first iteration of a small, dual-opposed sealed, equalized, high-powered subwoofer was built in early 2003 using a driver sealing system and clamps so that I could quickly switch out the drivers to immediately see any differences in performance.