In the last few years, the popularity of high performance speaker systems has grown immensely. This is primarily due to the introduction of affordable home theater equipment, such as wide-screen TV monitors. The cost effectiveness of most commercially available home theater speaker systems has improved remarkably over this time, and it is now possible to purchase a reasonably high quality surround "5.1" system for under $1000. The weakest link in most of these affordable systems is the subwoofer. To get the kind of "earth shaking" power output you need to duplicate the sound you hear in a real movie theater, will cost anywhere from $1000 to $3000 for the subwoofer alone. In a large listening room, you will typically require two subwoofers, effectively doubling this cost.
Internal Stiffening of Enclosure
Final Assemly of Enclosure
Titan Driver
One thing which makes commercial subwoofers so expensive is that most of them are designed to be very compact. This stems from the (probably mistaken) assumption that people don't like to see speakers sitting in their living or family room. Another reason why commercial high-performance subwoofers are expensive is that typical mass-production techniques do not work well on this kind of product, so the cost of these speakers climbs rapidly as performance goes up. In order to keep their size very small, most of the available subwoofers today are designed as what is called an "acoustic suspension" system. This type of speaker is very inefficient, has a poor frequency response, and requires huge amounts of amplifier power. One such system now on the market actually has a 2000 watt amplifier built into it! Over the past ten years, I have watched this situation develop, and always thought that something could be done about it. When I decided to put together a new home theater system for my home, I was dismayed to find that two of the subwoofers I needed would cost more than the 65 inch top of the line projection HDTV monitor I was buying. So I began to think about what it would take to create a more cost effective solution.
After much research I concluded that the best solution would be to design a more efficient subwoofer system than what is typically available. This is actually not as difficult as it sounds, because the technology to do so has been around for over 60 years. It is called a "bass reflex" design and is normally at least twice as efficient as the acoustic suspension type of speaker. Not only that, but it also has a far better frequency range and response than the more inefficient speakers. The major difference between the compact, expensive acoustic suspension subwoofers and the bass reflex, is that its cabinet has a carefully designed "port" which couples the sound energy from inside the enclosure to the outside. Just cutting a hole in the box will not help. It must be carefully calculated to produce exactly the right frequency dependent distribution of energy, known as a "resonance" to match it to the loudspeaker "driver" installed. Many books and articles have been written describing various solutions to this problem, dating all the way back to work by Dr. Harry Olson at Bell Laboratories in the 1930's. Interestingly, many of the subwoofers installed in real movie theaters are this type of design.
There are several other important characteristics of an efficient, high quality subwoofer. It is very important that the enclosure or box be made out of extremely stiff and non-resonant materials. Unlike a musical instrument such as a violin or guitar, which derives much of its sound quality from the vibrations of its structure, the box of a high efficiency speaker system must not "give" or flex. This means that special care must be taken to design it in a way that provides the stiffest structure practically achievable.
The photos at the right show the internal construction of our design. The entire encosure is fabricated of heavy medium density fiberboard, one of the stiffest materials available. The area where the driver will be attached is over one inch thick. In the first photo, a large number of internal braces are glued in place, to provide additional stiffening, and prevent flexing of the enclosure walls. The enclosure is then completed, as shown in the next photo. All mating surfaces are held in alignment with splines, fastened with urethane glue, and clamped.
In order to properly match the characteristics of the box with those of the speaker "driver" a simple hole in the side of the enclosure is not usually sufficient. Instead, a carefully designed tube or "duct" is needed to provide the box with the correct dyamics. These as well as many other details need to be considered to design a really great bass reflex subwoofer.
Our solutions, called the Titan Mark I and Titan Mark II, are hand crafted subwoofers that are affordable, yet deliver incredible performance. The loudspeaker drivers, shown at the right, have cast aluminum frames with magnets weighing over six pounds. The built-in amplifier delivers an output of 250 watts of undistorted sound. Each unit is tested for sound quality and frequency response, and a detailed test report is included with each subwoofer.
Mk I Frequency Response
Mk II Frequency Response
The next set of photos shows the typical frequency response of the Mark I and Mark II subwoofers. These response curves were taken in the actual listening room, not an artificial anechoic chamber environment. We believe this kind of measurement gives a much better picture of the actual performance of the product. Data was taken using a calibrated sound level meter and signal generator. Note that the total variation in response in the critical range from 20 Hz to 100 Hz is 6 dB or less. Both models are very usable at frequencies up to 300 Hz, making them ideal for use in systems with "mini" type speakers. Typical acoustic suspension subwoofers have a variation of 10 to 20 dB over this range, and require electronic compensation to achieve a flat response.
We believe that the Titan Mark I is the ultimate home theater subwoofer, and at $895, it is also an excellent value. It is designed for room environments of up to 4000 cubic feet. The smaller Mark II has an amplifier and frequency response identical to the Mark I, but is only about two-thirds as large. It is designed for room environments of up to 3000 cubic feet, and sells for $695. A $100 (per pair) discount is given when a pair of either speakers is ordered. Each speaker is shipped with a detailed graph of its frequency response and output level. Because of their weight, these speakers must be shipped by motor freight.
The photos below show the finished speakers. The Titan Mark I is shown with its grill cloth assembly removed to show the speaker driver and ducted port design. The Titan Mark II has two versions, one with the driver on the left, and one with it on the right, for convenient placement in one- or two-speaker systems. The last photo shows a typical Mark I installation. The two subwoofers are matched up with an Atlantic Technologies THX-450 speaker system components to provide sound for a large (about 8000 cubic foot) viewing environment.
Titan Mark I |
Titan Mark II |
Typical Mark I Installation |
