Product Review - Sunfire True Subwoofer MK-II - December, 1997

J.E. Johnson, Jr.

Sunfire True Subwoofer MK-II 10" Drivers - Passive Radiator Design Manufacturer's FR Specs: 18 Hz - 75 Hz � 3 dB Built-in Amplifier: 2,700 watts rms Size: 11" H x 11" W x 11" D Weight: 43 pounds Price: $1,250 USA (Black lacquer finish)

It was only a couple of years ago when I first heard the Sunfire subwoofer in prototype form at the CES in Las Vegas. It was moving so much air, the curtains behind it were shaking. Since that time, the Sunfire has been a major success in the marketplace, not so much because it is powerful, but because it is powerful in a SMALL box. Everything about it is unique. The 9" driver (10" if you include the rubber surround and the mounting ring) has a huge excursion for its size. The magnet structure (14 pounds) is also enormous. The amplifier is capable of delivering several thousand watts into the 4 Ohm impedance driver, although the system never demands this much power on a continual basis. In order to achieve large amplifier capability, the power transformer was removed, allowing 120 V rms from the wall direct access to the power capacitors, reducing cost, but improving current delivery. Extremely clever. To increase efficiency, the tracking downconverter from Bob Carver's Sunfire Amplifier was used. The entire package is in an 11" cube. All in all, a totally new approach to subwoofer design. Testamony to the fact that a powerful but small subwoofer is very useful can be seen at any hi-fi show. Many of the manufacturers use this sub in their booths to demonstrate various home theater components.

The MK-II version of the Sunfire Subwoofer has an improved driver which allows a little more power to be delivered to it (although 2,700 watts from the amplifier is theoretically possible, the driver would never require it, except perhaps on a short impulse). The amplifier itself is basically the same, and the control panel has the same switches and knobs for volume, variable low-pass (40 Hz - 75 Hz), variable phase (0⁰ - 180⁰), RCA inputs (L/R), RCA outputs (high-pass), and speaker-level inputs/outputs.

For a complete description of the design and principles, see the original review of the first model (click here). That info already having been stored in the archive, let's get right to the performance of the MK-II.

We tested the original version out from the wall, like we test other subwoofers, but we decided to test the MK-II where it was designed to be placed, namely in a corner. We faced it sideways, so that the active driver and passive radiator were facing towards the two side walls in the corner. An angle of 45⁰ exists between the surface of each driver and the wall. The sub is so small, it fits very nicely in the corner, with only a few inches of space behind it. Actually, just enough room to reach behind the sub and make any adjustments you want (the power stays on all the time since there is no on/off switch).

One of the first things I noticed about the MK-II was that it does not hop around as much as the first version. Obviously, the balance of the passive radiator with the active driver has been improved. Secondly, it plays somewhat louder than the first edition. The really low end (10 Hz - 16 Hz) produced no audible harmonics. However, the built-in limiter attenuates everything below 20 Hz (below 30 Hz in the "Video Contour" switch mode), so that the driver barely moves when input with sine waves below 20 Hz.

As you can see, the room response is pretty flat down to 25 Hz, which is truly remarkable for such a small package. We were able to obtain 105.3 dB at 25 Hz (near field) at which limiters began operating.

Musically, the MK-II performed very well. I put the MK-II into one of our audio reference systems, which includes a pair of Monitor Audio Studio 20 SE floorstanding speakers. The 20 SEs are marvelous speakers, but they do not put out much SPL below 40 Hz. The MK-II complimented these fine speakers with all types of music, whether it was a Vivaldi Concerto, Beethoven Symphony, or Enya. The lowest note on a piano has a fundamental of about 28 Hz. Electronic music, such as on a typical Enya CD, also has low frequencies that are beyond most floorstanding speakers' capability. The Sunfire put in that last, very important lowest octave. In the home theater, the MK-II did equally well. "True Lies" in DD, and "Apollo 13" in DTS thundered across the room. The "Video Contour" setting truncates the lowest frequencies, so that the sub can concentrate on the region that movies have a lot of, namely at around 40 Hz. However, the sub is so powerful, I preferred to use it in the "Flat" setting, to get everything. I could not hear any boominess at all, regardless of the output. The engineering that went into this product is really amazing.

THE INEVITABLE COMPARISON: Click here.

In conclusion, the first version of the Sunfire Subwoofer received laudatory comments from just about everyone. The MK-II has improved on that product by smoothing out the hip hops that the older one took across the floor, and increasing the maximum output. It was a bargain then, and remains not only a bargain now, but one of the most interesting and useful subwoofer innovations to come along in years.

John E. Johnson, Jr.

� Copyright 1997 Secrets of Home Theater & High Fidelity
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