Sunfire SDS-10 Subwoofer


Sunfire didn’t build the first small subwoofer, but they did begin the trend towards small, powerful subwoofers, characterized by having drivers with long excursion and high power class D amplifiers. The SDS-10 is the 10″ model in a line that also has 8″ and 12″ versions. It uses a front-firing driver with a 10″ down-firing passive radiator. The amplifier is rated at 250 watts RMS. For $500 MSRP, I was pretty amazed at its performance. It won’t crack the plaster, but it will party hard.


  • Design: Sealed Enclosure (Passive Radiator)
  • Driver: 10″; Long Excursion
  • Power: 250 Watts RMS, 500 Watts Peak, Class D
  • MFR: 30 Hz – 150 Hz
  • Inputs: Line-Level RCA
  • Outputs: High-Pass Line-Level RCA
  • Controls: On/Off, Volume, Continuously Variable Phase, Continuously Variable Low-Pass (50 Hz – 150 Hz)
  • Dimensions: 13.3″ H x 15.1″ W x 14″ D
  • Weight: 34 Pounds
  • Finish: Black Ash Vinyl
  • MSRP: $500 USA
  • Sunfire

The Design

If you bought this subwoofer, took it home, plugged it in, and started using it, you might not ever realize that it has a passive radiator on the bottom. A passive radiator is like a normal speaker driver, but no magnet. Just the cone, rubber surround, spider, and frame.

A speaker with a passive radiator is somewhere between a ported speaker and a sealed enclosure. It does similar things as a port does, but it does it more in an active way. There will be a frequency where the active driver on the front doesn’t seem to be moving at all, and the passive radiator is going like crazy. In fact, I didn’t even realize it had a passive radiator until I was moving it around the lab, because I wasn’t expecting one at this price point. But thar’ she blows.


The rear panel has the On/Off toggle, Volume Control, Phase Control, and Low-Pass Crossover setting. Inputs and outputs are line-level RCA. The outputs are high-passed. You can set the power to turn on when it senses a signal or just leave it on all the time. The AC socket is more like one sees with CD players. It is non-grounded.


In Use

I tested the Sunfire SDS-10 with an OPPO BDP-83 universal player, Lamm LL1 preamplifier, Emotive XPA-1 monoblock power amplifiers, and Krix Equinox bookshelf speakers. Cables were Emotiva and Marc Audio. I set the SDS-10 crossover at 80 Hz and adjusted the volume until it sounded balanced with the main speakers, and fiddled with the phase until it sounded even more balanced.

Well, I must say that I never cease to be amazed at the products that Bob Carver has his fingers into. The SDS-10 is no exception.

The Ray Brown Trio is exceptional in that it is a jazz trio without a drummer. Being a drummer myself, I don’t know why I like the album, but I do. The SDS-10 did a very convincing job of adding the fundamental frequencies in the piano’s lower registers, as well as with Brown’s string bass. There was no boominess or chestiness to the sound at all.


Classical piano also fared well with the SDS-10, and if there is anything that will challenge a sound system, it is Chopin’s tendency to play every key on the piano. The Kris Equinox is a rather small bookshelf speaker, and the overall sound truly benefited from having the SDS-10 in the system.


So, after all that sweet jazz and relaxing Chopin, I decided it was time to heat things up. Big band means lots of instruments, and they don’t play lullabys. This SACD moves right along, and the SDS-10 stayed with the music all the way to the end. Now, I am not saying it will compete with the big guys, like the Paradigm SUB 2 or Velodyne DD-18+ that we reviewed recently, but within its boundaries, it plays just fine. Those Emotiva monoblocks will put out 500 watts RMS, and there were a few transients along the way that I am sure were climbing into the stratosphere that the Emotivas can deliver. Small speakers like the Equinox can take high power transients for a short time as long as the amp is not clipping, but the little SDS-10 held its head high and came through unscathed.


I watched a few movies with the SDS-10 in our home theater lab, and as long as there weren’t any digitally synthesized subterrainian low frequencies (~ 18 Hz), the sub did its job. Mind you, this subs is not for a big home theater setup, but is more for a family style, small, cozy room setup, where everyone is happy with the volume at modest levels.

On the Bench

Distortion tests were performed within an 80 kHz bandwidth. The crossover was set to Bypass.

I was unable to get significant output at 20 Hz, so I am reporting the tests starting at 25 Hz, where at 82 dB, there was 10% THD+N, which has become the standard in maximum acceptable distortion for a subwoofer. So, for all subsequent tests, I set the volume at 82 dB.


At 31.5 Hz, distortion was 3%, which is pretty good for this little guy.


At 40 Hz, there was only 1.8% THD+N. Again, a little surprising for a small enclosure subwoofer.


At 50 Hz, distortion was somewhat higher than it was at 40 Hz, but still acceptable.


The in-room frequency response at 1 foot was reasonably flat between 32 Hz and 100 Hz.


Averaging six frequency response measurements from different positions in the room, ranging from 1 foot to 3 meters, produced the following curve. The dip between 40 Hz and 50 Hz is a room issue.



Bob Carver – who now serves as a design consultant for Sunfire – continues to make products that perform beyond expectations based on their price. Although the SDS-10 will not handle massive digital synth explosions in movie sound tracks, it will work very well in modest sound systems and home theaters.