Introduction

I have known Bob Carver, designer of this subwoofer and many other unique products, for a long time. In fact, his company (Sunfire) was one of the first to send us products for review, way back in the mid-1990s.

Bob is a very interesting guy. Physicist by training, audio designer by fascination.

I still have the Carver Amazing Loudspeakers, a pair of the Platinums and a pair of the Silvers. They are ribbon speakers (quasi-ribbon actually), and I would not part with them for anything.

A few years ago, Bob designed a subwoofer in a small box, but with a driver that had a very large excursion, and of course, a powerful amplifier with his "Tracking Downconverter". The combination set the subwoofer world on fire, and it has not been the same since.

The beauty of the package was that consumers could finally get powerful deep bass, without having to put a huge box (enclosure) in their listening rooms.

The EQ Signature

Bob Carver's latest version is called the EQ Signature. It looks pretty much the same as the early designs, being a cube about 1 foot on all sides. There is a 12" active driver and 12" passive radiator. The drivers have a 10" piston (bore) size, meaning this is the part that moves in and out. The excursion is specified as 2.35". The 2,700 watt power amplifier with Tracking Downconverter is still there.

The review unit had a beautiful finish that appeared to be deep violet stained oak, covered by many coats of hand rubbed polyurethane. I suspect the enclosure was made in China. They are getting to be renown for their incredible finishes on speaker enclosures.

So, what is different now? Well, for one thing, this sub has an Auto EQ feature, which lets you set the included microphone in your listening position (where your head is, not your tail), push a button on the side of the subwoofer, wait a minute or two, and voila, some of your room's bass problems are partially corrected. I say partially, because no EQ can totally correct the peaks and valleys in a typical listening room. But every little bit helps, and the EQ Signature provides some help, as you will see below. The EQ consists of four bands spread between 20 Hz and 100 Hz.

Secondly, the EQ Signature has lower distortion than the original version, as I found out with the Bench Tests. I don't know how he did it, because getting a driver that is moving back and forth about 2", with low distortion, is no easy task.

The Set-Up

Although you can get a lot more bass out of a subwoofer if you place it in a corner, I tested it several feet out from the side and front walls.

I put the included microphone on the top of my easy chair (about 10 feet away from the subwoofer), plugged the other end of the long cable into the jack (shown in the photo below to the left of the word MICROPHONE), turned the subwoofer on, and set the controls according to the instruction manual.

The photo below shows the control panel. For configuring Auto EQ, the Volume Control is set to 0 dB, the Crossover Frequency is set to Bypass, and the Phase Control is set to 0⁰. The Equalizer Authority is set to Normal.

Then, I pressed the Auto EQ Start button (the tiny button to the left of the word START in the photo).

I heard the subwoofer emitting a sweep of low frequencies, and the row of lights on the top of the panel flickered in sequence as the sweep passed through four EQ bands that the subwoofer adjusts. Then the sweep repeated itself, and it was done.

I measured the room response with and without the EQ active (you can turn it off by setting the Equalizer Authority dial to 0). Our calibrated microphone was placed in the same spot as the subwoofer EQ microphone for the measurements.

The graph below shows the results. The red line indicates the room response without the EQ, while the green line indicates the room response with the EQ active. You can see that, while the EQ did not fix all of the issues, it certainly improved the situation. A bump at 23 Hz was reduced, and the response at 47 Hz was raised.

So, the Auto EQ function works. You can switch into manual mode and tweak the response in any of the four bands (you can change only the level, not the frequency or the spread), but I figure that most consumers who buy this thing will do the Auto EQ routine and start watching movies or listening to music, which is what I did.

In Use

I tested the Sunfire with several systems, including our two-channel music system and home theater systems.

The amount of deep bass coming out of the EQ Signature belies its diminutive size. I was truly amazed. It is not what I can get out my 18" subs, but it is not supposed to do that. This is a product for those people who want something small, but powerful.

I did not hear boominess, which can be an indication of harmonic distortion. And, I threw all my sub-buster movies at it, such as the "Here is my invitation," scene from Terminator 2.

Another great movie for bass is Daylight. Try Chapter 8. The Sunfire didn't even flinch.

The distortion graphs are shown below. For these tests, I placed our calibrated microphone 12" from the center of the driver. For the lowest tones, the passive radiator was moving the most, so I put the microphone on that side. At 40 Hz, the active driver was moving more, so I put it on that side for the measurement.

Maximum output, using a combination of 20 Hz, 31.5 Hz, and 50 Hz, was 110 dB. Putting the subwoofer in a corner would add a few more dB, bringing it in right about at the manufacturer specification of 116 dB.

At 20 Hz, and 100 dB SPL, THD+N was less than 8%. This is great performance from such a small box.

At 25 Hz, THD+N was about 3%. Again, excellent!

Having less than 2% THD at 31.5 Hz and 100 dB really surprised me.

At 40 Hz, THD+N went up. Hard to say why, perhaps room suckout.

At 50 Hz, THD+N went down again, and in fact, way down.

Because of the low distortion, listening to my favorite CDs was a real pleasure. While bass distortion can be tolerated with movie sound tracks (explosions), it is easy to hear when an orchestra is playing.

My Magneplanar speakers don't have much deep bass, but the Sunfire sure fixed that right away. It adds a great deal to the listening experience to have the lowest octave. Don't forget, the lowest note on a piano has a 28 Hz fundamental, so a good subwoofer is important in the music domain, just as it is with movie sound tracks. We listened to numerous piano discs, from Liszt to Rachmaninov, and were delighted. My wife really liked the low profile, so guys, this is something that will give you the satisfying bass power you want, but your spouse will be less likely to toss you out the door for bringing it home.

Keep in mind that the distortion graphs shown above are at 100 dB output. In most cases, the SPL will be much lower, and so will the distortion.

Conclusions

The Sunfire EQ Signature Subwoofer is a significant improvement over the older Sunfire subs, and they were pretty good.

The Auto EQ feature helps with room problems, which we all have, and it is easy to use.

I have no hesitation in recommending the EQ Signature to anyone who wants powerful, clean, deep bass, in a box that will be unobtrusive. It's expensive, but quality products tend to be that way.