Unity Audio Signature 3
To get these overgrown bookends to stand up, you slide little black boards into the slots in their bottoms. Each board is held in place by two set screws, and sticks out to support the speaker with two of the four spikes. The board also tilts the speaker back a little. How do they get sufficient bass out of such slim cabinets? Unity Audio is glad you asked. They call it "Inverse Force Vector Coupling," and are very proud of their development, isolated through "extensive physics research." Basically it consists of one woofer pushing while the other woofer pulls. They can tune this system by varying the dimensions of the tube that runs through the middle of the cabinet. Unlike an acoustic suspension system or a ported system, this type of bass alignment is said to be able to work with an extremely small internal volume.
The Signature 3 has a 7" polypropylene-cone, cast-basket woofer mounted at the top of the front baffle, and a second one mounted at the bottom of the speaker's back wall. This rear woofer puts out midrange as well as bass, so whatever is behind the speaker will affect the sound more than with an ordinary front-firing speaker. It also has a 1" silk-dome tweeter. My first samples were old enough to not have the ceramic coating on the tweeters, and they looked like the same units as in the Swans Baton reviewed in this issue, but without the Marigo dots. Unity Audio apparently has done quite a bit of resonance-structure research for the development of their new tweeter, investigating different ways of getting the best transient speed from the dome while trying to avoid ringing. They found a lightweight ceramic material more than 10 times as rigid as aluminum, and which can be deposited in very thin layers. Multiple layers of this are used on the dome, alternating with thin layers of a very effective damping material. All recent production of the speaker has featured the new tweeter.
Remember what I said about packaging costs? The crossovers of these beauties feature copper-foil air-core inductors, Kimber Kap polypropylene capacitors, and pure silver wire. The cabinets are internally braced, and small enough to not want to resonate much anyway. They did seem a little wobbleriffic, though, so I placed some disks on them. Was it those neato bingo thingos? No, these were 2kg of cast concrete (with calcium!) encapsulated in a luxurious no-scratch plastic casing and delightfully contoured for maximum domestic appeal. That's right, kids, it's Orbatron! I bet, like me, you have some hiding in your basement that you can fetch if you need it for resonance damping. Just remember to ask your parents first. (By the way, I put the weights on the speakers' bottom braces.)
The Way the Signature 3 Used to Sound
When I was taking a look at the first pair, I saw a little bump on the woofer surround. It felt hard. I removed the woofer and found some nice things inside. The input wires are soldered directly to the woofer terminals, eliminating crossover components. The woofer crossover is accomplished mechanically, by mass loading the cone with a coating of hot glue.
Which brings me back to the bump. It was a stray piece of glue that had accidentally splashed onto the surround and stuck there. By reducing the elasticity of that side of the surround this could theoretically be bad for the sound. In my listening, though, I had difficulty detecting any difference between the sounds of the two speakers. At least this little defect proves that Unity Audio doesn't give preferential treatment to speakers that will be sent to reviewers, which is nice to know. I only found such bumps on two out of the eight woofers of the two review samples; they don't seem to affect the sound much, but Unity's glue people should be more careful.
I substituted the Signature 3s after listening to the Swans Batons for a week. It was immediately obvious that the Unity Audio reproduced well-recorded music in a more neutral fashion than the Canadian design, and this impression continued throughout my listening. I listened with the grilles off, mostly with the speakers in the same positions as the Batons. I found the bottom of the woofer to be a good listening axisthough this is a low 27" from the floorand preferred a slight toe-in.
With Steve Tibbetts' The Fall of Us All, I got the sense that the Signature 3 was well-balanced, with better top-octave air and a much more spacious presentation than the Swans. The only part of their presentation that seemed to be substandard was the midbass: there wasn't much. True, the upper bass was of high quality and at a good level, but a certain visceral push was missing. The bass-frequency tones on Stereophile's Test CD 3 (STPH006-2) went missing in action below about 60Hz.
Despite being endowed with what looked like the same tweeter as in the Batons, this pair of Signature 3s had a brighter presentation. Instrumental timbres were more natural with source material of the trustworthy, unequalized type. They also had more treble detail to offer the listener, although I felt they couldn't quite equal the Thiel CS1.5 and B&W 804 in this department. Partly because of their nice top end, they provided a large sense of space from their reproduction of the reverberation info on the recording. Their spaciousness was also augmented by the rear firing mid-woofer. While this was a bit too much to be strictly realistic, it was very pleasing, and certainly closer to reality than the Batons' persistent tendency to reduce soundstages to the equivalent of a Sonexed bedroom.
This first pair of Signature 3s had a good midrange: fairly smooth in terms of tonal balance, but with a few small departures from linearity. The really cool thing about their midrange, though, was the amazing transient speed. With no crossover to get in the way, the Signature 3 reproduced all the mid detail that the amp could feed it. After all of my mod madness, and other listening escapades, I know how well simplicity can take me closer to the original event of the performance. With this setup there were only two resistors, two capacitors, one MOSFET, and four mechanical connections between the CD player's output and the midrange's voice-coil. I was a happy little pew-wrist.
The Sound of the Current Signature 3
Towards the end of the review period, Unity submitted a revised pair of Signature 3s (footnote 1), these featuring the revised ceramic-coated tweeters.
These new tweeters were great. They seemed to do well with transient details such as twinkly little sounds. Maybe they were a little too twinkly, but not much. Because the woofer has no electrical crossover, the upper end of its range invades the tweeter's territory. Nevertheless, the crossover region sounded quite smooth with the speakers arranged for only a small amount of toe-in. I felt the top octave was a little clearer with the new tweeter. Timbres sounded a bit too bright and steely, but this was to a very slight degree. Overall, the Unity Audio crusaders seem to have succeeded in their quest to lower the excess tweeter-dome ringing.
Footnote 1: This was basically Stereophile's fault in that we took such a long time reviewing the Signature 3s. By the time the original writer commissioned to perform the review, Guy Lemcoe, ultimately recused himself, we had already had the first samples of the speaker for quite a long while before we sent them to Muse Kastanovich.John Atkinson