Ambience is well and truly on the map these days, and there's been a recent addition to the family the Ambience subwoofer. If you're not familiar with the brand, Ambience manufactures a hybrid ribbon speaker that combines the sonic virtues of a conventional cone driver with that of a metal ribbon. The cone and its enclosure produce the speakers' low and lower midrange frequencies, while the long, crimped ribbon delivers the higher stuff.

The bass enclosure includes a 12 inch driver specifically made for Ambience by the Scandinavian driver manufacturer, SEAS, and with two of them in play, there's no way you'd describe a pair as bass shy. However, bass is an element of the audio spectrum that requires some physical hardware consideration, especially if you want to really excavate the really low stuff.
Size matters when it comes to truly low bass, and despite many speaker manufacturer's best efforts to achieve substantial bass weight from small drivers and enclosures, the physics simply don't allow it. And the reason for Ambience's sub? Well, it's twofold. It's been designed to perform with both home theatre and music applications, I use a pair of Ambience SuperSlim Ultra 1600s, primarily as stereo references, but also pop them into my A V system, from time to time. As front, or rear speakers in a multi channel setup, they're formidable, something that prompted Tony Moore to develop a tonally-matching ribbon centre channel speaker. All that then remained was the 'zero point one bit' of a Dolby Digital soundtrack, hence a subwoofer, but certainly not your average bass chuffer.

Tony's aim was to produce a subwoofer that would enhance stereo music as it would home theatre surround sound. He felt a lot of commercially made subwoofers, while performing OK with movies didn't work too well with music, by reproducing too wide a bass frequency range and subsequently imposing on the main audio channels. Addressing this problem, the Ambience subwoofer operates using a bandpass system and only reproduces a very narrow range of lower frequencies, having a useful low frequency response of 20Hz and a tapped upper frequency limit of 50Hz. The Ambience sub is a reasonably substantially-sized unit, although Tony was able to significantly decrease its eventual volume compared to prototypes and still maintain the desired bass output.

The cabinet is of solid and extensively braced MDF construction, finished with a solid timber top and Tung oil's been used to give the wood its distinctive finish. It's a passive design and there's just two sets of 4mm binding post connections on the rear. Typical system installation would be taking the subwoofer output channel from a decoder or processor directly into a power amp and then out to the sub. Passive subs are very much few and far between these days, but the bandpass System that has been used here is paramount to the Ambience's bass performance. The system works by incorporating two chambers, back to back, with a single driver mounted between the two boxes. The rear chamber operates as a Sealed box and combined with the drivers' parameters, governs the lower frequency response. The front chamber is ported and the tuning frequency of the port is crucial in this sort of design. The prototype sub had two circular baffle ports, but the finished article carries just the one rectangular port. The vent is tuned to a certain frequency, a good analogy being an organ pipe, and the relationship between the enclosure and vent becomes the natural resonant frequency of the subwoofer system.

The sub's 30cm driver comes from Peerless, choosen it for its high 45mm cone excursion and ability to cope with very low frequency demands. When a subwoofer driver starts having trouble with lower frequencies it's generally something you'll be able to hear, and with an externally-mounted driver, see. As the frequency response drops, cone excursion dramatically increases, and you need a driver that'll cope -hence Tony's use of the very capable Peerless.

In the right system, the Ambience sub delivers the sort of bass that's as musical as it is substantial. There's plenty of speed on tap to keep up with fast music or movie transients and bass timing and drive are superbly preserved. With music and used in conjunction with the Ambience ribbons, the three-sounds awesome. With their revealing nature (the sub included), high quality recordings are fully catered for and appreciated by the combination. The ribbons and subwoofer blend completely without any discernible sonic seam and thrive with powerful, dynamic recordings.

The subs muscularity is never in doubt-with all sorts of music there's an agility and texture to some very low frequencies that your average active 100 watter simply can't deliver. There's fine definition and timing, and even with the volume turned low, the Ambience provides an unusually firm presence. Acoustically crafted and superbly produced, David Sylvian's Secret's of the Beehive demonstrates well the limited bandwidth of the Ambience and its ability to remain within its design specs. The delicately plucked double-bass on the atmospheric The Boy with the Gun, although subtle, is delivered with bags of character and dexterity.

Nic Tatham
Audio & Video Lifestyle Magazine