The W9 challenges for largest speaker unit among all wireless multiroom systems, yet does so rather unobtrusively compared with the vast frontage of the Bose SoundTouch 30, say, or the relatively noticeable Bluesound Pulse. 
In comparison the W9’s black fabric grille and black Perspex-like topplate allow it to recede visually. It is also a useful few centimetres less deep than either of the other two, making placement a little easier — but be aware that like its smaller brother the W7, it has side-firing speakers, so it needs space on either side. 
W9The controls on the unit itself are unusually placed, sticking out from the bottom right corner on a protruding metal plate (see below), but these add a useful pause/play and next track selection to the usual volume controls — there’s no mute here, but the pause button does a similar job. 
Round the back is quite a tight port bay with an optical digital input, an auxiliary analogue minijack input, a USB port (upgrades and charging devices only), an Ethernet connection, and a little blue button marked ‘set-up’, which has a nice tactile bounce to it (but don’t hold it down too long, or you have to re-pair the speaker all over again).
The driver arrangement is also unusual — bass and treble fire forward from the front, using twin 5.25-inch bass drivers and 25mm aluminium-dome tweeters, while an additional stereo pair of 5cm “full-range” drivers fire sideways, in what Definitive Technology calls a “Tri-Polar dispersion pattern that radiates sound off of the surrounding walls”. The power behind these units is quoted at 2 x 70W for the big woofers, plus 10W each for the two tweeters and two full-range side drivers.  
How does this unusual arrangement perform? Impressively in many ways. Down low the W9 proved the only player in this group which could truly resonate along with the crazy bottom bass on Neil Young’s Walk With Me — the bottom note during the middle 8 of this song set our listening room a-thunder. This is dreadfully impressive performance. 
Diana Krall’s ‘Wallflower’ album showed how much brighter and potentially more clear a vocal could sound on the Definitive Technology when played alongside the relatively reserved Bluesound Pulse. On such gentle songs the W9 didn’t perhaps deliver as grand a scale as the Pulse, but many will prefer its crisp-edged vocal presentation to the reserved upper mids of the Bluesound.
Those side speakers do seem to assist the creation of a stereo image — on Pink Floyd’s Run Like Hell the W9 properly separated the dual vocals to left and right channels, and while the Bluesound Pulse gave the impression of more solid bass depth on this track, the W9 certainly opened the track up more in the higher frequencies for the vocals and echo-laden guitar parts to achieve cut-through. 
On occasion this liveliness can go too far, as it did from Deezer with Billy Joel’s recent power-packed take on 'Maybe I’m Amazed' — the vocal unreasonably raspy and the whole upper mids overpeaking on presence. But it excelled with a modern chart mix — OMI’s Cheerleader (Feliz Jaehn remix) got its best performance from the W9 — the treated vocal, the trumpet and its reverb, the low synth bass and the poppy percussion in marvellously layered and separated elements; it again exceeded the clarity of the Bluesound Pulse here. 
Ditto for Coldplay’s A Sky Full of Stars, another ‘best delivery’ through the DefTech — less insistently thumpy than on the big Bose, more spacious and less restrained than the Pulse. 
So while we found ourselves vacillating in a material-dependent way over whether we preferred the W9 overall to the Pulse, we are completely confident that nobody investing in this fine wireless speaker will regret it on the basis of sonic performance. Definitive Technology has more than proved its skills in the loudspeaker department.
Note: With the latest DTS Play-Fi app now available, we re-appraise the whole Definitive Technology W Series in the April-May 2016 issue ouf Sound+Image.
Definitive Technology W9 wireless speaker
Reviewed at $1099, now $1299
+ Excellent sound
+ Side drivers create a spread of sound
- Needs space at sides