This review page is supported in part by the sponsors whose ad banners are displayed below

Reviewer: David Kan
Financial Interests: click here
Digital Source: Macbook Pro, Apple iPad 2, Oppo BDP-105/95/83, Marantz SA8260
Preamp: KingRex Headquarters HQ1, Trends PA-10, Restek Sector, Symphonic Line RG3 MkIII
Integrated Amp/Power Amp: Trends TA-10.1, Winsome Labs Mouse, Virtue Audio TWO.2, SimAudio Celeste W4070 SE, Symphonic Line RG4 MkIII
Speakers: Mark & Daniel Maximus-Mini, Maximus-Ruby, Maximus-Sapphire, Maximus-Diamond+, Maximus-Monitor with Omni-Harmonizer
Subwoofers: Mark & Daniel Maximus-Subwoofer (pair), Yamaha YST-SW200 (pair)
Speaker stands: Mark & Daniel Maximus-stand, DIY stand
Cables:  Deltec Black Slink interconnect, OCOS speaker cables by Dynaudio, Dared OFC bi-wire and single-wire speaker cables
Power Cords: Ensemble Powerflux, Symphonic Line Reference, various generic
Power Line Conditioning: Belkin PureAV PF60, Monster Power HTS-1000 Mk II
Room Size: 11' x 18' x 7'/8' opens to 18' x 19' x 7'/8', long wall setup, carpeted concrete slab floor, suspended ceiling and all walls finished with drywall / 15' x 15' x 8' / 12' x 24' x 9' opens to 12' x 17' x 9' L-shape, short wall setup, suspended hardwood floor, suspended ceiling and all walls finished with drywall.
Review component retail: Maximus-Opal-air4 $1,400/unit, uTX package incl. uTX transmitter and 3m USB extension cord and wall mounting hardware $65, Maximus-stand I $840/pair, Maximus-wall-set $150/pair. NuForce: uTX transmitter: $59, iTX transmitter including charge cable $79

Part I: the analog active speaker. Different from the fields of science and technology, literature and arts or food and fashion, the word expert in our little audio review world just might have a deeper meaning. When someone calls me the expert of something, I usually have second thoughts about that well-intended flattering word.

I can’t stop thinking that an expert in our narrow field is someone who thinks he knows a certain topic so well (or is being thought of so) that he is actually biased by unaware favouritism and so is intellectually imprisoned within his own comfort zone. Since joining 6moons, I’ve been called the expert on Mark & Daniel speakers and budget Tripath amps. Consider yourself warned then. This review you’re going to read is about a pair of Mark & Daniel speakers powered by built-in Tripath amps. It couldn’t possibly get worse...

As though to counterbalance my favouritism, the new Maximum-Opal-air4 fortunately isn't strictly an active speaker. It's a wireless system. In addition to being bi-amped—one channel per driver—with built-in Tripath power, each speaker is also equipped with the wireless Air DAC audio streaming transceiver that was developed by NuForce. That brutally expelled me out of my usual comfort zone. Naturally when the review samples arrived in starry black rather than the solid white as I’m used to from owning many pairs, I tried to procrastinate on the wireless business as much as I could.

To that end I simply hooked up the speakers to my Marantz SACD player as I would any other active speaker. I noticed that the wireless DACs were sending me protesting signals as shown above. One had a red LED lit up, the other showed green. Was it Christmas? I didn't care.

Mark & Daniel definitely took a triple long jump with this ambitious new venture. There has never been an active nor wireless loudspeaker in their catalogue, let alone one with a wireless DAC for digital signal transmission. Nor has there been a Maximus-Opal before. The Maximus-Opal-air4 is a completely new entry. The seamless compound marble enclosure resembles that of the Maximus-Sapphire but is 2cm wider to come in at 19x29x22cm WxHxD.

Another visible difference is the circular instead of rectangular opening for the DM-2A wideband airmotion transformer (the same as in the Maximus-Mini) which covers a 5-octave bandwidth from 950Hz to 35kHz. This is quite an improvement over the DM-4 featured on the Sapphire, Topaz and Ruby models whose high frequencies plateau out at 25kHz.

Coverage below 950Hz is handled by the proprietary Super Xmax SX5.5h-0.6 capable of ±7.5mm linear excursion. This is the same driver as used in the Topaz, the lowest but now discontinued model in the precious stone series. Although on paper this woofer is one model down from the SX5.5h-0.8 which yields a more impressive linear excursion of ±10mm, during my initial run-in sessions the Opal-air4 delivered richer and tighter bass than either Sapphire and Ruby do with their more potent woofer. Whether that was due to the active crossover, direct drive or electronic equalization I had to investigate further. Another aesthetic and functional improvement for the Opal-air4 is the removable mesh grille neatly secured by four tiny well-hidden magnets.

Swinging the speaker around I noticed something else I'd never seen on any Mark & Daniel model before. There are no speaker binding posts, only a single RCA and IEC power socket with on/off rocker switch – understandably so for an active speaker. The three knobs respectively are for volume, input selection between RCA, Air DAC and ground and a channel switcher between L, L+R and R. I had no idea what that ground input was all about and the Mark & Daniel website offered no further explanation either. (Eventually I found out that ground is null.)

At least I could explain the channel switch without consulting the real experts. When the Opal-air4 is fed with wireless streaming signal, the signal is obviously stereo but the built-in Tripath amp was modified as a two-channel mono amp for the two-way speaker. So what I did was set up a pair of Opal-air4 on my Maximus stands and assigned the right speaker to handle right-channel data and the left speaker for the left-channel equivalent. Why the combined mono channel (L+R) then?