Air Tight Bonsai AL-05 Mini-Monitor

Tiny but Mighty

Equipment report
Air Tight Bonsai AL-05
Air Tight Bonsai AL-05 Mini-Monitor

If you think mini-monitor means small sound, the Air Tight Bonsai will have you thinking again. Forget mini; the sound here is decidedly, uh, maxi. For starters, the speaker’s wide dispersion and voluptuously full and rounded imaging will fool you into thinking you’re listening to a far larger transducer. Plus, in the midband the Bonsai delivers an exciting sense of immediacy and a bold presence, coupled with remarkable detail, that also belie its size and single 4" driver. It’s a thing of beauty to behold, to boot.

Air Tight, founded by the legendary Atsushi Miura and based outside of Osaka, Japan, is known first and foremost as a manufacturer of extraordinary handcrafted tube electronics. Indeed, the single-driver Bonsai is currently the sole loudspeaker bearing the marque’s name. But it’s quite a special speaker and one that’s certainly a delight to have around. Before I delve into why, let’s begin with a little background.

Mr. Takanori Ohmura, formerly of Luxman, designed the Bonsai’s driver and enclosure. An expert on speaker diaphragms, Mr. Ohmura has focused his research on full-range drivers for more than 15 years. His connection to Mr. Miura and Air Tight dates back to their days at Luxman, the company Mr. Miura’s father-in-law founded and that Mr. Ohmura joined in 1976. (For more about Mr. Miura, see JV’s recent Hall of Fame feature on the designer in Issue 268.) Mr. Ohmura now runs his own factory in Malaysia called AMM Laboratory where the Bonsai’s driver is made and where the speaker is assembled.

The version of the Bonsai I auditioned, also known as the AL-05, marks the monitor’s third iteration over a decade and a half; the previous versions are the MSM-1 and the AL-03. The “AL” designation refers to the multi-core Alnico magnet used in the driver assembly.

According to information provided by Air Tight, Mr. Ohmura’s ongoing interest in full-range drivers lies in their general phase correctness. All versions of the Bonsai have had 10cm-diameter diaphragms. (Ohmura-san has never increased diaphragm size—to obtain louder volumes and deeper bass—as this would lead to a loss of phase coherence due to time delays.) To offset single-transducer disadvantages—specifically, a lack of scale, impact, and power—Ohmura-san has not only improved the enclosure through the years, but has also concentrated on finding the most suitable coating materials and multi-polymer paints to apply to his nano-woven glass-fiber diaphragm to achieve the quickest transmission speeds. The Japanese have a long cultural tradition of polymer chemistry and lacquering techniques—and Ohmura-san’s chemistry degree helps, too, as does his studies of violin finishes and piano lacquers.

Speaking of finishes, the Bonsai’s wooden enclosure is available in either a high-gloss rosewood or piano-black; my review samples were the elegant rosewood. There are grilles that attach to four tiny pegs on the speaker’s face, but I never really used them. The drivers are too pretty to cover up! Surrounded by a near-square panel of glossy rosewood, the gold-toned coating of the diaphragm glows with a subtle sheen.

Setup and Sound
Given their diminutive dimensions and light weight (11 pounds) the Bonsais were a snap to set up. However, you will need to consider supplying stands for them, as none are included with the speaker. I used custom ones I had on-hand, but for a time I also placed the Bonsai’s atop another pair of speakers I have in house for an upcoming review. These are small guys, so just a touch of toe-in is all it takes to get them up and running with images snapping readily into place. My listening positions ranged from about 7–12 feet away from the speakers. Up close, I heard more detail; further back, more color. My room is quite large (approximately 35 feet by 17 feet with 12-foot plaster ceilings). For my critical listening I mostly drove the monitors with the superb Air Tight ATM-1S stereo power amp—a great match. I’d heard this combo demo’d at a few audio shows, too. (See below for the rest of the system.) To keep this review to its assigned length I’m going to stick to that tube amp pairing and to LP listening. (Analog all the way!)

Broadly speaking and on most program material (especially well-recorded music), playback through these transducers resulted in a big, full, highly engaging sound. These monitors ain’t no wallflowers. Thanks in part to the diaphragm’s unique proprietary coating, the Bonsai’s single driver offers a pacey presentation that feels evenhanded and effortless yet offers a roundedness that might be described as tube-like in its dimensionality. There’s also a decided midrange emphasis (as you would expect from a single-driver speaker of these dimensions).