Now for something completely different. Unique is the word for the California Cube monitors from Ambiance Acoustics.

Features
The monitors have a sporty granite finish and use four wide-range drivers instead of a woofer and tweeter. Each cabinet is a 13 5/8" cube. According to designer Robert J. Salvi, a cube provides the most volume (for deep bass) in the smallest overall size. One design goal was to provide lots of bottom end so you know what you're getting on tape - a goal I agree with.

When I pried off the black fabric grillecloth, I saw four 4.5" cone drivers mounted in the front baffle, something like the early Bose speakers. A bass reflex port with damping is on the rear of the box and each driver has a treated paper cone and rubber surround.

The California Cubes come with an active equalizer that connects between a mixer and power amp. The EQC-1 equalizer flattens the response of the speakers by effectively boosting the highs and lows. It also includes a sub-sonic filter and a bypass switch.

Why use four small, equalized drivers? Salvi's main goal in this design was to omit the crossover network, which can add distortion or phase shift. Also, the design is said to give tight dispersion, which helps to hear the speakers more than the room acoustics. Using small drivers is claimed to make the bass tight and quick.

Like any design, this one involves some compromise. When multiple drivers cover the same frequency range, there is phase interference between drivers off axis. This causes lobing in the polar pattern, as well as variable comb filtering vs. angle in the frequency response. Measurements and listening tests of the Cubes confirmed this.

My review sample came in a distinctive granite finish. It is eye-catching, unlike the traditional studio black. My teenage daughter liked it! I can imagine these speakers in a contemporary, stylized studio with lots of hanging plants. The box finish is available as granite or rust-colored laminate.

According to Ambiance Acoustics, each Cube has a response from 45 Hz-15 kHz, ±3 dB. Claimed sensitivity of the system is 91 dB/W/m. Impedance is an easy-to-drive 8 ohms. Rated power handling is 120 W, and suggested amplifier power is 10-250 W/ch.

Made of 3/4" MDF with a 3/4" polyethylene baffle, the cabinet is solid and weighs 26 lbs. It is a fourth order vented box. The unit is hand built and has audiophile copper wiring inside. In fact, the Cubes were originally designed for high-end consumer audio.

The front baffle is decoupled from the enclosure to isolate the driver resonances. On the back of the cabinet is a pair of gold-plated binding posts for easy connection to a dual banana plug or bare wires.

Great care has gone into the design of the equalizer. It uses audiophile grade components such as metal film resistors, polypropylene capacitors and gold-plated connectors. Both sides of the board are plated with 2 oz. copper. Other audiophile touches are low-ESR electrolytic capacitors, a toroidial transformer, and an HA7-5222 op amp. A switchable filter cuts the lows by 18 dB/octave below 64 Hz.

A $200 purist upgrade includes exotic ICs, silver wire internal box wiring and silver wire board jumpers.

On the bench
Using a Techron TEF-20 analyzer, I measured the on-axis, full space frequency response of the Cube. The microphone was one meter away, aiming at the center of the front baffle. I used 1/3-octave smoothing on the response curve so it would correlate better with perceived sound quality. The response is ±3 dB from 45 Hz to 15 kHz, exactly as specified. As shown in the dashed line, the bass response would be 4 to 6 dB higher if the speaker were near a mixing console or a wall. This is very good bass performance.

One problem is a broad 3 dB rise around 2 kHz, which is audible. It can add a nasal coloration or general hardness to the sound. I remeasured the Cube at 2 meters and found the same anomaly.

The measurement of the response at 0, 10 and 30 degrees off axis is anechoic, not smoothed, and taken from 300 Hz up. As expected, the response varies due to phase interference between the drivers, both vertically and horizontally. The measurements show that the speaker has a small sweet spot. On the other hand, the tight dispersion can reduce the effect of room acoustics.

The Energy Time Curve, or transient response is respectable. The direct-sound spike is sharp, and delayed sounds appear 11 to 18 dB down from the direct sound. Apparently the lack of a crossover resulted in a tight time response.

THD vs. frequency at 95 dB SPL is next. Over most of the frequency range, distortion is below audibility (less than 3%). THD reaches 3.6% at 50 Hz and 5.2% at 100 Hz (remember these are 4.5" drivers). THD at 40 Hz and below exceeds 10%, but switching in the subsonic filter reduces this problem. At 90 dB SPL (not shown) the THD is below audibility at nearly all frequencies, and 8% at 40 Hz. So except for the deepest bass, THD is extremely low.

In use
As recommended, I placed the Cubes on stands at ear height behind my mixer, about 18 inches from the wall behind them. The owner's manual says, "For nearfield applications, [the speakers] may be placed on stands behind the console with a four- to seven-foot spread."

Typically, closefields are placed about three to four feet apart. I tried the Cubes like that, but whenever I moved a few inches to the side, up or down, in or out, the treble got stronger or weaker and the stereo imaging changed. When I put them seven feet apart and aimed them at me, the tone quality stayed more uniform as I changed position. They are unusual speakers that need special placement.

The Cubes were more beamy than most speakers and lost highs when I listened off axis. But as long as I sat between them in the usual spot, they sounded good.

The stereo imaging gets "phasey" when listening out of the sweet spot and the stereo stage collapses if one gets too far. Find the best listening position and make all sonic decisions there. At that point, the imaging is sharp.

I auditioned the Cubes playing a variety of CDs and my master tapes. Here's how they sounded on various instruments:

• Cymbals and percussion: Crisp but not sweet. Lacks extreme highs.
• Drums: Aggressive impact.
• Kick drum: Realistic. Deep thud and strong impact. About the best I've heard in a closefield monitor. Deep bass-drum roll is weak, showing that the response below 40 Hz is rolled off.
• Acoustic guitar: Fairly realistic, slightly harsh.
• Electric guitar: Lots of bite, plenty of snarly "attitude."
• Bass: Tight, strong, and very deep. Some of the most impressive bass I've heard.
• Vocals: Pretty natural, not overly warm. A little midrange emphasis.
• Piano: Nasal or hard sounding.
• Strings: Smooth at the top but somewhat hard, rather than lush and pretty.

These speakers rock! Kick drum, drums and electric guitars are reproduced with plenty of power. Part of that effect is due to the 2 kHz peak, which contributes an aggressive edge. But it also lends a hard or harsh coloration to acoustic instruments.

Inventor Robert Salvi told me that he is revising the equalizer to remove the 2 kHz peak. By the time you read this, the Cubes should be well worth a listen.

Summary
I commend Ambiance Acoustics for being adventurous and doing something innovative.

Ambiance Acoustics California Cube Closefield Monitors with EQC-1 Equalizer
Plus
+	Fairly smooth and wide-range
+	Good transient response
+	Unique appearance and design
+	Strong, tight bass
+	Low distortion from 50 Hz up
Minus
-	Small sweet spot (but better at 7")
-	Needs wide spacing
-	Upper-mid hardness (remedied in later versions)
The Score
	Find the sweet spot and these innovative speakers are worth an audition.
Reprinted with permission. Copyright © 1997 by JRS Publishing Inc.