A few years ago I bought an Apple G4 Cube computer. I had wanted one when they came out back in 1999, but they were too expensive. Time marched on, prices came down, and I picked up a very nice example to play with.

The Cube’s audio system is entirely USB based. There is a small box which plugs into a USB port which contains a USB DAC, a Tripath class-D “digital” amplifier, and  a DC-DC converter to step the 5V from USB up to 12V for the amp chip. There are two 4” diameter clear acrylic balls fitted with 1.5” aluminum cone Genesis drivers made by Harman/Kardon. These look so cool every Chinese speaker manufacturer has cranked out cheap look-alikes, often simply gluing a shiny dish onto the cone of a 30-cent speaker.

So we have a pair of small aluminum cone drivers with long-travel suspension in heavy-wall plastic enclosures. The small drivers should cover a wide frequency range and image well, but the round enclosure ought to have a strong Helmholtz resonance. There is an inner structure which partially divides the cavity and might serve to damp standing waves.

What do they sound like? They do image well, respond without audible peaks through the midrange well into the treble. Maybe lacking a bit in ultimate top-end shimmer. Bass is surprising, reaching down to 100 Hz, lower on the typical desk top which the enthusiastic LF vibration of the ball makes into a sounding board.

Can we improve things? I think so.

Firstly, a slight chesty resonance around 125-150 Hz.

Perhaps a bit of damping material in the ball.

The first trial was with some of my wife’s cotton

make-up remover pads stuck into the interior recesses.

That sounded better, but looked a bit funky, and a Cube is elegant if it’s anything. So the cotton pads were covered with some grey felt which blends better with the overall decor.

That helped with male voices and improved imaging and transient response as well. On the other hand, it cut the apparent amount of bass, making the addition of a subwoofer more of a priority.

Building a sub for the Cube is another article.