Unity Audio Boulder Mk II Professional 3-Way Active Studio Monitors – Pair

For sale is my pair of Unity Audio Boulder Mk II professional 3-way active studio monitors.

I purchased these directly from Unity Audio in Essex as ex-demonstration units in 2019. Since then, they've been used exclusively in my domestic hi-fi system, averaging only around 3–4 hours of listening per week and never driven particularly hard. Consequently, they've had a much easier life than a typical studio pair.

Unity Audio are better known in professional studios than domestic hi-fi circles, but the Boulder competes strongly in the same league as monitors from manufacturers such as ATC, Genelec and PMC. Designed as a genuinely no-compromise reference monitor, each speaker contains four 100 W Class A/B power amplifiers custom-designed by the late and legendary Tim de Paravicini (Esoteric Audio Research), one of the world’s most respected amplifier designers. Drivers are twin 220 mm SEAS Excel woofers and ELAC's unique X-JET concentric ring-radiator midrange with centrally mounted JET folded ribbon tweeter. These speakers are analogue all the way through, no DSP is used. There are XLR inputs and adjustable gain to suit a range of preamps. Boost / cut filters for mid and treble are provided to help tune to your taste / environment.

The drive units are first class. The SEAS Excel aluminium drivers come from the same premium family used in a number of high-end loudspeakers (eg. Grimm LS1), while the ELAC X-JET delivers outstanding phase coherence, imaging and detail retrieval with low distortion and 50 kHz extension. Unity's implementation of these components is superb.

These are sealed-box monitors with a quoted low-frequency response of 32 Hz (-3 dB), although in-room they produce genuinely useful output into the upper-20 Hz region. Bass is exceptionally clean, fast and well controlled, with none of the overhang often associated with ported designs. I never felt the need for a subwoofer, even with pipe organ recordings. They reproduce music effortlessly, combining huge dynamic capability and scale with excellent transparency, superb imaging and neutral tonal balance.

The cabinets are in good used condition, according to the Reverb guidelines. The front baffles and all drive units are excellent. There are some cosmetic marks from previous ownership around the five other sides, with the worst being some scuffs on the undersides. Nothing major - please see the photographs. They are built like a tank, made with 18mm baltic birch plywood and a huge 30 mm Corian front baffle with large radius edges to reduce reflection and cabinet resonances.

Operationally they are fully functional. Like many active monitors they exhibit a small amount of self-noise when powered on with no signal present, although this becomes completely inaudible once music is playing, even at very low listening levels. They also produce a thump on power-up and a brief 'fizz' when switched off; I queried this with Unity Audio during ownership and was advised that this is normal behaviour for the design.

The only reason for sale is that I've recently downsized to a smaller pair of active monitors which are a better match for my 3.4 x 4.3 m listening room. These Boulders will work in a smaller space but may need some EQ to quell room modes depending on speaker / listening positions.

The original Unity Audio cartons are included but are not in the best condition having been stored in the garage. Given the size and weight of these monitors, collection is strongly preferred, although I would consider reinforcing the cartons and shipping at the buyer's risk and expense if required.

Serious prospective buyers are very welcome to hear them working before purchase.

The Boulder Mk II has now been superseded by the Mk III, which currently retails at around £7,800 per pair (ref. Funky Junk). Selling at £2,999; I believe these represent good value for anyone looking for a genuinely high-end active monitor.

Some reviews:

"Tonally, these monitors are right on the money, with instruments and voices sounding incredibly realistic."

"Transient response is first rate... Stereo imaging is also excellent."

"They can easily rival many bigger monitoring systems. True giant killers."

(Unity Audio The Boulder MK II Review | MusicTech)