Unity Audio The Boulder MKII - Single

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Three-way active monitor with coaxial midrange tweeter
Unity Audio The Boulder MKII - Single
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While the MKI has been very popular and well received by press and professional users, Unity Audio is always looking for ways to improve product performance and the areas they wanted to address were SPL figures and sub-bass extension. This has been achieved by increasing the woofer size from 6.5" to 8" supplied by SEAS, a Scandinavian company specialising in high quality woofers. Additional crossover buffer stages using high quality Burr Brown and Analog Devices components has increased SPL levels by 4dB and low frequencies now extend down to an impressive 30Hz! This upgrade will now have benefits for serious tracking applications, allowing the users to feel the music as well as hear it in amazing detail. 



To accommodate the larger SEAS 8" woofers, the cabinet dimensions have increased to 390mm D x 268mm W x 614mm H. The same interesting material and designs of the MkI have been retained such as the 18mm Baltic Birch plywood, and the same huge 30mm Corian front baffle with large radius edges to reduce reflection and cabinet resonances which in turn is bonded to an internal wooden baffle. 

SEAS 8" woofers

The 8" SEAS custom black aluminium woofer cone is extremely stiff, giving tremendous bass precision. The cone and the low loss rubber surround show no sign of the familiar 500-1500 Hz cone edge resonance and distortion associated with soft cones. Long, high temperature voice coil wound on an aluminium voice coil former gives low distortion and high power handling capacity. Phase plug reduces compression due to temperature variations in the voice coil, eliminates resonances that would occur in the volume between the dust cap and the pole piece and increases the power handling capacity.

Large magnet system provides reasonably high efficiency and low Q. Extremely stiff and stable injection moulded metal basket keeps the critical components in perfect alignment. 

Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum. 

ELAC Xjet dual coaxial 5" mid range & 50kHz tweeter

There are other great features and attributes from the MkI that we wanted to retain though, such as the amazing unique ELAC coax 5" mid range driver and 50kHz folded ribbon tweeter.

The dual coaxial unit is a unique combination of a flat aluminium honeycomb midrange ring radiator and a concentrically arranged folded ribbon tweeter. This design realizes the vision of an acoustic point source with zero phase shift. This facilitates an optimized acoustic power response and results in a homogeneous and very wide sound dispersion angle which provides for a new kind of relaxed but very precise reproduction.

Comparison between the 3D radiation patterns of a conventionally designed midrange-tweeter combination (left) and of the Boulder's coaxial midrange-tweeter system at the crossover frequency. 

The ultra lightweight honeycomb diaphragm provides a reduced stray magnetic field combined with a strong neodymium drive. The system is driven by a 78mm moving coil. High efficiency is achieved using coppered aluminium flat wire, edgewise-wound, on a ventilated capton bobbin. The resulting unit will deal with frequencies from 450Hz to 50kHz. 

Custom Discrete Class A/B amplifiers

The fantastic custom amplifiers from the Boulder MKI have also been retained for the new MkII. These amplifiers are the cornerstone of Unity Audio's performance, designed exclusively for Unity Audio by Tim de Paravicini, whose company Esoteric Audio Research is regarded as one of the worlds best amplifier designers. Due to the modular design of The Rock MKII amplifier, The Boulder MKII uses the same amplifier modules from the Rock MKII but it employs a total of four amplifier cards per cabinet, one for each 8" SEAS woofer, one for the 5" mid and one for the 50kHz folded ribbon tweeter. The amplifier design is a true discrete bi-polar low feedback amplifier with custom wound transformers and dedicated LF, Mid, HF sections which results in very fast and clean performance, and astoundingly accurate reproduction.

Like the MKI, this new MKII model will boost true fidelity, fast, accurate detailed sound but with extended bass response, even more detailed mid range and higher SPL's for larger rooms.



  • 3-way active monitor
  • 4 x bespoke true class A/B 100 watt E.A.R. discrete amplifiers, one per driver
  • Closed cabinet design
  • 30mm Corian front baffle
  • Coaxial 5'' midrange and 50kHz folded ribbon tweeter
  • 2 x 220mm ( 8" ) SEAS woofers.
  • 392mm deep x 268mm wide x 614mm high
  • 23kg each
  • Balanced XLR input
  • 18mm grey Baltic birch 9 ply plywood cabinet
  • HF EQ Shelf @ 10kHz +/- 2.5dB
  • Mid Cut/Boost +/- 2.5dB
  • High Pass Filter switch pre set @ 26hz, 24db per octave.
  • Frequency response -1db 40hz to 28khz
  • Frequency response -3db 32hz to 36khz
  • Brutally honest

Additional Information

Condition New
Length 15.4 in
Width 10.5 in
Height 24.2 in
Active or Passive Active
Monitor Application Mid-Field
driver_sizes 8"
Number of Speakers Single
Input Connectors Analog XLR
Amp Wattage 200 W
Frequency Range 32 Hz - 38 kHz, ±3 dB
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