Напольная акустика — Pbn Audio MR!777

PBN Audio built the MR!777 as a very large three-way tower, designed by company founder Peter Noerbaek. Each cabinet stands 2,057 mm tall and weighs 222 kg, and the retail price was USD 83,000 per pair.

Key specs that matter

Two 18 inch woofers with coated paper cones cover the bass, two 12 inch paper-cone drivers handle the midrange, and a 6 inch ribbon driver takes the treble. The bands are divided at 200 Hz and 1,200 Hz. Rated frequency range is 20 Hz to 20 kHz within plus or minus 1 dB, a tight tolerance for a speaker of this size. Sensitivity is 95 dB with 2.83 V at 1 m. Nominal impedance is 4 ohm, with a minimum of 2.5 ohm at 290 Hz and a maximum of 30 ohm at 3 kHz. Each cabinet is 660 mm wide and 699 mm deep.

Engineering and use context

The crossover is described as an eighth-order Linkwitz-Riley electro-acoustic network overall. The high-pass filter is of Linkwitz-Riley type, and the low-pass filter is a sixth-order Butterworth electro-acoustic section, meaning the published slopes include the natural roll-off of the drivers themselves and not only the electrical parts. The crossover is visible on the cabinet through a clear acrylic cover panel, so the components can be seen without opening the enclosure. The cabinet is braced at several points inside and finished in burled walnut veneer under a gloss varnish. Its sides are slightly scalloped and bevelled, the front baffle is elongated, and the overall profile has a slight hourglass shape. Castors are built into the base, which matters for a box of this weight, since it allows the speaker to be rolled into position instead of lifted. The impedance minimum falls just above the lower crossover point, in the region where the two midrange drivers take over from the woofers, while the impedance peak sits in the ribbon's range. The height and depth of the cabinet call for a large room with high ceilings.

Pairing

Its efficient design allows a moderate amplifier to reach high volume, yet the deep impedance dip calls for an amplifier able to supply ample current into loads far under 4 ohm without instability. Solid-state designs rated for 2 ohm operation are the safer match than output-transformer tube amplifiers with limited current.

Alternatives

PBN Audio's M2!5 is a more compact PBN floorstander, a two-way design with two 15 inch woofers and a compression driver on a waveguide.