SB Acoustics Xmax


We designed the successful Pennywise for the folks at Parts Express…then the extraordinary B741 for SB Acoustics… and now, we’re introducing the stunning XmaX speaker system for SB Acoustics.

The XmaX is a 3-way system comprised of two powerfully balanced 10-inch woofers, a pair of full-throated 6.5-inch midrange drivers, a pitch-perfect 1-inch Ring Radiator tweeter…and, for extra vibrancy and substance in the high frequencies, an ambient tweeter placed on the rear.

The 10-inch woofers (SB29NRX75-6) are placed in the lower enclosure, in a full 100-liter volume. They’re tuned in the low 20 Hz range, with a 5″ inner diameter pipe measuring 16″ long. (Pipe is available at, and they’ll cut it to length for you.) The woofers have, individually, a low 6 Ohm impedance, so the combined impedance hovers around 2.5 Ohms when connected in parallel operating below 500 Hz. However, it is almost resistive, so it will not tax your amplifier unreasonably. Bear in mind that the DCR on the inductors in the crossover is critical to maintain the electrical phase of the crossover, so the 15-gauge on the first inductor and the 17-gauge on the second are selected to maintain the DCR in the correct range.

The upper cabinet houses a pair 6.5 inch mid-range drivers (SB17NRXC35-8-UC) which flank a 1-inch ring radiator tweeter (SB29RDC-C000-4). The ambient tweeter on the rear (SB26-STAC-C000-4) completes the assemblage.

Enjoy building these magnificent SB Acoustics XmaX speakers – when constructed properly their performance will rival that of commercially available designs costing many times more.

If you simply want to enjoy the great audio, completed models are available from PBN Audio for $12,500 per pair. This includes the exposed crossovers behind the plexiglass windows on the upper rear of the cabinets.
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