On the back of the sub you'll find individual dials for volume and crossover, the latter ranging from 50Hz up to 200Hz, as well as controls that allow you to bypass the amplifier's filter, flip the phase by 180 degrees, select different bass modes (cinema or music) and activate auto standby, which shuts the power off when a signal can't be detected. Below these you'll find a line input and output.
The S-81 fronts support bi-amping and sport two pairs of binding posts on the back. The speakers are modelled on Pioneer's EX Series reference speakers and feature a 2.5cm metal dome tweeter, which is mounted in the centre of the midrange driver and allows the sound to be precisely controlled at all frequencies, as well as ensuring that all sounds arrive at the listening position at the same time.
There's plenty more technology where that came from. The Linear Drive Magnetic Circuit (LDMC) ensures linear displacement of the woofer cones and results in distortion-free reproduction of low frequencies. The unique Acoustic Balance Drive (ABD) and Acoustical Filter Assisted System Tuning (AFAST) improve the bass quality by eliminating the vertical standing waves that often occur in large floor-standing speaker enclosures, which can lead to uneven or boomy bass response.
But enough of the science stuff, what are they like in action? In short, phenomenal. Right from the opening scenes of Iron Man on Blu-ray, you're left with no doubt that these speakers mean business. As the Army convoy makes its way through the barren wasteland of Afghanistan, the speakers rip into the sudden explosion with relish, mustering a huge, foundation-shaking boom but harnessing the power with the sort of control and poise that you only get from top-quality speakers like these.
ABD and AFAST certainly appear to be doing a fantastic job too, as the bass output isn't flabby or imprecise but punchy and solid, and integrates beautifully with the midrange frequencies to make the soundstage wonderfully coherent.
Other action-packed scenes, such as Tony Stark's escape from the cave, sound potent and dynamic, with the front channels dispersing sharp gunfire effects and crashes with plenty of attack and not a hint of harshness at the top-end.
The rears join in gamely, flinging surround effects into the soundstage with illuminating clarity and pin-sharp precision, while the centre channel also displays terrific verbal dexterity, conveying Stark's wry dialogue with a clear, natural tone, even when there's a cacophony of noise surrounding it.