Tempting Fate?

Establishing a virtual baseline. The tape immediately in front of the rack is marked to parallel the rear wall, providing a reference for fore and aft speaker position. Note the lazer – and the tape measure anchored on the reference point.

Having established a musical baseline, it was time to go to work, the first task being to establish a geometrical baseline. With the racks and equipment arrayed along the rear wall, it was necessary (from the point of view of accessibility and accuracy) to create a virtual baseline in front of the racks to act as a fixed reference. This involves tape measures, lasers and the infamous blue tape, marked up with a Sharpie. The second step is to establish the centre line of the room, perpendicular to that base line. Again, given the age of the building, none of the walls are parallel, although the variation is surprisingly small. The biggest single asymmetry exists at the apex of the roof, which is around a foot to the left of middle, although it’s also a good ways distant from the speakers. The centre-line is somewhat arbitrary in absolute terms, but is defined by the width of the room and space for adjustment at the point where the speaker baffles will be located, the speaker/boundary relationship being far more critical than the precise width of the room behind the rack or the listening seat.

Basic tools: strap wrench (to tighten and loosen cones), allen keys, tape measures, lazer level to set reference lines and lazer range finder, basic spirit level, feeler gauge (to accurately measure a speaker’s height off of the floor, low-tack tape and a Sharpie (essential for marking up placement and reference lines). The large C-spanners are provided by Stenheim to adjust the U2 cones. The lower edge of the blue tape on the carpet marks the centre point in the room, level with the speaker baffles. Not shown: the all important speaker jack and digital level.

With the base axes established it was now possible to measure the relative positions/symmetry of the speakers. Set up doesn’t need to be – and often isn’t – symmetrical, given variations in room structure and materials, boundary conditions and even variations between the speakers themselves, but it’s often a good place to start. It involves what Stirling refers to as “zeroing out” the speakers: getting them vertical and the same height off of the floor. Thankfully, in this case we were dealing with a modern, solid, pored concrete and tile floor, which was well within the boundaries of acceptable level. Look at the first set of locational values and you’ll see that the initial settings for height reflect a 3 1/6th” or 4.75mm difference in height relative to absolute level – of which 1 1/6th or around 1.5mm was actual variation in the setting of the speakers’ feet. These might seem like trivial values, but as we’ll see, they are genuinely significant when it comes to maximising performance.