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Loss of Xmax due to driver sagging is the only downside I can think of.
According to Adire:
Many low-Fs drivers cannot be mounted in a downfiring (or horizontal) configuration; they must be
oriented vertically, with the cone/basket perpendicular to the floor. To achieve a very low Fs in other
subwoofer systems, the moving mass of the system is made quite high, while the stiffness of the suspension
is made low. These two changes work to create a system which will suffer excessive cone offset when
mounted so that gravity will pull the cone out, away from the normal “rest” position.
Because Shiva has an Fs of 21.6 Hz, the moving mass is not substantially more than competitive
subwoofers. However, the surround is considerably stiffer. This results in Shiva being rated for horizontal
mounting. In fact, given the T/S parameters, one can calculate the effective loss in Xmax that will occur
due to the offset of the cone from the force of gravity:
Basically, one looks at the mass of the cone (118.3 grams, in the case of Shiva), and the mechanical
deflection, Cms (0.47 mm/N, as measured by DUMAX). The acceleration of gravity (what's pulling the
cone down, or up) is 9.8 m/s2.
Now, a Newton (the N in Cms’ units) is in units of kg * m / s2, or kilogram meter/second squared. So,
multiply the mass of the cone by the force applied (gravity) by the mechanical deflection:
mass * force * deflection = 0.1183 kg * 9.8 m/s2 * 0.47 mm/N
= 1.1593 kg * m / s2 * 0.47 mm / (kg * m / s2)
Note that there's a kg * m / s2 term in the numerator and the denominator. Cancel the units out, and you're
left with 0.545 mm. Thus when Shiva is mounted horizontally, one will end up with an Xmax of
14.355mm one way (in the direction of gravity), and 15.44mm in the opposite way. As a comparison,
several other high-end 12” subwoofer drivers will exhibit up to 1mm of offset; considering these units
typically start with 2+mm less Xmax than Shiva, the result is a considerable drop in swept volume.
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