Last time we looked at a line array speaker system using 16 Jordan Eikonas per enclosure. Whilst capable of terrific performance, a 2.5m high loudspeaker may be more than many people (and rooms) require.
One of the requirements when assembling a loudspeaker array is to ensure that the total impedance of the drive units does not fall below that of a single unit. The next stage down from 16 units is – somewhat counter-intuitively – nine. Using the Eikonas in this way provides a system with 95 dB/watt sensitivity and 121 dB peak SPL and the opportunity to dispense with the cabinet altogether.
Mounting the array on a flat panel gives us a classic open baffle speaker with the benefit of no internal standing waves, fewer panel resonances and a cleaner sound. It also introduces a major drawback; an acoustic short circuit.
Below a certain frequency – approximately 500Hz for a 30cm wide panel – sound from the front of the speaker will leak round to the back, be out of phase and start to cancel out. This cancellation results in a 6dB per octave, which is considerably less than the 24dB/octave of a reflex enclosure. The array’s increased sensitivity and power handling means we can use equalisation to extend the bass below 500Hz. How low depends on the maximum loudness we’re trying to achieve. Nine Eikonas have the same cone area as a single, 30cm cone but for high SPL or large spaces, it might be prudent to add a pair of dedicated bass units.
The CAD drawings show a customer design for just such a system for installation in a church. The wall-mounted panels are manufactured from Perspex with the wiring loom bonded onto the surface. The panels fold away when not in use and the whole effect is extraordinarily elegant. It could easily be adapted to a home environment.
Next time we’ll conclude this short series with an enclosure project for a four Eikona array.
CAD drawings © David Smith, Fathomtree Ltd