Acoustic Energy L3 - Manual (Page 12)

Set-Up Considerations and Installation
increasingly important into the Legatia L3’s upper bandwidth, where the power response is
more uniform, and incident and reflected waves are indistinguishable. In layman’s terms,
keep baffle dimensions small with respect to the size of the Legatia L3, chamfer or round
sharp edges (including, in particular, the mounting hole’s rear inner edge), flush-mount the
speaker whenever possible, and use shallow, surface-mounted hardware. Also, remove all
unnecessary protrusions from the baffle surface.
In addition to the baffle’s construction requirements, it should also be either secured
extremely well to the car’s body, or completely isolated from the car’s body. The reasoning is
that the speaker baffle panel will vibrate, excite baffle modes, and thus will radiate sound.
Small vibrations such as this can result in the baffle itself radiating more sound than the actual
speaker at certain frequencies. In either installation scenario, the baffle should be damped
with a layer of typical sound damping to reduce the Q of the baffle and lower its vibrational
resonance frequency below the range of the driver’s frequency response. In many cases,
using thicker baffle panel in concert with asphaltic-style sound damping can also be
advantageous, providing the rearward wave of the speaker has no obstructions created by the
baffle itself. Finally, if possible, the speaker should be mechanically decoupled from the baffle.
This can be something as simple as a layer of self-adhesive foam tape, to more exotic
examples of decoupling, including rubberized rings or multiple-layer septum shielding.
Crossovers
One of the most fundamental and important considerations in the final tweaking of a car audio
system is the set-up of the speaker’s crossovers. The Legatia L3 utilizes a rigid paper cone
that exhibits little if any cone breakup in its upper frequency bandwidth. However, it is still
important to utilize crossovers, especially active crossover networks to suit the speaker system
to the car’s acoustic signature. It has been Hybrid Audio’s philosophy to tune the speaker
system to the vehicle’s acoustic signature using just active crossovers, and only a very minor
amount of equalization. Our very best world championship vehicles have always had one
thing in common: creative use of active crossover filters and very minimal equalization. Use
your crossovers to tune your car, and the equalizer to suit the vehicle’s speaker response to
your own tastes.
The first thing to remember is that every speaker exhibits some sort of a natural roll-off. This
rolloff typically amounts to about 12 dB/octave, and needs to be taken into account, especially
when designing passive crossover systems. Simply adding a capacitor and inductor in series
(6 dB/octave bandpass filter) to the Legatia L3 does not necessarily mean that you’ll see a
phase coherent 6 dB/octave bandpass filter at its crosspoints. In fact, summing the effect of
the L3’s natural bandpass roll-off, you might actually be approaching a theoretical 18
dB/octave bandpass filter. Not only this, but the speaker could potentially begin to exhibit
significant intermodulation distortion as the cone becomes non-linear trying to reproduce the
lowest octave of tones, not to mention irregular polar radiation patterns between the Legatia
L3 and it’s mated tweeter and midbass with wide frequency overlap.
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