Hybrid Audio Technologies Legatia SE Carbon - Manual (Page 29)

Legatia SE Carbon User’s Manual ©Hybrid Audio Technologies Page 29 of 30
Mounting baffle dimensions: While building baffles is important, it is notable that mounting baffle
size is equally important. All mounting baffles should be kept as small as possible with respect to the
size of the speaker. The purpose of using a small baffle is to avoid the potential for low amplitude
diffracted sound waves becoming summed with the incidental waves. A narrower baffle also becomes
increasingly important as frequencies range into the Legatia SE Carbon midbass’ upper bandwidth,
where the power response is more uniform and incident and reflected waves are indistinguishable. In
practical terms, keep baffle dimensions small with respect to the size of the Legatia SE Carbon
midbass, 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.
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 SE Carbon drivers use rigid carbon fiber
cones that exhibits cone breakup in its upper frequency bandwidth. The proper utilization of
crossovers, especially active crossover networks, can effectively mitigate this cone break-up
phenomenon at high-frequency. 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 a Legatia SE Carbon midbass driver 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
driver’s natural bandpass roll-off, you might actually be approaching a theoretical 18 dB/octave
bandpass filter at certain frequencies. On the other hand, with the cone break-up mode phenomenon,
a simple, low-order lowpass filter may be doing virtually nothing to abate the large break-up mode at
high-frequency. Furthermore, with respect to highpass frequency, 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 SE
Carbon midbass and the accompanying Legatia tweeter.
Given the large uncertainty of low-order crossover systems, Hybrid Audio recommends the use of
higher-order electronic crossovers so that fine tuning can be done electronically. The active network
benefits from easy correction of different speaker sensitivities and equalizing not only the individual
drivers but the combined response as well. Not having to account for the speaker’s impedance
verses frequency, as well as the passive device impedance and phase shift makes the active filter
superior to most passive crossover networks, due to the fact that each and every aspect can be
tailored to better suit the individual installation’s requirements. The ideal crossover system for most
users, is an active one that takes into account the Legatia SE Carbon driver location and its
characteristics, in concert with the polar radiation patterns of other speakers involved, all the while
balancing linear and non-linear distortion (non-linear harmonic distortion increases with sound
pressure level or cone displacement, and thus, crossover frequency is critical and can be vehicle and
user dependent).