Hybrid Audio Technologies Legatia SE - Manual (Page 62)

Legatia SE User’s Manual ©Hybrid Audio Technologies Page 62 of 73
good-quality, brand name self-adhesive damping product; a solid wood mounting baffle with sound
damping treatment will augment the Legatia SE installation by eliminating resonances.
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 midbass’ and/or midrange’s 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 midbass and/or midrange, 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 drivers use rigid paper cones 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 (this roll-off has been accounted for in the Legatia SE L2x and
L3x designs). Simply adding a capacitor and inductor in series (6 dB/octave bandpass filter) to a
Legatia SE midrange 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.
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 SE midbass/midrange and the accompanying Legatia
SE 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. However, we understand that in some
cases that passive filters are required, and thus the reason why we have manufactured the Legatia
L2x two-way and Legatia L3x three-way passive crossover systems. In our humble opinion, however,
the ideal crossover system for most users, is an active one that takes into account the Legatia SE
driver location and its characteristics, in concert with the polar radiation patterns of other speakers