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 Pro 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).
As mentioned previously in “Lesson Three”, imaging cues of near-field (within 3m) sources
come from effectively two auditory methods: ITD and IID. ITD is the time it takes for sound to
reach the far ear after reaching the near ear. Typical adult male heads have an ITD maximum
of approximately 400 microseconds. IID is the measure of intensity difference of the far ear as
compared to the near ear. ITD is typically used by the brain to localize low frequency sources
below 500 Hz. IID is typically used by the brain to localize high frequency sources, above 2,000 Hz.
HRTF is also used in conjunction with IID. Above approximately 4,000 Hz, the higher frequencies
are attenuated by the head for the far side ear. A sound to your left will have a different spectral
content for the left ear as compared to the right ear. The HRTF is unique for each individual (based
upon shape and size of the head and torso) but typically occurs at around 4,000-5,000 Hz. HRTF
will affect the IID at even higher frequencies, more so than simple average SPL. Above 6,000 Hz
or so, the HRTF portion of IID becomes the dominant factor. The spoken word (human voice)
comprises a fundamental frequency range of approximately 150 Hz to 6,000 Hz.
Taking the above into account, your desired crossover frequency for the Legatia Pro midrange
should be one that allows the midrange to play as much of the audible spectrum of the spoken
voice to ensure point-source delivery of the tones and pinpoint image definition. In many cases,
this would be around 320-400 Hz for high pass, and around 6,000 Hz, or higher, for low pass. In all
cases, the chosen crossover frequencies should be evaluated for sonic character, while balancing
distortion and power compression at high amplitude levels.
Advanced Installation of the Legatia Pro Component
Speakers (Continued)
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 Pro 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 Pro midrange,
chamfer or round sharp edges, flush-mount the speaker whenever possible, and use shallow,
surface-mounted hardware (or ideally use the supplied knurled attachment nuts). 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 Pro drivers use fine cloth diaphragms
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
L2x and L3x designs). Simply adding a capacitor and inductor in series (6 dB/octave bandpass
filter) to a Legatia Pro 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 Pro midrange and
the accompanying Legatia Pro tweeter.
© Hybrid Audio Technologies • Cumming, GA • 770.888.8200
© Hybrid Audio Technologies • Cumming, GA • 770.888.8200
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