Set-Up Considerations and Installation
Given the large uncertainty of low-order passive crossover systems, Hybrid Audio recommends
the use of higher-order passive crossover systems, namely fourth order (24 dB/octave) filters,
and ideally, 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, if not even
desired in certain circles, and although the work involved to make them right might be more
difficult than that of an active network, the results can be made to be the same. In our
humble opinion, however, the ideal crossover system for most users, is an active one that
takes into account the Legatia L3 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 is the product of all small midrange designs,
and the Legatia L3 is no different. Typically, 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: Interaural Time Delay (ITD) and Interaural
Intensity Difference (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. Head
Related Transfer Function (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 L3 should be
one that allows the L3 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 200-250 Hz for high pass, and around 6,000 Hz, or higher, for low pass. In very
controlled circumstances, Hybrid Audio has achieved excellent results with a passband of 140
Hz to 8,000 Hz with L3’s aimed on-axis to the listener. However, the low crossover point will
limit amplitude ability and potentially increase distortion, and was meant for a user with
realistic expectations of a small diameter driver and realistic listening levels. To summarize, in
all cases, the chosen crossover frequencies should be evaluated for sonic character, while
© 2006, All Rights Reserved
