Hybrid Audio Technologies Legatia Pro - Manual (Page 39)

Legatia Pro User’s Manual ©Hybrid Audio Technologies Page 39 of 43
acoustic treatment; just as some vehicles can benefit from some selectively applied treatments, there
is a point where the vehicle can begin to approach “semi-anechoic” conditions, and lose its liveliness,
which is not ideal. Reflections are all around us, and are a part of our day-to-day lives. It is our
opinion that some lateral reflection is a good thing; it helps to establish stage boundaries, and gives
the recoded playback and more visceral and “believable” sound.
The first principle to understand is that below 200 Hz, acoustic treatments are rendered virtually
useless. It is Hybrid Audio’s assertion that only those frequencies above 200 Hz benefit from the use
of treatments, given that a 200 Hz waveform is about 1.7 m long; 1.7 meters is less than or equal to
most vehicle widths. This is also the frequency where we believe pure tones in the vehicle are going
to be difficult, if not impossible to localize. Finally, most vehicles exhibit a Schroeder Frequency (Fs)
between 50 at 125 Hz; the Fs (or cabin-gain frequency) is vehicle dependent, and is the frequency at
which resonances become so tightly packed in frequency and space that the acoustical properties of
the vehicle behave quite uniformly. (As an aside, one significant benefit of car audio sound systems
is that frequencies below the lowest room resonance increase at a theoretical 12 dB/octave…it’s no
wonder car audio systems have such great bass!)
Acoustic treatment can be very effective above 200 Hz, depending mostly on the polar radiation
pattern of the speaker. In the case of the Legatia Pro midrange, the polar radiation pattern is quite
large at lower frequencies, with a narrowing of the radiation pattern (“beaming”) at frequencies into
the treble bandwidth.
Should the Legatia Pro midrange be placed in the kick panel locations, one may find that a notable
improvement can be made by adding acoustical treatments, such as open-cell foam, into the
underside of the dashboard. Likewise, should the midrange and/or tweeter be placed up high on a-
pillars, or in the dashboard, where comb filtering (reflective summation and cancellation off of a hard
surface, such as a windscreen) may become an issue, a dashboard “mat” or other soft furnishing may
be a noticeable improvement. It will require trial and error to get it right, but the learning is in the
experimentation!
Advanced Installation Conclusions
Sadly, there are no rules in mobile audio, only several hypothesis and theorems that seem to work for
most vehicles. Your vehicle may be different, and defy everything we know, and everything written in
this manual. You may find that getting that rich, detailed sound that you crave may require some
experimentation and a lot of work to make it right. Or you might be fortunate to have a vehicle that
sounds excellent with minimal work. Have patience and work through the issues; the result will be a
rewarding musical experience in your vehicle! Just remember, it is critical to get a reference, as
detailed in Lesson 5. Go out and become a student of music and audio, learn, and improve your
audio system one step at a time. The journey is exciting and rewarding!
What we have included above is only a very brief primer to the world of high-end mobile audio
systems. We invite you to read more by going to our website.