Hybrid Audio Technologies Legatia - Manual (Page 9)

Legatia User’s Manual ©Hybrid Audio Technologies Page 9 of 65
products (there are some minor exceptions, based upon application, intended use, power handling,
and etc., please contact us for details). Hybrid Audio has also had great success incorporating the
Legatia midrange and midbass drivers in dipole configuration (detailed below), transmission lines,
and in larger vented enclosures.
In a typical installation, Legatia midrange and midbass products should be mounted with unrestricted
access to airspace to ensure the speaker’s ability to effectively reproduce its wide frequency
bandwidth. The reason why the speaker was designed in this way is highly empirical. When a
speaker is mounted in a small closed box, it radiates as much energy forward of the cone as it does
rearward of the cone. All speaker cones and dust caps (diaphragms) are a weak sound barrier at
best, and the result of the high amount of energy being “pushed” into a small enclosure is the energy
transmitting through to the outside of the cone (an additive phenomenon to the incidental wave). It is
conjectured that this effect is most notable in the low hundreds of Hz region, where acoustical stuffing
materials are ineffective and the internal dimensions are not small enough for the internal air volume
to act as a pure compliance. Consequently, Hybrid Audio has designed this speaker to work well
without an enclosure, and as such, should not be significantly prone to enclosure back-pressure and
sound coloration when placed infinitely baffled. The “infinitely large” enclosure, per se, improves
spectral response and power response variation between high and low frequencies. And in the case
where an infinite baffle operation is difficult or impossible to achieve in your car’s environment, we
highly suggest the use of acoustic resistors (aperiodic membranes or trade name Variovents
®
) in
sealed enclosures to help dissipate the backwave energy. If you absolutely must use a sealed
enclosure, we recommend that you contact us for details and assistance in targeting a sealed
enclosure volume applicable for your intended purpose. In all cases, the use of loosely-packed
fibrous damping materials, such as fiberglass, Dacron, or long-fiber wool will also significantly
improve the final installation, no matter what type of baffle and enclosure configuration is chosen.
Dipole Applications
While infinite baffle or resistive sealed enclosures are highly recommended for this driver, you might
find that in the rare instance that the Legatia drivers can be placed in a completely open baffle, i.e.
dipole. A word of caution: Legatia drivers mounted in an open baffle have to move more air than a
similar Legatia driver mounted in a resistive sealed enclosure, or infinitely baffled, just simply for the
fact that there’s a progressive acoustic short circuit between front and back waves below the
speaker’s resonance frequency (Fs) in the open baffle configuration. Great care must be taken in this
instance, because there is no acoustic compliance afforded in a dipole configuration, and the speaker
will reach its mechanical limits much quicker (and will net increased distortion). However, in certain
instances, a dipole-style midrange may work well in a vehicular installation, in that radiation from the
rear of the baffle, having undergone enough phase shift as it comes around to the front, adds to the
total sound at off-axis angles. Of great importance in the dipole midrange configuration is the setting
up of crossovers and weighing the negative effects of distortion of elevated amplitude levels.