© Hybrid Audio Technologies, 2010
Page 19 of 22
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Building solid mounting baffles
: in many cases, it is advisable to mount your
Imagine midbass’ in high-stiffness wood or high-density fiberglass (or wood treated
with fiberglass resin). Hybrid Audio Technologies recommends the use of a solid
hardwood, such as birch or oak, namely because these woods are stiff and help to
dissipate resonance, and screws can be inserted and removed multiple times without
stripping. Avoid Medium Density Fiberboard (MDF), particularly in wet environments
like the door, as the MDF will act like a sponge with humidity and moisture, and not
only that, the MDF is a dense, but not stiff type of wood, and the results may not be
particularly noticeable if you use MDF. Once your baffle is built, it must be covered in
one or two layers of a good-quality, brand name self-adhesive damping product; a solid
wood mounting baffle with sound damping treatment will augment the Imagine
installation by eliminating resonances.
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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 Imagine midbass’ 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 Imagine
midbass, 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.
Acoustic Treatment
A considerable benefit can be made to any mobile audio system with the select placement of
acoustic treatments. The purpose of using acoustic treatments is to reduce the amount of
reflected energy in the hostile automotive environment, and hear more of the direct sound
being emanated from the speaker. It is akin to the signal to noise (S/N) ratio in a piece of
electronics, where the signal could be considered the direct energy coming from the speaker,
and the noise could be considered the reflected waves off of nearby surfaces, such as
windows, hard center consoles and door panels, windscreens, and etc. A word of warning
though: there is a fine line between too little and too much 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
