Legasy Silhouette Owner's Manual - page 17
Developing a Reference Class On-Wall
In summary, the natural dip in frequency response that wall mounted speakers suffer is the
result of phase difference between the direct radiation and the boundary reflection at the
listener. Legacy employs the additional filter poles created by this acoustic phenomenon
within the crossover strategy to advantage, thereby greatly reducing the dip while reducing
the electrical losses of conventional filter poles.
As we always pair match when tuning and verify all product performance when it leaves the
factory. See frequency response attached. Please note how consistent the Silhouettes are
with each other.
However, since we know the user is attaching them to a boundary, we then can factor the
natural woofer phase accumulation in this problematic region as an integral part of the low
pass filter of the 10” and high pass filter of the 7”. Customarily a second-order high pass and
low pass filter electrical filter (crossover) are 180 degrees out of phase at the center
frequency.
As a result, manufactures usually just flip the polarity on the high pass side to smooth the
summation (often neglecting polar tilt and the time domain). In our wall mounted case,
however, the wall dip is introducing additional poles to each side of the center frequency.
The side benefit is the 7” driver polarity no longer needs to be flipped. The acoustic
summation now has an in-phase characteristic similar to an even-order Linkwitz-Riley
network.
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