Heres some tips-
5.5 What is "rear fill", and how do I effectively use it? [HK, JSC]
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"Rear fill" refers to the presence of depth and ambiance in music. A
properly designed system using two channels will reproduce original
rear fill on the source without rear high frequency drivers. Since
recordings are made in two channels, that is all you will need to
reproduce it. What is captured at the recording session (coincident
pair mics, Blumlein mic patterns, etc.) by a two channel mic array will
capture the so called rear fill or ambiance. Many of the winning IASCA
vehicles have no rear high frequency drivers. Also a lot of this has
to do with system tuning. If rear high frequency drivers are added,
however, the power level of the rear fill speakers should be lower than
that of the front speakers, or else you will lose your front-primary
staging, which is not what you want (when was the last time you went to
a concert and stood backwards?). The proper amount of amplification
for rear fill speakers is the point where you can just barely detect
their presence while sitting in the front seat. Separates are not a
requirement for rear fill; in fact, you may be better of with a pair of
coaxial speakers, as separates may throw off your staging.
5.7 How do I select proper crossover points and slopes? [DK]
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Basically, this requires a degree of patience. The subwoofer should be
started off at about 100Hz and adjusted until you are happy with the
sound. Keep in mind that the higher the crossover point, the more
power the driver on the high-pass will be able to handle but raising
excessively may cause the low-pass driver to sound raspy or unnatural.
The idea here is to first make rough selections to protect the drivers
and then to fine tune crossover point selections to achieve optimum
fidelity. It's all a matter of what sounds good to you after that, but
remember that even *minute* changes in crossover frequency can make
dramatic differences in the way your system sounds and images.
As a rule, subs should be crossed over no higher than 120Hz, a 6 1/2
mid should be able to handle about 90 Hz, a 5 1/4" should be okay with
about 100Hz, a 4" - about 500Hz, and tweeters vary from about
3500-5000Hz. These points all assume the use of a 12dB/octave
crossover ... if you have a steeper roll-off a lower crossover point
may be chosen. Remember, these are not hard and fast rules but rather
a rule of thumb to help you get started (and so you don't blow up all
your speakers when you are setting your gains!).
