Subwoofers also offer a phase control so the upper frequencies they produce will
not cancel out the lower frequencies of the satellites. A judicious tweaking of this
control can pay major dividends in spectral smoothness in the crossover area.
Phase changes with frequency, however, so these controls may need readjusting
every time you vary the cutoff frequency. Section X details the adjustment of this and
other controls.
Also adjustable is the overall level of the subwoofer's output. Many users tend to set
this too high at first, in an effort to achieve truly impressive bass. Again, smooth
response is the aim, and it may well be that, if you use them, two subwoofers end up
being set differently—if, for example, one is in a corner and the other is not. It's all
part of the overall-balancing act that is bass management in real rooms.
We get virtually no inquiries about subwoofer placement from customers, which is a
good indication that it's not something over which people lose much sleep. A good
subwoofer is such a pleasure when used with a good main speaker that enjoyment
is definitely the rule.
VI. About “Bass Management”
As home theater systems became more complex with numerous options for
subwoofer connections and bass adjustments coming into play, the term “Bass
Management” has become common. A little explanation of the subject is in order
before we proceed to connecting and adjusting your subwoofer.
If you are playing a movie soundtrack on a DVD it probably contains a 5.1 channel
audio soundtrack. This means that AC3, DTS or other processing is used to encode
5 main channels (3 front speaker channels and 2 surround channels) and a “.1”
channel, more properly referred to as a “Low Frequency Effects” channel. This later
term comes from Cinema practice where, some years ago, movie theater owners
asked for a separate sound track for the explosions and effects of action movies.
Those who were willing to spend the money would add a low frequency effects
speaker (a subwoofer) to their system and play back the effects track. “Normal” bass,
say from dialog or music would still be sent to the original behind-screen speakers.
For the full impact of a movie in your home theater you obviously want to send this .1
channel to your subwoofer.
Note that the other 5 channels are also full range channels. Although they may not
contain explosions or other rumblings they probably have bass content from the
movie’s background music and dialog. Here you have a choice to make. Do you
want to keep that bass content in its respective channels or filter it out, combine it
into one channel and send it the subwoofer? Some aspects to consider are the size
and power handling of your main speakers. If your mains are fairly small then you will
get a great power handling and bass extension benefit from sending the bass of the
5 main channels to the subwoofer instead of to the smaller main speakers. If, on the
other hand, your main speakers are larger and you are satisfied with their bass
performance for most music, you could configure your subwoofer in such a way that
it handles the heavy lifting of the movie’s .1 soundtracks
only
. We generally
recommend the former approach (sending all bass to the subwoofer) since the bass
power handling and bass extension of a PSB HD Sub is probably much greater than
that of the typical front channel loudspeaker.
However you choose you will have to study the manual of your AV
Receiver/Surround Processor for the settings that must be made with it. Look for a
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