Thiel ss2 Guide De Référence

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Our goal in developing a subwoofer system was to
produce a product that achieved very high sonic quality and
that did not exhibit the sonic problems typical of subwoofers.
In particular, subwoofer systems usually do not integrate
well sonically with the other speakers in the system and this
product was originally inspired by the conception of an
electronic means of generating  subwoofer low-pass
crossover characteristics that could be made to perfectly
Most subwoofer crossovers attempt (or merely profess) to
deal with the unknown variables of the main speaker’s
response by providing additional controls, including phase,
polarity, and separately adjustable low- and high-pass
frequency. While it is possible that in some cases good
results can be obtained by use of these controls, in most
cases it is still not possible to achieve the desired blending
and integration of the subwoofer and the main speakers. And
even in cases where good results can be obtained, there is no
way to know how the controls should be set to achieve
optimum performance since the required settings are not
usually those that would seem logical.
We needed a completely different approach to
subwoofer crossovers that was able to take into account the
response of the main speakers in order to provide crossover
performance that achieves desired results with simple and
logical control settings. The conception of the technical
means to achieve such performance was the original impetus
for the THIEL SmartSub development.
Room effects
The effects of the third category of problem are well
known. Almost every subwoofer installation is plagued by
response irregularities that are habitually attributed to “room
resonances”. A study of the situation reveals that the majority
of serious problems are not, in fact, and strictly speaking,
room resonance problems, but rather, boundary problems of
cancellation and reinforcement. Even though the effects on
performance are similar, the distinction is important because
it indicates a quite different type of solution. Room
resonance problems cannot really be solved by any method
other than physically changing the proportions and size of
the room. Further, even mitigating the effects with equalizers
can only be accomplished for one listener location, with the
usual result of worsening the problems for other locations.
In constrast, boundary problems are fundamentally and
importantly different. Boundary effects are substantially
consistent throughout the room and therefore corrections are
improvements for all locations. Also, the effects of nearby
boundaries are predictable and therefore can be corrected
without measurements. Such a built-in system of boundary
compensation is an important aspect of the THIEL SmartSub
match any main speaker. Further impetus was added to the
project by the realization that the placement problems of
altered and unbalanced response caused by nearby walls
could also be solved.
We believe that the major problems of subwoofers have
been effectively eliminated in the SmartSub subwoofers and
the following details the highlights of their performance
Subwoofer performance problems can be categorized
into 3 types:
1) Output/distortion/uniformity problems.
2) Problems of sonic integration with the main speakers.
3) Room interaction problems.
Examples of the first type are thumpy, dirty and strained
low frequencies; of the second disjointed sound character,
misbalanced levels and seemingly disconnected low
frequencies; of the third are subjectively overly dominant or
“missing” tones and sonic balance and character that change
with different subwoofer placement.
Low Frequency performance
It is difficult and expensive to reproduce deep bass at
high loudness levels with the low distortion that can be
achieved by high quality speakers at higher frequencies and/
or lower loudness levels. Therefore, many subwoofers do not
attempt to reproduce truly deep bass but rather are designed
to accept very high input levels of bass energy without
obvious distress. Often this characteristic is achieved by
restricting reproduction of deep bass and by incorporating
severe compression of the signal so that demanding inputs do
not overtax woofers and amplifiers of modest ability.
These limitations of most subwoofers can be overcome
with normal engineering. However, such performance
requires very high output drivers and a large amount of
power, neither of which can be obtained at low cost. And
even when a product is engineered to provide a truly high
level of low frequency performance, this does not solve the
two other categories of problems subwoofers exhibit.
The second category of problem is the result of the fact
that the crossovers typically employed are generic types and
that they do not take into account the low frequency
characteristics of the main speakers. This is true whether the
crossover used is the bass management capability of the
processor or the built-in crossover included with most
subwoofers. Usually these crossovers will provide the
desired blending only for the theoretical case of the main
speakers and the subwoofer both having low frequency
response flat down to DC. Since this is never true, the results
obtained are off a little or a lot, depending on other variables.