Wisdom Audio Series SCS - Manual (Page 7)

7
Description
Your Sage SCS subwoofer uses a modern implementation of an old idea for high
quality, low distortion bass reproduction. While the roots of the Regenerative
Transmission Line
™ go back to the 1950’s, it is the combination of modern com-
puter modeling and the vastly more powerful motors of contemporary driver
design that make the RTL
™ so special.
Regenerative
Transmission Line™
There is a class of bass enclosures that has
been around since the 1950’s, which can
be described generically as “low frequency
tapped waveguides” or “tapped pipes.” It was
an idea that was a bit ahead of its time then,
since fully optimizing its use required both
powerful drivers and computer modeling.
But if you are into such things, check out US
Patent 2,765,864 (filed in 1955), and an AES paper published in 1959, “Analysis
of a Low Frequency Loudspeaker System.” We have published both on our web-
site for your convenience, at
http://www.wisdomaudio.com/support_documents.php
We have utilized sophisticated modeling software in order to fully optimize our
enclosures, and have developed drivers that are specifically optimized for this
application. We call our unique implementation of this relatively old idea a “Re-
generative Transmission Line
™ ” subwoofer, or “RTL” sub for short.
All dynamic drivers develop energy on both sides of the diaphragm, with the
rear energy being 180° out of phase with the front energy. If you allow the
driver to operate in free space (no enclosure), the front and rear energies largely
cancel each other out — especially at low frequencies.
In our Regenerative Transmission Line ™ subwoofer, the energy from the back
side of the driver is sent along a long, folded path in such a way that its lowest
frequencies arrive back at the front side of the driver in phase, effectively sum-
ming to an increase of 6 dB in output. Thus, the energy from both sides of the
woofer cone is used in a productive way, resulting in a substantial reduction in
distortion and an effective surface area that is twice what you would otherwise
expect. As an example, the effective radiating surface area in the SCS is roughly
equivalent to a 13” diameter round woofer, yet the enclosure is only about 7”
wide.
The results are quite stunning. Low frequencies are strikingly dynamic and re-
sponsive, and integrate quite seamlessly with the fast and detailed Sage Series
planar magnetic hybrids. As an example, the SCS is easily hidden behind a sofa,
or within a set of risers in a dedicated home theater, yet is only –3 dB at 20 Hz
and can output in excess of 120 dB at 22 Hz (measured at its output port to
minimize the room’s effects on the measurement).