Wisdom Audio Series SAS - Manual (Page 7)

7
Description
Your Wisdom Audio SAS 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 computer modeling and the vastly more powerful motors of contempo-
rary 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 optimiz-
ing 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 website 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.
The results are quite stunning. Low frequencies are strikingly dynamic and
responsive, and integrate quite seamlessly with the fast and detailed Wisdom
Audio planar magnetic hybrids.