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[email protected] envuelto@gmail.com is offline
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Default Yahoo group for LWE motional feedback loudspeakers made by Louis

BEAR wrote:
BEAR wrote:

wrote:

http://tech.groups.yahoo.com/group/lweusersgroup/

A bunch of us LWE speaker fanatics are collecting and sharing
information about these early (1965-71) servo loudspeakers. These are
the ones that Steve Zipser (RIP) used to rave about all the time on
usenet with the flat frequency response from 20hz-20khz:



I checked the site and the patents...

The trick is that the speakers have some networks worked in, I did not
look carefully at the networks to see their effect beyond that of an
xover. But the intended effect is to create a feedback loop from each
driver that results in a flattened response. In effect a sort of EQ it
would appear... maybe not a bad idea.

Bears some further investigation and maybe reading the patent carefully...


Hi Bear, thanks for stopping by the group and sharing the info about
the CM Labs 911 amplifier.

The best description i've found describing the LWE loudspeakers is
David Winebrenner's review over at audioreview.com:

http://www.audioreview.com/cat/speak...3_1594crx.aspx

or try this tinyurl version: http://tinyurl.com/pedle

Here is a snip:
"Surely there must be some of you out there that have dreamed of using
classic high efficiency large magnet woofers (normally reserved for
bigger reflex designs) in a relatively small bookshelf size box and
"somehow" designing the box or the venting or "tuning" or "something"
so that you could get the extended low end response of an acoustic
suspension system but at a much high efficency and not give up the
transient response. Erath...invented and developed a design that did
cheat and win handsomely. As a point of reference you can see what
happens if you mount old classic high efficiecy large magnet drivers in
a WAY-TOO-SMALL-BOX by referring to the Klipsch model H (Heresy). I
know there are some of you out there who love this little box system,
but frankly the extreme low end down at 32.7 HZ (LOW C on pipe organ)
just isn't there at all. ....The LWE approach to get around this is
based on "negative feedback control". OK....in a typical ampifier
(still mostly vacuum tube back in those days, of course) you have
anywhere from 25-80% of the output of an ampifier used in reverse phase
as negative "feed back" used to minimize distortion and in some gross
cases to make an amplifier stable (not oscillate or 'howl'). The out-of
-phase signal is fed from the output of an amplifier's final output
stage back to the input of that same stage. Actually the same concept
can be used in any intermediate stage of amplification as well. The
concept works well in lowering distortion and, in some cases,
increasing stability. ......Erath's principle was to reduce the
negative feedback selectively only at the extreme low frequencies where
a big 15" woofer in a really tiny box was just not capable of
responding fully. This would leave the feedback and distortion
character untouched at frequencies up above 50-70 HZ...."

If your curious, you can view the patent over at the US Patent and
Trademark Office, it is Publication Number: 03449518:

here is a tinyurl version as the original url is miles long:
http://tinyurl.com/gkc9u

Here is a julian hersch Stereo Review of the LWE-1A:
http://www.classicspeakerpages.net/acoustr/lwe.zip

Here is another review of the LWE-1 in Audio magazine:
http://www.dontgethungup.com/wbcam/E...ew_1968txt.zip

-sam