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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:
wrote:
wrote:

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

snipo


I'm curious, does anyone know of an earlier motional feedback/servo
loudspeaker, or is the LWE the first to make it into production?

The Audio magazine review (1968) in the previous post makes it sound
like the LWE is the first to make it to production while there had
been previous prototypes.

thanks
-Sam


I'm not sure that this can be called a "motional feedback" speaker.
Before I say any more, I did download a patent and read some on the
Yahoo site. What he's actually done, and how it actually works is still
slightly unclear to me - didn't have much time to look at it all.

But, no matter how you cut it, there is bass boost applied to the
speaker to extend the LF response. The only question is how is this bass
boost generated/created, and /does it have any actual feedback?/

The idea of comparing an "idealized" speaker circuit to the actual
speaker and then applying the difference, is valid in that within the
limits of the driver's capabilities it will try to follow the
"corrected" signal... however later "servo" speakers all have used a
separate sensing device: extra turn in the VC, external inductive
pickup, accelerometer, etc... to generate the sense leg of the system.

In most cases that is massaged with circuitry to produce the proper
signal, and adjust the overall response (back to the "idealized"
speaker, but without an explicit model to compare to) with respect to
the input signal.

It would be interesting to implement the LWE concept on a modern high
performance large X-max woofer and compare its performance to both an
EBS (equalized extended bass response in a too small box) and to an
actual accelerometer or other inductive pickup method servo - all in the
same volume enclosure. That would be a definitive sort of test.

Thanks for bringing this LWE thing to light! :_)

Regards,

_-_-bear


Its funny you should say that because Erath is now using an improved
version of his LWE feedback system on his new "Trout" loudspeakers;
they're a small, two-way, active system that use an 8" woofer and a
planar transducer. They go from 20hz-20khz all by themselves or with
an external 10" large X-max woofer in a tiny 14" cube.

I recently heard a pair of these and they sound pretty impressive.
Somebody close to where I live in Dallas just got a pair and invited me
over to check them out.

http://www.dontgethungup.com/wbcam/trouts+LWE-Is_01.jpg

I thought it would be fun to bring over my LWE-Is to compare since I
just scored an original LWE-I amplifier
off ebay:

http://www.dontgethungup.com/wbcam/lweamp01sm.jpg

I forgot how heavy the LWE-Is are though....good god!

Of course the Trouts sounded much better than the LWE-Is. As you can
see, the setup wasn't ideal, but I was a guest.

Erath's literature says that his improvments in the feedback system
focus more on minimizing harmonic distortion than with the LWE-I which
was mostly to improve bass response. He says that he can really hear
the difference between the SACD and CD tracks on a hybrid SACD. He
named them after the Schubert Quintet I'm pretty sure.

To answer your question, I'm sure there is definitely feedback, now is
it a precise measurement of the position of the speaker cone? Since
the "sense leg" is probably is based on a voltage reading accross voice
coil (in the case of the woofers) I guess it can't be as precise as an
accelerometer or the other methods you mention, yet it sounds
incredibly good. I agree with you that it should be tested as I'm
curious as to how effective it really is in reducing harmonic
distortion. If there is feedback, is it considered "motional
feedback"?

I think Erath's gift is his ability to "massage the circuitry" (as you
so eloquently put it!) because even my 40 year old LWE-Is with their
rather humble vintage components sound remarkably good. Its like "the
whole is greater than the sum of its parts" saying.

Thanks, and happy new year!...lets hope 2007 goes well,
-Sam