[[email protected]]

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

[BEAR]

wrote:
bear wrote:

wrote:

wrote:


BEAR wrote:


BEAR wrote:



wrote:



snipped old msgs



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

Should be fairly simple to measure.

There are a number of freeware FFT software/souncard measurement PC
based systems on the internet for download. That and a relatively cheap
microphone (solder, opamp, battery and $1 Panasonic element + straw =
measurement mic) DIY or storebought will give you more data than you can
shake a stick out.

That will do frequency response, impulse response an waterfall.

That will tell the entire story pretty fast.

I don't suppose Erath publishes those measurements?? I did not see much
on his website...

_-_-bear

[[email protected]]

bear wrote:
wrote:
bear wrote:

wrote:

wrote:


BEAR wrote:


BEAR wrote:



wrote:



snipped old msgs



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

Should be fairly simple to measure.

There are a number of freeware FFT software/souncard measurement PC
based systems on the internet for download. That and a relatively cheap
microphone (solder, opamp, battery and $1 Panasonic element + straw =
measurement mic) DIY or storebought will give you more data than you can
shake a stick out.

That will do frequency response, impulse response an waterfall.

That will tell the entire story pretty fast.

I don't suppose Erath publishes those measurements?? I did not see much
on his website...

No, there isn't much information on his website about the Trout
Loudspeakers. He doesn't administer his own website so the information
on there about his speakers is a few years out of date. You see, he
isn't quite up to speed on the computer and internet thing just yet so
he had a family member put that info on the web for him.

I gave him a call and asked him about testing for harmonic distortion
and he said measuring distortion at high frequencies is difficult
because you have to determine whether the source of any distortion is
from the speaker or your microphone etc...
I mentioned the FFT programs and that interested him enough that he
would like to take a look at it. I think I convinced him that he'll
want to test their performance as hard numbers are going to be
important to people scrutinizing his claims.

Google just turned up http://www.speakerworkshop.com which looks
promising, but I need to investigate it a bit more.

It sounds like you have had some experience with this type of thing so
any recommendations you might like to share would be great. ;-)

I mentioned using an accelerometer and other methods for implementing
feedback and he said: "the fallacy of using an accelorometer is that
you end up introducing the characteristics of the accelerometer into
the system - if the accelorometer has distortion it will be
introduced."

He said that using a second winding on the voicecoil has to be done in
such a way that they are isolated magnetically and the pickup coil has
to be essentially distortion free.

He has found using the same voice coil is quite possible....and he went
on but I don't understand what I wrote in my notes at this point but it
is obvious that he has given it much thought over a lifetime of
experimenting and still sees much potential in reading voltage accross
the existing coil.

It is fascinating listening to him expound on some of these concepts -
he later went on talking about Harry Olson's early motional feedback
prototype and then how succesfull Western Electric was in their use of
feedback for reducing distortion for LP cutting heads. The guy is a
walking encyclopedia of electronics/acoustic/physics data but it is
hard for me to keep up with him sometimes...lol

He wrote up some info about the development of the Trout:
http://www.dontgethungup.com/wbcam/E...Trout_Info.pdf

He mentioned some other random stuff about the Trouts:

-His feedback network flattens a upper frequency peak that the planar
has but there is a switch on the back that will bring it back for
people with "old ears" (-20db loss after 60)

-Both Planar and 8" woofer contribute to 2.5 - 5khz range using
6db/octave crossovers

-He has applied for a patent on his new feedback design (he turns 90
this year!)

Thanks! - Sam