[[email protected]]

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:

LWE-1 - a three way system using
a 15" CTS woofer, a 6" CTS solid-back midrange and an Electro-Voice T-
35 tweeter horn mounted in a speaker cabinet with dimensions of: 25"
H, 17" W, 12" D. Power rating: 50 watts. Resistance: 4 ohms.
Frequency response is 22 Hz - 20 kHz. SPL rated at 96 dB/per watt @
1m. Room gain control, mid and high level controls.

We've already got a lot of members (including Louis himself) sharing
historical data, photos, information about connecting the LWE's
negative feedback circuit to a suitable amplifer (we have clipkits!),
operating instructions, magazine reviews etc...

We have a growing library of clipkits, and now a manual from CM labs
with instructions on how to test any amplifier and fashion a clipkit to
enable the feedback network.

If you are looking for information about these speakers please come on
by and help yourself and if you have any information to share, that
would be great!

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

[Steven Sullivan]

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:

LWE-1 - a three way system using
a 15" CTS woofer, a 6" CTS solid-back midrange and an Electro-Voice T-
35 tweeter horn mounted in a speaker cabinet with dimensions of: 25"
H, 17" W, 12" D. Power rating: 50 watts. Resistance: 4 ohms.
Frequency response is 22 Hz - 20 kHz. SPL rated at 96 dB/per watt @
1m. Room gain control, mid and high level controls.

Has anyone measured frequency response of these by post-1971 methods?

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason

[BEAR]

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:

LWE-1 - a three way system using
a 15" CTS woofer, a 6" CTS solid-back midrange and an Electro-Voice T-
35 tweeter horn mounted in a speaker cabinet with dimensions of: 25"
H, 17" W, 12" D. Power rating: 50 watts. Resistance: 4 ohms.
Frequency response is 22 Hz - 20 kHz. SPL rated at 96 dB/per watt @
1m. Room gain control, mid and high level controls.

We've already got a lot of members (including Louis himself) sharing
historical data, photos, information about connecting the LWE's
negative feedback circuit to a suitable amplifer (we have clipkits!),
operating instructions, magazine reviews etc...

We have a growing library of clipkits, and now a manual from CM labs
with instructions on how to test any amplifier and fashion a clipkit to
enable the feedback network.

If you are looking for information about these speakers please come on
by and help yourself and if you have any information to share, that
would be great!

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

Clipkits?

Is this where the feedback for the amp is moved to the speaker terminals??

That's NOT "motional feedback", if this is what it is.

Motional feedback is when the actual position of the speaker cone is
derived, turned into an electrical value and that is used as "feedback"
to (hopefully) correct the difference between the input signal and the
speaker's actual attempt to follow it. For which there are limitations.

In particular, motional feedback methods up until now are primarily
useful for LF, and not particularly useful for midrange and HF.

In the case where the feedback is taken from the speaker terminals, the
effect is to *eliminate the effect of speaker wire*. Which is not at all
a bad idea. Of course, it is not perfect.

I'd take anything that Zippy said with a large grain of salt. I knew him
personally, and speak from that perspective.

_-_-bear

[BEAR]

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...

_-_-bear

[[email protected]]

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

[[email protected]]

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
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

Some details about the LWE negative feedback networks that I should
have mentioned in the previous post are that they electronically model
"ideal" speaker performance, and while connected in series with the
physical speaker, they compare the voltage across the speaker's voice
coil with "ideal" performance voltage. The difference between the two
is sent back to the amplifier as an inverse corrective voltage and fed
into the input of the amplifiers designated negative feedback output
stage creating an immediate, dynamic voltage correction for the
physical speaker at a specified frequency.

Erath told me that the coils he used in the feedback network were
uncommon at the time: a toroid-wound, powdered-permalloy core that was
previously used only by Bell Telephone in their loading coils and in
certain military electronics. The network also used a photo resistor
and light bulb to attenuate the amount of bass boost at higher volume
levels based on Fletcher Munson curves.

Their are some circuit diagrams on the US Patent website link in the
previous post, they are on the 2nd page. The navigation buttons to
select pages is on the left side of the screen (hard to find due to
bad website design) also, your browser will need a TIFF image viewer -
(IE will ask for ActiveX permission)

I have a detailed LWE history posted at the yahoo group that I put
together with notes taken after a few phone calls with Erath as well
as email conversations with people who worked in his shop:

http://tech.groups.yahoo.com/group/l...oup/message/61

It is probably much more than you will ever want to know, but it was
written for LWE fans. (Also, it is a work in progress)

Apparently Erath acted as a mentor and source of inspiration for quite
a few students of electronics and electronic engineering as everyone I
talked to that worked with him had fond memories and spoke/wrote in
reverential tones. The guy has pretty much had a full plate his entire
life, he was recruited by the US govt during WWII to oversee projects
developing depth charge fuses where he rubs elbows with Shockley and
Bardeen, all while pouring over Harold Stephen Black's patent,
utilizing Black's feedback concepts in military devices and later, in
geophysical instruments and of course the LWE loudspeakers.

Even more amazing is that he is still producing hand-built LWE
loudspeaker systems using updated versions of his feedback networks
and modern components:
http://www.lweloudspeakers.com/

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

[BEAR]

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

[[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