What was the real inspiration behind the Karlson Coupler?

[Horn Fanatic]

Many years ago while I was searching U.S. patent listings for anything and everything I could find that was audio related, I came across many other interesting unrelated patents. One of all things, was a contraption that used centrifugal force to assist in delivering a baby. LoL! I won't go into the rest, as most of them are even more preposterous too mention.

One device that I found most interesting, was a water nozzle. The image and description of it's operation bore a striking resemblance to the Karlson Coupler.

Now, I have visited some of the most popular Karlson forums, and have read a few long winded theories about how the tube was designed that actually make acoustical sense, some of which I have repeated and demonstrated to my colleagues, but a search of three Karlson patents revealed that the patent number for the nozzle never appeared in any of them.

So my question is, what was the real inspiration behind the Karlson Coupler? Could John Karlson have stumbled onto the the same patent I did?

I'll post the patent image for you to come to your own conclusion, and please note the date on the patent. If one choses to read the whole two page patent, it can be found at http://www.freepatentsonline.com/ It's free to join! Just enter the patent number under search.

View attachment Karlson.PDF

 

[freddi]

good question and cool old patent! -- we'll have to dig deeper - if its possible at this point in time. It could have related to a whistle or perhaps a cut in an organ pipe - - ? maybe he saw or had one of those nozzles??

Karlson's first microwave antenna patent of the 1940's was a variable beamwidth type of conventional parabolic design. In his 1964 radio appearance on HiFi Workbench hosted by Eric Towline (Mr. Towline is alive and working in film and tv), Karlson described K15 basically as a coupled cavity type with improved matching and dispersion characteristics.

1964 radio show with John Karlson - his K15 cabinet was used extensively by the Ford, GE, Disney
and other World's Fair exhibitors

https://archive.org/details/KarlsonHifi64

The original Karlson K15, finalized in the summer of 1951 is superior in ways to horns for its bulk and use as a wide bandwidth reproducer. (Steve Schell part of Cogent will attest - lol)

There's a missing patent - or something was made possibly by Sperry without giving direct credit to Karlson. Wayne Green had a falling out with Karlson but did say John had invented an antenna upon which things were based)

KR5 Rocket speaker ad "Patented by J.E. Karlson, leading radar systems engineer, microwave specialist and inventor of a widely used Navy antenna"
[IMGDEAD]http://imagizer.imageshack.us/a/img809/3239/rocketsheetfront.jpg[/IMGDEAD]


Karlson's antenna reference seems missing - the late Wayne Green says he gave the idea to Karlson to make a speaker using the principles.


Here's an early V-notch antenna - the so called Vivaldi antenna is credited to Peter Gibson in 1978

Karlson's Open End Waveguide Antenna patent 1968 - this was concurent with Karlson's
X15 speaker which employed a similar slotted waveguide.
[IMGDEAD]http://img43.imageshack.us/img43/1174/openendp.png [/IMGDEAD]
one excellent audio example of that waveguide
[IMGDEAD]http://usr.audioasylum.com/images/4/44410/Karlson_The_Tube.jpg[/IMGDEAD]

KARLSON AND KARLSON-RELATED SPEAKER PATENTS
KARLSON PATENTS:
J.E. Karlson US 2586827 “Directive Radiating System” Filed March 31 1945 - a
Parabolic dish microwave antenna with what appeared to be a variable directivity pattern
J.E. Karlson “Acoustic Transducers” US 2816619 filed Dec. 1951, granted 6 years later - deals with broadbanding slot both in loudspeakers and musical instuments.
J.E Karlson “Acoustic System” US 2896736 filed Aug. 1955 - use of a modified Karlson laying on its back using either corner or wall to create a diffused sound image - HiFiLit’s website shows a K12 used in this fashion (laid on back) on the 1955 Karlson brochure page and Bose references this K-patent.
J.E. Karlson “Open End Waveguide Antenna” US 3445852 filed 1968 - essentially analogous with the K-tube waveguide used in Karlson’s X15 2-way speaker ~1966.
J.E. Karlson “Acoustic Transducers” - US 3540544 filed 1968 - concurrent with X15 and described Karlson’s use of ellipse based reflectors to improve the Ultra-Fidlety type via
Fig.6 and Fig 8’s reflctors (Fig6 upper reflector was used in the X15) and introduced the Asymmetric Projector with tapered elipse profile which appeared commercially as the AP-9C ceiling speaker - also- slotted microphones were discussed.
J.E. Karlson “Jet Engine Silencer Nozzle...) US 3543876 filed 1968 - jet engine muffler and rocket nozzles.

LIST OF INVENTIONS 4/24/50
J.E. (Edward) Karlson
1. ELECTRONIC POTENTIOMETER. A variable element which is capable of linear variations of resistances with infinitesimal mechanical motion yet also have capabilities of broad variations in resistance.
2. CAPLESS DISPENSING TUBE. This device permits the use of toothpaste tubes, etc. without the necessity and bother of removing and replacing the cap after each usage.
3. GEOLOGICAL PROSPECTING SYSTEM. A system for use in the prospecting for oil, minerals, etc. This system may also be used for radar applications.
4. RADAR ANTENNA WITH AUTOMATICALLY VARIABLE BEAM PATTERN. This invention provides a simple means of automatically changing the beam pattern of a radar antenna from a pencil beam to a cosecant beam.
5. DIELECTRIC ANTENNA. This invention provides a technique for designing commercial and military antennas which will have overall dimensions than conventional antennae, and yet have equivalent gain and directivity characteristics.
6. BRUSHLESS DC MOTOR
7. ASHTRAY. An extremely simple design for an ash tray which quickly extinguishes cigarettes.
8. PRECISION DELAY CIRCUIT. This circuit provides a delayed pulse at a precise interval following an initial pulse.
9. CHATTERLESS CONTACTS FOR RELAYS
10. TELEVISION ANTENNA. This invention provides a simple, low cost antenna which can be readily hidden or obscured in the average room and is suitable for both F.M. and television.
11. SLOT ANTENNA. This design provides a slot antenna with broad band matching possibilities.
12. HYBRID WAVEGUIDE JUNCTION. This is a wave guide section which has variable propagation characteristics dependant upon the direction of propagation.
13. R.F. TUNER. a simplified tuner for F.M. and television use.
14. ADVERTISING SIGN. Novel electric sigh with quick change possibilities.
15. LIGHT VALVE FOR TELEVISION PROJECTION AND PICKUP TUBE.
16. ACOUSTIC TRANSDUCER. A novel loudspeaker enclosure with improved matching characteristics and controlled reverberation.
17. FISHING DEVICE
18. TELEPHONE AMPLIFIER WITH SPECIAL ACOUSTIC CHARACTERISTICS

RELATED:
W.O Swinyard US 2020166 filed 1935 “Sound Reproduction Apparatus” - a wedge-shaped 20 degree coupler with “V” deflector having non-parallel walls
N.C. Fulmer US 2787332 filed 1952 “Loud-Speaker System” - a folded 1/4 wave pipe with last section broadbanded with tapered slot.
R-J Enclosure:
(1) "The R-J Speaker Enclosure" by William Joseph and Franklin Robbins. Published in Audio Engineering Magazine December 1951.
(2) "Practical Aspects of the R-J Speaker Enclosure" by William Joseph and Franklin Robbins. Published in Audio Engineering Magazine January 1953.
"Acoustic System for Loud-Speaker" US# 2694463; Robbins et al filed April 17, 1952 granted 11/54
(nephew of William) Jeff Joseph's Loudspeakers: http://www.josephaudio.com/
J.J. Baruch US2766839 "Loudspeaker System" Filed March 16th 1953, granted Oct. 16th 1956 - deals with math of distributive resistive vents using round holes
- Marty Poppe built X15 copy of Ann Karlson's organ speaker using 42-0.375" holes to damp the system for a particular 15" woofer.
John A. McKenzie US 3590941 filed 1969 “Speaker Enclosure” - a dual mouth K-coupler like stacked “Asymmetric-Projector” having a final deflector at each mouth
Robert W. Reams US 4196790 filed 1978 “Acoustic Transducer having Multiple Frequency Resonance” - novel use of Karlson’s slot to create a broad-banded throat in a
PA-application quasi-scoop horn with sealed back chamber - Gregory Raw termed it a Sci-fi-scoop”.
Rodden, M. Raymond US 4313521 filed Feb. 2 1982 "Speaker Housing"
Sapkowski September 3, 1996 "Exponential multi-ported acoustic enclosure" United States Patent 5,552,569
Weiss et al US 5943431 August 24, 1999 “Loudspeaker With Tapered Slot Coupler And Sound Reproduction System” - basically a wedge-shaped asymmetric projector waveguide for 1” compression driver

 

[xrk971]

With patents there is the idea of different fields of invention and then there are the claims. Just because there is something that looks the same does not mean there is inherent infringement or lack of citation, but if it
is in a completely different field, the patents will not be related and there is no problem with prior art because it would not be obvious to one skilled in the art of speaker or acoustic design to take a water nozzle to turn into a speaker. Then in the claims, that is where the actual use of the novelty is stated specifically or broadly. I would doubt that the water nozzle had any claims on wavelength of resonances and modes and efforts to smooth them out. Finally due to limits of technology in database searches back in 1950's it is not surprising that some similar prior art is missed.

 

[Horn Fanatic]

As a former defense contractor employee in the late eighties working for a company that manufactured microwave antennas, I am familiar with waveguides. My prior experience in audio got me even more inquisitive about antennas. There were a couple of engineers I worked with who were also interested in audio to a lesser degree, whom I showed photographs of acoustic lenses. They steered me to two names, Winston Kock, and Fred Manley.

We used similar waveguide horns to the one of which I've posted a photograph of here.

On another note regarding my patent search, I found the patent for what can only be construed as a ring radiator tweeter. The patent is dated 1935!

http://cdn2.mdltechnologies.co.uk/wp-content/uploads/2012/05/3116B-Double-Ridged-Waveguide-Horn.png

BTW - I have the Martin Poppe article that was based on the analysis of the "K-Coupler". Nowhere in the article is John Karlson's name mentioned for some odd reason, but it does give the math for the flare. It's quite simple. It's the one I use from a spread sheet I wrote for all the Karlson enclosures I build. If anyone would like to read it let me know and I'll post it here.

 

[freddi]

hi Horn Fanatic, in Poppe's posted paper, the acknowledgement thanks J. Karlson but as you said no where mentions why the "K".

http://www.cameng.com/pdf/the_k-coupler_a_new_acoustical-impedance_transformer.pdf

I'd love to see anything relating to building and understanding how to size and make good Karlson couplers !!!!

tell us what really works well for you. -- have you built the asymmetric projector type?

what other than a stock K12 would make a really good "K10"?

 

[Greg B]

With patents there is the idea of different fields of invention and then there are the claims. Just because there is something that looks the same does not mean there is inherent infringement or lack of citation, but if it
is in a completely different field, the patents will not be related and there is no problem with prior art because it would not be obvious to one skilled in the art of speaker or acoustic design to take a water nozzle to turn into a speaker. Then in the claims, that is where the actual use of the novelty is stated specifically or broadly. I would doubt that the water nozzle had any claims on wavelength of resonances and modes and efforts to smooth them out. Finally due to limits of technology in database searches back in 1950's it is not surprising that some similar prior art is missed.

Yeah, searching patents was once a great deal more difficult. Think card catalog and microfilm. I remember doing this the old fashioned way in the Sunnyvale CA patent library a couple times when I was in school around 1989 or so. It would have been unlikely that a sprinkler patent would have been found if searching for waveguides, horns, speaker enclosures and even antennae.

Also, just because this sprinkler patent was issued doesn't mean that the item was ever manufactured. Most patents aren't. Still, it would be funny if it was the inspiration. As you say, the fact that it is for a totally different purpose means that the claims are totally different, so it really has no legal bearing on Karlson's patents.

Is there a vintage sprinkler enthusiasts club/forum/etc? There's groups for everything. If so, they would know.

 

[Horn Fanatic]

Yeah, searching patents was once a great deal more difficult. Think card catalog and microfilm. I remember doing this the old fashioned way in the Sunnyvale CA patent library a couple times when I was in school around 1989 or so. It would have been unlikely that a sprinkler patent would have been found if searching for waveguides, horns, speaker enclosures and even antennae.

Also, just because this sprinkler patent was issued doesn't mean that the item was ever manufactured. Most patents aren't. Still, it would be funny if it was the inspiration. As you say, the fact that it is for a totally different purpose means that the claims are totally different, so it really has no legal bearing on Karlson's patents.

Is there a vintage sprinkler enthusiasts club/forum/etc? There's groups for everything. If so, they would know.

Sunnyvale?

What a coinkidink. I used to live close by off of Wolfe Road. I spent many hours sitting on the floor between the stacks reading patents.

"Is there a vintage sprinkler enthusiasts club/forum/etc?"

I don't know, but damnit, I'm going to find one!

 

[Horn Fanatic]

hi Horn Fanatic, in Poppe's posted paper, the acknowledgement thanks J. Karlson but as you said no where mentions why the "K".

http://www.cameng.com/pdf/the_k-coupler_a_new_acoustical-impedance_transformer.pdf

I'd love to see anything relating to building and understanding how to size and make good Karlson couplers !!!!

tell us what really works well for you. -- have you built the asymmetric projector type?

what other than a stock K12 would make a really good "K10"?

Hi freddi -

The only K's I've built in numbers were of the K12 & K15 variety. My spreadsheet is simple. It consists of blocks of tables that are interlinked to the equation, which in turn are linked to two cells where I enter in a frequency and initial width of the slot, that being a constant 1/2". As I enter the frequency I locate the block which has the closest dimension of the horn length and width at it's termination. I change the frequency until the length and width matches the internal dimensions of the cabinet. It's a bit time consuming, but I get a perfect exponential curve every time no matter what the box dimensions are. I then tune the box based on the driver, and the internal volume of the rear chamber. The Karlson design is not without an acoustical problem though, an anomaly which presented itself with the K15 that I later soon discovered was present with the K12 as well. I will elaborate on that in another post.

I began building K12's loaded with the JBL D & K 120 in the late seventies for use as electric bass rigs. I sold scores of them, some of which were sales to folks who were reccomended to me by Walter Woods. At the time in southern California, there was no one building Karlsons. I did build only one pair of K10's for a bass player by the name of Steve Anderson, who came to me with a pair of Gauss 10", and the design criteria was that the enclosures had to fit along with his amp in the back seat of his sports car. LoL! After 33 years since I last saw him, I contacted him to see if he was still using them, but he told me they had been stolen long ago. Needless to say, with the permanent heat sink on the back of the Gauss driver I nearly had to use a shoe horn to load them. Seven months ago I decided to resurrect the K12, and built a prototype loaded with an EVM 12L which has been out for evaluation ever since.

The only photographic evidence I have other than those taken in my back yard 35 years ago, are of a home audio system I built for a friend and customer of mine. I built his entire horn system. The Karlson enclosures in John Tucker's system are used as sub-woofers, and they do a phenomenal job of it. Tight, articulate, without an inkling of boom.

http://www.jenalabs.com/images/vsac2008-12-r.png

 

[freddi]

(wish I could do decent woodwork - never any good - anymore its difficult to raise my arms) how did you vent your K12's? were they different than Karlson's cabinets in that regard? were they roughly the same size? did they play well for home use say with a more domesticated woofer than D120?

 

[EddieT]

Has anyone ever heard the big Karlson in the coffee table configuration? I would think the front chamber loading would be impacted due to the proximity of the glass to the slot.

I am beginning to think I am more concerned with how it sounds to me in my listening area. One can be try to be a purist but music anymore has been mixed, remixed, compressed and whatever so why not just go for what we like? My friends and I used to go to the big hi-fi shows and be impressed by EV Patricians, Bozemans, Wharfdales,ARs or whatever nearfield in those big arenas but how would they sound in a home environment? Bottom line Karlsons have always pleased my ears at home.

 

[freddi]

that table top would have to kill things - ridiculous idea imo- it would be like my "Murray Tone" or whatever a little parameter slot firing speaker was called.

here's a nabbed picture of a pair of Murray Tone cabinets -I would have to dig for my cabinet
- there's something like a 1/2" spacing of the front panel from the driver and the sound comes
out the whole perimeter. Think of the coloration of the Klipschorn bass section but moved up several octaves
and done with a cheap radio speaker.

I am fond of the R-J and its Eliptoflex spinoff.

 

[EddieT]

I was intrigued with the eliptoflex when it first came out and disappointed that no plans ever appeared.

I wonder if a movable shutter could be designed for a K15 rectangular port. Say a piece of foam board suspended in a track and controlled by a threaded rod so that the aperture could be controlled from the exterior while actual program material was playing. Since I no longer have any test equipment that would fit my seat-of-the-pants approach. But just a thought as I no longer have a K15 or a space for one, much less a pair.

Although I have a couple of radial arm saws I find it easier to use a Kreg Rip-Cut Jig for sheet goods.

 

[freddi]

I've tuned K15 lower both with a tunnel to extend its port and also like Exemplar with two 3" pvc elbows . The original vent area of ~40 to 32 square inches works well for most situations - 32 sq. inches doesn't seem to make it go lower - but does have maybe a bit less output in the 220Hz region. Some little K's will exhibit deep response holes if their vent area is too small. (Ken Lehman came up with a clever way to make a smooth measuring coupler)

system tuning and subjective damping is sensitive to the first few inches of slot. Up close to K15, it seemed I could sense the effect of a 1.5" ball of mortite sitting in the port boundary. K15 can exhibit a holographic midrange - I think some of that comes from the rear wave. I remember how cool an EV SP15B (weak motor but nice mids) sounded on a soprano in K15. Those afraid of the Karlson and worry about insetting their rough fullrange flush with a cabinet face are ignorant. Sure there will be effects but neither
the direct radiator nor the K are truly "real" or perfect.

for fun, I'm wanting a new "K10" - maybe 14-14.5" wide, 24-26" tall and 12-13 deep - load it with something which can play 120dB peaks comfortably and use a K-tube for highs. K12 work well with some 10" and might be tough to beat. K12's rear chamber may be too large for some situations and it might be helpful to have the front chamber tune lower than what a fully scaled K10 would tune.

the Eliptoflex and its spinoffs in patents are pretty much the R-J sans aperture constriction. That's a tidy
way to vent a reflex. The R-J used some constriction and my R-J with the nice EV SP15 fullrange measures well and sounds nice. Much better on bass viola transients than a reflex with the Nirvana10. I have four 18" cabinets vented like R-J/Eliptoflex.

these were made for me in two sizes - 6.2 and 8 cubic feet - all four at once were pretty good

[IMGDEAD]http://img213.imageshack.us/img213/5608/rjsigmajpgca9.jpg[/IMGDEAD]

 

[Horn Fanatic]

(wish I could do decent woodwork - never any good - anymore its difficult to raise my arms) how did you vent your K12's? were they different than Karlson's cabinets in that regard? were they roughly the same size? did they play well for home use say with a more domesticated woofer than D120?

Hi freddi -

Funny thing, as I was cruising some Karlson forums last year I came across a profile drawing of a K12 with the exact vent configuration I used back in 1978. I suspect that someone acquired one of my boxes years later and took credit for it. My vent arrangement was a kind of a quasi-double bass reflex. ??? The driver chamber vented into the upper chamber by way of a rear slot, which vented into the coupler chamber by way of another slot above the baffle. The panel above the shelf was adjustable for alternate tunings. My enclosures were of the same dimension as Karlson's K12.

The original K12 drawing called for two wide cletes to tie in the sides, back, and baffle. I used a full width shelf that extended 1.5" in front of the baffle, to an inch or two shy of the rear panel. The adjustable panel had a 45 degree mitered cleat on the face bottom that was in line with the shelf front.

At the moment I'm using a fixed panel above the shelf to mount right angle venting. The shelf amounts to a panel that services more as a lateral brace about 3" or so in depth behind the baffle.

I've never tried the multiple slot arrangement that Karlson used, although I may on another prototype. I say so because I had the opportunity to load an RCA "Furnace" cabinet with an ALTEC 604C. The Furnace cabinet has decorative louvers under the speaker which act as vents. I was astonished to discover the slots on that box acted more like an auxiliary radiator, than a vent. I would have sworn there were two drivers in that box.

 

[freddi]

the first commercially available K12 had the full width rear shelf and featured a clever three-position movable bar on the rear panel for damping adjustments. Here is its plan reconstructed by Greg B. (the lip on the reversible port panel normally faces forwards) http://img228.imageshack.us/img228/8316/karlsonetteib7.png

the rear lowpass gap can be tweaked for best subjective transient response using good recordings
of plucked/slapped bass viola and drumkit

adjusting that bar also slightly alters the input input impedance
[IMGDEAD]http://imagizer.imageshack.us/a/img714/4944/karlsonetteb12cxdamping.gif[/IMGDEAD]

the slit vent on the best known K12 has dynamic advantages but may harbor some disadvantages. When driven with sine-wave near Fb, there is a lot of harmonic distortion and high vent velocities - but music, at least music of my time, is comprised of transients so there aren't overt effects even if an electric bass is played directly through a slit vent K12. At high levels that slit vent must compress and the impedance curve alter towards a sealed condition.

if you don't mind, draw your K12's vent arrangement

the full width rear shelf re-appeared in Karlson's K12 of the late 1960s - that kit seemed to be provided un-vented with instructions on how to vent
for specific drivers.

K12 introduced at the 1954 HiFi Show - look at the damping bar - I have
a full size factory blueprint for this cabinet ! I need appropriate grill cloth
to fix it where I ripped it off to gather dimensions.
[IMGDEAD]http://img119.imageshack.us/img119/581/striplowbjpgjpgiw9.jpg[/IMGDEAD]

here's a pair of those late K12, factory vented for Tannoy Red speakers
[IMGDEAD]http://img683.imageshack.us/img683/508/rdk12rearvents.jpg[/IMGDEAD]

here's the same late K12 model which showed up on audioasylum's high efficiency speaker forum

unvented ! - its interesting that there's no damping material under the rear shelf.
This must be the way Karlson intended for that version to be damped as the Tannoy
units above have their Kimsul pads in the same locations.

[IMGDEAD]http://usr.audioasylum.com/images/6/66574/University_200_0021.jpg[/IMGDEAD]

 

[freddi]

the late Wayne Green didn't seem impressed by K12 compared to K15, but imo, K12 is a cool little cabinet which can do a lot of things well. They work nicely with the inexpensive Beta10cx or with a K-tube on top. For two way operation, I recommend using a K-tube rather than horn or CD waveguide.

K12 loaded with a strong motor 12 and driven with 200 watt peaks can be punchy as some know.

 

[EddieT]

It would be fairly easy to make the original K12 tuning strip adjustable from the exterior by mounting it in slotted holes using carriage bolts and knobs on the rear. I don't know if it would be worth the effort.

 

[freddi]

a K10 size set of couplers of mine had slotted rear shelf boards so the gap could be adjusted and locked with wing nuts - of course that meant removing the back panel so not as convenient nor as fast as your idea.

 

[freddi]

after Karlson's death, it appeared that his widow issued a number of licenses which spawned X15 size cabinets for PA and bass guitar use

I count seven for the little X15:KHS, KK-Audio, Westwood, Acoustic Control, BEC, LEECH, and Transylvania Power Company. Cetec-Gauss produced their 5181 K18 so that's eight Karlson-couplers perhaps almost at the same time.

were their others? In the 1970's I could have almost sworn l saw something K-related which mounted on a tripod that was not like either a regular Karlson or the klam-projector type.

KK-Audio
[IMGHTTPDEAD]http://a.imageshack.us/img843/8972/kk1front1.jpg[/IMGHTTPDEAD]

Acoustic 115BK
[IMGHTTPDEAD]http://img386.imageshack.us/img386/5376/115bkftxb1.jpg[/IMGHTTPDEAD]

Doug's little couplers built by the Transylvania Team
[IMGHTTPDEAD]http://img214.imageshack.us/img214/8149/superk6lv.jpg[/IMGHTTPDEAD]

Stanley Clark's Ks from Transylvania (-told that's who delivered them)
[IMGHTTPDEAD]http://img84.imageshack.us/img84/9134/scgz6.jpg[/IMGHTTPDEAD]

LEECH under license from Transylvania Power Co.

Ernst Georg Beck's BEC-1
[IMGHTTPDEAD]http://imagizer.imageshack.us/a/img442/256/kk1111143img.jpg[/IMGHTTPDEAD]

Westwood

Gauss 5181 K18 - -Karlson made a K18 so this wasn't without precedent

good ol' K15 (think that's a 15-?) JC sounds great on a good Karlson
[IMGHTTPDEAD]http://imagizer.imageshack.us/a/img199/2566/spaker1.jpg[/IMGHTTPDEAD]

 

[Horn Fanatic]

The first time I heard a Transylvania Power Tube was in the mid seventies. It was mounted on an ALTEC 808 driver. My buddy held it in his hand over his head as he stood in the door way of his store. I walked around the parking lot 60 feet away, and that gizmo was all over the place as good as any large radial horn. I was blown away. I still have the original sales brochure for "The Tube". Never had the heart to part with it.

More photos;

http://img.canuckaudiomart.com/uploads/large/410619-stromberg_carlson_cabinets_empty.jpg

http://usr.audioasylum.com/images/4/40270/lambda-2.jpg

http://img685.imageshack.us/img685/4966/smallklam.jpg

http://i159.photobucket.com/albums/t144/Jazomir/Speakers/MSIKarlsonClams.jpg

http://img120.imageshack.us/img120/5034/quackjpgzy2.jpg

http://forums.prosoundweb.com/index.php?topic=119951.0

http://img138.imageshack.us/img138/1435/ftprwi3.jpg

http://s665.photobucket.com/user/FUCHSAUDIO/media/POWERPROJECTOR.jpg.html

Karlson interview: http://www.youtube.com/watch?v=AGSqs9zmNO4